@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 {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}
}
@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 {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}
}
@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}
}
@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}
}
@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}
}
@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}
}
@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 {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 {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 {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 {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}
}
@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 {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}
}
@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}
}
@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 {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}
}
@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 {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 {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}
}
@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 {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 {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 {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 {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 {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 {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}
}
@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}
}
@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}
}
@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}
}
@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}
}
@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}
}
@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}
}
@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 {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 {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 {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}
}
@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}
}
