@inbook {2021m-PieFra,
	title = {Cooperative Manipulation},
	booktitle = {Encyclopedia of Robotics},
	year = {2023},
	publisher = {Springer},
	organization = {Springer},
	author = {Francesco Pierri and Antonio Franchi}
}
@article {2022d-SanTogJimCorFra,
	title = {Indirect Force Control of a Cable-suspended Aerial Multi-Robot Manipulator},
	journal = {IEEE Robotics and Automation Letters},
	volume = {7},
	year = {2022},
	month = {07/2022},
	pages = {6726-6733},
	doi = {10.1109/LRA.2022.3176457},
	attachments = {https://homepages.laas.fr/afranchi/robotics/sites/default/files/2022d-SanTogJimCorFra.pdf , https://homepages.laas.fr/afranchi/robotics/sites/default/files/2022d-SanTogJimCorFra-video.mp4},
	author = {Dario Sanalitro and Marco Tognon and Anotnio-Enrique Jimenez-Cano and Juan Cort{\'e}s and Antonio Franchi}
}
@article {2022a-JacKivDasFra,
	title = {Motor-level N-MPC for Cooperative Active Perception with Multiple Heterogeneous UAVs},
	journal = {IEEE Robotics and Automation Letters},
	volume = {7},
	year = {2022},
	month = {01/2022},
	pages = {2063-2070},
	doi = {10.1109/LRA.2022.3143218},
	attachments = {https://homepages.laas.fr/afranchi/robotics/sites/default/files/2022a-JacKivDasFra.pdf , https://homepages.laas.fr/afranchi/robotics/sites/default/files/2022a-JacKivDasFra.mp4},
	author = {Martin Jacquet and Max Kivits and Hemjyoti Das and Antonio Franchi}
}
@conference {2022b-AfiVanFra,
	title = {Toward Physical Human-Robot Interaction Control with Aerial Manipulators: Compliance, Redundancy Resolution, and Input Limits},
	booktitle = {2022 IEEE Int. Conf. on Robotics and Automation},
	year = {2022},
	month = {05/2022},
	address = {Philadelphia, PA},
	author = {Amr Afifi and Mark van Holland and Antonio Franchi}
}
@article {2022m-MohBicFraBarPra,
	title = {Aerial Tele-Manipulation with Passive Tool via Parallel Position/Force Control},
	journal = {Applied Sciences, Special issue on Aerial Robotics for Inspection and Maintenance},
	volume = {11},
	year = {2021},
	doi = {10.3390/app11198955},
	author = {Mostafa Mohammadi and Davide Bicego and Antonio Franchi and Davide Barcelli and Domenico Prattichizzo}
}
@article {2021f-HamUsaSabStaTogFra,
	title = {Design of Multirotor Aerial Vehicles: a Taxonomy Based on Input Allocation},
	journal = {The International Journal of Robotics Research},
	volume = {40},
	year = {2021},
	pages = {1015-1044},
	doi = {10.1177/02783649211025998},
	attachments = {https://homepages.laas.fr/afranchi/robotics/sites/default/files/2021f-HamUsaSabStaTogFra.pdf},
	author = {Mahmoud Hamandi and Federico Usai and Quentin Sabl{\'e} and Nicolas Staub and Marco Tognon and Antonio Franchi}
}
@article {2021e-RylBicGiuLovFra,
	title = {FAST-Hex - A Morphing Hexarotor: Design, Mechanical Implementation, Control and Experimental Validation},
	journal = {IEEE/ASME Transactions on Mechatronics},
	year = {2021},
	doi = {10.1109/TMECH.2021.3099197},
	attachments = {https://homepages.laas.fr/afranchi/robotics/sites/default/files/2021e-RylBicGiuLovFra.pdf , https://homepages.laas.fr/afranchi/robotics/sites/default/files/2021e-RylBicGiuLovFra.mp4},
	author = {Markus Ryll and Davide Bicego and Mattia Giurato and Marco Lovera and Antonio Franchi}
}
@conference {2021k-CorJacJimAfiSidFra,
	title = {A General Control Architecture for Visual Servoing and Physical Interaction Tasks for Fully-actuated Aerial Vehicles},
	booktitle = {2021 Aerial Robotic Systems Physically Interacting with the Environment (AIRPHARO)},
	year = {2021},
	month = {Oct.},
	address = {Biograd na Moru, Croatia},
	author = {Gianluca Corsini and Martin Jacquet and Antonio-Enrique Jimenez-Cano and Amr Afifi and Daniel Sidobre and Antonio Franchi}
}
@conference {2021h-CoeSarLeeBalFraKonOtt,
	title = {Hierarchical Control of Redundant Aerial Manipulators with Enhanced Field of View},
	booktitle = {2021 Int. Conf. on Unmanned Aircraft Systems},
	year = {2021},
	month = {Sep.},
	address = {Athens, Greece},
	author = {Andre Coelho and Yuri Sarkisov and Jongseok Lee and Ribin Balachandran and Antonio Franchi and Konstantin Kondak and Christian Ott}
}
@article {2021a-JacFra,
	title = {Motor and Perception Constrained NMPC for Torque-controlled Generic Aerial Vehicles},
	journal = {IEEE Robotics and Automation Letters},
	volume = {6},
	year = {2021},
	month = {04/2021},
	pages = {518-525},
	abstract = {This letter presents a perception-aware and motor- level non-linear model predictive control scheme for multi-rotor aerial vehicles. Our formulation considers both real actuation limitations of the platform, and realistic perception objectives for the visibility coverage of an environmental feature while performing a reference task. It directly produces the rotor-level (torque) inputs of the platform motors at high frequency, hence it does not require an intermediate unconstrained controller to work. It is also meant to be generic, by covering standard coplanar quadrotors as well as tilted-propeller multi-rotors. We propose an open-source fully onboard implementation of the method, capable of running at 500 Hz under the intermittent and noisy measurements of one or more cameras. The implementation is extensively tested both in simulation and in real experiments with two substantially different multi-rotor platforms, an underactuated and a fully actuated one, both equipped with two cameras, clearly demonstrating the practicability and high performance of the method.},
	doi = {10.1109/LRA.2020.3045654},
	attachments = {https://homepages.laas.fr/afranchi/robotics/sites/default/files/2021a-JacFra.pdf , https://homepages.laas.fr/afranchi/robotics/sites/default/files/2021a-JacFra.mp4},
	author = {Martin Jacquet and Antonio Franchi}
}
@article {2021c-BasHamBroFra,
	title = {A Novel Robust Hexarotor Capable of Static Hovering in Presence of Propeller Failure},
	journal = {IEEE Robotics and Automation Letters},
	year = {2021},
	month = {03/2021},
	abstract = {This paper presents a novel open source design of the Y-shaped hexarotor Unmanned Aerial Vehicle (UAV), and proves both in theory and real experiments its robustness to the failure of any of its propellers. An intuitive geometrical interpretation of UAV static hovering ability is presented, through which the robustness of different coplanar/collinear hexarotor designs is analyzed. Following the presented geometrical interpretation, we also show the conditions that allow the Star-shaped hexarotor to be robust to the failure of some of its propellers, while showing its incapability to static hover in the case of the failure of any of its propellers. Finally, the efficiency of the Y-shaped and Star-shaped hexarotors are tested experimentally, and conclusions on the advantages and disadvantages of the two designs are drawn.},
	doi = {10.1109/LRA.2021.3067182},
	attachments = {https://homepages.laas.fr/afranchi/robotics/sites/default/files/2021c-BasHamBroFra.pdf , https://homepages.laas.fr/afranchi/robotics/sites/default/files/2021c-BasHamBroFra.mp4},
	author = {Elgiz Baskaya and Mahmoud Hamandi and Murat Bronz and Antonio Franchi}
}
@article {2021d-HorHamGieFra,
	title = {Optimal Tuning of the Lateral-Dynamics Parameters for Aerial Vehicles with Bounded Lateral Force},
	journal = {IEEE Robotics and Automation Letters},
	volume = {6},
	year = {2021},
	pages = {3949-3955},
	doi = {10.1109/LRA.2021.3067229},
	attachments = {https://homepages.laas.fr/afranchi/robotics/sites/default/files/2021d-HorHamGieFra.pdf , https://homepages.laas.fr/afranchi/robotics/sites/default/files/2021d-HorHamGieFra.mp4},
	author = {Dariusz Horla and Mahmoud Hamandi and Wojciech Giernacki and Antonio Franchi}
}
@article {2021g-OllTogSuaLeeFra,
	title = {Past, Present, and Future of Aerial Robotic Manipulators},
	journal = {IEEE Transactions on Robotics},
	year = {2021},
	doi = {10.1109/TRO.2021.3084395},
	attachments = {https://homepages.laas.fr/afranchi/robotics/sites/default/files/2021g-OllTogSuaLeeFra.pdf},
	author = {Anibal Ollero and Marco Tognon and Alejandro Suarez and Dongjun Lee and Antonio Franchi}
}
@article {2021j-BarFraOri,
	title = {Towards Safe Human-Quadrotor Interaction: Mixed-Initiative Control via Real-Time NMPC},
	journal = {IEEE Robotics and Automation Letters, Special Issue on Shared Autonomy for Physical Human-Robot Interaction},
	volume = {6},
	year = {2021},
	pages = {7611-7618},
	abstract = {This paper presents a novel algorithm for blending human inputs and automatic controller commands, guarantee- ing safety in mixed-initiative interactions between humans and quadrotors. The algorithm is based on nonlinear model predictive control (NMPC) and involves using the state solution to assess whether safety- and/or task-related rules are met to mix control authority. The mixing is attained through the convex combination of human and actual robot costs and is driven by a continuous function that measures the rules{\textquoteright} violation. To achieve real-time feasibility, we rely on an efficient real-time iteration (RTI) variant of a sequential quadratic programming (SQP) scheme to cast the mixed-initiative controller. We demonstrate the effectiveness of our algorithm through numerical simulations, where a second autonomous algorithm is used to emulate the behavior of pilots with different skill levels. Simulations show that our scheme provides suitable assistance to pilots, especially novices, in a workspace with obstacles while underpinning computational efficiency.},
	doi = {10.1109/LRA.2021.3096502},
	attachments = {https://homepages.laas.fr/afranchi/robotics/sites/default/files/2021j-BarFraOri.pdf , https://homepages.laas.fr/afranchi/robotics/sites/default/files/2021j-BarFraOri.mp4},
	author = {Barbara Barros Carlos and Antonio Franchi and Giuseppe Oriolo}
}
@conference {2021l-HamSabTogFra,
	title = {Understanding the Omnidirectional Capability of a Generic Multi-rotor Aerial Vehicle},
	booktitle = {2021 Aerial Robotic Systems Physically Interacting with the Environment (AIRPHARO)},
	year = {2021},
	month = {Oct.},
	address = {Biograd na Moru, Croatia},
	author = {Mahmoud Hamandi and Quentin Sabl{\'e} and Marco Tognon and Antonio Franchi}
}
@article {2021b-CoeSarWu_MisSinDieFraKonOtt,
	title = {Whole-Body Teleoperation and Shared Control of Redundant Robots with Applications to Aerial Manipulation},
	journal = {Journal of Intelligent \& Robotic Systems},
	volume = {102},
	year = {2021},
	doi = {10.1007/s10846-021-01365-7},
	author = {Andre Coelho and Yuri Sarkisov and Xuwei Wu and Hrishik Mishra and Harsimran Singh and Alexander Dietrich and Antonio Franchi and Konstantin Kondak and Christian Ott}
}
@conference {2020k-UmiTogSanOriFra,
	title = {Communication-based and Communication-less approaches for Robust Cooperative Planning in Construction with a Team of UAVs},
	booktitle = {2020 Int. Conf. on Unmanned Aircraft Systems},
	year = {2020},
	month = {07/2020},
	address = {Athens, Greece},
	abstract = {In this paper, we analyze the coordination problem of groups of aerial robots for assembly applications. With the enhancement of aerial physical interaction, construction applications are becoming more and more popular. In this domain, the multi-robot solution is very interesting to reduce the execution time. However, new methods to coordinate teams of aerial robots for the construction of complex structures are required. In this work, we propose an assembly planner that considers both assembly and geometric constraints imposed by the particular desired structure and employed robots, respectively. An efficient graph representation of the task dependencies is employed. Based on this framework, we design two assembly planning algorithms that are robust to robot failures. The first is centralized and communication-based. The second is distributed and communication-less. The latter is a solution for scenarios in which the communication network is not reliable. Both methods are validated by numerical simulations based on the assembly scenario of Challenge 2 of the robotic competition MBZIRC2020.},
	attachments = {https://homepages.laas.fr/afranchi/robotics/sites/default/files/2020k-UmiTogSanOriFra.pdf , https://homepages.laas.fr/afranchi/robotics/sites/default/files/2020k-UmiTogSanOriFra.mp4},
	author = {Elena Umili and Marco Tognon and Dario Sanalitro and Giuseppe Oriolo and Antonio Franchi}
}
@conference {2020d-HamTogFra,
	title = {Direct Acceleration Feedback Control of Quadrotor Aerial Vehicles},
	booktitle = {2020 IEEE Int. Conf. on Robotics and Automation},
	year = {2020},
	month = {05/2020},
	address = {Paris, France},
	attachments = {https://homepages.laas.fr/afranchi/robotics/sites/default/files/2020d-HamTogFra-preprint.pdf , https://homepages.laas.fr/afranchi/robotics/sites/default/files/2020d-HamTogFra.mp4},
	author = {Mahmoud Hamandi and Marco Tognon and Antonio Franchi}
}
@article {2020a-NavSabTogPucFra,
	title = {Direct Force Feedback Control and Online Multi-task Optimization for Aerial Manipulators},
	journal = {IEEE Robotics and Automation Letters},
	volume = {5},
	year = {2020},
	month = {04/2020},
	pages = {331-338},
	abstract = {In this paper, we present an optimization-based method for controlling aerial manipulators in physical contact with the environment. The multi-task control problem, which includes hybrid force-motion tasks, energetic tasks, and position/postural tasks, is recast as a quadratic programming problem with equality and inequality constraints, which is solved online. Thanks to this method, the aerial platform can be exploited at its best to perform the multi-objective tasks, with tunable priorities, while hard constraints such as contact maintenance, friction cones, joint limits, maximum and minimum propeller speeds are all respected. An on-board force/torque sensor mounted at the end effector is used in the feedback loop in order to cope with model inaccuracies and reject external disturbances. Real experiments with a multi-rotor platform and a multi-DoF lightweight manipulator demonstrate the applicability and effectiveness of the proposed approach in the real world.},
	keywords = {Aerial Physical Interaction, Aerial Robotics},
	doi = {10.1109/LRA.2019.2958473},
	attachments = {https://homepages.laas.fr/afranchi/robotics/sites/default/files/2020a-NavSabTogPucFra.pdf , https://homepages.laas.fr/afranchi/robotics/sites/default/files/2020a-NavSabTogPucFra.mp4},
	author = {Gabriele Nava and Quentin Sabl{\'e} and Marco Tognon and Daniele Pucci and Antonio Franchi}
}
@article {2020b-SanSavTogCorFra,
	title = {Full-pose Manipulation Control of a Cable-suspended load with Multiple UAVs under Uncertainties},
	journal = {IEEE Robotics and Automation Letters},
	volume = {5},
	year = {2020},
	month = {04/2020},
	pages = {2185-2191},
	abstract = {In this work, we propose an uncertainty-aware controller for the Fly-Crane system, a statically rigid cable-suspended aerial manipulator using the minimum number of aerial robots and cables. The force closure property of the Fly- Crane makes it ideal for applications where high precision is required and external disturbances should be compensated. The proposed control requires the knowledge of the nominal values of a minimum number of uncertain kinematic parameters, thus simplifying the identification process and the controller implementation. We propose an optimization-based tuning method of the control gains that ensures stability despite parameter uncertainty and maximizes the H$\infty$ performance. The validity of the proposed framework is shown through real experiments.},
	doi = {10.1109/LRA.2020.2969930},
	attachments = {https://homepages.laas.fr/afranchi/robotics/sites/default/files/2020b-SanSavTogCorFra.pdf , https://homepages.laas.fr/afranchi/robotics/sites/default/files/2020b-SanSavTogCorFra.mp4},
	author = {Dario Sanalitro and Heitor J. Savino and Marco Tognon and Juan Cort{\'e}s and Antonio Franchi}
}
@article {2020e-MicCenZacFra,
	title = {Hierarchical nonlinear control for multi-rotor asymptotic stabilization based on zero-moment direction},
	journal = {Automatica},
	year = {2020},
	abstract = {
We consider the hovering control problem for a class of multi-rotor aerial platforms with generically oriented propellers, characterized by intrinsically coupled translational and rotational dynamics. In doing this, we first discuss some assumptions guaranteeing the rejection of generic disturbance torques while compensating for the gravity force. These assumptions are translated into a geometric condition usually satisfied by both standard models and more general configurations. Then, we propose a control strategy based on the identification of a zero-moment direction for the exerted force and a dynamic state feedback linearization based on this preferential direction, which locally asymptotically stabilizes the platform to a static hovering condition. Stability properties of the control law are rigorously proved through Lyapunov-based methods and reduction theorems for the stability of nested sets. Asymptotic zeroing of the error dynamics and convergence to the static hovering condition are then confirmed by simulation results on a star-shaped hexarotor model with tilted propellers.},
	attachments = {https://homepages.laas.fr/afranchi/robotics/sites/default/files/2020e-MicCenZacFra.pdf},
	author = {Giulia Michieletto and Angelo Cenedese and Luca Zaccarian and Antonio Franchi}
}
@conference {2020h-PetSanTogMilCorFra,
	title = {Inertial Estimation and Energy-Efficient Control of a Cable-suspended Load with a Team of UAVs},
	booktitle = {2020 Int. Conf. on Unmanned Aircraft Systems},
	year = {2020},
	month = {07/2020},
	address = {Athens, Greece},
	abstract = {The Fly-Crane is a multi-robot aerial manipulator system composed of three aerial vehicles towed to a platform by means of six cables. This paper presents a method to estimate the mass and the position of the center of mass of a loaded platform (i.e. the Fly-Crane platform including a transported load). The precise knowledge of these parameters allows to sensibly minimize the total effort exerted during a full-pose manipulation task The estimation is based on the measure of the forces applied by the aerial vehicles to the platform in different static configurations. We demonstrate that only two different configurations are sufficient to estimate the inertial parameters. Far-from-ideal numerical simulations show the effectiveness of the estimation method. Once the parameters are estimated, we show the enhancement of the system performances by minimizing the total exerted effort. The validity of the proposed algorithm in non-ideal conditions is presented through simulations based on the Gazebo simulator.},
	doi = {10.1109/ICUAS48674.2020.9213842},
	attachments = {https://homepages.laas.fr/afranchi/robotics/sites/default/files/2020h-PetSanTogMilCorFra.pdf},
	author = {Antonio Petitti and Dario Sanalitro and Marco Tognon and A. Milella and Juan Cort{\'e}s and Antonio Franchi}
}
@article {2020l-BicMazFarCarFra,
	title = {Nonlinear Model Predictive Control with Enhanced Actuator Model for Multi-Rotor Aerial Vehicles with Generic Designs},
	journal = {Journal of Intelligent and Robotic Systems},
	volume = {100},
	year = {2020},
	pages = {1213-1247},
	abstract = {In this paper, we propose, discuss, and validate an online Nonlinear Model Predictive Control (NMPC) method for multi-rotor aerial systems with arbitrarily positioned and oriented rotors which simultaneously addresses the local ref- erence trajectory planning and tracking problems. This work brings into question some common modeling and control design choices that are typically adopted to guarantee ro- bustness and reliability but which may severely limit the at- tainable performance. Unlike most of state of the art works, the proposed method takes advantages of a unified nonlinear model which aims to describe the whole robot dynamics by explicitly including a realistic physical description of the ac- tuator dynamics and limitations. As a matter of fact, our so- lution does not resort to common simplifications such as: 1) linear model approximation, 2) cascaded control paradigm used to decouple the translational and the rotational dynam- ics of the rigid body, 3) use of low-level reactive trackers for the stabilization of the internal loop, and 4) unconstrained optimization resolution or use of fictitious constraints. More in detail, we consider as control inputs the derivatives of the propeller forces and propose a novel method to suit- ably identify the actuator limitations by leveraging experi- mental data. Differently from previous approaches, the con- straints of the optimization problem are defined only by the real physics of the actuators, avoiding conservative {\textendash} and often not physical {\textendash} input/state saturations which are present, e.g., in cascaded approaches. The control algorithm is im- plemented using a state-of-the-art Real Time Iteration (RTI) scheme with partial sensitivity update method. The perfor- mances of the control system are finally validated by means of real-time simulations and in real experiments, with a large spectrum of heterogeneous multi-rotor systems: an under- actuated quadrotor, a fully-actuated hexarotor, a multi-rotor with orientable propellers, and a multi-rotor with an unex- pected rotor failure. To the best of our knowledge, this is the first time that a predictive controller framework with all the valuable aforementioned features is presented and exten- sively validated in real-time experiments and simulations},
	doi = {10.1007/s10846-020-01250-9},
	attachments = {https://homepages.laas.fr/afranchi/robotics/sites/default/files/2020l-BicMazFarCarFra.pdf},
	author = {Davide Bicego and Jacopo Mazzetto and Marcello Farina and Ruggero Carli and Antonio Franchi}
}
@conference {2020j-HamSawTogFra,
	title = {Omni-Plus-Seven (O7+): An Omnidirectional Aerial Prototype with a Minimal Number of Uni-directional Thrusters},
	booktitle = {2020 Int. Conf. on Unmanned Aircraft Systems},
	year = {2020},
	month = {07/2020},
	address = {Athens, Greece},
	abstract = {The aim of this paper is to present the design of a novel omnidirectional Unmanned Aerial Vehicle (UAV) with seven uni-directional thrusters, called O+7. The paper formally defines the O+ design for a generic number of propellers and presents its necessary conditions; then it illustrates a method to optimize the placement and orientation of the platform{\textquoteright}s propellers to achieve a balanced O+ design. The paper then details the choice of the parameters of the O7+ UAV, and highlights the required mechanical and electrical components. The resultant platform is tested in simulation, before being implemented as a prototype. The prototype is firstly static-bench tested to match its nominal and physical models, followed by hovering tests in multiple orientations. The presented prototype shows the ability to fly horizontally, upside down and at a tilted angle.},
	attachments = {https://homepages.laas.fr/afranchi/robotics/sites/default/files/2020j-HamSawTogFra.pdf , https://homepages.laas.fr/afranchi/robotics/sites/default/files/2020j-HamSawTogFra.mp4},
	author = {Mahmoud Hamandi and Kapil Sawant and Marco Tognon and Antonio Franchi}
}
@conference {2020c-JacCorBicFra,
	title = {Perception-constrained and Motor-level Nonlinear MPC for both Underactuated and Tilted-propeller UAVs},
	booktitle = {2020 IEEE Int. Conf. on Robotics and Automation},
	year = {2020},
	month = {05/2020},
	address = {Paris, France},
	attachments = {https://homepages.laas.fr/afranchi/robotics/sites/default/files/2020c-JacCorBicFra.mp4 , https://homepages.laas.fr/afranchi/robotics/sites/default/files/2020c-JacCorBicFra-preprint.pdf},
	author = {Martin Jacquet and Gianluca Corsini and Davide Bicego and Antonio Franchi}
}
@book {2020g-TogFra,
	title = {Theory and Applications for Control of Aerial Robots in Physical Interaction Through Tethers},
	series = {Springer Tracts in Advanced Robotics},
	volume = {140},
	year = {2020},
	month = {07/2020},
	abstract = {This book focuses on the study of autonomous aerial robots interacting with the surrounding environment, and in particular on the design of new control and motion planning methods for such systems. Nowadays, autonomous aerial vehicles are extensively employed in many fields of application but mostly as autonomously moving sensors used only to sense the environment. On the other hand, in the recent field of aerial physical interaction, the goal is to go beyond sensing-only applications and to fully exploit aerial robots capabilities in order to interact with the environment, exchanging forces for pushing/pulling/sliding, and manipulating objects. However, due to the different nature of the problems, new control methods are needed. These methods have to preserve the system stability during the interaction and to be robust against external disturbances, finally enabling the robot to perform a given task. Moreover, researchers and engineers need to face other challenges generated by the high complexity of aerial manipulators, e.g., a large number of degrees of freedom, strong nonlinearities, and actuation limits. Furthermore, trajectories of the aerial robots have to be carefully computed using motion planning techniques. To perform the sough task in a safe way, the planned trajectory must avoid obstacles and has to be suitable for the dynamics of the system and its actuation limits. With the aim of achieving the previously mentioned general goals, this book considers the analysis of a particular class of aerial robots interacting with the environment: tethered aerial vehicles. The study of particular systems, still encapsulating all the challenges of the general problem, helps on acquiring the knowledge and the expertise for a subsequent development of more general methods applicable to aerial physical interaction. This work focuses on the thorough formal analysis of tethered aerial vehicles ranging from control and state estimation to motion planning. In particular, the differential flatness property of the system is investigated, finding two possible sets of flat outputs that reveal new capabilities of such a system. One contains the position of the vehicle and the link internal force (equivalently the interaction force with the environment), while the second contains the position and a variable linked to the attitude of the vehicle. This shows new control and physical interaction capabilities different from standard aerial robots in contact-free flight. In particular, the first set of flat outputs allows realizing one of the first {\textquotedblleft}free-floating{\textquotedblright} versions of the classical hybrid force-motion control for standard grounded manipulators. Based on these results we designed two types of controllers. The first is an easy-to-implement controller based on a hierarchical approach. Although it shows good performance in quasi-static conditions, actually the tracking error increases when tracking a dynamic trajectory. Thus, a second controller more suited for tracking problems has been designed based on the dynamic feedback linearization technique. Two observers, for the 3D and 2D environments, respectively, have been designed in order to close the control loop using a minimal sensorial setup. We showed that the tether makes possible to retrieve an estimation of the full state from only an IMU plus three encoders for the 3D case, while from just an IMU for the 2D case. Parts of those results were extended to a novel and original multi-robots case as well. We considered a multi-tethered system composed of two aerial robots linked to the ground and to each other by two links. The theoretical results on generic tethered aerial vehicles were finally employed to solve the practical and challenging problem of landing and takeoff on/from a sloped surface, enhancing the robustness and reliability of the maneuvers with respect to the contact-free flight solution.},
	isbn = {978-3-030-48659-4},
	doi = {10.1007/978-3-030-48659-4},
	attachments = {https://homepages.laas.fr/afranchi/robotics/sites/default/files/2020g-TogFra-preprint.pdf},
	author = {Marco Tognon and Antonio Franchi}
}
@article {2019h-RylMusPieCatAntCacFra,
	title = {6D Interaction Control with Aerial Robots: The Flying End-Effector Paradigm},
	journal = {The International Journal of Robotics Research},
	volume = {38},
	year = {2019},
	pages = {1045-1062},
	doi = {10.1177/0278364919856694},
	attachments = {https://homepages.laas.fr/afranchi/robotics/sites/default/files/2019h-RylMusPieCatAntCacFra-preprint.pdf , https://homepages.laas.fr/afranchi/robotics/sites/default/files/2019h-RylMusPieCatAntCacFra-1.mp4 , https://homepages.laas.fr/afranchi/robotics/sites/default/files/2019h-RylMusPieCatAntCacFra-2.mp4 , https://homepages.laas.fr/afranchi/robotics/sites/default/files/2019h-RylMusPieCatAntCacFra-3.mp4},
	author = {Markus Ryll and Giuseppe Muscio and Francesco Pierri and Elisabetta Cataldi and Gianluca Antonelli and Fabrizio Caccavale and Davide Bicego and Antonio Franchi}
}
@article {2019b-YueSecBueFra,
	title = {Aerial Physical Interaction via IDA-PBC},
	journal = {The International Journal of Robotics Research},
	volume = {38},
	year = {2019},
	pages = {403{\textendash}421},
	abstract = {This paper proposes the use of a novel control method based on IDA-PBC in order to address the Aerial Physical Interaction (APhI) problem for a quadrotor UAV. The apparent physical properties of the quadrotor are reshaped in order to achieve better APhI performances, while ensuring the stability of the interaction through passivity preservation. The robustness of the IDA-PBC method with respect to sensor noise is also analyzed. The direct measurement of the external wrench {\textendash} needed to implement the control method {\textendash} is compared to the use of a nonlinear Lyapunov-based wrench observer and advantages/disadvantages of both methods are discussed. The validity and practicability of the proposed APhI method is evaluated through experiments, where for the first time in the literature, a light-weight all- in-one low-cost F/T sensor is used onboard of a quadrotor. Two main scenarios are shown: a quadrotor responding external disturbances while hovering (physical human-quadrotor interaction), and the same quadrotor sliding with a rigid tool along an uneven ceiling surface (inspection/painting-like task).},
	doi = {10.1177/0278364919835605},
	attachments = {https://homepages.laas.fr/afranchi/robotics/sites/default/files/2019b-YueSecBueFra-preprint.pdf , https://homepages.laas.fr/afranchi/robotics/sites/default/files/2019b-YueSecBueFra.mp4},
	author = {Burak Y{\"u}ksel and Cristian Secchi and Heinrich H. B{\"u}lthoff and Antonio Franchi}
}
@article {2019i-RosTogCarSchCorFra,
	title = {Cooperative Aerial Load Transportation via Sampled Communication},
	journal = {IEEE Control Systems Letters},
	volume = {4},
	year = {2019},
	month = {06/2019},
	pages = {277-282},
	abstract = {In this work, we propose a feedback-based motion planner for a class of multi-agent manipulation systems with a sparse kinematics structure. In other words, the agents are coupled together only by the transported object. The goal is to steer the load into a desired configuration. We suppose that a global motion planner generates a sequence of desired configurations that satisfy constraints as obstacles and singularities avoidance. Then, a local planner receives these references and generates the desired agents velocities, which are converted into force inputs for the vehicles. We focus on the local planner design both in the case of continuously available measurements and when they are transmitted to the agents via sampled communication. For the latter problem, we propose two strategies. The first is the discretization of the continuous-time strategy that preserves  stability and guarantees exponential convergence regardless of the sampling period. In this case, the planner gain is static and computed off-line. The second strategy requires to collect the measurements from all sensors and to solve online a set of differential equations at each sampling period. However, it has the advantage to provide doubly exponential convergence. Numerical simulations of these strategies are provided for the cooperative aerial manipulation of a cable-suspended load.},
	doi = {10.1109/LCSYS.2019.2924413},
	attachments = {https://homepages.laas.fr/afranchi/robotics/sites/default/files/2019i-RosTogCarSchCorFra.pdf},
	author = {Enrica Rossi and Marco Tognon and Ruggero Carli and Luca Schenato and Juan Cort{\'e}s and Antonio Franchi}
}
@conference {2019f-SarKimBicTseOttFraKon,
	title = {Development of SAM: cable-Suspended Aerial Manipulator},
	booktitle = {2019 IEEE Int. Conf. on Robotics and Automation},
	year = {2019},
	month = {05/2019},
	address = {Montreal, Canada},
	abstract = { High risk of a collision between rotor blades and the obstacles in a complex environment imposes restrictions on the aerial manipulators. To solve this issue, a novel system cable-Suspended Aerial Manipulator (SAM) is presented in this paper. Instead of attaching a robotic manipulator directly to an aerial carrier, it is mounted on an active platform which is suspended on the carrier by means of a cable. As a result, higher safety can be achieved because the aerial carrier can keep a distance from the obstacles. For self-stabilization, the SAM is equipped with two actuation systems: winches and propulsion units. This paper presents an overview of the SAM including the concept behind, hardware realization, control strategy, and the first experimental results.},
	attachments = {https://homepages.laas.fr/afranchi/robotics/sites/default/files/2019f-SarKimBicTseOttFraKon-preprint.pdf},
	author = {Yuri Sarkisov and Min J. Kim and Davide Bicego and D. Tsetserukou and Christian Ott and Antonio Franchi and Konstantin Kondak}
}
@article {2018q-FraPetRiz,
	title = {Distributed Estimation of State and Parameters in Multi-Agent Cooperative Manipulation},
	journal = {IEEE Trans. on Control of Network Systems},
	volume = {6},
	year = {2019},
	month = {11/2018},
	pages = {690-701},
	abstract = {We present two distributed methods for the estimation of the kinematic parameters, the dynamic parameters, and the kinematic state of an unknown planar body manipulated by a decentralized multi-agent system. The proposed approaches rely on the rigid body kinematics and dynamics, on nonlinear observation theory, and on consensus algorithms. The only three requirements are that each agent can exert a 2D wrench on the load, it can measure the velocity of its contact point, and that the communication graph is connected. Both theoretical nonlinear observability analysis and convergence proofs are provided. The first method assumes constant parameters while the second one can deal with time-varying parameters and can be applied in parallel to any task-oriented control law. For the cases in which a control law is not provided, we propose a distributed and safe control strategy satisfying the observability condition. The effectiveness and robustness of the estimation strategy is showcased by means of realistic MonteCarlo simulations.},
	doi = {10.1109/TCNS.2018.2873153},
	attachments = {https://homepages.laas.fr/afranchi/robotics/sites/default/files/2018q-FraPetRiz-preprint.pdf},
	author = {Antonio Franchi and Antonio Petitti and Alessandro Rizzo}
}
@conference {2019j-MicCenFra,
	title = {Force-Moment Decoupling and Rotor-Failure Robustness for Star-Shaped Generically-Tilted Multi-Rotors},
	booktitle = {In 58th IEEE Conference on Decision and Control},
	year = {2019},
	month = {12/2019},
	address = {Nice, France},
	abstract = {Aerial robotics is increasingly becoming an at- tractive field of research thanks to the peculiar mixture of theoretical issues to be solved and technological challenges to be faced. In particular, recent developments have seen the multiplication of multi-rotor platforms that aim at improving the maneuverability of classical quadrotors in standard and harsh flying conditions, thus opening the field to compre- hensive studies over the structural multi-rotor properties of actuation, decoupling, and robustness, which strongly depend on the mechanical configuration of the systems. This work collocates along this line of research by considering star-shaped generically-tilted multi-rotors (SGTMs), namely platforms with more than four possibly tilted propellers (along two tilting orthogonal axes). For these platforms, we investigate how the structural choices over the number of propellers and the tilting angles affect the force-moment decoupling features and, by recalling the robustness definition that refers to the hovering capabilities of the platform, we provide a robustness analysis and an hoverability assessment for SGTMs having five to eight actuators against the loss of one and two propellers.},
	author = {Giulia Michieletto and Angelo Cenedese and Antonio Franchi}
}
@article {2019k-FurNaiZacFra,
	title = {Input Allocation for the Propeller-Based Overactuated Platform ROSPO},
	journal = {IEEE Trans. on Control Systems Technology},
	volume = {18},
	year = {2019},
	month = {11/2020},
	pages = {2720-2727},
	abstract = {We apply input allocation to a redundantly actu- ated platform driven by tilting aerodynamic propulsion units: the ROtor graSPing Omnidirectional (ROSPO). This platform represents a novel testbed for redundancy allocation designs in propeller driven platforms. The control solution is based on a hierarchical architecture, made of a high level controller for trajectory tracking, and a nonlinear input allocation algorithm. The algorithm exploits the input redundancy to take into account soft constraints associated to physical saturation limits of the actuators, and also induce reduced energy consumption. The actuator dynamics is fully taken into account in the framework and a rigorous proof of asymptotic tracking of time-varying references is guaranteed despite the impossibility of an instanta- neous force execution. The experiments on the ROSPO platform clearly show the practicability and effectiveness of the proposed approach, as well as its scalability with different degrees of over- actuation levels.},
	doi = {10.1109/TCST.2019.2944341},
	attachments = {https://homepages.laas.fr/afranchi/robotics/sites/default/files/2019k-FurNaiZacFra.pdf},
	author = {Michele Furci and Carlo Nainer and Luca Zaccarian and Antonio Franchi}
}
@inbook {2019d-Fra,
	title = {Interaction Control of Platforms with Multi-directional Total Thrust},
	booktitle = {Aerial Robotic Manipulation},
	volume = {129},
	number = {STAR},
	year = {2019},
	month = {06/2019},
	pages = {175-189},
	publisher = {Springer},
	organization = {Springer},
	chapter = {3.6},
	abstract = {The chapter provides an overview of the basic modeling and the intrinsic properties of aerial platforms with multi-directional total thrust ability. When also fully-actuated, such platforms can modify the total wrench in body frame in any direction, thus allowing the control of position and orientation independently. There- fore, they are best suited for dexterous tasks, physical interaction, and for carrying aerial manipulators, because they do not suffer from the underactuation of standard collinear multirotors. The chapter includes a rigorous classification, a discussion on the possible input coupling, and on the capabilities and pitfalls of inverse-dynamics control approach for such platforms.},
	doi = {10.1007/978-3-030-12945-3},
	attachments = {https://homepages.laas.fr/afranchi/robotics/sites/default/files/2019d-Fra-preprint.pdf},
	author = {Antonio Franchi}
}
@article {2019a-FraRobMic,
	title = {Online Leader Selection for Improved Collective Tracking and Formation Control: the Second Order Case},
	journal = {IEEE Transactions on Control of Network Systems},
	volume = {6},
	year = {2019},
	month = {12/2019},
	pages = {1415-1425},
	abstract = {In this work, we deal with a double control task for a group of interacting agents having a second-order dynamics. Adopting the leader-follower paradigm, the given multi-agent system is required to maintain a desired formation and to collectively track a velocity reference provided by an external source only to a single agent at time, called the {\textquoteleft}leader{\textquoteright}. We prove that it is possible to optimize the group performance by persistently selecting online the leader among the agents. To do this, we first define a suitable error metric able to capture the tracking performance of the multi-agent group while maintaining a desired formation through a (even time-varying) communication-graph topology. Then we show that this depends on the algebraic connectivity and on the maximum eigenvalue of the Laplacian matrix of a special directed graph depending on the selected leader. By exploiting these theoretical results, we finally design a fully-distributed adaptive procedure able to periodically select online the optimum leader among the neighbors of the current one. The effectiveness of the proposed solution against other possible strategies is confirmed by numerical simulations.},
	doi = {10.1109/TCNS.2019.2891011},
	attachments = {https://homepages.laas.fr/afranchi/robotics/sites/default/files/2019a-FraRobMic-preprint.pdf},
	author = {Antonio Franchi and Paolo Robuffo Giordano and Giulia Michieletto}
}
@inbook {2019c-Fra,
	title = {Platforms with Multi-directional Total Thrust},
	booktitle = {Aerial Robotic Manipulation},
	year = {2019},
	month = {06/2019},
	pages = {53-65},
	publisher = {Springer},
	organization = {Springer},
	abstract = {The chapter provides an overview of the basic modeling and the intrinsic properties of aerial platforms with multi-directional total thrust ability. When also fully-actuated, such platforms can modify the total wrench in body frame in any direction, thus allowing the control of position and orientation independently. Therefore, they are best suited for dexterous tasks, physical interaction, and for carrying aerial manipulators, because they do not suffer from the underactuation of standard collinear multirotors. The chapter includes a rigorous classification, a discussion on the possible input coupling, and on the capabilities and pitfalls of inverse-dynamics control approach for such platforms.},
	doi = {10.1007/978-3-030-12945-3},
	attachments = {https://homepages.laas.fr/afranchi/robotics/sites/default/files/2019c-Fra-preprint.pdf},
	author = {Antonio Franchi}
}
@article {2019l-GabTogPalFra,
	title = {A Study on Force-based Collaboration in Swarms},
	journal = {Swarm Intelligence},
	volume = {14},
	year = {2019},
	month = {11/2019},
	pages = {57-82},
	abstract = {Cooperative manipulation is a basic skill in groups of humans, ani- mals, and in many robotic applications. Besides being an interesting challenge, communication-less approaches have been applied to groups of robots in order to achieve higher scalability and simpler hardware and software design. We present a generic model and control law for robots cooperatively manipulating an object, for both ground and floating systems.
The control method exploits a leader-follower scheme and is based only on implicit communication (i.e., the sensing of contact forces). The control objective mainly consists of steering the object manipulated by the swarm of robots to a desired position and orientation in a cooperative way. For a system with just one leader, we present analytical results on the equilibrium configurations and their stability that are then validated by numerical simulations. The role of object in- ternal forces (induced by the robots through contact forces) is discussed in terms of convergence of the object position and orientation to the desired values. We also present a discussion on additional properties of the controlled system that were investigated using thorough numerical analysis, namely, the robustness of the system when the object is subject to external disturbances in non-ideal condi- tions, and how the number of leaders in the swarm can affect the aforementioned convergence and robustness.},
	doi = {10.1007/s11721-019-00178-7},
	attachments = {https://homepages.laas.fr/afranchi/robotics/sites/default/files/2019l-GabTogPalFra.pdf},
	author = {Chiara Gabellieri and Marco Tognon and Dario Sanalitro and Lucia Pallottino and Antonio Franchi}
}
@article {2019e-TogTelGasSabBicMalLanSanRevCorFra,
	title = {A Truly Redundant Aerial Manipulator System with Application to Push-And-Slide Inspection in Industrial Plants},
	journal = {IEEE Robotics and Automation Letters},
	volume = {4},
	year = {2019},
	month = {04/2019},
	pages = {1846-1851},
	abstract = {We present the design, motion planning and control of an aerial manipulator for non-trivial physical interaction tasks, such as pushing while sliding on curved surfaces {\textendash} a task which is motivated by the increasing interest in autonomous non-destructive tests for industrial plants. The proposed aerial manipulator consists of a multidirectional-thrust aerial vehicle {\textendash} to enhance physical interaction capabilities {\textendash} endowed with a 2-DoFs lightweight arm {\textendash} to enlarge its workspace. This combination makes it a truly-redundant manipulator going beyond standard aerial manipulators based on collinear multi- rotor platforms. The controller is based on a PID method with a {\textquoteleft}displaced{\textquoteright} positional part that ensures asymptotic stability despite the arm elasticity. A kinodynamic task-constrained and control-aware global motion planner is used. Experiments show that the proposed aerial manipulator system, equipped with an Eddy Current probe, is able to scan a metallic pipe sliding the sensor over its surface and preserving the contact. From the measures, a weld on the pipe is successfully detected and mapped.},
	doi = {10.1109/LRA.2019.2895880},
	attachments = {https://homepages.laas.fr/afranchi/robotics/sites/default/files/2019e-TogTelGasSabBicMalLanSanRevCorFra-preprint.pdf , https://homepages.laas.fr/afranchi/robotics/sites/default/files/2019e-TogTelGasSabBicMalLanSanRevCorFra.mp4},
	author = {Marco Tognon and Hermes Tello Chavez and Enrico Gasparin and Quentin Sabl{\'e} and Davide Bicego and Anthony Mallet and Marc Lany and Gilles Santi and Bernard Revaz and Juan Cort{\'e}s and Antonio Franchi}
}
@article {2019g-WalStaFraSas,
	title = {UVDAR System for Visual Relative Localization with application to Leader-Follower Formations of Multirotor UAVs},
	journal = {IEEE Robotics and Automation Letters},
	volume = {4},
	year = {2019},
	month = {02/2019},
	pages = {2637-2644},
	abstract = {A novel onboard relative localization method, based on ultraviolet light, used for real-time control of a leader- follower formation of multirotor UAVs is presented in this paper. A new smart sensor, UVDAR, is employed in an innovative way, which does not require communication and is extremely reliable in real-world conditions. This innovative sensing system exploits UV spectrum and provides relative position and yaw measurements independently of environment conditions such as changing illumination and presence of undesirable light sources and their reflections. The proposed approach exploits this re- trieved information to steer the follower to a given 3D position and orientation relative to the leader, which may be considered as the main building block of any multi-UAV system operating with small mutual distances among team-members. The proposed solution was verified in demanding outdoor conditions, validating usage of UVDAR in real flight scenario and paving the way for further usage of UVDAR for practical multi-UAV formation deployments.},
	doi = {10.1109/LRA.2019.2901683},
	attachments = {https://homepages.laas.fr/afranchi/robotics/sites/default/files/2019g-WalStaFraSas-preprint.pdf , https://homepages.laas.fr/afranchi/robotics/sites/default/files/2019g-WalStaFraSas.mp4},
	author = {Viktor Walter and Nicolas Staub and Antonio Franchi and Martin Saska}
}
@article {2017b-AntCatArrRobChiFra,
	title = {Adaptive Trajectory Tracking for Quadrotor MAVs in Presence of Parameter Uncertainties and External Disturbances},
	journal = {IEEE Trans. on Control Systems Technology},
	volume = {26},
	year = {2018},
	month = {01/2018},
	pages = {248{\textendash}254},
	abstract = {This paper presents an adaptive trajectory tracking control strategy for quadrotor Micro Aerial Vehicles (MAVs). The proposed approach, while maintaining the typical assumption of an orientation dynamics faster than the translational one, re- moves that of absence of external disturbances and of Geometric Center coincident with the Center of Mass. In particular, the trajectory tracking control law is made adaptive with respect to the presence of external forces and moments (due, e.g., to wind), and to the uncertainty of dynamic parameters such as the position of the center of mass of the vehicle. A stability analysis is provided to analytically support the proposed controller. Finally, numerical simulations and experimental evaluations, performed with a commercially-available quadrotor MAV, are provided in order to validate the performance of the proposed adaptive control strategy.},
	author = {Gianluca Antonelli and Elisabetta Cataldi and Filippo Arrichiello and Paolo Robuffo Giordano and Stefano Chiaverini and Antonio Franchi}
}
@article {2018h-TogGabPalFra,
	title = {Aerial Co-Manipulation with Cables: The Role of Internal Force for Equilibria, Stability, and Passivity},
	journal = {IEEE Robotics and Automation Letters, Special Issue on Aerial Manipulation},
	volume = {3},
	year = {2018},
	note = {Also selected for presentation at the 2018 IEEE Int. Conf. on Robotics and Automation, Brisbane , Australia},
	month = {02/2018},
	pages = {2577-2583},
	abstract = {This paper considers the cooperative manipulation of a cable-suspended load with two generic aerial robots without the need of explicit communication. The role of the internal force for the asymptotic stability of the beam position-and- attitude equilibria is analyzed in depth. Using a nonlinear Lyapunov-based approach, we prove that if a non-zero internal force is chosen, then the asymptotic stabilization of any desired beam attitude can be achieved with a decentralized and communication-less master-slave admittance controller. If, conversely, a zero internal force is chosen, as done in the majority of the state-of-the-art algorithms, the attitude of the beam is not controllable without communication. Furthermore, we formally prove the output-strictly passivity of the system with respect to an energy-like storage function and a certain input-output pair. This proves the stability and the robustness of the method during motion and in non-ideal conditions. The theoretical findings are validated through extensive simulations.},
	doi = {10.1109/LRA.2018.2803811},
	attachments = {https://homepages.laas.fr/afranchi/robotics/sites/default/files/2018h-TogGabPalFra-preprint.pdf},
	author = {Marco Tognon and Chiara Gabellieri and Lucia Pallottino and Antonio Franchi}
}
@article {2018m-OllHerFraAntKonSanVigSanTruBalAndRod,
	title = {The AEROARMS Project: Aerial Robots with Advanced Manipulation Capabilities for Inspection and Maintenance},
	journal = {IEEE Robotics and Automation Magazine, Special Issue on Floating-base (Aerial and Underwater) Manipulation},
	volume = {25},
	year = {2018},
	month = {12/2018},
	pages = {12-23},
	abstract = {This paper summarizes new aerial robotic manipu- lation technologies and methods, required for outdoor industrial inspection and maintenance, developed in the AEROARMS project. It presents aerial robotic manipulators with dual arms and multi-directional thrusters. It deals with the control systems, including the control of the interaction forces and the compliance, the teleoperation, which uses passivity to tackle the trade- off between stability and performance, perception methods for localization, mapping and inspection, and planning methods, including a new control-aware approach for aerial manipulation. Finally, it describes a novel industrial platform with multi- directional thrusters and a new arm design to increase the robustness in industrial contact inspections. The lessons learned in the application to outdoor aerial manipulation for inspection and maintenance are pointed out.},
	attachments = {https://homepages.laas.fr/afranchi/robotics/sites/default/files/2018m-OllHerFraAntKonSanVigSanTruBalAndRod-preprint_3.pdf},
	author = {Anibal Ollero and Guillermo Heredia and Antonio Franchi and Gianluca Antonelli and Konstantin Kondak and Alberto Sanfeliu and Antidio Viguria and Jose R. Martinez-de Dios and Francesco Pierri and Juan Cort{\'e}s and A. Santamaria-Navarro and Miguel A. Trujillo and Ribin Balachandran and Juan Andrade-Cetto and Angel Rodriguez}
}
@article {2018i-TogCatTelAntCorFra,
	title = {Control-Aware Motion Planning for Task-Constrained Aerial Manipulation},
	journal = {IEEE Robotics and Automation Letters, Special Issue on Aerial Manipulation},
	volume = {3},
	year = {2018},
	note = {Also selected for presentation at the 2018 IEEE Int. Conf. on Robotics and Automation, Brisbane , Australia},
	month = {02/2018},
	pages = {2478-2484},
	attachments = {https://homepages.laas.fr/afranchi/robotics/sites/default/files/2018i-TogCatTelAntCorFra-preprint.pdf , https://homepages.laas.fr/afranchi/robotics/sites/default/files/2018i-TogCatTelAntCorFra.mp4},
	author = {Marco Tognon and Elisabetta Cataldi and Hermes Tello Chavez and Gianluca Antonelli and Juan Cort{\'e}s and Antonio Franchi}
}
@conference {2018o-FurBicFra,
	title = {Design and Input Allocation for Robots with Saturated Inputs via Genetic Algorithms},
	booktitle = {12th IFAC Symposium on Robot Control},
	year = {2018},
	month = {08/2018},
	address = {Budapest, Hungary},
	abstract = {In this paper we consider fully-actuated and redundantly-actuated robots, whose saturated inputs can have high bandwidth or can be slowly varying (with dynamics). The slowly varying inputs can be considered as configurations for the system. The proposed strategy allows to find the optimal actuators{\textquoteright} configuration to optimize a cost function as the manipulability or the energy consumption. The approach allows for both a static design, which can include actuators{\textquoteright} parameters such as position, orientation, saturations, numbers of actuators, and for a dynamic design, where the configurations can be controlled by an input of the system. A generalized solution to the optimal problem is proposed with the use of genetic algorithms. The results are validated in two simulation scenarios: a reconfiguration of the actuators orientation of an redundantly-actuated planar robot for trajectory tracking and the design optimization of the orientation of the motors in a generalized hexa-rotor with arbitrary propeller orientation.},
	attachments = {https://homepages.laas.fr/afranchi/robotics/sites/default/files/2018o-FurBicFra-preprint.pdf},
	author = {Michele Furci and Davide Bicego and Antonio Franchi}
}
@article {2018c-FaeFraSca,
	title = {Differential Flatness of Quadrotor Dynamics Subject to Rotor Drag for Accurate Tracking of High-Speed Trajectories},
	journal = {IEEE Robotics and Automation Letters},
	volume = {3},
	year = {2018},
	note = {Also selected for presentation at the 2018 IEEE Int. Conf. on Robotics and Automation, Brisbane , Australia},
	month = {04/2018},
	pages = {620-626},
	abstract = {In this paper, we prove that the dynamical model of a quadrotor subject to linear rotor drag effects is differentially flat in its position and heading. We use this property to compute feed-forward control terms directly from a reference trajectory to be tracked. The obtained feed-forward terms are then used in a cascaded, nonlinear feedback control law that enables accurate agile flight with quadrotors. Compared to state-of-the-art control methods, which treat the rotor drag as an unknown disturbance, our method reduces the trajectory tracking error significantly. Finally, we present a method based on a gradient-free optimization to identify the rotor drag coefficients, which are required to compute the feed-forward control terms. The new theoretical results are thoroughly validated trough extensive comparative experiments.},
	doi = {10.1109/LRA.2017.2776353},
	attachments = {https://homepages.laas.fr/afranchi/robotics/sites/default/files/2018c-FaeFraSca-preprint.pdf , https://homepages.laas.fr/afranchi/robotics/sites/default/files/2018c-FaeFraSca.mp4},
	author = {Matthias Faessler and Antonio Franchi and Davide Scaramuzza}
}
@conference {2018r-MorBicRylFra,
	title = {Energy-Efficient Trajectory Generation for a Hexarotor with Dual-Tilting Propellers},
	booktitle = {2018 IEEE/RSJ Int. Conf. on Intelligent Robots and Systems},
	year = {2018},
	month = {10/2018},
	address = {Madrid, Spain},
	abstract = {In this paper, we consider a non-conventional hexarotor whose propellers can be simultaneously tilted about two orthogonal axes: in this way, its underactuation degree can be easily adapted to the task at hand. For a given tilt profile, the minimum-energy trajectory between two prescribed boundary states is explicitly determined by solving an optimal control problem with respect to the angular accelerations of the six brushless motors. We also perform, for the first time, a systematic study of the singularities of the control allocation matrix of the hexarotor, showing the presence of subtle singular configurations that should be carefully avoided in the design phase. Numerical experiments conducted with the FAST-Hex platform illustrate the theory and delineate the pros and cons of dual-tilting paradigm in terms of maneuverability and energy efficiency.},
	attachments = {https://homepages.laas.fr/afranchi/robotics/sites/default/files/2018r-MorBicRylFra-preprint.pdf},
	author = {Fabio Morbidi and Davide Bicego and Markus Ryll and Antonio Franchi}
}
@conference {2018k-WalSasFra,
	title = {Fast Mutual Relative Localization of UAVs using Ultraviolet LED markers},
	booktitle = {2018 International Conference on Unmanned Aircraft Systems},
	year = {2018},
	month = {06/2018},
	pages = {1217-1226},
	address = {Dallas, TX},
	abstract = {This paper proposes a new methodology for out- door mutual relative localization of UAVs equipped with active ultraviolet markers and a suitable camera with specialized bandpass filters. Mutual relative localization is a crucial tool for formation preservation, swarming and cooperative task completion in scenarios in which UAVs share working space in small relative distances. In most current systems of compact UAV swarms the localization of particular UAVs is based on the data obtained from motion capture systems for indoor experiments or on precise RTK-GNSS data outdoor. Such an external infrastructure is unavailable in most of real multi- UAV applications and often cannot be pre-installed. To account for such situations, as well as to make the system more autonomous, reliance on onboard sensors only is desirable. In the proposed approach, we rely on ultraviolet LED markers, that emit light in frequencies that are less common in nature than the visible light or infrared radiation, especially in high intensities. Additionally, common camera sensors are sensitive to ultraviolet light, making the addition of a filter the only necessary modification, keeping the platform low-cost, which is one of the key requirements on swarm systems. This also allows for a smaller size of the markers to be sufficient, without burdening the processing resources. Thus the proposed system aspires to be an enabling technology for deployment of large swarms of possibly micro-scale aerial vehicles in real world conditions and without any dependency on an external infrastructure.},
	attachments = {https://homepages.laas.fr/afranchi/robotics/sites/default/files/2018k-WalSasFra-preprint.pdf , https://homepages.laas.fr/afranchi/robotics/sites/default/files/2018k-WalSasFra.mp4},
	author = {Viktor Walter and Martin Saska and Antonio Franchi}
}
@article {2018d-FraCarBicRyl,
	title = {Full-Pose Tracking Control for Aerial Robotic Systems with Laterally-Bounded Input Force},
	journal = {IEEE Trans. on Robotics},
	volume = {34},
	year = {2018},
	month = {04/2018},
	pages = {534-541},
	abstract = {A class of abstract aerial robotic systems is introduced, the Laterally Bounded Force (LBF) vehicles, in which most of the control authority is expressed along a principal thrust direction, while in the lateral directions a (smaller and possibly null) force may be exploited to achieve full-pose tracking. This class approximates platforms endowed with non-collinear rotors that can modify the orientation of the total thrust in body frame. The proposed SE(3)-based control strategy achieves, if made possible by the force constraints, the independent tracking of position-plus-orientation trajectories. The method, which is proven using a Lyapunov technique, deals seamlessly with both under- and fully-actuated platforms, and guarantees at least the position tracking in the case of an unfeasible full-pose reference trajectory. Several experimental tests are presented, that clearly shown the approach practicability and the sharp improvement with respect to state of-the-art.},
	doi = {10.1109/TRO.2017.2786734},
	attachments = {https://homepages.laas.fr/afranchi/robotics/sites/default/files/2018d-FraCarBicRyl.pdf , https://homepages.laas.fr/afranchi/robotics/sites/default/files/2018d-FraCarBicRyl-1.mp4 , https://homepages.laas.fr/afranchi/robotics/sites/default/files/2018d-FraCarBicRyl-2.mp4 , https://homepages.laas.fr/afranchi/robotics/sites/default/files/2018d-FraCarBicRyl-3.mp4},
	author = {Antonio Franchi and Ruggero Carli and Davide Bicego and Markus Ryll}
}
@article {2018a-MicRylFra,
	title = {Fundamental Actuation Properties of Multi-rotors: Force-Moment Decoupling and Fail-safe Robustness},
	journal = {IEEE Trans. on Robotics},
	volume = {34},
	year = {2018},
	month = {06/2018},
	doi = {10.1109/TRO.2018.2821155},
	attachments = {https://homepages.laas.fr/afranchi/robotics/sites/default/files/2018a-MicRylFra-preprint.pdf , https://homepages.laas.fr/afranchi/robotics/sites/default/files/video1_explaination.mp4 , https://homepages.laas.fr/afranchi/robotics/sites/default/files/video2_triggered_failures.mp4 , https://homepages.laas.fr/afranchi/robotics/sites/default/files/video3_hitting_failures.mp4},
	author = {Giulia Michieletto and Markus Ryll and Antonio Franchi}
}
@conference {2018s-YanStaFraLee,
	title = {Modeling and Control of Multiple Aerial-Ground Manipulator System with Load Flexibility},
	booktitle = {2018 IEEE/RSJ Int. Conf. on Intelligent Robots and Systems},
	year = {2018},
	month = {10/2018},
	address = {Madrid, Spain},
	abstract = {The MAGMaS (Multiple Aerial-Ground Manipulator System) was proposed in [1] as a heterogeneous system composed of multiple ground (mobile) manipulators and aerial robots to collaboratively manipulate a long/large-size object and demonstrated therein for rigid load manipulation. Here, we extend this result of [1] to the case of load manipulation with flexibility, which is crucial for long/slender object manipulation, yet, not considered in [1]. We first provide a rigorous modeling of the load flexibility and its effects on the MAGMaS dynamics. We then propose a novel collaborative control framework for flexible load-tip pose tracking, where the ground manipulator provides slower nominal pose tracking with overall load weight holding, whereas the aerial robot faster vibration suppression with some load weight sharing. We also discuss the issue of controllability stemming from that the aerial robot provides less number of actuation than the modes of the load flexibility; and elucidate some peculiar conditions for this vibration suppression controllability. Simulations are also performed to demonstrate the effectiveness of the proposed theory.},
	attachments = {https://homepages.laas.fr/afranchi/robotics/sites/default/files/2018s-YanStaFraLee-preprint.pdf , https://homepages.laas.fr/afranchi/robotics/sites/default/files/2018s-YanStaFraLee.mp4},
	author = {Hyunsoo Yang and Nicolas Staub and Antonio Franchi and Dongjun Lee}
}
@conference {2018l-WalSasStaFra,
	title = {Mutual Localization of UAVs based on Blinking Ultraviolet Markers and 3D Time-Position Hough Transform},
	booktitle = {14th IEEE International Conference on Automation Science and Engineering},
	year = {2018},
	month = {08/2018},
	address = {Munich, Germany},
	abstract = {A novel vision-based approach for indoor/outdoor mutual localization on Unmanned Aerial Vehicles (UAVs) with low computational requirements and without external infras- tructure is proposed in this paper. The proposed solution exploits the low natural emissions in the near-Ultra-Violet (UV) spectrum to avoid major drawbacks of the visible spec- trum.Such approach provides much better reliability while be- ing less computationally intensive. Working in near-UV requires active markers, which can be leveraged by enriching the infor- mation content through blinking patterns encoded marker-ID. In order to track the markers motion and identify their blinking frequency, we propose an innovative use of three dimensional Hough Transform, applied to stored position-time points. The proposed method was intensively tested onboard multi-UAV systems in real-world scenarios that are very challenging for visible-spectrum methods.The results of our methods in terms of robustness, reliability and precision, as well as the low requirement on the system deployment, predestine this method to be an enabling technology for using swarms of UAVs.},
	attachments = {https://homepages.laas.fr/afranchi/robotics/sites/default/files/2018l-WalSasStaFra-preprint.pdf , https://homepages.laas.fr/afranchi/robotics/sites/default/files/2018l-WalSasStaFra.mp4},
	author = {Viktor Walter and Nicolas Staub and Martin Saska and Antonio Franchi}
}
@article {2018v-AreMerFra,
	title = {A Novel Experimental Model and a Drag-optimal Allocation Method for Variable-Pitch Propellers in Multirotors},
	journal = {IEEE Access},
	volume = {6},
	year = {2018},
	month = {11/2018},
	pages = {68155-68168},
	abstract = {This paper proposes a new mathematical model to map the rotational speed and angle of attack (pitch) of small- size propellers typically used in multirotors and the aerodynamic thrust force and drag moment produced by the propeller itself. The new model is inspired by standard models using the blade- element and momentum theories, which have been suitably modified in order to allow for explicit fast computation of the direct and inverse map (useful for high-frequency control) and obtain a better adherence to experimental data. The new model allows and captures all the main nonlinear characteristics of the thrust/drag generation. An extensive experimental comparison shows that the prediction capability of the proposed model outperforms the most commonly used models at date. In the second part of the paper, two optimization methods are proposed in order to exploit the redundancy of the inputs of variable-pitch propellers to decrease the power consumption due to the drag dissipation. The first method deals with optimal allocation for thrust generation on a single propeller, while the second method is aimed at solving the optimal allocation of the rotational speed and pitch of all the propellers in a multi-rotor with any number of propellers. Simulations results show the viability and effectiveness of the proposed methods.},
	doi = {10.1109/ACCESS.2018.2879636},
	attachments = {https://homepages.laas.fr/afranchi/robotics/sites/default/files/2018v-AreMerFra-preprint.pdf},
	author = {Victor Arellano-Quintana and Emmanuel Merchan-Cruz and Antonio Franchi}
}
@article {2018e-TogFra,
	title = {Omnidirectional Aerial Vehicles with Unidirectional Thrusters: Theory, Optimal Design, and Control},
	journal = {IEEE Robotics and Automation Letters},
	volume = {3},
	year = {2018},
	month = {02/2018},
	pages = {2277-2282},
	abstract = {This letter presents a theoretical study on omnidirectional aerial vehicles with body-frame fixed unidirectional thrusters. Omniplus multirotor designs are defined as the ones that allow to exert a total wrench in any direction using positive-only lift force and drag moment (i.e., positive rotational speed) for each rotor blade. Algebraic conditions for a design to be omniplus are derived, a simple necessary condition being the fact that at least seven propellers have to be used. An energy optimal design strategy is then defined as the one minimizing the maximum norm of the input set needed to span a certain wrench ellipsoid for the adopted input allocation strategy. Two corresponding major design criteria are then introduced: first, a minimum allocation-matrix condition number aims at an equal sharing of the effort needed to generate wrenches in any direction; second, imposing a balanced design guarantees an equal sharing of the extra effort needed to keep the input in the nonnegative orthant. We propose a numerical algorithm to solve such optimal design problem and a control algorithm to control any omnidirectional platform. The work is concluded with informative simulation results in nonideal conditions.},
	attachments = {https://homepages.laas.fr/afranchi/robotics/sites/default/files/2018e-TogFra-preprint.pdf},
	author = {Marco Tognon and Antonio Franchi}
}
@article {2016e-FraRob,
	title = {Online Leader Selection for Improved Collective Tracking and Formation Maintenance},
	journal = {IEEE Trans. on Control of Network Systems},
	volume = {5},
	year = {2018},
	month = {01/2018},
	pages = {3-13},
	abstract = {The goal of this work is to propose an extension of the popular leader-follower framework for multi-agent collective tracking and formation maintenance in presence of a time- varying leader. In particular, the leader is persistently selected online so as to optimize the tracking performance of an exogenous collective velocity command while also maintaining a desired formation via a (possibly time-varying) communication-graph topology. The effects of a change in the leader identity are theoretically analyzed and exploited for defining a suitable error metric able to capture the tracking performance of the multi- agent group. Both the group performance and the metric design are found to depend upon the spectral properties of a special directed graph induced by the identity of the chosen leader. By exploiting these results, as well as distributed estimation techniques, we are then able to detail a fully-decentralized adaptive strategy able to periodically select online the best leader among the neighbors of the current leader. Numerical simulations show that the application of the proposed technique results in an improvement of the overall performance of the group behavior w.r.t. other possible strategies.},
	keywords = {Leader selection},
	attachments = {https://homepages.laas.fr/afranchi/robotics/sites/default/files/1305.5719v2.pdf},
	author = {Antonio Franchi and Paolo Robuffo Giordano}
}
@article {2018t-MasMohRobFra,
	title = {Shared Planning and Control for Mobile Robots with Integral Haptic Feedback},
	journal = {The International Journal of Robotics Research},
	volume = {37},
	year = {2018},
	month = {10/2018},
	pages = {1395-1420},
	abstract = {This paper presents a novel bilateral shared framework for online trajectory generation for mobile robots. The robot navigates along a dynamic path, represented as a B-spline, whose parameters are jointly controlled by a human supervisor and by an autonomous algorithm. The human steers the reference (ideal) path by acting on the path parameters which are also affected, at the same time, by the autonomous algorithm in order to ensure: i) collision avoidance, ii) path regularity and iii) proximity to some points of interest. These goals are achieved by combining a gradient descent-like control action with an automatic algorithm that re-initializes the traveled path (replanning) in cluttered environments in order to mitigate the effects of local minima. The control actions of both the human and the autonomous algorithm are fused via a filter that preserves a set of local geometrical properties of the path in order to ease the tracking task of the mobile robot. The bilateral component of the interaction is implemented via a force feedback that accounts for both human and autonomous control actions along the whole path, thus providing information about the mismatch between the reference and traveled path in an integral sense. The proposed framework is validated by means of realistic simulations and actual experiments deploying a quadrotor UAV supervised by a human operator acting via a force-feedback haptic interface. Finally, a user study is presented in order to validate the effectiveness of the proposed framework and the usefulness of the provided force cues.},
	keywords = {Aerial Robotics, Optimal Trajectory Planning},
	attachments = {https://homepages.laas.fr/afranchi/robotics/sites/default/files/2018t-MasMohRobFra-preprint.pdf , https://homepages.laas.fr/afranchi/robotics/sites/default/files/2018t-MasMohRobFra-video1.mp4 , https://homepages.laas.fr/afranchi/robotics/sites/default/files/2018t-MasMohRobFra-video2.mp4 , https://homepages.laas.fr/afranchi/robotics/sites/default/files/2018t-MasMohRobFra-video3.mp4},
	author = {Carlo Masone and Mostafa Mohammadi and Paolo Robuffo Giordano and Antonio Franchi}
}
@conference {2018p-GabTogPalFra,
	title = {A Study on Force-based Collaboration in Flying Swarms},
	booktitle = {11th Int. Conf. on Swarm Intelligence ANTS 2018},
	year = {2018},
	month = {10/2018},
	address = {Rome, Italy},
	abstract = {This work investigates collaborative aerial transportation by swarms of agents based only on implicit information, enabled by the physical interaction among the agents and the environment. Such a coordinating mechanism in collaborative transportation is a basic skill in groups of social animals. We consider cable-suspended objects transported by a swarm of flying robots and we formu- late several hypothesis on the behavior of the overall system which are validated thorough numerical study. In particular, we show that a nonzero internal force re- duces to one the number of asymptotically stable equilibria and that the internal force intensity is directly connected to the convergence rate. As such, the internal force represents the cornerstone of a communication-less cooperative manipula- tion paradigm in swarms of flying robots. We also show how a swarm can achieve a stable transportation despite the imprecise knowledge of the system parameters.},
	attachments = {https://homepages.laas.fr/afranchi/robotics/sites/default/files/2018p-GabTogPalFra-preprint.pdf},
	author = {Chiara Gabellieri and Marco Tognon and Lucia Palottino and Antonio Franchi}
}
@article {2018u-StaMohBicDelYaPraRobLeeFra,
	title = {The Tele-MAGMaS: an Aerial-Ground Co-manipulator System},
	journal = {IEEE Robotics and Automation Magazine},
	volume = {25},
	year = {2018},
	month = {12/2018},
	pages = {66-75},
	attachments = {https://homepages.laas.fr/afranchi/robotics/sites/default/files/2018u-StaMohBicDelYaPraRobLeeFra-preprint.pdf , https://homepages.laas.fr/afranchi/robotics/sites/default/files/2018u-StaMohBicDelYaPraRobLeeFra.mp4},
	author = {Nicolas Staub and Mostafa Mohammadi and Davide Bicego and Quentin Delamare and Hyunsoo Yang and Domenico Prattichizzo and Paolo Robuffo Giordano and Dongjun Lee and Antonio Franchi}
}
@conference {2018g-BicStaSabAreMisFra,
	title = {Towards a Flying Assistant Paradigm: the OTHex},
	booktitle = {2018 IEEE Int. Conf. on Robotics and Automation},
	year = {2018},
	month = {05/2018},
	pages = {6997-7002},
	address = {Brisbane, Australia},
	abstract = {This paper presents the OTHex platform for aerial manipulation developed at LAAS{\textendash}CNRS. The OTHex is probably the first multi-directional thrust platform designed to act as Flying Assistant which can aid human operators and/or Ground Manipulators to move long bars for assembly and maintenance tasks. The work emphasis is on task-driven custom design and experimental validations. The proposed control framework is built around a low-level geometric controller, and includes an external wrench estimator, an admittance filter, and a trajectory generator. This tool gives the system the necessary compliance to resist external force disturbances arising from contact with the surrounding environment or to parameter uncertainties in the load. A set of experiments validates the real-world applicability and robustness of the overall system.},
	attachments = {https://homepages.laas.fr/afranchi/robotics/sites/default/files/2018g-BicStaSabAreMisFra-preprint.pdf , https://homepages.laas.fr/afranchi/robotics/sites/default/files/2018g-BicStaSabAreMisFra.mp4},
	author = {Nicolas Staub and Davide Bicego and Quentin Sabl{\'e} and Victor Arellano-Quintana and Subodh Mishra and Antonio Franchi}
}
@article {2018j-DelRobFra,
	title = {Towards Aerial Physical Locomotion: the Contact-Fly-Contact Problem},
	journal = {IEEE Robotics and Automation Letters, Special Issue on Aerial Manipulation},
	volume = {3},
	year = {2018},
	note = {Also selected for presentation at the 2018 IEEE Int. Conf. on Robotics and Automation, Brisbane , Australia},
	month = {02/2018},
	pages = {1514-1521},
	attachments = {https://homepages.laas.fr/afranchi/robotics/sites/default/files/2018f-RobDelFra-preprint.pdf , https://homepages.laas.fr/afranchi/robotics/sites/default/files/2018f-RobDelFra.mp4},
	author = {Quentin Delamare and Paolo Robuffo Giordano and Antonio Franchi}
}
@conference {2018f-RobDelFra,
	title = {Trajectory Generation for Minimum Closed-Loop State Sensitivity},
	booktitle = {2018 IEEE Int. Conf. on Robotics and Automation},
	year = {2018},
	month = {05/2018},
	pages = {286-293},
	address = {Brisbane, Australia},
	abstract = {In this paper we propose a novel general method to let a dynamical system fulfil at best a control task when the nominal parameters are not perfectly known. The approach is based on the introduction of the novel concept of closed- loop sensitivity, a quantity that relates parameter variations to deviations of the closed-loop trajectory of the system/controller pair. This new definition takes into account the dependency of the control inputs from the system states and nominal param- eters as well as from the controller dynamics. The reference trajectory to be tracked is taken as optimization variable, and the dynamics of both the sensitivity and of its gradient are computed analytically along the system trajectories. We then show how this computation can be effectively exploited for solving trajectory optimization problems aimed at generating a reference trajectory that minimizes a norm of the closed-loop sensitivity. The theoretical results are validated via an extensive campaign of Monte Carlo simulations for two relevant robotic systems: a unicycle and a quadrotor UAV.},
	attachments = {https://homepages.laas.fr/afranchi/robotics/sites/default/files/2018f-RobDelFra-preprint_1.pdf , https://homepages.laas.fr/afranchi/robotics/sites/default/files/2018f-RobDelFra_0.mp4},
	author = {Paolo Robuffo Giordano and Quentin Delamare and Antonio Franchi}
}
@conference {2018n-RylBicFra,
	title = {A Truly Redundant Aerial Manipulator exploiting a Multi-directional Thrust Base},
	booktitle = {12th IFAC Symposium on Robot Control},
	year = {2018},
	month = {08/2018},
	address = {Budapest, Hungary},
	abstract = {We present a novel aerial manipulator concept composed of a fully actuated hexarotor aerial vehicle and an n degree of freedom manipulator. Aiming at interaction tasks, we present a trajectory following control framework for the end-effector of the manipulator. The system is modeled in Euler-Lagrangian formalism and in Denavit-Hartenberg form. Benefiting from the redundancy of the system, we present several cost function strategies based on the projected gradient method to optimize the aerial manipulator behavior. The control framework is based on exact feedback linearization. In an advanced simulation section, we thoroughly present the robustness of the system and its limits in two typical configuration constituted by an 8 and a 10 degrees of freedom redundant aerial manipulator.},
	attachments = {https://homepages.laas.fr/afranchi/robotics/sites/default/files/2018n-RylBicFra-preprint.pdf},
	author = {Markus Ryll and Davide Bicego and Antonio Franchi}
}
@conference {2017e-RylMusPieCatAntCacFra,
	title = {6D Physical Interaction with a Fully Actuated Aerial Robot},
	booktitle = {2017 IEEE Int. Conf. on Robotics and Automation},
	year = {2017},
	month = {05/2017},
	pages = {5190-5195},
	address = {Singapore},
	abstract = {This paper presents the design, control, and experimental validation of a novel fully{\textendash}actuated aerial robot for physically interactive tasks, named Tilt-Hex. We show how the Tilt-Hex, a tilted-propeller hexarotor is able to control the full pose (position and orientation independently) using a geometric control, and to exert a full-wrench (force and torque independently) with a rigidly attached end-effector using an admittance control paradigm. An outer loop control governs the desired admittance behavior and an inner loop based on geometric control ensures pose tracking. The interaction forces are estimated by a momentum based observer. Control and observation are made possible by a precise control and measurement of the speed of each propeller. An extensive experimental campaign shows that the Tilt-Hex is able to outperform the classical underactuated multi-rotors in terms of stability, accuracy and dexterity and represent one of the best choice at date for tasks requiring aerial physical interaction.},
	attachments = {https://homepages.laas.fr/afranchi/robotics/sites/default/files/2017e-RylMusPieCatAntCacFra-preprint.pdf , https://homepages.laas.fr/afranchi/robotics/sites/default/files/2017e-RylMusPieCatAntCacFra.mp4},
	author = {Markus Ryll and Giuseppe Muscio and Francesco Pierri and Elisabetta Cataldi and Gianluca Antonelli and Fabrizio Caccavale and Antonio Franchi}
}
@conference {2017c-FraMal,
	title = {Adaptive Closed-loop Speed Control of BLDC Motors with Applications to Multi-rotor Aerial Vehicles},
	booktitle = {2017 IEEE Int. Conf. on Robotics and Automation},
	year = {2017},
	month = {05/2017},
	address = {Singapore},
	abstract = { This paper introduces the adaptive bias and adaptive gain (ABAG) algorithm for closed-loop electronic speed control (ESC) of the brushless direct current (BLDC) motors typically used to spin the propellers in multi-rotor aerial robots. The ABAG algorithm is adaptive and robust in the sense that it does not require the knowledge of any mechanical/electrical parameter of the motor/propeller group and that neither a pre-calibration nor the knowledge of the feedforward/nominal input is needed. The ABAG algorithm is amenable to an extremely low complexity implementation. We experimentally prove that it can run in 27.5 μs on a 8 MHz microcontroller with no floating point unit and limited arithmetic capabilities allowing only 8-bit additions, subtractions and multiplications. Besides the controller implementation we present a self-contained open source software architecture that handles the entire speed control process, including clock synchronization, and over- current and blockage safeties. The excellent performance and robustness of ABAG are shown by experimental tests and aerial physical interaction experiments.},
	attachments = {https://homepages.laas.fr/afranchi/robotics/sites/default/files/2017c-FraMal-preprint.pdf},
	author = {Antonio Franchi and Anthony Mallet}
}
@conference {2017f-MicRylFra,
	title = {Control of Statically Hoverable Multi-Rotor Aerial Vehicles and Application to Rotor-Failure Robustness for Hexarotors},
	booktitle = {2017 IEEE Int. Conf. on Robotics and Automation},
	year = {2017},
	month = {05/2017},
	address = {Singapore},
	abstract = {Standard hexarotors are often mistakenly considered {\textquoteleft}by definition{\textquoteright} fail-safe multi-rotor platforms because of the two additional propellers when compared to quadrotors. However this is not true, in fact, a standard hexarotor cannot statically hover with {\textquoteleft}only{\textquoteright} five propellers. In this paper we provide a set of new general algebraic conditions to ensure static hover for any multi-rotor platform with any number of generically oriented rotors. These are elegantly formulated as the full-rankness of the control moment input matrix, and the non-orthogonality between its null-space and the row space of the control force input matrix. Input saturations and safety margins are also taken into account with an additional condition on the null-space of control moment input matrix. A deep analysis on the hoverability properties is then carried out focusing on the propeller loss in a hexarotor platform. Leveraging our general results we explain why a standard hexarotor is not robust and how it can be made robust thanks to a particular tilt of the rotors. We finally propose a novel cascaded controller based on a preferential direction in the null-space of the control moment input matrix for the large class of statically hoverable multi-rotors, which goes far beyond standard platforms, and we apply this controller to the case of failed tilted hexarotor.},
	attachments = {https://homepages.laas.fr/afranchi/robotics/sites/default/files/2017f-MicRylFra-preprint.pdf , https://homepages.laas.fr/afranchi/robotics/sites/default/files/2017f-MicRylFra.mp4},
	author = {Giulia Michieletto and Markus Ryll and Antonio Franchi}
}
@article {2017k-NesRobBueFra,
	title = {Decentralized Simultaneous Multi-target Exploration using a Connected Network of Multiple Robots},
	journal = {Autonomous Robots},
	volume = {41},
	year = {2017},
	month = {03/2016},
	pages = {989-1011},
	abstract = {This paper presents a novel decentralized control strategy for a multi-robot system that enables parallel multi-target exploration while ensuring a time-varying connected topology in cluttered 3D environments. Flexible continuous connectivity is guaranteed by building upon a recent connectivity maintenance method, in which limited range, line-of-sight visibility, and collision avoidance are taken into account at the same time.
Completeness of the decentralized multi-target exploration algorithm is guaranteed by dynamically assigning the robots with different motion behaviors during the exploration task. One major group is subject to a suitable downscaling of the main traveling force based on the traveling efficiency of the current leader and the direction alignment between traveling and connectivity force. This supports the leader in always reaching its current target and, on a larger time horizon, that the whole team realizes the overall task in finite time.
Extensive Monte~Carlo simulations with a group of several quadrotor UAVs show the scalability and effectiveness of the proposed method and experiments validate its practicability. },
	keywords = {Connectivity maintenance, Exploration, Motion control of multiple robots, Patrolling / Surveillance},
	attachments = {https://homepages.laas.fr/afranchi/robotics/sites/default/files/1505.05441v3.pdf , https://homepages.laas.fr/afranchi/robotics/sites/default/files/2016g-NesRobBueFra-exp.mp4 , https://homepages.laas.fr/afranchi/robotics/sites/default/files/2016g-NesRobBueFra-empty.mp4 , https://homepages.laas.fr/afranchi/robotics/sites/default/files/2016g-NesRobBueFra-office.mp4 , https://homepages.laas.fr/afranchi/robotics/sites/default/files/2016g-NesRobBueFra-town.mp4},
	author = {Thomas Nestmeyer and Paolo Robuffo Giordano and Heinrich H. B{\"u}lthoff and Antonio Franchi}
}
@conference {2017g-TogYueBuoFra,
	title = {Dynamic Decentralized Control for Protocentric Aerial Manipulators},
	booktitle = {2017 IEEE Int. Conf. on Robotics and Automation},
	year = {2017},
	month = {05/2017},
	pages = {6375-6380},
	address = {Singapore},
	abstract = {We present a control methodology for underactuated aerial manipulators that is both easy to implement on real systems and able to achieve highly dynamic behaviors. The method is composed by two parts: i) a nominal input/state trajectory generator that takes into account the full-body dynamics of the system exploiting its differential flatness property; ii) a decentralized feedback controller acting on the actuated degrees of freedom that confers the needed robustness to the closed-loop system. We demonstrate that the proposed controller is able to precisely track dynamic trajectories when implemented on a standard hardware. Comparative experiments clearly show the benefit of using the nominal input/state generator.},
	attachments = {https://homepages.laas.fr/afranchi/robotics/sites/default/files/2017g-TogYueBuoFra-preprint.pdf , https://homepages.laas.fr/afranchi/robotics/sites/default/files/2017g-TogYueBuoFra.mp4},
	author = {Marco Tognon and Burak Y{\"u}ksel and Gabriele Buondonno and Antonio Franchi}
}
@article {2017a-TogFra,
	title = {Dynamics, Control, and Estimation for Aerial Robots Tethered by Cables or Bars},
	journal = {IEEE Transaction on Robotics},
	volume = {33},
	year = {2017},
	month = {08/2017},
	pages = {834-845},
	keywords = {submitted},
	attachments = {https://homepages.laas.fr/afranchi/robotics/sites/default/files/1603.07567-v2.pdf},
	author = {Marco Tognon and Antonio Franchi}
}
@conference {2017j-NaiFurSeuZacFra,
	title = {Hierarchical Control of the Over-Actuated ROSPO Platform via Static Input Allocation},
	booktitle = {20th IFAC World Congress},
	year = {2017},
	month = {07/2017},
	address = {Toulouse, France},
	abstract = {This paper addresses the problem of control allocation applied to an over-actuated hovercraft-type vehicle. A hierarchical control architecture, consisting of a high level controller for trajectory tracking, and a control allocation algorithm, is developed and proved to be effective in tracking a desired trajectory while optimizing some cost related to actuator constraints. The control allocation algorithm exploits the redundancy of the system in order to keep the actuator states inside their saturation limits and tries to minimize the power consumption of the propellers. Unlike other papers on control allocation, actuator dynamics is taken into account. The control architecture is tested through simulations that well illustrate the capabilities of the proposed control design},
	attachments = {https://homepages.laas.fr/afranchi/robotics/sites/default/files/2017j-NaiFurSeuZacFra-preprint.pdf},
	author = {Carlo Nainer and Michele Furci and Alexandre Seuret and Luca Zaccarian and Antonio Franchi}
}
@inbook {2016f-Fra,
	title = {Human-Collaborative Schemes in the Motion Control of Single and Multiple Mobile Robots},
	booktitle = {Trends in Control and Decision-Making for Human-Robot Collaboration Systems},
	year = {2017},
	month = {02/2017},
	pages = {301-324},
	publisher = {Springer},
	organization = {Springer},
	abstract = {In this chapter we show and compare several representative examples of human-collaborative schemes in the control of mobile robots, with a particular emphasis on the aerial robot case. We first provide a simplified yet descriptive model of the robot and its interactions. We then use this model to define a taxonomy that highlights the main aspects of these collaboration schemes, such as: the physical domain of the robots, the degree of autonomy, the force interaction with the operator (e.g., the unilateral versus the bilateral haptic shared control), the near-operation versus the teleoperation, the contact-free versus the physically interactive situation, the use of onboard sensors, and the presence of a time-horizon in the operator reference. We then specialize the proposed taxonomy to the multi-robot case in which we further distinguish the methods depending on their level of centralization, the presence of leader-follower schemes, of formation control schemes, the ability to preserve graph theoretical properties, and to perform cooperative physical interaction. The common denominator of all the examples presented in this chapter is the presence of a human operator in the control loop. The main goal of the chapter is to introduce the reader and provide a first-level analysis on the several ways to effectively include human operators in the control of both single and multiple aerial robots and, by extension, of more generic mobile robots.},
	attachments = {https://homepages.laas.fr/afranchi/robotics/sites/default/files/2016f-Fra-preprint.pdf},
	author = {Antonio Franchi}
}
@conference {2017o-TogFra,
	title = {Landing and take-off on/from sloped and non-planar surfaces with more than 50 degrees of inclination},
	booktitle = {2017 International Micro Air Vehicle Conference},
	year = {2017},
	month = {09/2017},
	pages = {97-102},
	address = {Toulouse, France},
	abstract = {This technical paper summarizes the recent experimental results concerning the challenging problem of landing and take-off on/from a sloped surface with an aerial vehicle exploiting the force provided by an anchored taut tether. A special regard is given to the practical aspects concern- ing the experimental part. In this manuscript we show extreme landing and take-off maneuvers on slopes with at least 50{\textopenbullet} inclination and non flat surfaces, such as, e.g., on industrial pipes.},
	attachments = {https://homepages.laas.fr/afranchi/robotics/sites/default/files/2017o-TogFra-preprint.pdf},
	author = {Marco Tognon and Antonio Franchi}
}
@conference {2017m-SolFurCorFra,
	title = {Multi-Robot Path Planning with Maintenance of Generalized Connectivity},
	booktitle = {The 1st Int. Symp. on Multi-Robot and Multi-Agent Systems},
	year = {2017},
	month = {12/2017},
	address = {Los Angeles, CA},
	abstract = { This paper addresses the problem of generating a path for a fleet of robots navigating in a cluttered environment, while maintaining the so called generalized connectivity. The main challenge in the management of a group of robots is to ensure the coordination between them, taking into account limitations in communication range and sensors, possible obstacles, inter-robot avoidance and other constraints. The Generalized Connectivity Maintenance (GCM) theory already provides a way to represent and consider the aforementioned constraints, but previous works only find solutions via locally-steering functions that do not provide global and optimal solutions. In this work, we merge the GCM theory with randomized path- planning approaches, and local path optimization techniques to derive a tool that can provide global, good-quality paths. The proposed approach has been intensively tested and verified by mean of numerical simulations.},
	attachments = {https://homepages.laas.fr/afranchi/robotics/sites/default/files/2017m-SolFurCorFra-preprint.pdf},
	author = {Yoann Solana and Michele Furci and Juan Cort{\'e}s and Antonio Franchi}
}
@conference {2017i-MicCenZacFra,
	title = {Nonlinear Control of Multi-Rotor Aerial Vehicles Based on the Zero-Moment Direction},
	booktitle = {20th IFAC World Congress},
	year = {2017},
	month = {07/2017},
	address = {Toulouse, France},
	abstract = {A quaternion-based nonlinear control strategy is here presented to steer and keep a generic multi-rotor platform in a given reference position. Exploiting a state feedback structure, the proposed solution ensures the stabilization of the aerial vehicle so that its linear and angular velocity are zero and its attitude is constant. The main feature of the designed controller is the identification of a zero-moment direction in the feasible force space, i.e., a direction along which the control force intensity can be assigned independently of the control moment. The asymptotic convergence of the error dynamics is confirmed by simulation results on a hexarotor with tilted propellers.
},
	attachments = {https://homepages.laas.fr/afranchi/robotics/sites/default/files/2017i-MicCenZacFra-preprint.pdf},
	author = {Giulia Michieletto and Angelo Cenedese and Luca Zaccarian and Antonio Franchi}
}
@conference {2016l-TogFra,
	title = {Position Tracking Control for an Aerial Robot Passively Tethered to an Independently Moving Platform},
	booktitle = {20th IFAC World Congress},
	year = {2017},
	month = {07/2017},
	address = {Toulouse, France},
	abstract = {We study the control problem of an aerial vehicle moving in the 3D space and connected to an independently moving platform through a physical link (e.g., a cable, a chain or a rope). The link is attached to the moving platform by means of a passive winch. The latter differs from an active winch by producing only a constant uncontrollable torque. We solve the problem of exact tracking of the 3D position of the aerial vehicle, either absolute or with respect to the moving platform, while the platform is independently moving. We prove two intrinsic properties of the system, namely, the dynamic feedback linearizability and the differential flatness with respect to the output of interest. Exploiting this properties we design a nonlinear controller able to exponentially steer the position of the aerial robot along any sufficiently smooth time-varying trajectory. The proposed method is tested through numerical simulations in several non-ideal cases.},
	attachments = {https://homepages.laas.fr/afranchi/robotics/sites/default/files/2016l-TogFra-preprint.pdf},
	author = {Marco Tognon and Antonio Franchi}
}
@conference {2017d-StaMohBicPraFra,
	title = {Towards Robotic MAGMaS: Multiple Aerial-Ground Manipulator Systems},
	booktitle = {2017 IEEE Int. Conf. on Robotics and Automation},
	year = {2017},
	month = {05/2017},
	pages = {1307-1312},
	address = {Singapore},
	abstract = {In this paper we lay the foundation of the first heterogeneous multi-robot system of the Multiple Aerial-Ground Manipulator System (MAGMaS) type. A MAGMaS consists of a ground manipulator and a team of aerial robots equipped with a simple gripper manipulator the same object. The idea is to benefit from the advantages of both kinds of platforms, i.e., physical strength versus large workspace. The dynamic model of such robotic systems is derived, and R Ro its characteristic structure exhibited. Based on the dynamical i structure of the system a nonlinear control scheme, augmented with a disturbance observer is proposed to perform trajectory tracking tasks in presence of model inaccuracies and external disturbances. The system redundancy is exploited by solving an optimal force/torque allocation problem that takes into account the heterogeneous system constraints and maximizes the force manipulability ellipsoid. Simulation results validated the proposed control scheme for this novel heterogeneous robotic system. We finally present a prototypical mechanical design and preliminary experimental evaluation of a MAGMaS composed by a kuka LWR4 and quadrotor based aerial robot.},
	attachments = {https://homepages.laas.fr/afranchi/robotics/sites/default/files/2017d-StaMohBicPraFra-preprint.pdf , https://homepages.laas.fr/afranchi/robotics/sites/default/files/2017d-StaMohBicPraFra.mp4},
	author = {Nicolas Staub and Mostafa Mohammadi and Davide Bicego and Domenico Prattichizzo and Antonio Franchi}
}
@conference {2017h-SanAreTogCamFra,
	title = {Visual Marker based Multi-Sensor Fusion State Estimation},
	booktitle = {20th IFAC World Congress},
	year = {2017},
	month = {07/2017},
	address = {Toulouse, France},
	abstract = {This paper presents the description and experimental results of a versatile Visual Marker based Multi-Sensor Fusion State Estimation that allows to combine a variable optional number of sensors and positioning algorithms in a loosely-coupling fashion, incorporating visual markers to increase its performances. This technique allows an aerial robot to navigate in different environments and carrying out different missions with the same state estimation architecture, exploiting the best from every sensor. The state estimation algorithm has been successfully tested controlling a quadrotor equipped with an extra IMU and a RGB camera used only to detect visual markers. The entire framework runs on an onboard computer, including the controllers and the proposed state estimator. The whole software is made publicly available to the scientific community through an open source implementation.},
	attachments = {https://homepages.laas.fr/afranchi/robotics/sites/default/files/2017h-SanAreTogCamFra-preprint.pdf},
	author = {Jos{\'e}-Luis-L. Sanchez-Lopez and Victor Arellano-Quintana and Marco Tognon and Pascual Campoy and Antonio Franchi}
}
@conference {2016l-YueStaFra,
	title = {Aerial Robots with Rigid/Elastic-joint Arms: Single-joint Controllability Study and Preliminary Experiments},
	booktitle = {2016 IEEE/RSJ Int. Conf. on Intelligent Robots and System},
	year = {2016},
	month = {10/2016},
	pages = {1667-1672},
	address = {Daejeon, South Korea},
	abstract = {We present the dynamic modeling, analysis, and control design of a Planar-Vertical Take-Off and Landing (PVTOL) underactuated aerial vehicle equipped either with a rigid- or an elastic-joint arm. We prove that in both cases the system is exactly linearizable with a dynamic feedback and differentially flat for the same set of outputs (but different controllers). We compare the two cases with extensive and realistic simulations, which show that the rigid-joint case outperforms the elastic-joint case for aerial grasping tasks while the converse holds for link-velocity amplification tasks. We present preliminary experimental results using a actuated joint with variable stiffness (VSA) on a quadrotor platform.},
	attachments = {https://homepages.laas.fr/afranchi/robotics/sites/default/files/2016l-YueStaFra-preprint.pdf},
	author = {Burak Y{\"u}ksel and Nicolas Staub and Antonio Franchi}
}
@inbook {2013n-SpeNotBueFra,
	title = {Aggressive Maneuver Regulation of a Quadrotor UAV},
	booktitle = {Robotics Research, The 16th International Symposium ISRR},
	volume = {114},
	number = {Springer Tracts in Advanced Robotics},
	year = {2016},
	month = {04/2016},
	pages = {95-112},
	publisher = {Springer},
	organization = {Springer},
	abstract = {In this paper we design a nonlinear controller for aggressive maneuvering of a quadrotor. We take a maneuver regulation perspective. Differently from the classical trajectory tracking approach, maneuver regulation does not require following a timed reference state, but a geometric {\textquotedblleft}path{\textquotedblright} with a velocity (and possibly orientation) profile assigned on it. The proposed controller re- lies on three main ideas. Given a desired maneuver, i.e., a set of state trajectories equivalent under time translations, the system dynamics is decomposed into dynamics longitudinal and transverse to the maneuver. A space-dependent version of the transverse dynamics is derived, by using the longitudinal state, i.e., the arc-length of the path, as an independent variable. Then the controller is obtained as a function of the arc-length consisting of two terms: a feedforward term, being the nominal input to apply when on the path at the current arc-length, and a feedback term exponentially stabilizing the state-dependent transverse dynamics. Numerical computations are presented to prove the effectiveness of the proposed strategy. The controller performances are tested in presence of uncertainty of the model parameters and input noise and saturations. The controller is also tested in a realistic simulation environment validated against an experimental test-bed.},
	keywords = {Aerial Robotics},
	attachments = {https://homepages.laas.fr/afranchi/robotics/sites/default/files/2013n-SpeNotBueFra-preprint.pdf , https://homepages.laas.fr/afranchi/robotics/sites/default/files/2013n-SpeNotBueFra-1_no_sat.mp4 , https://homepages.laas.fr/afranchi/robotics/sites/default/files/2013n-SpeNotBueFra-1_no_sat_zoom.mp4 , https://homepages.laas.fr/afranchi/robotics/sites/default/files/2013n-SpeNotBueFra-2_sat_8_5.mp4 , https://homepages.laas.fr/afranchi/robotics/sites/default/files/2013n-SpeNotBueFra-2_sat_8_5_zoom.mp4 , https://homepages.laas.fr/afranchi/robotics/sites/default/files/2013n-SpeNotBueFra-2_sat_7.mp4 , https://homepages.laas.fr/afranchi/robotics/sites/default/files/2013n-SpeNotBueFra-2_sat_7_zoom.mp4},
	author = {Sara Spedicato and Giuseppe Notarstefano and Heinrich H. B{\"u}lthoff and Antonio Franchi}
}
@conference {2016o-MicCenFra,
	title = {Bearing Rigidity Theory in SE(3)},
	booktitle = {55th IEEE Conference on Decision and Control},
	year = {2016},
	month = {12/2016},
	pages = {5950-5955},
	address = {Las Vegas, NV},
	abstract = {Rigidity theory has recently emerged as an efficient tool in the control field of coordinated multi-agent systems, such as multi-robot formations and UAVs swarms, that are characterized by sensing, communication and movement capabilities. This work aims at describing the rigidity properties for frameworks embedded in the three-dimensional Special Euclidean space SE(3) wherein each agent has 6DoF. In such scenario, it is assumed that the devices are able to gather bearing measurements w.r.t. their neighbors, expressing them into their own body frame. The goal is then to identify the framework transformations that allow to preserve such measurements maintaining it rigid. Rigidity properties are mathematically formalized in this work which differs from the previous ones as it faces the extension in three-dimensional space dealing with the 3D rotations manifold. In particular, the attention is focused on the infinitesimal SE(3)-rigidity for which a necessary and sufficient condition is provided.},
	attachments = {https://homepages.laas.fr/afranchi/robotics/sites/default/files/2016o-MicCenFra-preprint.pdf},
	author = {Giulia Michieletto and Angelo Cenedese and Antonio Franchi}
}
@conference {2016n-MohFraBarPra,
	title = {Cooperative Aerial Tele-Manipulation with Haptic Feedback},
	booktitle = {2016 IEEE/RSJ Int. Conf. on Intelligent Robots and System},
	year = {2016},
	month = {10/2016},
	pages = {5092-5098},
	address = {Daejeon, South Korea},
	abstract = {In this paper, we propose a bilateral tele-operation scheme for cooperative aerial manipulation in which a human operator drives a team of Vertical Take-Off and Landing (VTOL) aerial vehicles, that grasped an object beforehand, and receives a force feedback depending on the states of the system. For application scenarios in which dexterous manipulation by each robot is not necessary, we propose using a rigid tool attached to the vehicle through a passive spherical joint, equipped with a simple adhesive mechanism at the tool-tip that can stick to the grasped object. Having more than two robots, we use the extra degrees of freedom to find the optimal force allocation in term of minimum power and forces smoothness. The human operator commands a desired trajectory for the robot team through a haptic interface to a pose controller, and the output of the pose controller along with system constraints, e.g., VTOL limited forces and contact maintenance, defines the feasible set of forces. Then, an on-line optimization allocates forces by minimizing a cost function of forces and their variation. Finally, propeller thrusts are computed by a dedicated attitude and thrust controller in a decentralized fashion. Human/Hardware in the loop simulation study shows efficiency of the proposed scheme, and the importance of haptic feedback to achieve a better performance.},
	attachments = {https://homepages.laas.fr/afranchi/robotics/sites/default/files/2016n-MohFraBarPra-preprint.pdf , https://homepages.laas.fr/afranchi/robotics/sites/default/files/2016n-MohFraBarPra.mp4},
	author = {Mostafa Mohammadi and Antonio Franchi and Davide Barcelli and Domenico Prattichizzo}
}
@conference {2016b-PetFraDipRiz,
	title = {Decentralized Motion Control for Cooperative Manipulation with a Team of Networked Mobile Manipulators},
	booktitle = {2016 IEEE Int. Conf. on Robotics and Automation},
	year = {2016},
	month = {05/2016},
	pages = {441-446},
	address = {Stockholm, Sweden},
	abstract = { In this paper we consider the cooperative control of the manipulation of a load on a plane by a team of mobile robots. We propose two different novel solutions. The first is a controller which ensures exact tracking of the load twist. This controller is partially decentralized since, locally, it does not rely on the state of all the robots but needs only to know the system parameters and load twist. Then we propose a fully decentralized controller that differs from the first one for the use of i) a decentralized estimation of the parameters and twist of the load based only on local measurements of the velocity of the contact points and ii) a discontinuous robustification term in the control law. The second controller ensures a practical stabilization of the twist in presence of estimation errors. The theoretical results are finally corroborated with a simulation campaign evaluating different manipulation settings.},
	keywords = {Calibration of ground robots, Motion control of multiple robots},
	attachments = {https://homepages.laas.fr/afranchi/robotics/sites/default/files/2016b-PetFraDipRiz-preprint.pdf , https://homepages.laas.fr/afranchi/robotics/sites/default/files/2016b-PetFraDipRiz.mp4},
	author = {Antonio Petitti and Antonio Franchi and Donato Di Paola and Alessandro Rizzo}
}
@article {2015i-FraSteOri,
	title = {Decentralized Multi-Robot Encirclement of a 3D Target with Guaranteed Collision Avoidance},
	journal = {Autonomous Robots},
	volume = {40},
	year = {2016},
	month = {02/2016},
	pages = {245-265},
	abstract = {We present a control framework for achieving encirclement of a target moving in 3D using a multi-robot system. Three variations of a basic control strategy are proposed for different versions of the encirclement problem, and their effectiveness is formally established. An extension ensuring maintenance of a safe inter-robot distance is also discussed. The proposed framework is fully decentralized and only requires local communication among robots; in particular, each robot locally estimates all the relevant global quantities. We validate the proposed strategy through simulations on kinematic point robots and quadrotor UAVs, as well as  experiments on differential-drive wheeled mobile robots.},
	keywords = {Motion control of multiple robots},
	attachments = {https://homepages.laas.fr/afranchi/robotics/sites/default/files/1307.7170v2.pdf , https://homepages.laas.fr/afranchi/robotics/sites/default/files/1307.7170v1.pdf},
	author = {Antonio Franchi and Paolo Stegagno and Giuseppe Oriolo}
}
@conference {2016k-YueBuoFra,
	title = {Differential Flatness and Control of Protocentric Aerial Manipulators with Any Number of Arms and Mixed Rigid-/Elastic-Joints},
	booktitle = {2016 IEEE/RSJ Int. Conf. on Intelligent Robots and System},
	year = {2016},
	month = {10/2016},
	pages = {561-566},
	address = {Daejeon, South Korea},
	abstract = {In this paper we introduce a particularly relevant class of aerial manipulators that we name protocentric. These robots are formed by an underactuated aerial vehicle, a planarVertical Take-Off and Landing (PVTOL), equipped with any number of different parallel manipulator arms with the only property that all the first joints are attached at the Center of Mass (CoM) of the PVTOL, while the center of actuation of the PVTOL can be anywhere. We prove that protocentric aerial manipulators (PAMs) are differentially flat systems regardless the number of joints of each arm and their kinematic and dynamic parameters. The set of flat outputs is constituted by the CoM of the PVTOL and the absolute orientation angles of all the links. The relative degree of each output is equal to four. More amazingly, we prove that PAMs are differentially flat even in the case that any number of the joints are elastic, no matter the internal distribution between elastic and rigid joints. The set of flat outputs is the same but in this case the total relative degree grows quadratically with the number of elastic joints. We validate the theory by simulating object grasping and transportation tasks with unknown mass and parameters and using a controller based on dynamic feedback linearization.},
	attachments = {https://homepages.laas.fr/afranchi/robotics/sites/default/files/2016k-YueBuoFra-preprint.pdf , https://homepages.laas.fr/afranchi/robotics/sites/default/files/2016k-YueBuoFra-tech_report.pdf , https://homepages.laas.fr/afranchi/robotics/sites/default/files/2016k-YueBuoFra.mp4},
	author = {Burak Y{\"u}ksel and Gabriele Buondonno and Antonio Franchi}
}
@conference {2016a-SpeFraNot,
	title = {From Tracking to Robust Maneuver Regulation: an Easy-to-Design Approach for VTOL Aerial Robots},
	booktitle = {2016 IEEE Int. Conf. on Robotics and Automation},
	year = {2016},
	month = {05/2016},
	pages = {2965-2970},
	address = {Stockholm, Sweden},
	abstract = {In this paper we present a maneuver regulation scheme for Vertical Take-Off and Landing (VTOL) micro aerial vehicles (MAV). Differently from standard trajectory tracking, maneuver regulation has an intrinsic robustness due to the fact that the vehicle is not required to chase a virtual target, but just to stay on a (properly designed) desired path with a given velocity profile. In this paper we show how a robust maneuver regulation controller can be easily designed by converting an existing tracking scheme. The resulting maneuvering controller has three main appealing features, namely it: (i) inherits the robustness properties of the tracking controller, (ii) gains the appealing features of maneuver regulation, and (iii) does not need any additional tuning with respect to the tracking controller. We prove the correctness of the proposed scheme and show its effectiveness in experiments on a nano-quadrotor. In particular, we show on a nontrivial maneuver how external disturbances acting on the quadrotor cause instabilities in the standard tracking, while marginally affect the maneuver regulation scheme.},
	keywords = {Aerial Robotics},
	attachments = {https://homepages.laas.fr/afranchi/robotics/sites/default/files/2016a-SpeFraNot-preprint.pdf , https://homepages.laas.fr/afranchi/robotics/sites/default/files/2016a-SpeFraNot.mp4},
	author = {Sara Spedicato and Antonio Franchi and Giuseppe Notarstefano}
}
@article {2016h-SteCogOriBueFra,
	title = {Ground and Aerial Mutual Localization using Anonymous Relative-Bearing Measurements},
	journal = {IEEE Transaction on Robotics},
	volume = {32},
	year = {2016},
	month = {09/2017},
	pages = {1133-1151},
	abstract = {We present a  decentralized algorithm for estimating mutual poses (i.e., relative positions and orientations) in a group of mobile robots. The algorithm uses only anonymous relative-bearing measurements obtainable, e.g., using onboard monocular cameras, and onboard motion measurements, such as inertial ones (acceleration and angular velocity). 
Onboard relative-bearing sensors supply anonymous measurements, i.e., they  provide the directions along which other robots are located but each direction is not associated to any robot (identities are unknown).
The issue of anonymity is often overlooked in theory but represents a real problem in practice, especially when employing onboard vision.
The solution is first presented for ground robots, in SE(2), and then for aerial robots, in SE(3), in order to emphasize the difference between the two cases.
The proposed method is based on a two-step approach, the first uses instantaneous geometrical arguments on the anonymous measurements in order to retrieve the most likely unscaled relative configurations together with the identities, the second uses a numeric Bayesian filtering in order to take advantage of the motion model over time and to retrieve the scale.
The proposed method exhibits robustness w.r.t. false positives and negatives of the robot detector.
An extensive experimental validation of the algorithm is performed using Khepera III ground mobile robots and quadrotor aerial robots.},
	attachments = {https://homepages.laas.fr/afranchi/robotics/sites/default/files/2016h-SteCogOriBueFra-preprint.pdf , https://homepages.laas.fr/afranchi/robotics/sites/default/files/2016h-SteCogOriBueFra.mp4},
	author = {Paolo Stegagno and Marco Cognetti and Giuseppe Oriolo and Heinrich H. B{\"u}lthoff and Antonio Franchi}
}
@conference {2016j-RylBicFra,
	title = {Modeling and Control of FAST-Hex: a Fully-Actuated by Synchronized-Tilting Hexarotor},
	booktitle = {2016 IEEE/RSJ Int. Conf. on Intelligent Robots and System},
	year = {2016},
	month = {10/2016},
	pages = {1689-1694},
	address = {Daejeon, South Korea},
	abstract = {We present FAST-Hex, a novel UAV concept which is able to smoothly change its configuration from underactuated to fully actuated by using only one additional motor that tilts all propellers at the same time. FAST-Hex can adapt to the task at hand by finely tuning its configuration from the efficient (but underactuated) flight (typical of coplanar multi{\textendash} rotor platforms) to the full-pose-tracking (but less efficient) flight, which is attainable by non-coplanar multi-rotors. We also introduce a novel full-pose geometric controller for generic multi-rotors (not only the FAST-Hex) that outperforms classical inverse dynamics approaches. The controller receives as input any reference pose in R^3{\texttimes}SO(3) (3D position + 3D orientation). Exact tracking is achieved if the reference pose is feasible with respect to the propeller spinning rate saturations. In case of unfeasibility a new feasible desired trajectory is generated online giving priority to the positional part. The new controller is tested with the FAST-Hex but can be used for many other multi-rotor platforms: underactuated, slightly fully-actuated and completely fully-actuated.},
	attachments = {https://homepages.laas.fr/afranchi/robotics/sites/default/files/2016j-RylBicFra-preprint.pdf , https://homepages.laas.fr/afranchi/robotics/sites/default/files/2016j-RylBicFra.mp4},
	author = {Markus Ryll and Davide Bicego and Antonio Franchi}
}
@conference {2016d-CarTodCarFraSch,
	title = {Multi-Robot Localization via GPS and Relative Measurements in the Presence of Asynchronous and Lossy Communication},
	booktitle = {15th European Control Conference},
	year = {2016},
	month = {07/2016},
	address = {Aalborg, Denmark},
	author = {Andrea Carron and Marco Todescato and Ruggero Carli and Antonio Franchi and Luca Schenato}
}
@article {2016c-TogDasFra,
	title = {Observer-based Control of Position and Tension  for an Aerial Robot Tethered to a Moving Platform},
	journal = {IEEE Robotics and Automation Letters},
	volume = {1},
	year = {2016},
	note = {Also selected for presentation at the 2016 IEEE Int. Conf. on Robotics and Automation, Stockholm , Sweden},
	month = {01/2016},
	pages = {732-737},
	abstract = {In this paper we address a challenging version of the problem of controlling tethered aerial vehicles (also known as UAV, MAV, and UAS) by considering the aerial robot linked to a generic and independently moving platform. We solve the exact tracking control problem for both the 3D position of the robot (either absolute or with respect to the platform) and the tension along the link. To achieve this goal we prove some fundamental system properties, useful to design a nonlinear controller, such as differential flatness and dynamic feedback linearizability. To close the control loop a set of minimal and standard sensors is proposed. Then we show that it is possible to retrieve the full system state from those sensors by means of nonlinear measurements transformations and a bank of low-dimension estimators based on the nonlinear high gain observer. The ability of the proposed observer-controller method is tested by extensive numerical simulations spanning many non-ideal conditions.},
	keywords = {Aerial Physical Interaction, Aerial Robotics},
	attachments = {https://homepages.laas.fr/afranchi/robotics/sites/default/files/2016c-TogDasFra-preprint.pdf , https://homepages.laas.fr/afranchi/robotics/sites/default/files/2016c-TogDasFra..mp4},
	author = {Marco Tognon and Sanket S. Dash and Antonio Franchi}
}
@conference {2016m-SchFraZelRob,
	title = {A Rigidity-Based Decentralized Bearing Formation Controller for Groups of Quadrotor UAVs},
	booktitle = {2016 IEEE/RSJ Int. Conf. on Intelligent Robots and System},
	year = {2016},
	month = {10/2016},
	pages = {5099-5106},
	address = {Daejeon, South Korea},
	abstract = {This paper considers the problem of controlling a formation of quadrotor UAVs equipped with onboard cameras able to measure relative bearings in their local body frames w.r.t. neighboring UAVs. The control goal is twofold: (i) steering the agent group towards a formation defined in terms of desired bearings, and (ii) actuating the group motions in the {\textquoteleft}null-space{\textquoteright} of the current bearing formation. The proposed control strategy relies on an extension of the rigidity theory to the case of directed bearing frameworks in R 3{\texttimes}S1 . This extension allows to devise a decentralized bearing controller which, unlike most of the present literature, does not need presence of a common reference frame or of reciprocal bearing measurements for the agents. Simulation and experimental results are then presented for illustrating and validating the approach.},
	attachments = {https://homepages.laas.fr/afranchi/robotics/sites/default/files/2016m-SchFraZelRob-preprint.pdf , https://homepages.laas.fr/afranchi/robotics/sites/default/files/2016m-SchFraZelRob.mp4},
	author = {Fabrizio Schiano and Antonio Franchi and Daniel Zelazo and Paolo Robuffo Giordano}
}
@conference {2016i-TogTesRosFra,
	title = {Takeoff and Landing on Slopes via Inclined Hovering with a Tethered Aerial Robot},
	booktitle = {2016 IEEE/RSJ Int. Conf. on Intelligent Robots and Systems},
	year = {2016},
	month = {10/2016},
	pages = {1702-1707},
	address = {Daejeon, South Korea},
	abstract = {In this paper we face the challenging problem of takeoff and landing on sloped surfaces for a VTOL aerial vehicle. We define the general conditions for a safe and robust maneuver and we analyze and compare two classes of methods to fulfill these conditions: free-flight vs. passively tethered. Focusing on the less studied tethered method, we show its advantages w.r.t. the free-flight method thanks to the possibility of inclined hovering equilibria. We prove that the tether configuration and the inclination of the aerial vehicle w.r.t. the slope are flat outputs of the system and we design a hierarchical nonlinear controller based on this property. We then show how this controller can be used to land and takeoff in a robust way without the need of either a planner or a perfect tracking. The validity and applicability of the method in the real world is shown by experiments with a quadrotor that is able to perform a safe landing and takeoff on a sloped surface.},
	attachments = {https://homepages.laas.fr/afranchi/robotics/sites/default/files/2016i-TogTesRosFra-preprint.pdf , https://homepages.laas.fr/afranchi/robotics/sites/default/files/2016i-TogTesRosFra_0.mp4},
	author = {Marco Tognon and Andrea Testa and Enrica Rossi and Antonio Franchi}
}
@conference {2015d-StaFra,
	title = {Battery-aware Dynamical Modeling and Identification for the Total Thrust in Multi-rotor UAVs using only an Onboard Accelerometer},
	booktitle = {2015 IEEE Int. Conf. on Robotics and Automation},
	year = {2015},
	month = {05/2015},
	pages = {3341-3346},
	address = {Seattle, WA},
	abstract = {We propose and experimentally validate a new class of models for the total thrust generation in multi-rotor UAVs which is suitable for low- and middle-end platforms. Differently from typical models assuming to instantaneously control the rotor spinning velocity, in the proposed class we consider that the total thrust has its own dynamics and its final value explicitly depends both on the pseudo-setpoint commands given to the motor driver and the measurement of the battery terminal voltage. We compare the different model instances within the class using a principled experimental setup in which the total thrust is precisely measured using a motion capture system as ground truth, instead of relying on a setup based or noise-prone force sensors. We then show that the use of a dynamical model that includes also the battery terminal voltage significantly improves the prediction ability of the model in terms of accuracy. Finally we show how the proposed model can be identified using on-board only acceleration measurements, achieving a surprisingly good accuracy when compared with the ground truth case. We expect that the use of the proposed model will be important both in case of precise flight control and in the case of aerial physical interactive tasks.},
	attachments = {https://homepages.laas.fr/afranchi/robotics/sites/default/files/2015d-StaFra-preprint_0.pdf , https://homepages.laas.fr/afranchi/robotics/sites/default/files/2015d-StaFra.mp4},
	author = {Nicolas Staub and Antonio Franchi}
}
@conference {2015k-ZelRobFra,
	title = {Bearing-Only Formation Control Using an SE(2) Rigidity Theory},
	booktitle = {54rd IEEE Conference on Decision and Control},
	year = {2015},
	month = {12/2015},
	pages = {6121-6126},
	address = {Osaka, Japan},
	attachments = {https://homepages.laas.fr/afranchi/robotics/sites/default/files/2015k-ZelRobFra-preprint.pdf},
	author = {Daniel Zelazo and Paolo Robuffo Giordano and Antonio Franchi}
}
@conference {2015h-TogFra,
	title = {Control of Motion and Internal Stresses for a Chain of Two Underactuated Aerial Robots},
	booktitle = {14th European Control Conference},
	year = {2015},
	month = {07/2015},
	pages = {1620-1625},
	address = {Linz, Austria},
	attachments = {https://homepages.laas.fr/afranchi/robotics/sites/default/files/2015h-TogFra-preprint.pdf},
	author = {Marco Tognon and Antonio Franchi}
}
@conference {2015b-FraPetRiz,
	title = {Decentralized Parameter Estimation and Observation for Cooperative Mobile Manipulation of an Unknown Load using Noisy Measurements},
	booktitle = {2015 IEEE Int. Conf. on Robotics and Automation},
	year = {2015},
	month = {05/2015},
	pages = {5517-5522},
	address = {Seattle, WA},
	abstract = {In this paper, a distributed approach for the estimation of kinematic and inertial parameters of an unknown rigid body is presented. The body is manipulated by a pool of ground mobile manipulators. Each robot retrieves a noisy measurement of its velocity and the contact forces applied to the body. Kinematics and dynamics arguments are used to distributively estimate the relative positions of the contact points. Subsequently, distributed estimation filters and nonlinear observers are used to estimate the body mass, the relative position between its geometric center and its center of mass, and its moment of inertia. The manipulation strategy is functional to the estimation process, and is suitably designed to satisfy nonlinear observability conditions that are necessary for the success of the estimation. Numerical results corroborate our theoretical findings.},
	attachments = {https://homepages.laas.fr/afranchi/robotics/sites/default/files/2015b-FraPetRiz-preprint_0.pdf},
	author = {Antonio Franchi and Antonio Petitti and Alessandro Rizzo}
}
@conference {2015f-YueMahSecBueFra,
	title = {Design, Identification and Experimental Testing of a Light-Weight Flexible-joint Arm for Aerial Physical Interaction},
	booktitle = {2015 IEEE Int. Conf. on Robotics and Automation},
	year = {2015},
	month = {05/2015},
	pages = {870-876},
	address = {Seattle, WA},
	abstract = {In this paper we introduce the design of a light- weight novel flexible-joint arm for light-weight unmanned aerial vehicles (UAVs), which can be used both for safe physical interaction with the environment and it represents also a preliminary step in the direction of performing quick motions for tasks such as hammering or throwing. The actuator consists of an active pulley driven by a rotational servo motor, a passive pulley which is attached to a rigid link, and the elastic connections (springs) between these two pulleys. We identify the physical parameters of the system, and use an optimal control strategy to maximize its velocity by taking advantage of elastic components. The prototype can be extended to a light-weight variable stiffness actuator. The flexible-joint arm is applied on a quadrotor, to be used in aerial physical interaction tasks, which implies that the elastic components can also be used for stable interaction absorbing the interactive disturbances which might damage the flying system and its hardware. The design is validated through several experiments, and future developments are discussed in the paper.},
	keywords = {Aerial Physical Interaction, Aerial Robotics},
	attachments = {https://homepages.laas.fr/afranchi/robotics/sites/default/files/2015f-YueMahSecBueFra-preprint_0.pdf , https://homepages.laas.fr/afranchi/robotics/sites/default/files/2015f-YueMahSecBueFra.mp4},
	author = {Burak Y{\"u}ksel and Saber Mahboubi and Cristian Secchi and Heinrich H. B{\"u}lthoff and Antonio Franchi}
}
@conference {2015c-GioMohFraPra,
	title = {A Force-based Bilateral Teleoperation Framework for Aerial Robots in Contact with the Environment},
	booktitle = {2015 IEEE Int. Conf. on Robotics and Automation},
	year = {2015},
	month = {05/2015},
	pages = {318-324},
	address = {Seattle, WA},
	keywords = {Aerial Physical Interaction, Aerial Robotics, Bilateral Shared Control of Mobile Robots},
	attachments = {https://homepages.laas.fr/afranchi/robotics/sites/default/files/2015c-GioMohFraPra-preprint.pdf , https://homepages.laas.fr/afranchi/robotics/sites/default/files/2015c-GioMohFraPra.mp4},
	author = {Guido Gioioso and Mostafa Mohammadi and Antonio Franchi and Domenico Prattichizzo}
}
@conference {2015e-RajRylBueFra,
	title = {Modeling, Control and Design Optimization for a Fully-actuated Hexarotor Aerial Vehicle with Tilted Propellers},
	booktitle = {2015 IEEE Int. Conf. on Robotics and Automation},
	year = {2015},
	month = {05/2015},
	pages = {4006-4013},
	address = {Seattle, WA},
	keywords = {Aerial Robotics, UAV hardware platforms},
	attachments = {https://homepages.laas.fr/afranchi/robotics/sites/default/files/2015e-RajRylBueFra-preprint.pdf , https://homepages.laas.fr/afranchi/robotics/sites/default/files/2015e-RajRylBueFra.mp4},
	author = {Sujit Rajappa and Markus Ryll and Heinrich H. B{\"u}lthoff and Antonio Franchi}
}
@conference {2015j-TogFra,
	title = {Nonlinear Observer for the Control of Bi-Tethered Multi Aerial Robots},
	booktitle = {2015 IEEE/RSJ Int. Conf. on Intelligent Robots and Systems},
	year = {2015},
	month = {09/2015},
	pages = {1852-1857},
	address = {Hamburg, Germany},
	abstract = {We consider the problem of state-observation and control for a bi-tethered aerial system composed by a physical chain of two underactuated aerial robots, also called UAVs.  The controlled outputs are the Cartesian position of the last robot and the internal forces along the links. We aim at a minimal use of sensors in order to retrieve the full state. For this goal we propose an output transformation method whose applicability implies the system observability.  When this is the case we prove that it is possible to design a nonlinear state estimator based on the  high gain- and Luenberger-  observers that is able to retrieve the state from any dynamic condition. We also demonstrate how this estimator can be employed with a nonlinear controller for the Cartesian position and the link stresses while ensuring the stability in  closed-loop. We show the validity of the method for sensorial configurations composed only by two accelerometers (no gyros) and just two encoders, or two accelerometers (no gyros) and just two inclinometers. A realistic simulative validation concludes the paper.},
	keywords = {Aerial Physical Interaction, Aerial Robotics},
	attachments = {https://homepages.laas.fr/afranchi/robotics/sites/default/files/2015j-TogFra-preprint.pdf , https://homepages.laas.fr/afranchi/robotics/sites/default/files/2015j-TogFra.mp4},
	author = {Marco Tognon and Antonio Franchi}
}
@conference {2015a-TogFra,
	title = {Nonlinear Observer-based Tracking Control of Link Stress and Elevation for a Tethered Aerial Robot using Inertial-only Measurements},
	booktitle = {2015 IEEE Int. Conf. on Robotics and Automation},
	year = {2015},
	month = {05/2015},
	pages = {3994-3999},
	address = {Seattle, WA},
	attachments = {https://homepages.laas.fr/afranchi/robotics/sites/default/files/2015a-TogFra-preprint.pdf , https://homepages.laas.fr/afranchi/robotics/sites/default/files/2015a-TogFra.mp4},
	author = {Marco Tognon and Antonio Franchi}
}
@article {2014i-ZelRobBueFra,
	title = {Decentralized Rigidity Maintenance Control with Range Measurements for Multi-Robot Systems},
	journal = {The International Journal of Robotics Research},
	volume = {34},
	year = {2014},
	pages = {105-128},
	abstract = {This work proposes a fully decentralized strategy for maintaining the formation rigidity of a multi-robot system using only range measurements, while still allowing the graph topology to change freely over time. In this direction, a first contribution of this work is the new concept of weighted frameworks and rigidity, and of the rigidity eigenvalue, which when positive ensures the infinitesimal rigidity of a weighted framework. We then propose a distributed algorithm for estimating a common relative position reference frame amongst a team of robots with only range measurements in addition to one agent endowed with the capability of measuring the bearing to two other agents. This first estimation step is embedded into a subsequent distributed algorithm for estimating the rigidity eigenvalue associated with the weighted framework. The estimate of the rigidity eigenvalue is finally used to generate a local control action for each agent that both maintains the rigidity property and enforces additional constraints such as collision avoidance and sensing/communication range limits and occlusions. As an additional feature of our approach, the communication and sensing links among the robots are also left free to change over time while preserving rigidity of the whole framework. The proposed scheme is then experimentally validated with a robotic testbed consisting of 6 quadrotor UAVs operating in a cluttered environment.},
	keywords = {Motion control of multiple robots, Rigidity mainenance},
	attachments = {https://homepages.laas.fr/afranchi/robotics/sites/default/files/1309.0535v3.pdf , https://homepages.laas.fr/afranchi/robotics/sites/default/files/1309.0535v2.pdf},
	author = {Daniel Zelazo and Antonio Franchi and Heinrich H. B{\"u}lthoff and Paolo Robuffo Giordano}
}
@conference {2014k-FraPetRiz,
	title = {Distributed Estimation of the Inertial Parameters of an Unknown Load via Multi-Robot Manipulation},
	booktitle = {53rd IEEE Conference on Decision and Control},
	year = {2014},
	month = {12/2014},
	pages = {6111-6116},
	address = {Los Angeles, CA},
	abstract = {In this paper, we propose a distributed strategy for the estimation of the kinematic and inertial parameters of an unknown body manipulated by a team of mobile robots. We assume that each robot can measure its own velocity, as well as the contact forces exerted during the body manipulation, but neither the accelerations nor the positions of the contact points are directly accessible. Through kinematics and dynamics arguments, the relative positions of the contact points are estimated in a distributed fashion, and an observability condition is defined. Then, the inertial parameters (i.e., mass, relative position of the center of mass and moment of inertia) are estimated using distributed estimation filters and a nonlinear observer in cooperation with suitable control actions that ensure the observability of the parameters. Finally, we provide numerical simulations that corroborate our theoretical analysis.},
	attachments = {https://homepages.laas.fr/afranchi/robotics/sites/default/files/2014k-FraPetRiz-preprint.pdf},
	author = {Antonio Franchi and Antonio Petitti and Alessandro Rizzo}
}
@conference {2014a-GioFraSalSchPra,
	title = {The Flying Hand: a Formation of UAVs for Cooperative Aerial Tele-Manipulation},
	booktitle = {2014 IEEE Int. Conf. on Robotics and Automation},
	year = {2014},
	month = {05/2014},
	pages = {4335-4341},
	address = {Hong Kong, China},
	abstract = {The flying hand is a robotic hand consisting of a swarm of UAVs able to grasp an object where each UAV contributes to the grasping task with a single contact point at the tooltip. The swarm of robots is teleoperated by a human hand whose fingertip motions are tracked, e.g., using an RGB-D camera. We solve the kinematic dissimilarity of this unique master-slave system using a multi-layered approach that includes: a hand interpreter that translates the fingertip motion in a desired motion for the object to be manipulated; a mapping algorithm that transforms the desired object motions into a suitable set of virtual points deviating from the planned contact points; a compliant force control for the case of quadrotor UAVs that allows to use them as indirect 3D force effectors. Visual feedback is also used as sensory substitution technique to provide a hint on the internal forces exerted on the object. We validate the approach with several human-in-the-loop simulations including the full physical model of the object, contact points and UAVs.},
	keywords = {Aerial Physical Interaction, Aerial Robotics, Bilateral Shared Control of Mobile Robots, Motion control of multiple robots},
	attachments = {https://homepages.laas.fr/afranchi/robotics/sites/default/files/2014a-GioFraSalSchPra-preprint.pdf , https://homepages.laas.fr/afranchi/robotics/sites/default/files/2014a-GioFraSalSchPra.mp4},
	author = {Guido Gioioso and Antonio Franchi and Gionata Salvietti and Stefano Scheggi and Domenico Prattichizzo}
}
@booklet {2014l-GioSalFraMalSchMelRylBuePra,
	title = {The Flying Hand: a Teleoperation Framework for Cooperative Aerial Grasping and Transportation},
	howpublished = {Automatica.it 2014, Convegno Annuale dei Docenti e Ricercatori Italiani in Automatica},
	year = {2014},
	month = {09/2014},
	address = {Bergamo, Italy},
	keywords = {workshop},
	author = {Guido Gioioso and Gionata Salvietti and Antonio Franchi and Monica Malvezzi and Stefano Scheggi and L. Meli and Markus Ryll and Heinrich H. B{\"u}lthoff and Domenico Prattichizzo}
}
@conference {2014g-GagOriBueFra,
	title = {Image-based Road Network Clearing without Localization and without Maps using a Team of UAVs},
	booktitle = {2014 European Control Conference},
	year = {2014},
	month = {06/2014},
	pages = {1902-1908},
	address = {Strasbourg, France},
	abstract = {We address the problem of clearing an arbitrary and unknown network of roads using an organized team of Unmanned Aerial Vehicles (UAVs) equipped with a monocular down-facing camera, an altimeter, plus high-bandwidth short- range and low-bandwidth long-range communication systems. We allow the UAVs to possibly split in several subgroups. In each subgroup a leader guides the motion employing a hierarchical coordination. A feature/image-based algorithm guides the subgroup toward the unexplored region without any use of global localization or environmental mapping. At the same time all the entry-points of the the explored region are kept under control, so that any moving object that enters or exits the previously cleared area. Simulative results on real aerial images demonstrate the functionalities and the effectiveness of the proposed algorithm. },
	keywords = {Aerial Robotics, Exploration, Motion control of multiple robots, Patrolling / Surveillance, Pursuit-evasion / Clearing},
	attachments = {https://homepages.laas.fr/afranchi/robotics/sites/default/files/2014g-GagOriBueFra-preprint.pdf , https://homepages.laas.fr/afranchi/robotics/sites/default/files/2014g-GagOriBueFra-video.mp4},
	author = {Matteo Gagliardi and Giuseppe Oriolo and Heinrich H. B{\"u}lthoff and Antonio Franchi}
}
@conference {185,
	title = {Multi-Target Visual Tracking with UAVs},
	booktitle = {2014 IEEE/RSJ Int. Conf. on Intelligent Robots and Systems},
	year = {2014},
	month = {09/2014},
	pages = {656-661},
	address = {Chicago, IL},
	abstract = {We study the problem of tracking mobile targets using a team of aerial robots. Each robot carries a camera to detect targets moving on the ground. The overall goal is to plan for the trajectories of the robots in order to track the most number of targets, and accurately estimate the target locations using the images. The two objectives can conflict since a robot may fly to a higher altitude and potentially cover a larger number of targets at the expense of accuracy.
We start by showing that k >= 3 robots may not be able to track all n targets while maintaining a constant factor approximation of the optimal quality of tracking at all times. Next, we study the problem of choosing robot trajectories to maximize either the number of targets tracked or the quality of tracking. We formulate this problem as the weighted version of a combinatorial optimization problem known as the Maximum Group Coverage (MGC) problem. A greedy algorithm yields a 1/2 approximation for the weighted MGC problem. Finally, we evaluate the algorithm and the sensing model through simulations and preliminary experiments.},
	attachments = {https://homepages.laas.fr/afranchi/robotics/sites/default/files/2014j-TokIslFra-preprint.pdf},
	author = {Pratap Tokekar and Volkan Isler and Antonio Franchi}
}
@conference {184,
	title = {A Nonlinear Force Observer for Quadrotors and Application to Physical Interactive Tasks},
	booktitle = {IEEE/ASME International Conference on Advanced Intelligent Mechatronics},
	year = {2014},
	month = {07/2014},
	pages = {433-440},
	address = {Besan{\c c}on, France},
	abstract = {In order to properly control the physical interactive behavior of a flying vehicle, the information about the forces acting on the robot is very useful. Force/torque sensors can be exploited for measuring such information but their use increases the cost of the equipment, the weight to be carried by the robot and, consequently, it reduces the flying autonomy. Furthermore, a sensor can measure only the force/torque applied to the point it is mounted in. In order to overcome these limitations, in this paper we introduce a Lyapunov based nonlinear observer for estimating the external forces applied to a quadrotor. Furthermore, we show how to exploit the estimated force for shaping the interactive behavior of the quadrotor using Interconnection and Damping Assignment Passivity Based Controller (IDA-PBC). The results of the paper are validated by means of simulations.},
	attachments = {https://homepages.laas.fr/afranchi/robotics/sites/default/files/2014h-YueSecBueFra-preprint.pdf},
	author = {Burak Y{\"u}ksel and Cristian Secchi and Heinrich H. B{\"u}lthoff and Antonio Franchi}
}
@conference {2014d-YueSecBueFra,
	title = {Reshaping the Physical Properties of a Quadrotor through IDA-PBC and its Application to Aerial Physical Interaction},
	booktitle = {2014 IEEE Int. Conf. on Robotics and Automation},
	year = {2014},
	month = {05/2014},
	pages = {6258-6265},
	address = {Hong Kong, China},
	abstract = {In this paper we propose a controller, based on an extension of Interconnection and Damping Assignment Passivity Based Control (IDA-PBC) framework, for shaping the whole physical characteristics of a quadrotor and for obtaining a desired interactive behavior between the robot and the environment. In the control design, we shape the total energy (kinetic and potential) of the undamped original system by first excluding external effects. In this way we can assign a new dynamics to the system. Then we apply damping injection to the new system for achieving a desired damped behavior. Then we show how to connect a high-level control input to such system by taking advantage of the new desired physics. We support the theory with extensive simulations by changing the overall behavior of the UAV for different desired dynamics, and show the advantage of this method for sliding on a surface tasks, such as ceiling painting, cleaning or surface inspection.},
	keywords = {Aerial Physical Interaction, Aerial Robotics},
	attachments = {https://homepages.laas.fr/afranchi/robotics/sites/default/files/2014d-YueSecBueFra-preprint.pdf , https://homepages.laas.fr/afranchi/robotics/sites/default/files/2014d-YueSecBueFra.mp4},
	author = {Burak Y{\"u}ksel and Cristian Secchi and Heinrich H. B{\"u}lthoff and Antonio Franchi}
}
@conference {2014f-ZelFraRob,
	title = {Rigidity Theory in SE(2) for Unscaled Relative Position Estimation using only Bearing},
	booktitle = {2014 European Control Conference},
	year = {2014},
	month = {06/2014},
	pages = {2703-2708},
	address = {Strasbourg, France},
	abstract = {This work considers the problem of estimating the unscaled relative positions of a multi-robot team in a common reference frame from bearing-only measurements. Each robot has access to a relative bearing measurement taken from the local body frame of the robot, and the robots have no knowledge of a common reference frame. An extension of rigidity theory is made for frameworks embedded in the special Euclidean group SE(2) = R^2  {\texttimes} S1. We introduce definitions describing rigidity for SE(2) frameworks and provide necessary and sufficient conditions for when such a framework is infinitesimally rigid in SE(2). We then introduce the directed bearing rigidity matrix and show that an SE(2) framework is infinitesimally rigid if and only if the rank of this matrix is equal to 2|V| - 4, where |V| is the number of agents in the ensemble. The directed bearing rigidity matrix and its properties are then used in the implementation and convergence proof of a distributed estimator to determine the unscaled relative positions in a common frame. Simulation results are given to support the
analysis.},
	keywords = {Localization of ground robots, Motion control of multiple robots, Rigidity mainenance},
	attachments = {https://homepages.laas.fr/afranchi/robotics/sites/default/files/2014f-ZelFraRob-preprint.pdf},
	author = {Daniel Zelazo and Antonio Franchi and Paolo Robuffo Giordano}
}
@conference {2014c-MasRobBueFra,
	title = {Semi-autonomous Trajectory Generation for Mobile Robots with Integral Haptic Shared Control},
	booktitle = {2014 IEEE Int. Conf. on Robotics and Automation},
	year = {2014},
	month = {05/2014},
	pages = {6468-6475},
	address = {Hong Kong, China},
	abstract = {A new framework for semi-autonomous path plan- ning for mobile robots that extends the classical paradigm of bilateral shared control is presented. The path is represented as a B-spline and the human operator can modify its shape by controlling the motion of a finite number of control points. An autonomous algorithm corrects in real time the human directives in order to facilitate path tracking for the mobile robot and ensures i) collision avoidance, ii) path regularity, and iii) attraction to nearby points of interest. A haptic feedback algorithm processes both human{\textquoteright}s and autonomous control terms, and their integrals, to provide an information of the mismatch between the path specified by the operator and the one corrected by the autonomous algorithm. The framework is validated with extensive experiments using a quadrotor UAV and a human in the loop with two haptic interfaces.
},
	keywords = {Bilateral Shared Control of Mobile Robots},
	attachments = {https://homepages.laas.fr/afranchi/robotics/sites/default/files/2014c-MasRobBueFra-preprint.pdf , https://homepages.laas.fr/afranchi/robotics/sites/default/files/2014c-MasRobBueFra.mp4},
	author = {Carlo Masone and Paolo Robuffo Giordano and Heinrich H. B{\"u}lthoff and Antonio Franchi}
}
@conference {2014e-SteBasBueFra,
	title = {A Semi-autonomous UAV Platform for Indoor Remote Operation with Visual and Haptic Feedback},
	booktitle = {2014 IEEE Int. Conf. on Robotics and Automation},
	year = {2014},
	month = {05/2014},
	pages = {3862-3869},
	address = {Hong Kong, China},
	abstract = {We present the development of a semi-autonomous quadrotor UAV platform for indoor teleoperation using RGB- D technology as exteroceptive sensor. The platform integrates IMU and Dense Visual Odometry pose estimation in order to stabilize the UAV velocity and track the desired velocity commanded by a remote operator though an haptic inter- face. While being commanded, the quadrotor autonomously performs a persistent pan-scanning of the surrounding area in order to extend the intrinsically limited field of view. The RGB-D sensor is used also for collision-safe navigation using a probabilistically updated local obstacle map. In the operator visual feedback, pan-scanning movement is real time compensated by an IMU-based adaptive filtering algorithm that lets the operator perform the drive experience in a oscillation- free frame. An additional sensory channel for the operator is provided by the haptic feedback, which is based on the obstacle map and velocity tracking error in order to convey information about the environment and quadrotor state. The effectiveness of the platform is validated by means of experiments performed without the aid of any external positioning system.},
	keywords = {Aerial Robotics, Localization of aerial robots, UAV hardware platforms},
	attachments = {https://homepages.laas.fr/afranchi/robotics/sites/default/files/2014e-SteBasBueFra-preprint.pdf , https://homepages.laas.fr/afranchi/robotics/sites/default/files/2014e-SteBasBueFra.mp4},
	author = {Paolo Stegagno and Massimo Basile and Heinrich H. B{\"u}lthoff and Antonio Franchi}
}
@conference {2014b-GioRylPraBueFra,
	title = {Turning a Near-hovering Controlled Quadrotor into a 3D Force Effector},
	booktitle = {2014 IEEE Int. Conf. on Robotics and Automation},
	year = {2014},
	month = {05/2014},
	pages = {6278-6284},
	address = {Hong Kong, China},
	abstract = {In this paper the problem of a quadrotor that physically interacts with the surrounding environment through a rigid tool is considered. We present a theoretical design that allows to exert an arbitrary 3D force by using a standard near-hovering controller that was originally developed for contact-free flight control. This is achieved by analytically solving the nonlinear system that relates the quadrotor state, the force exerted by the rigid tool on the environment, and the near-hovering controller action at the equilibrium points, during any generic contact. Stability of the equilibria for the most relevant actions (pushing, releasing, lifting, dropping, and left-right shifting) are proven by means of numerical analysis using the indirect Lyapunov method. An experimental platform, including a suitable tool design, has been developed and used to validate the theory with preliminary experiments.},
	keywords = {Aerial Physical Interaction, Aerial Robotics, UAV hardware platforms},
	attachments = {https://homepages.laas.fr/afranchi/robotics/sites/default/files/2014b-GioRylPraBueFra-preprint.pdf , https://homepages.laas.fr/afranchi/robotics/sites/default/files/2014b-GioRylPraBueFra.mp4},
	author = {Guido Gioioso and Markus Ryll and Domenico Prattichizzo and Heinrich H. B{\"u}lthoff and Antonio Franchi}
}
@conference {2013d-SecFraBueRob,
	title = {Bilateral Control of the Degree of Connectivity in Multiple Mobile-robot Teleoperation},
	booktitle = {2013 IEEE Int. Conf. on Robotics and Automation},
	year = {2013},
	month = {05/2013},
	address = {Karlsruhe, Germany},
	abstract = {This paper presents a novel bilateral controller that allows to stably teleoperate the degree of connectivity in the mutual interaction between a remote group of mobile robots considered as the slave-side.
A distributed leader-follower scheme allows the human operator to command the overall group motion. The group autonomously maintains the connectivity of the interaction graph by using a decentralized gradient descent approach applied to the Fiedler eigenvalue of a properly weighted Laplacian matrix. 
The degree of connectivity, and then the flexibility, of the interaction graph can be finely tuned by the human operator through an additional bilateral teleoperation channel. Passivity of the overall system is theoretically proven and  extensive human/hardware in-the-loop simulations are presented to empirically validate the theoretical analysis.},
	keywords = {Bilateral Shared Control of Mobile Robots, Connectivity maintenance},
	attachments = {https://homepages.laas.fr/afranchi/robotics/sites/default/files/2013d-SecFraBueRob.pdf , https://homepages.laas.fr/afranchi/robotics/sites/default/files/2013d-SecFraBueRob.mp4},
	author = {Cristian Secchi and Antonio Franchi and Heinrich H. B{\"u}lthoff and Paolo Robuffo Giordano}
}
@conference {2013k-AntCatRobChiFra,
	title = {Experimental Validation of a New Adaptive Control for Quadrotors},
	booktitle = {2013 IEEE/RSJ Int. Conf. on Intelligent Robots and Systems},
	year = {2013},
	month = {11/2013},
	address = {Tokyo, Japan},
	keywords = {UAV hardware platforms},
	attachments = {https://homepages.laas.fr/afranchi/robotics/sites/default/files/2013k-AntCatRobChiFra-preprint.pdf},
	author = {Gianluca Antonelli and Elisabetta Cataldi and Paolo Robuffo Giordano and Stefano Chiaverini and Antonio Franchi}
}
@booklet {2013m-GioFraSalSchPra,
	title = {Hand Driven UAV Formation for Cooperative Grasping and Transportation: the Flying Hand},
	howpublished = {RSS 2013 Work. on Aerial Mobile Manipulation},
	year = {2013},
	month = {06/2013},
	address = {Berlin, Germany},
	keywords = {Aerial Physical Interaction, Motion control of multiple robots},
	author = {Guido Gioioso and Antonio Franchi and Gionata Salvietti and Stefano Scheggi and Domenico Prattichizzo}
}
@booklet {2013l-NesRobFra,
	title = {Human-assisted Parallel Multi-target Visiting in a Connected Topology},
	howpublished = {6th Int. Work. on Human-Friendly Robotics},
	year = {2013},
	month = {10/2012},
	address = {Rome, Italy},
	keywords = {Bilateral Shared Control of Mobile Robots, Connectivity maintenance, Motion control of multiple robots},
	author = {Thomas Nestmeyer and Paolo Robuffo Giordano and Antonio Franchi}
}
@article {2011q-SonFraChuKimBueRob,
	title = {Human-Centered Design and Evaluation of Haptic Cueing for Teleoperation of Multiple Mobile Robots},
	journal = {IEEE Transactions on Systems, Man, \& Cybernetics. Part B: Cybernetics},
	volume = {43},
	year = {2013},
	month = {04/2013},
	pages = {597-609},
	abstract = {In this paper, we investigate the effect of haptic cueing on human operator{\textquoteright}s performance in the field of bilateral teleoperation of multiple mobile robots, in particular multiple unmanned aerial vehicles (UAVs). Two aspects of human performance are deemed important in this area, namely the maneuverability of mobile robots and perceptual sensitivity of the remote environment. We introduce metrics that allow us to address these aspects in two psychophysical studies, which are reported here. Three fundamental haptic cue types were evaluated. The Force cue conveys information on the proximity of the commanded trajectory to obstacles in the remote environment. The Velocity cue represents the mismatch between the commanded and actual velocity of the UAVs and can implicitly provide a rich amount of information regarding the actual behavior of the UAVs. Finally, the Velocity+Force cue is a linear combination of the two.
Our experimental results show that while maneuverability is best supported by the Force cue feedback, perceptual sensitivity is best served by the Velocity cue feedback. In addition, we show that large gains in the haptic feedbacks do not always guarantee an enhancement in teleoperator{\textquoteright}s performance.},
	keywords = {Evaluation, Force feedback, Haptics, Multi-robot systems, Psychophysical evaluation of haptic feedback, Psychophysics, Teleoperation},
	attachments = {https://homepages.laas.fr/afranchi/robotics/sites/default/files/2013a-SonFraChuKimBueRob_1.pdf},
	author = {Hyoung Il Son and Antonio Franchi and Lewis L. Chuang and Junsuk Kim and Heinrich H. B{\"u}lthoff and Paolo Robuffo Giordano}
}
@booklet {2013h-NesRieLaeHarBotRobFra,
	title = {Interactive Demo: Haptic Remote Control of Multiple UAVs with Autonomous Cohesive Behavior},
	howpublished = {Int. Work. on Towards Fully Decentralized Multi-Robot Systems: Hardware, Software and Integration, at 2013 IEEE Int. Conf. on Robotics and Automation},
	year = {2013},
	month = {05/2013},
	address = {Karlsruhe, Germany},
	keywords = {Bilateral Shared Control of Mobile Robots, Connectivity maintenance, Middleware for robotics, UAV hardware platforms},
	url = {http://icra2013mrs.tuebingen.mpg.de/},
	author = {Thomas Nestmeyer and Martin Riedel and Johannes L{\"a}chele and Simon Hartmann and Fiete Botschen and Paolo Robuffo Giordano and Antonio Franchi}
}
@booklet {2012f-NesRobFra,
	title = {Multi-target Simultaneous Exploration with Continual Connectivity},
	howpublished = {2th Int. Work. on Crossing the Reality Gap - From Single to Multi- to Many Robot Systems, at 2013 IEEE Int. Conf. on Robotics and Automation},
	year = {2013},
	month = {05/2013},
	address = {Karlsruhe, Germany},
	keywords = {Connectivity maintenance, Exploration, Motion control of multiple robots},
	author = {Thomas Nestmeyer and Paolo Robuffo Giordano and Antonio Franchi}
}
@article {2013g-FraOriSte,
	title = {Mutual Localization in Multi-Robot Systems using Anonymous Relative Measurements},
	journal = {The International Journal of Robotics Research},
	volume = {32},
	year = {2013},
	month = {09/2013},
	pages = {1303-1322},
	abstract = {We propose a decentralized method to perform mutual localization in multi-robot systems using anonymous relative measurements, i.e., measurements that do not include the identity of the measured robot. This is a challenging and practically relevant operating scenario that has received little attention in the literature. Our mutual localization algorithm includes two main components: a probabilistic multiple registration stage, which provides all data associations that are consistent with the relative robot measurements and the current belief, and a dynamic filtering stage, which incorporates odometric data into the estimation process. The design of the proposed method proceeds from a detailed formal analysis of the implications of anonymity on the mutual localization problem. Experimental results on a team of differential-drive robots illustrate the effectiveness of the approach, and in particular its robustness against false positives and negatives that may affect the robot measurement process. We also provide an experimental comparison that shows how the proposed method outperforms more classical approaches that may be designed building on existing techniques. The source code of the proposed method is available within the MLAM ROS stack.},
	keywords = {Localization of ground robots},
	attachments = {https://homepages.laas.fr/afranchi/robotics/sites/default/files/2013g-FraOriSte.pdf , https://homepages.laas.fr/afranchi/robotics/sites/default/files/2013g-FraOriSte.mp4},
	author = {Antonio Franchi and Giuseppe Oriolo and Paolo Stegagno}
}
@conference {2013o-SpiRobRylBueFra,
	title = {An Open-Source Hardware/Software Architecture for Quadrotor UAVs},
	booktitle = {2nd IFAC Workshop on Research, Education and Development of Unmanned Aerial Systems},
	year = {2013},
	month = {11/2013},
	address = {Compiegne, France},
	abstract = {In this paper, we illustrate an open-source ready-to-use hardware/software architecture for a quadrotor UAV. The presented platform is price effective, highly customizable, and easily exploitable by other researchers involved in high-level UAV control tasks and for educational purposes as well. The use of object-oriented programming and full support of Robot Operating System (ROS) and Matlab Simulink allows for an efficient customization, code reuse, functionality expansion and rapid prototyping of new algorithms. We provide an extensive illustration of the various UAV components and a thorough description of the main basic algorithms and calibration procedures. Finally, we present some experimental case studies aimed at showing the effectiveness of the proposed architecture.},
	keywords = {Aerial Robotics, UAV hardware platforms},
	attachments = {https://homepages.laas.fr/afranchi/robotics/sites/default/files/2013o-SpiRobRylBueFra-preprint.pdf},
	author = {Riccardo Spica and Paolo Robuffo Giordano and Markus Ryll and Heinrich H. B{\"u}lthoff and Antonio Franchi}
}
@article {2013l-RobFraSecBue,
	title = {A Passivity-Based Decentralized Strategy for Generalized Connectivity Maintenance},
	journal = {The International Journal of Robotics Research},
	volume = {32},
	year = {2013},
	month = {03/2013},
	pages = { 299-323},
	abstract = {The design of decentralized controllers coping with the typical constraints on the inter-robot sensing/communication capabilities represents a promising direction in multi-robot research thanks to the inherent scalability and fault tolerance of these approaches. In these cases, connectivity of the underlying interaction graph plays a fundamental role: it represents a necessary condition for allowing a group or robots achieving a common task by resorting to only local information. Goal of this paper is to present a novel decentralized strategy able to enforce connectivity maintenance for a group of robots in a flexible way, that is, by granting large freedom to the group internal configuration so as to allow establishment/deletion of interaction links at anytime as long as global connectivity is preserved. A peculiar feature of our approach is that we are able to embed into a unique connectivity preserving action a large number of constraints and requirements for the group: (i) presence of specific inter-robot sensing/communication models, (ii) group requirements such as formation control, and (iii) individual requirements such as collision avoidance. This is achieved by defining a suitable global potential function of the second smallest eigenvalue λ2 of the graph Laplacian, and by computing, in a decentralized way, a gradient-like controller built on top of this potential. Simulation results obtained with a group of quadorotor UAVs and UGVs, and experimental results obtained with four quadrotor UAVs, are finally presented to thoroughly illustrate the features of our approach on a concrete case study.},
	keywords = {Bilateral Shared Control of Mobile Robots, Connectivity maintenance, Motion control of multiple robots},
	attachments = {https://homepages.laas.fr/afranchi/robotics/sites/default/files/2013l-RobFraSecBue-preprint.pdf , https://homepages.laas.fr/afranchi/robotics/sites/default/files/IJRRConn_MM_1_LQ.mp4},
	author = {Paolo Robuffo Giordano and Antonio Franchi and Cristian Secchi and Heinrich H. B{\"u}lthoff}
}
@conference {2013q-SteBasBueFra,
	title = {RGB-D based Haptic Teleoperation of UAVs with Onboard Sensors: Development and Preliminary Results},
	booktitle = {2013 IROS Work. on Vision-based Closed-Loop Control and Navigation of Micro Helicopters in GPS-denied Environments},
	year = {2013},
	month = {11/2013},
	address = {Tokyo, Japan},
	keywords = {Aerial Robotics, UAV hardware platforms},
	author = {Paolo Stegagno and Massimo Basile and Heinrich H. B{\"u}lthoff and Antonio Franchi}
}
@article {2013b-LeeFraSonBueRob,
	title = {Semi-Autonomous Haptic Teleoperation Control Architecture of Multiple Unmanned Aerial Vehicles},
	journal = {IEEE/ASME Transaction on Mechatronics, Focused Section on Aerospace Mechatronics},
	volume = {18},
	year = {2013},
	month = {08/2013},
	pages = {1334-1345},
	abstract = {We propose a novel semi-autonomous haptic teleoperation control architecture for multiple unmanned aerial vehicles (UAVs), consisting of three control layers: 1) UAV control layer, where each UAV is abstracted by, and is controlled to follow
the trajectory of, its own kinematic Cartesian virtual point (VP); 2) VP control layer, which modulates each VP{\textquoteright}s motion according to the teleoperation commands and local artificial potentials (for VP-VP/VP-obstacle collision avoidance and VP-VP connectivity preservation); and 3) teleoperation layer, through which a single remote human user can command all (or some) of the VPs{\textquoteright} velocity while haptically perceiving the state of all (or some) of the UAVs and obstacles. Master-passivity/slave-stability and some asymptotic performance measures are proved. Experimental results using four custom-built quadrotor-type UAVs are also presented to illustrate the theory.},
	keywords = {Bilateral Shared Control of Mobile Robots, Motion control of multiple robots, UAV hardware platforms},
	attachments = {https://homepages.laas.fr/afranchi/robotics/sites/default/files/2013b-LeeFraSonBueRob.pdf},
	author = {Dongjun Lee and Antonio Franchi and Hyoung Il Son and Heinrich H. B{\"u}lthoff and Paolo Robuffo Giordano}
}
@article {2013i-CenFraMarOri,
	title = {Simultaneous Calibration of Odometry  and Sensor Parameters for Mobile Robots},
	journal = {IEEE Transaction on Robotics},
	volume = {29},
	year = {2013},
	month = {04/2013},
	pages = {475-492},
	abstract = {Consider a differential-drive mobile robot equipped with an on-board exteroceptive sensor that can estimate its own motion, e.g., a range-finder. Calibration of this robot involves estimating six parameters: three for the odometry (radii and distance between the wheels), and three for the pose of the sensor with respect to the robot. After analyzing the observability of this problem, this paper describes a method for calibrating all parameters at the same time, without the need for external sensors or devices, using only the measurement of the wheels velocities and the data from the exteroceptive sensor. The method does not require the robot to move along particular trajectories. Simultaneous calibration is formulated as a maximum-likelihood problem and the solution is found in a closed form. Experimental results show that the accuracy of the proposed calibration method is very close to the attainable limit given by the Cram{\`e}r{\textendash}Rao bound.},
	keywords = {Calibration, Calibration of ground robots, Estimation},
	attachments = {https://homepages.laas.fr/afranchi/robotics/sites/default/files/2013i-CenFraMarOri.pdf},
	author = {Andrea Censi and Antonio Franchi and Luca Marchionni and Giuseppe Oriolo}
}
@booklet {2013i-LaeRieRobFra,
	title = {SwarmSimX and TeleKyb: Two ROS-integrated Software Frameworks for Single- and Multi-Robot Applications},
	howpublished = {Int. Work. on Towards Fully Decentralized Multi-Robot Systems: Hardware, Software and Integration, at 2013 IEEE Int. Conf. on Robotics and Automation},
	year = {2013},
	month = {05/2013},
	address = {Karlsruhe, Germany},
	keywords = {Middleware for robotics, Simulators for robotics},
	url = {http://icra2013mrs.tuebingen.mpg.de/},
	author = {Johannes L{\"a}chele and Martin Riedel and Paolo Robuffo Giordano and Antonio Franchi}
}
@conference {2013j-GraRieBueRobFra,
	title = {The TeleKyb Framework for a Modular and Extendible ROS-based Quadrotor Control},
	booktitle = {6th European Conference on Mobile Robots},
	year = {2013},
	month = {09/2013},
	address = {Barcelona, Spain},
	abstract = {The free and open source Tele-Operation Platform of the MPI for Biological Cybernetics (TeleKyb) is an end- to-end software framework for the development of bilateral teleoperation systems between human interfaces (e.g., haptic force feedback devices or gamepads) and groups of quadrotor Unmanned Aerial Vehicles (UAVs). Among drivers for devices and robots from various hardware manufactures, TeleKyb provides a high-level closed-loop robotic controller for mobile robots that can be extended dynamically with modules for state estimation, trajectory planning, processing, and tracking. Since all internal communication is based on the Robot Operating System (ROS), TeleKyb can be easily extended to meet future needs. The capabilities of the overall framework are demonstrated in both an experimental validation of the controller for an individual quadrotor and a complex experimental setup involving bilateral human-robot interaction and shared formation control of multiple UAVs.},
	keywords = {Middleware for robotics, UAV hardware platforms},
	url = {http://www.ros.org/wiki/telekyb},
	attachments = {https://homepages.laas.fr/afranchi/robotics/sites/default/files/2013j-GraRieBueRobFra-preprint.pdf},
	author = {Volker Grabe and Martin Riedel and Heinrich H. B{\"u}lthoff and Paolo Robuffo Giordano and Antonio Franchi}
}
@conference {2013r-Fra,
	title = {Towards Autonomous-collaborative and Haptic-tele-operated UAVs with Fully-onboard State Estimation and Physical Interaction Capabilities},
	booktitle = {2013 IROS Work. on From Remotely-Controlled to Autonomous-Collaborative Robots},
	year = {2013},
	month = {11/2013},
	address = {Tokyo, Japan},
	keywords = {Aerial Physical Interaction, Aerial Robotics, UAV hardware platforms},
	author = {Antonio Franchi}
}
@conference {2013p-SteBasBueFra,
	title = {Vision-based Autonomous Control of a Quadrotor UAV using an Onboard RGB-D Camera and its Application to Haptic Teleoperation},
	booktitle = {2nd IFAC Workshop on Research, Education and Development of Unmanned Aerial Systems},
	year = {2013},
	month = {11/2013},
	address = {Compiegne, France},
	keywords = {Aerial Robotics},
	attachments = {https://homepages.laas.fr/afranchi/robotics/sites/default/files/2013p-SteBasBueFra-preprint.pdf},
	author = {Paolo Stegagno and Massimo Basile and Heinrich H. B{\"u}lthoff and Antonio Franchi}
}
@conference {2012c-CogSteFraOriBue,
	title = {3D Mutual Localization with Anonymous Bearing Measurements},
	booktitle = {2012 IEEE Int. Conf. on Robotics and Automation},
	year = {2012},
	month = {05/2012},
	address = {St. Paul, MN},
	abstract = {We present a decentralized algorithm for estimating mutual 3-D poses in a group of mobile robots, such as a team of UAVs. Our algorithm uses bearing measurements reconstructed, e.g., by a visual sensor, and inertial measurements coming from the robot IMU. Since identification of a specific robot in a group would require visual tagging and may be cumbersome in practice, we simply assume that the bear- ing measurements are anonymous. The proposed localization method is a non-trivial extension of our previous algorithm for the 2-D case, and exhibits similar performance and robustness. An experimental validation of the algorithm has been performed using quadrotor UAVs.},
	keywords = {Distributed algorithms, Estimation, Localization, Localization of aerial robots, Multi-robot systems},
	attachments = {https://homepages.laas.fr/afranchi/robotics/sites/default/files/2012c-CogSteFraOriBue.pdf},
	author = {Marco Cognetti and Paolo Stegagno and Antonio Franchi and Giuseppe Oriolo and Heinrich H. B{\"u}lthoff}
}
@conference {2012j-SpiFraOriBueRob,
	title = {Aerial Grasping of a Moving Target with a Quadrotor UAV},
	booktitle = {2012 IEEE/RSJ Int. Conf. on Intelligent Robots and Systems},
	year = {2012},
	month = {10/2012},
	pages = {4985-4992},
	address = {Vilamoura, Portugal},
	abstract = {For a quadrotor aircraft, we study the problem of planning a trajectory that connects two arbitrary states while allowing the UAV to grasp a moving target at some intermediate time.
To this end, two classes of canonical grasping maneuvers are defined and characterized. A planning strategy relying on differential flatness is then proposed to concatenate one or more grasping maneuvers by means of spline-based subtrajectories, with the additional objective of minimizing the total transfer time.
The proposed planning algorithm is not restricted to pure hovering-to-hovering motions and takes into account practical constraints, such as the finite duration of the grasping phase. 
The effectiveness of the proposed approach is shown by means of physically-based simulations.},
	keywords = {Motion Planning, Optimal Trajectory Planning},
	attachments = {https://homepages.laas.fr/afranchi/robotics/sites/default/files/2012j-SpiFraOriBueRob.pdf , https://homepages.laas.fr/afranchi/robotics/sites/default/files/2012j-SpiFraOriBueRob.mp4},
	author = {Riccardo Spica and Antonio Franchi and Giuseppe Oriolo and Heinrich H. B{\"u}lthoff and Paolo Robuffo Giordano}
}
@conference {2012b-SecFraBueRob,
	title = {Bilateral Teleoperation of a Group of UAVs with Communication Delays and Switching Topology},
	booktitle = {2012 IEEE Int. Conf. on Robotics and Automation},
	year = {2012},
	month = {05/2012},
	address = {St. Paul, MN},
	abstract = {In this paper, we present a passivity-based decentralized approach for bilaterally teleoperating a group of UAVs composing the slave side of the teleoperation system. In particular, we explicitly consider the presence of time delays, both among the master and slave, and within UAVs composing the group. Our focus is on analyzing suitable (passive) strategies that allow a stable teloperation of the group despite presence of delays, while still ensuring high flexibility to the group topology (e.g., possibility to autonomously split or join during the motion). The performance and soundness of the approach is validated by means of human/hardware-in-the-loop simulations (HHIL).},
	keywords = {Bilateral Shared Control of Mobile Robots, Decentralized control, Distributed algorithms, Force feedback, Motion control of multiple robots, Multi-robot systems, Teleoperation},
	attachments = {https://homepages.laas.fr/afranchi/robotics/sites/default/files/2012d-SecFraBueRob.pdf , https://homepages.laas.fr/afranchi/robotics/sites/default/files/2012d-SecFraBueRob.mp4},
	author = {Cristian Secchi and Antonio Franchi and Heinrich H. B{\"u}lthoff and Paolo Robuffo Giordano}
}
@article {2012e-FraSecSonBueRob,
	title = {Bilateral Teleoperation of Groups of Mobile Robots with Time-Varying Topology},
	journal = {IEEE Transaction on Robotics},
	volume = {28},
	year = {2012},
	month = {10/2012},
	pages = {1019	-1033},
	abstract = {In this paper, a novel decentralized control strategy for bilaterally teleoperating heterogeneous groups of mobile robots from different domains (aerial, ground, marine and under- water) is proposed. By using a decentralized control architecture, the group of robots, treated as the slave-side, is made able to navigate in a cluttered environment while avoiding obstacles, inter-robot collisions and following the human motion commands. Simultaneously, the human operator acting on the master side is provided with a suitable force feedback informative of the group response and of the interaction with the surrounding environment. Using passivity based techniques, we allow the behavior of the group to be as flexible as possible with arbitrary split and join events (e.g., due to inter-robot visibility/packet losses or specific task requirements) while guaranteeing the stability of the system. We provide a rigorous analysis of the system stability and steady-state characteristics, and validate performance through human/hardware-in-the-tloop simulations by considering a heterogeneous fleet of UAVs and UGVs as case study. Finally, we also provide an experimental validation with 4 quadrotor UAV},
	keywords = {Bilateral Shared Control of Mobile Robots, Decentralized control, Distributed algorithms, Force feedback, Haptics, Motion control of multiple robots, Multi-robot systems, Teleoperation},
	attachments = {https://homepages.laas.fr/afranchi/robotics/sites/default/files/2012e-FraSecSonBueRob.pdf},
	author = {Antonio Franchi and Cristian Secchi and Hyoung Il Son and Heinrich H. B{\"u}lthoff and Paolo Robuffo Giordano}
}
@article {2010f-FraPasBul,
	title = {On Cooperative Patrolling: Optimal Trajectories, Complexity Analysis, and Approximation Algorithms},
	journal = {IEEE Transaction on Robotics},
	volume = {28},
	year = {2012},
	month = {06/2012},
	pages = {592-606},
	abstract = {The subject of this work is the patrolling of an environment with the aid of a team of autonomous agents. We consider both the design of open-loop trajectories with optimal properties, and of distributed control laws converging to optimal trajectories. As performance criteria, the refresh time and the latency are considered, i.e., respectively, time gap between any two visits of the same region, and the time necessary to inform every agent about an event occurred in the environment. We associate a graph with the environment, and we study separately the case of a chain, tree, and cyclic graph. For the case of chain graph, we first describe a minimum refresh time and latency team trajectory, and we propose a polynomial time algorithm for its computation. Then, we describe a distributed procedure that steers the robots toward an optimal trajectory. For the case of tree graph, a polynomial time algorithm is developed for the minimum refresh time problem, under the technical assumption of a constant number of robots involved in the patrolling task. Finally, we show that the design of a minimum refresh time trajectory for a cyclic graph is NP-hard, and we develop a constant factor approximation algorithm.},
	keywords = {Coverage, Distributed algorithms, Multi-robot systems, Patrolling / Surveillance},
	attachments = {https://homepages.laas.fr/afranchi/robotics/sites/default/files/2010f-FraPasBul-preprint.pdf},
	author = {Fabio Pasqualetti and Antonio Franchi and Francesco Bullo}
}
@conference {2012i-FraRob,
	title = {Decentralized Control of Parallel Rigid Formations with Direction Constraints and Bearing Measurements},
	booktitle = {51th IEEE Conference on Decision and Control },
	year = {2012},
	month = {12/2012},
	pages = {5310-5317},
	address = {Maui, HI},
	abstract = {In this paper we analyze the relationship between scalability, minimality and rigidity, and its application to cooperative control. As a case study, we address the problem of multi-agent formation control by proposing a distributed control strategy that stabilizes a formation described with bearing (direction) constraints, and that only requires bearing measurements and parallel rigidity of the interaction graph. We also consider the possibility of having different graphs modeling the interaction network in order to explicitly take into account the conceptual difference between sensing, communication, control, and parameters stored in the network. We then show how the information can be {\textquoteleft}moved{\textquoteright} from a graph to another making use of decentralized estimation, provided the parallel rigidity property. Finally we present simulative examples in order to show the validity of the theoretical analysis in some illustrative cases.},
	keywords = {Decentralized control, Distributed algorithms, Estimation, Formation control, Motion control of multiple robots, Multi-robot systems},
	attachments = {https://homepages.laas.fr/afranchi/robotics/sites/default/files/2012i-FraRob-preprint.pdf},
	author = {Antonio Franchi and Paolo Robuffo Giordano}
}
@article {2011c-DurFraBul,
	title = {Distributed Pursuit-Evasion without Mapping or Global Localization via Local Frontiers},
	journal = {Autonomous Robots},
	volume = {32},
	year = {2012},
	month = {01/2012},
	pages = {81-95},
	abstract = {This paper addresses a visibility-based pursuit-evasion problem in which a team of mobile robots with limited sensing and communication capabilities must coordinate to detect any evaders in an unknown, multiply-connected planar environment. Our distributed algorithm to guarantee evader detection is built around maintaining complete coverage of the frontier between cleared and contaminated regions while expanding the cleared region. We detail a novel distributed method for storing and updating this frontier without building a map of the environment or requiring global localization. We demonstrate the functionality of the algorithm through simulations in realistic environments and through hardware experiments. We also compare Monte Carlo results for our algorithm to the theoretical optimum area cleared as a function of the number of robots available.},
	keywords = {Coverage, Distributed algorithms, Multi-robot systems, Pursuit-evasion / Clearing},
	url = {http://www.springerlink.com/content/a02pr41790ll754w/},
	attachments = {https://homepages.laas.fr/afranchi/robotics/sites/default/files/2011c-DurFraBul-preprint.pdf , https://homepages.laas.fr/afranchi/robotics/sites/default/files/2011c-DurFraBul-video1.mp4},
	author = {Joseph W. Durham and Antonio Franchi and Francesco Bullo}
}
@conference {2012h-RieFraRobBueSon,
	title = {Experiments on Intercontinental Haptic Control of Multiple UAVs},
	booktitle = {12th Int. Conf. on Intelligent Autonomous Systems},
	year = {2012},
	month = {06/2012},
	pages = {227-238},
	address = {Jeju Island, Korea},
	abstract = {In this paper we propose and experimentally validate a bilateral teleoperation framework where a group of UAVs are controlled over an unreliable network with typical intercontinental time delays and packet losses. This setting is meant to represent a realistic and challenging situation for the stability the bilateral closed-loop system.
In order to increase human telepresence, the system provides the operator with both a video stream coming from the onboard cameras mounted on the UAVs, and with a suitable haptic cue, generated by a force-feedback device, informative of the UAV tracking performance and presence of impediments on the remote site.

In addition to the theoretical background, we describe the hardware and software implementation of this intercontinental teleoperation: this is composed of a semi-autonomous group of multiple quadrotor UAVs, a 3-DOF haptic interface, and a network connection based on a VPN tunnel between Germany and South Korea. The whole software framework is based upon the Robotic Operating System (ROS) communication standard.},
	keywords = {Bilateral Shared Control of Mobile Robots, Haptics, Middleware for robotics, Multi-robot systems, Teleoperation, UAV hardware platforms},
	attachments = {https://homepages.laas.fr/afranchi/robotics/sites/default/files/2012h-RieFraRobBueSon.pdf , https://homepages.laas.fr/afranchi/robotics/sites/default/files/2012h-RieFraRobBueSon.mp4},
	author = {Martin Riedel and Antonio Franchi and Heinrich H. B{\"u}lthoff and Paolo Robuffo Giordano and Hyoung Il Son}
}
@conference {2012k-MasFraBueRob,
	title = {Interactive Planning of Persistent Trajectories for Human-Assisted Navigation of Mobile Robots},
	booktitle = {2012 IEEE/RSJ Int. Conf. on Intelligent Robots and Systems},
	year = {2012},
	month = {10/2012},
	pages = {2641-2648},
	address = {Vilamoura, Portugal},
	abstract = {This work extends the framework of bilateral shared control of mobile robots with the aim of increasing the robot autonomy and decreasing the operator commitment. We consider persistent autonomous behaviors where a cyclic motion must be executed by the robot. The human operator is in charge of modifying online some geometric properties of the desired path. This is then autonomously processed by the robot in order to produce an actual path guaranteeing: i) tracking feasibility, ii) collision avoidance with obstacles, iii) closeness to the desired path set by the human operator, and iv) proximity to some points of interest. A force feedback is implemented to inform the human operator of the global deformation of the pathrather than using the classical mismatch between desired and executed motion commands. Physically-based simulations, with human/hardware-in-the-loop and a quadrotor UAV as robotic platform, demonstrate the feasibility of the method. },
	keywords = {Bilateral Shared Control of Mobile Robots, Force feedback, Haptics, Motion Planning, Optimal Trajectory Planning, Teleoperation},
	attachments = {https://homepages.laas.fr/afranchi/robotics/sites/default/files/2012k-MasFraBueRob.pdf , https://homepages.laas.fr/afranchi/robotics/sites/default/files/2012k-MasFraBueRob.mp4},
	author = {Carlo Masone and Antonio Franchi and Heinrich H. B{\"u}lthoff and Paolo Robuffo Giordano}
}
@booklet {2012q-RieFraBueRob,
	title = {Intercontinental Haptic Control and Advanced Supervisory Interfaces for Groups of Multiple UAVs},
	howpublished = {5th Int. Work. on Human-Friendly Robotics},
	year = {2012},
	month = {10/2012},
	address = {Bruxelles, Belgium},
	keywords = {Bilateral Shared Control of Mobile Robots, Middleware for robotics, Motion control of multiple robots, UAV hardware platforms},
	author = {Martin Riedel and Heinrich H. B{\"u}lthoff and Antonio Franchi and Paolo Robuffo Giordano}
}
@article {2012q-FraMasGraRylBueRob,
	title = {Modeling and Control of UAV Bearing-Formations with Bilateral High-Level Steering},
	journal = {The International Journal of Robotics Research, Special Issue on 3D Exploration, Mapping, and Surveillance},
	volume = {31},
	year = {2012},
	month = {10/2012},
	pages = {1504-1525},
	abstract = {In this paper we address the problem of controlling the motion of a group of UAVs bound to keep a formation defined in terms of only relative angles (i.e., a bearing-formation). This problem can naturally arise within the context of several multi-robot applications such as, e.g., exploration, coverage, and surveillance. First, we introduce and thoroughly analyze the concept and properties of bearing-formations, and provide a class of minimally linear sets of bearings sufficient to uniquely define such formations. We then propose a bearing-only formation controller requiring only bearing measurements, converging almost globally, and maintaining bounded inter-agent distances despite the lack of direct metric information. The controller still leaves the possibility to impose group motions tangent to the current bearing-formation. These can be either autonomously chosen by the robots because of any additional task (e.g., exploration), or exploited by an assisting human co-operator. For this latter {\textquoteleft}human-in-the-loop{\textquoteright} case, we propose a multi-master/multi-slave bilateral shared control system providing the co-operator with some suitable force cues informative of the UAV performance. The proposed theoretical framework is extensively validated by means of simulations
and experiments with quadrotor UAVs equipped with onboard cameras. Practical limitations, e.g., limited field-of-view, are also considered.},
	keywords = {Bilateral Shared Control of Mobile Robots, Decentralized control, Force feedback, Formation control, Haptics, Motion control of multiple robots, Multi-robot systems, Teleoperation},
	attachments = {https://homepages.laas.fr/afranchi/robotics/sites/default/files/2012q-FraMasGraRylBueRob-preprint.pdf},
	author = {Antonio Franchi and Carlo Masone and Volker Grabe and Markus Ryll and Heinrich H. B{\"u}lthoff and Paolo Robuffo Giordano}
}
@conference {2012g-ZelFraAlgBueRob,
	title = {Rigidity Maintenance Control for Multi-Robot Systems},
	booktitle = {2012 Robotics: Science and Systems Conference},
	year = {2012},
	month = {07/2012},
	address = {Sydney, Australia},
	abstract = {Rigidity of formations in multi-robot systems is important for formation control, localization, and sensor fusion.  This work proposes a rigidity maintenance gradient controller for a multi-agent robot team.  To develop such a controller, we first provide an alternative characterization of the rigidity matrix and use that to introduce the novel concept of the rigidity eigenvalue.  We provide a necessary and sufficient condition relating the positivity of the rigidity eigenvalue to the rigidity of the formation.  The rigidity maintenance controller is based on the gradient of the rigidity eigenvalue with respect to each robot position.  This gradient has a naturally distributed structure, and is thus amenable to a distributed implementation.  Additional requirements such as obstacle and inter-agent collision avoidance, as well as typical constraints such as limited sensing/communication ranges and line-of-sight occlusions, are also explicitly considered.  Finally, we present a simulation with a group of seven quadrotor UAVs to demonstrate and validate the theoretical results.},
	keywords = {Decentralized control, Formation control, Motion control of multiple robots, Multi-robot systems, Rigidity mainenance},
	attachments = {https://homepages.laas.fr/afranchi/robotics/sites/default/files/2012g-ZelFraAlgBueRob-preprint.pdf},
	author = {Daniel Zelazo and Antonio Franchi and Frank Allg{\"o}wer and Heinrich H. B{\"u}lthoff and Paolo Robuffo Giordano}
}
@article {2012f-FraSecRylBueRob,
	title = {Shared Control: Balancing Autonomy and Human Assistance with a Group of Quadrotor UAVs.},
	journal = {IEEE Robotics and Automation Magazine, Special Issue on Aerial Robotics and the Quadrotor Platform},
	volume = {19},
	year = {2012},
	month = {09/2012},
	pages = {57-68},
	abstract = {In this paper, we present a complete control framework and associated experimental testbed for the bilateral shared control of a group of quadrotor UAVs. This control architecture is applicable to any task and allows to integrate: i) a decentralized topological motion control (responsible for the mutual interactions in the UAV formation), ii) a human assistance module (allowing human intervention, whenever needed, on some aspects of the UAV group behavior), and iii) a force-feedback possibility (increasing the telepresence of the human assistants by providing suitable haptic cues informative of the UAV behavior). 
We will show, as worked-out case studies, how to specialize the topological motion controller to the relevant cases of constant, unconstrained and connected group topologies, and how to let a human operator intervening at the level of single UAVs or of the whole group dynamics.
A detailed description of the experimental testbed is also provided with emphasis on the quadrotor UAV hardware and software architectures. Finally, the versatility of the proposed framework is demonstrated by means of experiments with real UAVs. Although quadrotors are used as actual robotic platforms, the proposed framework can be straightforwardly extended to many different kinds of UAVs with similar motion characteristics.},
	keywords = {Bilateral Shared Control of Mobile Robots, Decentralized control, Force feedback, Formation control, Haptics, Middleware for robotics, Motion control of multiple robots, Multi-robot systems, UAV hardware platforms},
	attachments = {https://homepages.laas.fr/afranchi/robotics/sites/default/files/2012f-FraSecRylBueRob-preprint.pdf},
	author = {Antonio Franchi and Cristian Secchi and Markus Ryll and Heinrich H. B{\"u}lthoff and Paolo Robuffo Giordano}
}
@booklet {2012p-MasFraBueRob,
	title = {Shared Trajectory Planning for Human-in-the-loop Navigation of Mobile Robots in Cluttered Environments},
	howpublished = {5th Int. Work. on Human-Friendly Robotics},
	year = {2012},
	month = {10/2012},
	address = {Bruxelles, Belgium},
	keywords = {Bilateral Shared Control of Mobile Robots, Optimal Trajectory Planning},
	author = {Carlo Masone and Antonio Franchi and Heinrich H. B{\"u}lthoff and Paolo Robuffo Giordano}
}
@inbook {2012m-LaeFraBueRob,
	title = {SwarmSimX: Real-time Simulation Environment for Multi-robot Systems},
	booktitle = {3rd Int. Conf. on Simulation, Modeling, and Programming for Autonomous Robots},
	year = {2012},
	month = {11/2012},
	address = {Tsukuba, Japan},
	abstract = {In this paper we present a novel simulation environment called SwarmSimX with the ability to simulate dozens of robots in a realistic 3D environment. The software architecture of SwarmSimX allows new robots, sensors, and other libraries to be loaded at runtime, extending the functionality of the simulation environment significantly. In addition, SwarmSimX allows an easy exchange of the underlying libraries used for the visual and physical simulation to incorporate different libraries (e.g., improved or future versions). A major feature is also the possibility to perform the whole simulation in real-time allowing for human-in-the-loop or hardware-in-the-loop scenarios. SwarmSimX has been already employed in several works presenting haptic shared control of multiple mobile robots (e.g., quadrotor UAVs). Additionally, we present here two validation tests showing the physical delity and the real-time performance of SwarmSimX. For the tests we used NVIDIA PhysX and Ogre3D as physics and rendering libraries, respectively},
	keywords = {Multi-robot systems, Simulators for robotics},
	attachments = {https://homepages.laas.fr/afranchi/robotics/sites/default/files/2012m-LaeFraBueRob-preprint.pdf},
	author = {Johannes L{\"a}chele and Antonio Franchi and Heinrich H. B{\"u}lthoff and Paolo Robuffo Giordano}
}
@booklet {2012o-FraMasRob,
	title = {A Synergetic High-level/Reactive Planning Framework with Application to Human-Assisted Navigation},
	howpublished = {2012 IEEE IROS Work. on Real-time Motion Planning: Online, Reactive, and in Real-time},
	year = {2012},
	month = {10/2012},
	address = {Vilamoura, Portugal},
	keywords = {Bilateral Shared Control of Mobile Robots, Optimal Trajectory Planning},
	attachments = {https://homepages.laas.fr/afranchi/robotics/sites/default/files/2012o-FraMasRob-preprint.pdf},
	author = {Antonio Franchi and Carlo Masone and Paolo Robuffo Giordano}
}
@conference {2012l-CogSteFraOri,
	title = {Two Measurement Scenarios for Anonymous Mutual Localization in Multi-UAV Systems},
	booktitle = {2nd IFAC Workshop on Multivehicle Systems},
	year = {2012},
	month = {10/2012},
	address = {Espoo, Finland},
	keywords = {Estimation, Localization, Localization of aerial robots, Multi-robot systems},
	attachments = {https://homepages.laas.fr/afranchi/robotics/sites/default/files/2012l-CogSteFraOri-preprint.pdf},
	author = {Marco Cognetti and Paolo Stegagno and Antonio Franchi and Giuseppe Oriolo}
}
@conference {2011e-RobFraSecBue,
	title = {Bilateral Teleoperation of Groups of UAVs with Decentralized Connectivity Maintenance},
	booktitle = {2011 Robotics: Science and Systems Conference},
	year = {2011},
	month = {06/2011},
	address = {Los Angeles, CA},
	abstract = {In this paper, we present a decentralized passivity-based control strategy for the bilateral teleoperation of a fleet of Unmanned Aerial Vehicles (UAVs). The human operator at the master side can command the fleet motion and receive suitable force cues informative about the remote environment. By properly controlling the energy exchanged within the slave side (the UAV fleet), we guarantee that the connectivity of the fleet is preserved and we prevent inter-agent and obstacle collisions. At the same time, we allow the behavior of the UAVs to be as flexible as possible with arbitrary split and join maneuvers. The results of the paper are validated through semi-experiments.},
	keywords = {Bilateral Shared Control of Mobile Robots, Connectivity maintenance, Decentralized control, Distributed algorithms, Estimation, Force feedback, Haptics, Multi-robot systems, Teleoperation},
	attachments = {https://homepages.laas.fr/afranchi/robotics/sites/default/files/2011e-RobFraSecBue-preprint.pdf , https://homepages.laas.fr/afranchi/robotics/sites/default/files/2011e-RobFraSecBue-almost_preprint.pdf , https://homepages.laas.fr/afranchi/robotics/sites/default/files/2011e-RobFraSecBue.mp4},
	author = {Paolo Robuffo Giordano and Antonio Franchi and Cristian Secchi and Heinrich H. B{\"u}lthoff}
}
@conference {2011i-FraMasBueRob,
	title = {Bilateral Teleoperation of Multiple UAVs with Decentralized Bearing-only Formation Control},
	booktitle = {2011 IEEE/RSJ Int. Conf. on Intelligent Robots and Systems},
	year = {2011},
	month = {09/2011},
	pages = {2215-2222},
	address = {San Francisco, CA},
	abstract = {We present a decentralized system for the bilateral teleoperation of groups of UAVs which only relies
on relative bearing measurements, i.e., without the need of distance information or global localization. The properties of a 3D bearing-formation are analyzed, and a minimal set of bearings needed for its definition is provided. We also design a novel decentralized formation control almost globally convergent and able to maintain bounded and non-vanishing inter-distances among the agents despite the absence of direct distance measurements. Furthermore, we develop a multimaster/multi-slave teleoperation setup in order to control the overall behavior of the group and to convey to the human operator suitable force cues, while ensuring stability in presence of delays and packet losses over the master-slave communication channel. The theoretical framework is validated by means of extensive human/hardware in-the-loop simulations using two force-feedback devices and a group of quadrotors.},
	keywords = {Bilateral Shared Control of Mobile Robots, Decentralized control, Force feedback, Formation control, Haptics, Motion control of multiple robots, Multi-robot systems, Teleoperation},
	attachments = {https://homepages.laas.fr/afranchi/robotics/sites/default/files/2011i-FraMasBueRob-preprint.pdf , https://homepages.laas.fr/afranchi/robotics/sites/default/files/2011i-FraMasBueRob.mp4},
	author = {Antonio Franchi and Carlo Masone and Heinrich H. B{\"u}lthoff and Paolo Robuffo Giordano}
}
@booklet {2011o-Fra,
	title = {Decentralized Bilateral Aerial Teleoperation of Multiple UAVs - Part I: a Top-Down Perspective},
	howpublished = {RSS 2011 Workshop on 3D Exploration, Mapping, and Surveillance with Aerial Robots},
	year = {2011},
	month = {06/2011},
	address = {Los Angeles, CA},
	keywords = {Bilateral Shared Control of Mobile Robots, Decentralized control, Force feedback, Formation control, Haptics, Multi-robot systems, Teleoperation},
	author = {Antonio Franchi}
}
@conference {2011g-FraBueRob,
	title = {Distributed Online Leader Selection in the Bilateral Teleoperation of Multiple UAVs},
	booktitle = {50th IEEE Conference on Decision and Control },
	year = {2011},
	month = {12/2011},
	pages = {3559-3565},
	address = {Orlando, FL},
	abstract = {For several applications like data collection, surveillance, search and rescue and exploration of wide areas, the use of a group of simple robots rather than a single complex robot has proven to be very effective and promising, and the problem of coordinating a group of agents has received a lot of attention over the last years. In this paper, we consider the challenge of establishing a bilateral force-feedback teleoperation channel between a human operator (the master side) and a remote multi-robot system (the slave side) where a special agent, the leader, is selected and directly controlled by the master. In particular, we study the problem of distributed online optimal leader selection, i.e., how to choose, and possibly change, the leader online in order to maximize some suitable criteria related to the tracking performance of the whole group w.r.t. the master commands. Human/hardware-in-the-loop simulation results with a group of UAVs support the theoretical claims of the paper.},
	keywords = {Decentralized control, Distributed algorithms, Force feedback, Haptics, Leader selection, Multi-robot systems, Teleoperation},
	attachments = {https://homepages.laas.fr/afranchi/robotics/sites/default/files/2011g-FraBueRob-preprint.pdf},
	author = {Antonio Franchi and Heinrich H. B{\"u}lthoff and Paolo Robuffo Giordano}
}
@conference {2011d-SonKimChuFraRobLeeBue,
	title = {An Evaluation of Haptic Cues on the Tele-Operator{\textquoteright}s Perceptual  Awareness of Multiple UAVs{\textquoteright} Environments},
	booktitle = { IEEE  World Haptics Conference},
	year = {2011},
	month = {06/2011},
	pages = {149-154},
	address = {Istanbul, Turkey},
	abstract = {The use of multiple unmanned aerial vehicles (UAVs) is increasingly being incorporated into a wide range of teleoperation applications. To date, relevant research has largely been focused on the development of appropriate control schemes. In this paper, we extend previous research by investigating how control performance could be improved by providing the teleoperator with haptic feedback cues. First, we describe a control scheme that allows a teleoperator to manipulate the flight of multiple UAVs in a remote environment. Next, we present three designs of haptic cue feedback that could increase the teleoperator{\textquoteright}s environmental awareness of such a remote environment. These cues are based on the UAVs{\textquoteright} i) velocity information, ii) proximity to obstacles, and iii) a combination of these two sources of information. Finally, we present an experimental evaluation of these haptic cue designs. Our evaluation is based on the teleoperator{\textquoteright}s perceptual sensitivity to the physical environment inhabited by the multiple UAVs. We conclude that a teleoperator{\textquoteright}s perceptual sensitivity is best served by haptic feedback cues that are based on the velocity information of multiple UAVs.},
	keywords = {Evaluation, Force feedback, Haptics, Multi-robot systems, Psychophysics, Teleoperation},
	attachments = {https://homepages.laas.fr/afranchi/robotics/sites/default/files/2011d-SonKimChuFraRobLeeBue-preprint.pdf},
	author = {Hyoung Il Son and Junsuk Kim and Lewis L. Chuang and Antonio Franchi and Paolo Robuffo Giordano and Dongjun Lee and Heinrich H. B{\"u}lthoff}
}
@conference {2011k-RobFraSecBue,
	title = {Experiments of Passivity-Based Bilateral Aerial Teleoperation of a Group of UAVs with Decentralized Velocity Synchronization},
	booktitle = {2011 IEEE/RSJ Int. Conf. on Intelligent Robots and Systems},
	year = {2011},
	month = {09/2011},
	pages = {163-170},
	address = {San Francisco, CA},
	abstract = {In this paper, we present an experimental validation of a novel decentralized passivity-based control strategy for teleoperating a group of Unmanned Aerial Vehicles (UAVs): the slave side, consisting of the UAVs, is endowed with large group autonomy by allowing time-varying topology and interrobot/obstacle collision avoidance. The master side, represented by a human operator, controls the group motion and receives suitable force feedback cues informing her/him about the remote slave motion status. Passivity theory is exploited for guaranteeing stability of the slave side and of the overall teleoperation channel. Results of experiments involving the use of 4 quadcopters are reported and discussed, confirming the soundness of the paper theoretical claims.},
	keywords = {Bilateral Shared Control of Mobile Robots, Decentralized control, Distributed algorithms, Force feedback, Haptics, Motion control of multiple robots, Multi-robot systems, Teleoperation},
	attachments = {https://homepages.laas.fr/afranchi/robotics/sites/default/files/2011k-RobFraSecBue-preprint.pdf , https://homepages.laas.fr/afranchi/robotics/sites/default/files/2011k-RobFraSecBue.mp4},
	author = {Paolo Robuffo Giordano and Antonio Franchi and Cristian Secchi and Heinrich H. B{\"u}lthoff}
}
@conference {2011b-LeeFraRobSonBue,
	title = {Haptic Teleoperation of Multiple Unmanned Aerial Vehicles over the Internet},
	booktitle = { 2011 IEEE Int. Conf. on Robotics and Automation},
	year = {2011},
	month = {05/2011},
	pages = {1341-1347},
	address = {Shanghai, China},
	abstract = {We propose a novel haptic teleoperation control framework for multiple unmanned aerial vehicles (UAVs) over the Internet, consisting of the three control layers: 1) UAV control layer, where each UAV is abstracted by, and is controlled to follow the trajectory of, its own kinematic virtual point (VP); 2) VP control layer, which modulates each VP{\textquoteright}s motion according to the teleoperation commands and local artificial potentials (for inter-VP/VP-obstacle collision avoidance and inter-VP connectivity preservation); and 3) teleoperation layer, through which a remote human user can command all (or some) of the VPs{\textquoteright} velocity while haptically perceiving the state of all (or some) of the UAVs over the Internet.
Master-passivity/slave-stability and some asymptotic performance measures are proved. Semi-experiment results are presented to validate the theory.},
	keywords = {Bilateral Shared Control of Mobile Robots, Decentralized control, Force feedback, Formation control, Haptics, Multi-robot systems, Teleoperation},
	attachments = {https://homepages.laas.fr/afranchi/robotics/sites/default/files/2011b-LeeFraRobSonBue-preprint.pdf , https://homepages.laas.fr/afranchi/robotics/sites/default/files/2011b-LeeFraRobSonBue-low_qlty.mp4},
	author = {Dongjun Lee and Antonio Franchi and Paolo Robuffo Giordano and Hyoung Il Son and Heinrich H. B{\"u}lthoff}
}
@conference {2011h-SonChuFraKimLeeLeeBueRob,
	title = {Measuring an Operator{\textquoteright}s Maneuverability Performance in the Haptic Teleoperation of Multiple Robots},
	booktitle = {2011 IEEE/RSJ Int. Conf. on Intelligent Robots and Systems},
	year = {2011},
	month = {09/2011},
	pages = {3039-3046},
	address = {San Francisco, CA},
	abstract = {In this paper, we investigate the maneuverability performance of human teleoperators on multi-robots. First, we propose that maneuverability performance can be assessed by a frequency response function that jointly considers the input force of the operator and the position errors of the multi-robot system that is being maneuvered. Doing so allows us to evaluate maneuverability performance in terms of the human teleoperator{\textquoteright}s interaction with the controlled system. This allowed us to effectively determine the suitability of different haptic cue algorithms in improving teleoperation maneuverability. Performance metrics based on the human teleoperator{\textquoteright}s frequency response function indicate that maneuverability performance is best supported by a haptic feedback algorithm which is based on an obstacle avoidance force.},
	keywords = {Evaluation, Force feedback, Haptics, Multi-robot systems, Psychophysics, Teleoperation},
	attachments = {https://homepages.laas.fr/afranchi/robotics/sites/default/files/2011h-SonChuFraKimLeeLeeBueRob-preprint.pdf},
	author = {Hyoung Il Son and Lewis L. Chuang and Antonio Franchi and Junsuk Kim and Dongjun Lee and Seong-Whan Lee and Heinrich H. B{\"u}lthoff and Paolo Robuffo Giordano}
}
@conference {2011m-SteCogFraOri,
	title = {Mutual Localization using Anonymous Bearing Measurements},
	booktitle = {2011 IEEE/RSJ Int. Conf. on Intelligent Robots and Systems},
	year = {2011},
	month = {09/2011},
	pages = {469-474},
	address = {San Francisco, CA},
	abstract = {This paper addresses the problem of mutual localization in multi-robot systems in presence of anonymous (i.e., without the identity information) bearing-only measurements. The solution of this problem is relevant for the design and implementation of any decentralized multi-robot algorithm/control. A novel algorithm for probabilistic multiple registration of these measurements is presented, where no global localization, distances, or identity are used. With respect to more conventional solutions that could be conceived on the basis of the current literature, our method is theoretically suitable for tasks requiring frequent, many-to-many encounters among agents (e.g., formation control, cooperative exploration, multiple-view environment sensing). An extensive experimental study validates our method and compares it with the fullinformative case of bearing plus-distance measurements. The results show that the proposed localization system exhibits an accuracy commensurate to our previous method [1] which uses bearing-plus-distance information.},
	keywords = {Distributed algorithms, Estimation, Localization, Multi-robot systems},
	attachments = {https://homepages.laas.fr/afranchi/robotics/sites/default/files/2011m-SteCogFraOri-preprint.pdf , https://homepages.laas.fr/afranchi/robotics/sites/default/files/2011m-SteCogFraOri.mp4},
	author = {Paolo Stegagno and Marco Cognetti and Antonio Franchi and Giuseppe Oriolo}
}
@conference {2011a-FraRobSecSonBue,
	title = {A Passivity-Based Decentralized Approach for the Bilateral Teleoperation of a Group of UAVs with Switching Topology},
	booktitle = {2011 IEEE Int. Conf. on Robotics and Automation},
	year = {2011},
	month = {05/2011},
	pages = {898-905},
	address = {Shanghai, China},
	abstract = {In this paper, a novel distributed control strategy for teleoperating a fleet of Unmanned Aerial Vehicles (UAVs) is proposed. Using passivity based techniques, we allow the behavior of the UAVs to be as flexible as possible with arbitrary split and join decisions while guaranteeing stability of the system. Furthermore, the overall teleoperation system is also made passive and, therefore, characterized by a stable behavior both in free motion and when interacting with unknown {passive} obstacles. The performance of the system is validated through semi-experiments.},
	keywords = {Bilateral Shared Control of Mobile Robots, Decentralized control, Distributed algorithms, Force feedback, Haptics, Motion control of multiple robots, Multi-robot systems, Teleoperation},
	attachments = {https://homepages.laas.fr/afranchi/robotics/sites/default/files/2011a-FraRobSecSonBue-preprint.pdf , https://homepages.laas.fr/afranchi/robotics/sites/default/files/2011a-FraRobSecSonBue-low_qlty.mp4},
	author = {Antonio Franchi and Paolo Robuffo Giordano and Cristian Secchi and Hyoung Il Son and Heinrich H. B{\"u}lthoff}
}
@conference {2010b-DurFraBul,
	title = {Distributed Pursuit-Evasion with Limited-Visibility Sensor Via Frontier-based Exploration},
	booktitle = {2010 IEEE Int. Conf. on Robotics and Automation},
	year = {2010},
	month = {05/2010},
	pages = {3562-3568},
	address = {Anchorage, AK},
	abstract = {This paper addresses a novel visibility-based pursuit-evasion problem in which a team of searchers with limited range sensors must coordinate to clear any evaders from an unknown planar environment. We present a distributed algorithm built around guaranteeing complete coverage of the frontier between cleared and contaminated areas while expanding the cleared area. Our frontier-based algorithm can guarantee detection of evaders in unknown, multiply-connected planar environments which may be non-polygonal. We also detail a method for storing and updating the global frontier between cleared and contaminated areas without building a global map or requiring global localization, which enables our algorithm to be truly distributed. We demonstrate the functionality of the algorithm through Player/Stage simulations. },
	keywords = {Coverage, Distributed algorithms, Multi-robot systems, Pursuit-evasion / Clearing},
	attachments = {https://homepages.laas.fr/afranchi/robotics/sites/default/files/2010b-DurFraBul.pdf , https://homepages.laas.fr/afranchi/robotics/sites/default/files/ICRA10-FinalSub.mp4},
	author = {Joseph W. Durham and Antonio Franchi and Francesco Bullo}
}
@conference {2010c-FraSteDirOri,
	title = {Distributed Target Localization and Encirclement with a Multi-robot System},
	booktitle = {7th IFAC Symposium on Intelligent Autonomous Vehicles},
	year = {2010},
	month = {09/2010},
	address = {Lecce, Italy},
	abstract = {This paper presents a control scheme for localizing and encircling a target using a multi-robot system. The task is achieved in a distributed way, in that each robot only uses local information gathered by on-board relative-position sensors assumed to be noisy, anisotropic, and unable to detect the identity of the measured object. Communication between the robots is provided by limited-range transceivers.  Experimental results with stationary and Multi-robot systems, distributed control, mutual localization, encirclement.moving targets support the theoretical analysis.  
},
	keywords = {Decentralized control, Distributed algorithms, Estimation, Formation control, Multi-robot systems},
	attachments = {https://homepages.laas.fr/afranchi/robotics/sites/default/files/2010c-FraSteDirOri-preprint.pdf},
	author = {Antonio Franchi and Paolo Stegagno and Maurizio Di~Rocco and Giuseppe Oriolo}
}
@conference {2010e-PasFraBul,
	title = {On Optimal Cooperative Patrolling},
	booktitle = {49th IEEE Conference on Decision and Control},
	year = {2010},
	month = {12/2010},
	pages = {7153-7158},
	address = {Atlanta, GA, USA},
	abstract = {This work considers the problem of designing optimal multi-agent trajectories to patrol an environment. As performance criterion for optimal patrolling we consider the worst-case time gap between any two visits of the same region. We represent the area to be patrolled with a graph, and we characterize the computational complexity of the trajectory design (patrolling) problem with respect to the environment topology and to the number of robots employed in the patrolling task. Even though the patrolling problem is generally NP-hard, we identify particular cases that are solvable efficiently, and we describe optimal patrolling trajectories. Finally, we present a heuristic with performance guarantees, and an 8-approximation algorithm to solve the NP-hard patrolling problem.},
	keywords = {Coverage, Distributed algorithms, Multi-robot systems, Patrolling / Surveillance},
	attachments = {https://homepages.laas.fr/afranchi/robotics/sites/default/files/2010e-PasFraBul-preprint.pdf , https://homepages.laas.fr/afranchi/robotics/sites/default/files/2010e-PasFraBul.pdf},
	author = {Fabio Pasqualetti and Antonio Franchi and Francesco Bullo}
}
@conference {2010d-FraOriSte,
	title = {Probabilistic Mutual Localization in Multi-agent Systems from Anonymous Position Measures},
	booktitle = {49th IEEE Conference on Decision and Control},
	year = {2010},
	month = {12/2010},
	pages = {6534-6540},
	address = {Atlanta, GA, USA},
	abstract = {Recent research on multi-agent systems has produced a plethora of decentralized controllers that implicitly assume various degrees of agent localization. However, many practical arrangements commonly taken to allow and achieve localization imply some form of centralization, from the use of physical tagging to allow the identification of the single agent to the adoption of global positioning systems based on cameras or GPS.
These devices clearly decrease the system autonomy and range of applicability, and should be avoided if possible. Following this guideline, this work addresses the mutual localization problem with anonymous relative position measures, presenting a robust solution based on a probabilistic framework. The proposed localization system exhibits higher accuracy and lower complexity ($O(n^2)$) than our previous method~[bib]2009c-FraOriSte[/bib].  Moreover, with respect to more conventional solutions that could be conceived on the basis of the current literature, our method is theoretically suitable for tasks requiring frequent, many-to-many encounters among agents (e.g., formation control, cooperative exploration, multiple-view environment sensing).  The proposed localization system has been validated by means of an extensive experimental study},
	keywords = {Distributed algorithms, Estimation, Localization, Multi-robot systems},
	attachments = {https://homepages.laas.fr/afranchi/robotics/sites/default/files/2010d-FraOriSte-preprint.pdf , https://homepages.laas.fr/afranchi/robotics/sites/default/files/2010d-FraOriSte.pdf},
	author = {Antonio Franchi and Giuseppe Oriolo and Paolo Stegagno}
}
@conference {2010a-FraOriSte,
	title = {On the Solvability of the Mutual Localization Problem with Anonymous Position Measures},
	booktitle = {2010 IEEE Int. Conf. on Robotics and Automation},
	year = {2010},
	month = {05/2010},
	pages = {3193-3199},
	address = {Anchorage, AK},
	abstract = {This paper formulates and investigates a novel problem called Mutual Localization with Anonymous Position Measures. This is an extension of Mutual Localization with Position Measures, with the additional assumption that the identities of the measured robots are not known. A necessary and sufficient condition for the uniqueness of the solution is presented, which requires O(n^2/\log n) to be verified and is based on the notion of rotational symmetry in R^2. We also derive the relationship between the number of robots and the number of possible solutions, and classify the solutions in a number of equivalence classes which is linear in n. A control law is finally proposed that effectively breaks symmetric formations so as to guarantee unique solvability of the problem is also proposed; its performance is illustrated through simulations.},
	keywords = {Estimation, Formation control, Localization, Multi-robot systems},
	attachments = {https://homepages.laas.fr/afranchi/robotics/sites/default/files/2010a-FraOriSte.pdf , https://homepages.laas.fr/afranchi/robotics/sites/default/files/ICRA10-Final.mp4},
	author = {Antonio Franchi and Giuseppe Oriolo and Paolo Stegagno}
}
@booklet {2010d-RobFraSonSecLeeBue,
	title = {Towards Bilateral Teleoperation of Multi-Robot Systems},
	howpublished = {3rd Int. Work. on Human-Friendly Robotics},
	year = {2010},
	month = {10/2010},
	address = {Tuebingen, Germany},
	keywords = {Bilateral Shared Control of Mobile Robots, Decentralized control, Distributed algorithms, Force feedback, Haptics, Multi-robot systems, Teleoperation},
	author = {Paolo Robuffo Giordano and Antonio Franchi and Hyoung Il Son and Cristian Secchi and Dongjun Lee and Heinrich H. B{\"u}lthoff}
}
@mastersthesis {60,
	title = {Decentralized Methods for Cooperative Task  Execution in Multi-robot Systems},
	year = {2009},
	month = {12/2009},
	school = {"La Sapienza" University of Rome},
	type = {PhD},
	keywords = {Coverage, Decentralized control, Distributed algorithms, Estimation, Exploration, Formation control, Localization of ground robots, Middleware for robotics, Motion control of multiple robots, Multi-robot systems, Patrolling / Surveillance, Pursuit-evasion / Clearing},
	attachments = {https://homepages.laas.fr/afranchi/robotics/sites/default/files/2009-Franchi_PhDThesis.pdf},
	author = {Antonio Franchi}
}
@article {2009a-FraOriSte,
	title = {Mutual Localization in a Multi-Robot System with Anonymous Relative Position Measures},
	year = {2009},
	month = {01/2009},
	institution = {Department of Computer and System Sciences Antonio Ruberti},
	abstract = {In this paper we formulate and solve the mutual localization problem for a multi-robot system under the assumption of anonymous relative position measures. The anonymity hypothesis can cause a combinatorial ambiguity in the inversion of the measure equation giving more than one possible solution to the problem. We propose MultiReg, an innovative algorithm aimed at obtaining sets ofpossible relative pose hypotheses, whose output is processed by a data associator and a multiple EKF to select the best hypothesis. We study the performance of the developed localization system using both simulations and real robot experiments.},
	keywords = {Distributed algorithms, Estimation, Localization, Multi-robot systems},
	attachments = {https://homepages.laas.fr/afranchi/robotics/sites/default/files/2009a-FraOriSte.pdf},
	author = {Antonio Franchi and Giuseppe Oriolo and Paolo Stegagno}
}
@conference {2009c-FraOriSte,
	title = {Mutual Localization in a Multi-Robot System with Anonymous Relative Position Measures},
	booktitle = {2009 IEEE/RSJ Int. Conf. on Intelligent Robots and Systems},
	year = {2009},
	month = {11/2009},
	pages = {3974-3980},
	address = {St. Louis, MO},
	abstract = {We address the mutual localization problem for a multi-robot system, under the assumption that each robot is equipped with a sensor that provides a measure of the relative position of nearby robots without their identity. Anonymity generates a combinatorial ambiguity in the inversion of the measure equations, leading to a multiplicity of admissible relative pose hypotheses. To solve the problem, we propose a two-stage localization system based on MultiReg, an innovative algorithm that computes on-line all the possible relative pose hypotheses, whose output is processed by a data associator and a multiple EKF to isolate and refine the best estimates. The performance of the mutual localization system is analyzed through experiments, proving the effectiveness of the method and, in particular, its robustness with respect to false positives (objects that look like robots) and false negatives (robots that are not detected) of the measure process.},
	keywords = {Distributed algorithms, Estimation, Localization, Multi-robot systems},
	attachments = {https://homepages.laas.fr/afranchi/robotics/sites/default/files/2009c-FraOriSte.pdf , https://homepages.laas.fr/afranchi/robotics/sites/default/files/IROS09_MutualLoc.mp4},
	author = {Antonio Franchi and Giuseppe Oriolo and Paolo Stegagno}
}
@article {2009b-FraFreOriVen,
	title = {The Sensor-based Random Graph Method for Cooperative Robot Exploration},
	journal = {IEEE/ASME Transaction on Mechatronics},
	volume = {14},
	number = {2},
	year = {2009},
	note = {Winner of the IEEE RAS ICYA Best Paper Award 2010 <a href="http://homepages.laas.fr/afranchi//robotics/?q=node/64">link</a></p>},
	month = {04/2009},
	pages = {163-175},
	abstract = {We present a decentralized cooperative exploration strategy for a team of mobile robots equipped with range finders. A roadmap of the explored area, with the associate safe region, is built in the form of a Sensor-based Random Graph (SRG). This is expanded by the robots by using a randomized local planner which automatically realizes a trade-off between information gain and navigation cost. The nodes of the SRG represent view configurations that have been visited by at least one robot, and are connected by arcs that represent safe paths. These paths have been actually traveled by the robots or added to the SRG to improve its connectivity. Decentralized cooperation and coordination mechanisms are used so as to guarantee exploration efficiency and avoid conflicts. Simulations and experiments are presented to show the performance of the proposed technique.},
	keywords = {Coverage, Distributed algorithms, Exploration, Multi-robot systems},
	attachments = {https://homepages.laas.fr/afranchi/robotics/sites/default/files/2009b-FraFreOriVen.pdf},
	author = {Antonio Franchi and Luigi Freda and Giuseppe Oriolo and Marilena Vendittelli}
}
@conference {2008a-FraFreMarOriVen,
	title = {Decentralized cooperative exploration: Implementation and experiments},
	booktitle = {10th Int. Conf. on Intelligent Autonomous Systems},
	year = {2008},
	month = {07/2008},
	pages = {348-355},
	address = {Baden-Baden, Germany},
	keywords = {Coverage, Distributed algorithms, Multi-robot systems},
	attachments = {https://homepages.laas.fr/afranchi/robotics/sites/default/files/2008a-FraFreMarOriVen.pdf},
	author = {Antonio Franchi and Luigi Freda and Luca Marchionni and Giuseppe Oriolo and Marilena Vendittelli}
}
@conference {2007b-FraFreOriVen,
	title = {A decentralized strategy for cooperative robot exploration},
	booktitle = {ACM International Conference Proceeding Series, Proceedings of the 1st international conference on Robot communication and coordination},
	volume = {318},
	number = {7},
	year = {2007},
	month = {11/2007},
	address = {Athens, Greece},
	keywords = {Coverage, Distributed algorithms, Multi-robot systems},
	attachments = {https://homepages.laas.fr/afranchi/robotics/sites/default/files/2007b-FraFreOriVen.pdf},
	author = {Antonio Franchi and Luigi Freda and Giuseppe Oriolo and Marilena Vendittelli}
}
@conference {2007a-FraFreOriVen,
	title = {A Randomized Strategy for Cooperative Robot Exploration},
	booktitle = {2007 IEEE Int. Conf. on Robotics and Automation},
	year = {2007},
	month = {04/2007},
	pages = {768-774},
	address = {Rome, Italy},
	keywords = {Coverage, Decentralized control, Distributed algorithms, Multi-robot systems},
	attachments = {https://homepages.laas.fr/afranchi/robotics/sites/default/files/2007a-FraFreOriVen.pdf},
	author = {Antonio Franchi and Luigi Freda and Giuseppe Oriolo and Marilena Vendittelli}
}
