@article {2022m-MohBicFraBarPra,
	title = {Aerial Tele-Manipulation with Passive Tool via Parallel Position/Force Control},
	journal = {Applied Sciences, Special issue on Aerial Robotics for Inspection and Maintenance},
	volume = {11},
	year = {2021},
	doi = {10.3390/app11198955},
	author = {Mostafa Mohammadi and Davide Bicego and Antonio Franchi and Davide Barcelli and Domenico Prattichizzo}
}
@article {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}
}
@article {2020e-MicCenZacFra,
	title = {Hierarchical nonlinear control for multi-rotor asymptotic stabilization based on zero-moment direction},
	journal = {Automatica},
	year = {2020},
	abstract = {
We consider the hovering control problem for a class of multi-rotor aerial platforms with generically oriented propellers, characterized by intrinsically coupled translational and rotational dynamics. In doing this, we first discuss some assumptions guaranteeing the rejection of generic disturbance torques while compensating for the gravity force. These assumptions are translated into a geometric condition usually satisfied by both standard models and more general configurations. Then, we propose a control strategy based on the identification of a zero-moment direction for the exerted force and a dynamic state feedback linearization based on this preferential direction, which locally asymptotically stabilizes the platform to a static hovering condition. Stability properties of the control law are rigorously proved through Lyapunov-based methods and reduction theorems for the stability of nested sets. Asymptotic zeroing of the error dynamics and convergence to the static hovering condition are then confirmed by simulation results on a star-shaped hexarotor model with tilted propellers.},
	attachments = {https://homepages.laas.fr/afranchi/robotics/sites/default/files/2020e-MicCenZacFra.pdf},
	author = {Giulia Michieletto and Angelo Cenedese and Luca Zaccarian and Antonio Franchi}
}
@conference {2020h-PetSanTogMilCorFra,
	title = {Inertial Estimation and Energy-Efficient Control of a Cable-suspended Load with a Team of UAVs},
	booktitle = {2020 Int. Conf. on Unmanned Aircraft Systems},
	year = {2020},
	month = {07/2020},
	address = {Athens, Greece},
	abstract = {The Fly-Crane is a multi-robot aerial manipulator system composed of three aerial vehicles towed to a platform by means of six cables. This paper presents a method to estimate the mass and the position of the center of mass of a loaded platform (i.e. the Fly-Crane platform including a transported load). The precise knowledge of these parameters allows to sensibly minimize the total effort exerted during a full-pose manipulation task The estimation is based on the measure of the forces applied by the aerial vehicles to the platform in different static configurations. We demonstrate that only two different configurations are sufficient to estimate the inertial parameters. Far-from-ideal numerical simulations show the effectiveness of the estimation method. Once the parameters are estimated, we show the enhancement of the system performances by minimizing the total exerted effort. The validity of the proposed algorithm in non-ideal conditions is presented through simulations based on the Gazebo simulator.},
	doi = {10.1109/ICUAS48674.2020.9213842},
	attachments = {https://homepages.laas.fr/afranchi/robotics/sites/default/files/2020h-PetSanTogMilCorFra.pdf},
	author = {Antonio Petitti and Dario Sanalitro and Marco Tognon and A. Milella and Juan Cort{\'e}s and Antonio Franchi}
}
@article {2020l-BicMazFarCarFra,
	title = {Nonlinear Model Predictive Control with Enhanced Actuator Model for Multi-Rotor Aerial Vehicles with Generic Designs},
	journal = {Journal of Intelligent and Robotic Systems},
	volume = {100},
	year = {2020},
	pages = {1213-1247},
	abstract = {In this paper, we propose, discuss, and validate an online Nonlinear Model Predictive Control (NMPC) method for multi-rotor aerial systems with arbitrarily positioned and oriented rotors which simultaneously addresses the local ref- erence trajectory planning and tracking problems. This work brings into question some common modeling and control design choices that are typically adopted to guarantee ro- bustness and reliability but which may severely limit the at- tainable performance. Unlike most of state of the art works, the proposed method takes advantages of a unified nonlinear model which aims to describe the whole robot dynamics by explicitly including a realistic physical description of the ac- tuator dynamics and limitations. As a matter of fact, our so- lution does not resort to common simplifications such as: 1) linear model approximation, 2) cascaded control paradigm used to decouple the translational and the rotational dynam- ics of the rigid body, 3) use of low-level reactive trackers for the stabilization of the internal loop, and 4) unconstrained optimization resolution or use of fictitious constraints. More in detail, we consider as control inputs the derivatives of the propeller forces and propose a novel method to suit- ably identify the actuator limitations by leveraging experi- mental data. Differently from previous approaches, the con- straints of the optimization problem are defined only by the real physics of the actuators, avoiding conservative {\textendash} and often not physical {\textendash} input/state saturations which are present, e.g., in cascaded approaches. The control algorithm is im- plemented using a state-of-the-art Real Time Iteration (RTI) scheme with partial sensitivity update method. The perfor- mances of the control system are finally validated by means of real-time simulations and in real experiments, with a large spectrum of heterogeneous multi-rotor systems: an under- actuated quadrotor, a fully-actuated hexarotor, a multi-rotor with orientable propellers, and a multi-rotor with an unex- pected rotor failure. To the best of our knowledge, this is the first time that a predictive controller framework with all the valuable aforementioned features is presented and exten- sively validated in real-time experiments and simulations},
	doi = {10.1007/s10846-020-01250-9},
	attachments = {https://homepages.laas.fr/afranchi/robotics/sites/default/files/2020l-BicMazFarCarFra.pdf},
	author = {Davide Bicego and Jacopo Mazzetto and Marcello Farina and Ruggero Carli and Antonio Franchi}
}
@article {2019h-RylMusPieCatAntCacFra,
	title = {6D Interaction Control with Aerial Robots: The Flying End-Effector Paradigm},
	journal = {The International Journal of Robotics Research},
	volume = {38},
	year = {2019},
	pages = {1045-1062},
	doi = {10.1177/0278364919856694},
	attachments = {https://homepages.laas.fr/afranchi/robotics/sites/default/files/2019h-RylMusPieCatAntCacFra-preprint.pdf , https://homepages.laas.fr/afranchi/robotics/sites/default/files/2019h-RylMusPieCatAntCacFra-1.mp4 , https://homepages.laas.fr/afranchi/robotics/sites/default/files/2019h-RylMusPieCatAntCacFra-2.mp4 , https://homepages.laas.fr/afranchi/robotics/sites/default/files/2019h-RylMusPieCatAntCacFra-3.mp4},
	author = {Markus Ryll and Giuseppe Muscio and Francesco Pierri and Elisabetta Cataldi and Gianluca Antonelli and Fabrizio Caccavale and Davide Bicego and Antonio Franchi}
}
@conference {2019j-MicCenFra,
	title = {Force-Moment Decoupling and Rotor-Failure Robustness for Star-Shaped Generically-Tilted Multi-Rotors},
	booktitle = {In 58th IEEE Conference on Decision and Control},
	year = {2019},
	month = {12/2019},
	address = {Nice, France},
	abstract = {Aerial robotics is increasingly becoming an at- tractive field of research thanks to the peculiar mixture of theoretical issues to be solved and technological challenges to be faced. In particular, recent developments have seen the multiplication of multi-rotor platforms that aim at improving the maneuverability of classical quadrotors in standard and harsh flying conditions, thus opening the field to compre- hensive studies over the structural multi-rotor properties of actuation, decoupling, and robustness, which strongly depend on the mechanical configuration of the systems. This work collocates along this line of research by considering star-shaped generically-tilted multi-rotors (SGTMs), namely platforms with more than four possibly tilted propellers (along two tilting orthogonal axes). For these platforms, we investigate how the structural choices over the number of propellers and the tilting angles affect the force-moment decoupling features and, by recalling the robustness definition that refers to the hovering capabilities of the platform, we provide a robustness analysis and an hoverability assessment for SGTMs having five to eight actuators against the loss of one and two propellers.},
	author = {Giulia Michieletto and Angelo Cenedese and Antonio Franchi}
}
@article {2019a-FraRobMic,
	title = {Online Leader Selection for Improved Collective Tracking and Formation Control: the Second Order Case},
	journal = {IEEE Transactions on Control of Network Systems},
	volume = {6},
	year = {2019},
	month = {12/2019},
	pages = {1415-1425},
	abstract = {In this work, we deal with a double control task for a group of interacting agents having a second-order dynamics. Adopting the leader-follower paradigm, the given multi-agent system is required to maintain a desired formation and to collectively track a velocity reference provided by an external source only to a single agent at time, called the {\textquoteleft}leader{\textquoteright}. We prove that it is possible to optimize the group performance by persistently selecting online the leader among the agents. To do this, we first define a suitable error metric able to capture the tracking performance of the multi-agent group while maintaining a desired formation through a (even time-varying) communication-graph topology. Then we show that this depends on the algebraic connectivity and on the maximum eigenvalue of the Laplacian matrix of a special directed graph depending on the selected leader. By exploiting these theoretical results, we finally design a fully-distributed adaptive procedure able to periodically select online the optimum leader among the neighbors of the current one. The effectiveness of the proposed solution against other possible strategies is confirmed by numerical simulations.},
	doi = {10.1109/TCNS.2019.2891011},
	attachments = {https://homepages.laas.fr/afranchi/robotics/sites/default/files/2019a-FraRobMic-preprint.pdf},
	author = {Antonio Franchi and Paolo Robuffo Giordano and Giulia Michieletto}
}
@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}
}
@conference {2018r-MorBicRylFra,
	title = {Energy-Efficient Trajectory Generation for a Hexarotor with Dual-Tilting Propellers},
	booktitle = {2018 IEEE/RSJ Int. Conf. on Intelligent Robots and Systems},
	year = {2018},
	month = {10/2018},
	address = {Madrid, Spain},
	abstract = {In this paper, we consider a non-conventional hexarotor whose propellers can be simultaneously tilted about two orthogonal axes: in this way, its underactuation degree can be easily adapted to the task at hand. For a given tilt profile, the minimum-energy trajectory between two prescribed boundary states is explicitly determined by solving an optimal control problem with respect to the angular accelerations of the six brushless motors. We also perform, for the first time, a systematic study of the singularities of the control allocation matrix of the hexarotor, showing the presence of subtle singular configurations that should be carefully avoided in the design phase. Numerical experiments conducted with the FAST-Hex platform illustrate the theory and delineate the pros and cons of dual-tilting paradigm in terms of maneuverability and energy efficiency.},
	attachments = {https://homepages.laas.fr/afranchi/robotics/sites/default/files/2018r-MorBicRylFra-preprint.pdf},
	author = {Fabio Morbidi and Davide Bicego and Markus Ryll and Antonio Franchi}
}
@article {2018a-MicRylFra,
	title = {Fundamental Actuation Properties of Multi-rotors: Force-Moment Decoupling and Fail-safe Robustness},
	journal = {IEEE Trans. on Robotics},
	volume = {34},
	year = {2018},
	month = {06/2018},
	doi = {10.1109/TRO.2018.2821155},
	attachments = {https://homepages.laas.fr/afranchi/robotics/sites/default/files/2018a-MicRylFra-preprint.pdf , https://homepages.laas.fr/afranchi/robotics/sites/default/files/video1_explaination.mp4 , https://homepages.laas.fr/afranchi/robotics/sites/default/files/video2_triggered_failures.mp4 , https://homepages.laas.fr/afranchi/robotics/sites/default/files/video3_hitting_failures.mp4},
	author = {Giulia Michieletto and Markus Ryll and Antonio Franchi}
}
@article {2018v-AreMerFra,
	title = {A Novel Experimental Model and a Drag-optimal Allocation Method for Variable-Pitch Propellers in Multirotors},
	journal = {IEEE Access},
	volume = {6},
	year = {2018},
	month = {11/2018},
	pages = {68155-68168},
	abstract = {This paper proposes a new mathematical model to map the rotational speed and angle of attack (pitch) of small- size propellers typically used in multirotors and the aerodynamic thrust force and drag moment produced by the propeller itself. The new model is inspired by standard models using the blade- element and momentum theories, which have been suitably modified in order to allow for explicit fast computation of the direct and inverse map (useful for high-frequency control) and obtain a better adherence to experimental data. The new model allows and captures all the main nonlinear characteristics of the thrust/drag generation. An extensive experimental comparison shows that the prediction capability of the proposed model outperforms the most commonly used models at date. In the second part of the paper, two optimization methods are proposed in order to exploit the redundancy of the inputs of variable-pitch propellers to decrease the power consumption due to the drag dissipation. The first method deals with optimal allocation for thrust generation on a single propeller, while the second method is aimed at solving the optimal allocation of the rotational speed and pitch of all the propellers in a multi-rotor with any number of propellers. Simulations results show the viability and effectiveness of the proposed methods.},
	doi = {10.1109/ACCESS.2018.2879636},
	attachments = {https://homepages.laas.fr/afranchi/robotics/sites/default/files/2018v-AreMerFra-preprint.pdf},
	author = {Victor Arellano-Quintana and Emmanuel Merchan-Cruz and Antonio Franchi}
}
@article {2018t-MasMohRobFra,
	title = {Shared Planning and Control for Mobile Robots with Integral Haptic Feedback},
	journal = {The International Journal of Robotics Research},
	volume = {37},
	year = {2018},
	month = {10/2018},
	pages = {1395-1420},
	abstract = {This paper presents a novel bilateral shared framework for online trajectory generation for mobile robots. The robot navigates along a dynamic path, represented as a B-spline, whose parameters are jointly controlled by a human supervisor and by an autonomous algorithm. The human steers the reference (ideal) path by acting on the path parameters which are also affected, at the same time, by the autonomous algorithm in order to ensure: i) collision avoidance, ii) path regularity and iii) proximity to some points of interest. These goals are achieved by combining a gradient descent-like control action with an automatic algorithm that re-initializes the traveled path (replanning) in cluttered environments in order to mitigate the effects of local minima. The control actions of both the human and the autonomous algorithm are fused via a filter that preserves a set of local geometrical properties of the path in order to ease the tracking task of the mobile robot. The bilateral component of the interaction is implemented via a force feedback that accounts for both human and autonomous control actions along the whole path, thus providing information about the mismatch between the reference and traveled path in an integral sense. The proposed framework is validated by means of realistic simulations and actual experiments deploying a quadrotor UAV supervised by a human operator acting via a force-feedback haptic interface. Finally, a user study is presented in order to validate the effectiveness of the proposed framework and the usefulness of the provided force cues.},
	keywords = {Aerial Robotics, Optimal Trajectory Planning},
	attachments = {https://homepages.laas.fr/afranchi/robotics/sites/default/files/2018t-MasMohRobFra-preprint.pdf , https://homepages.laas.fr/afranchi/robotics/sites/default/files/2018t-MasMohRobFra-video1.mp4 , https://homepages.laas.fr/afranchi/robotics/sites/default/files/2018t-MasMohRobFra-video2.mp4 , https://homepages.laas.fr/afranchi/robotics/sites/default/files/2018t-MasMohRobFra-video3.mp4},
	author = {Carlo Masone and Mostafa Mohammadi and Paolo Robuffo Giordano and Antonio Franchi}
}
@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 {2017e-RylMusPieCatAntCacFra,
	title = {6D Physical Interaction with a Fully Actuated Aerial Robot},
	booktitle = {2017 IEEE Int. Conf. on Robotics and Automation},
	year = {2017},
	month = {05/2017},
	pages = {5190-5195},
	address = {Singapore},
	abstract = {This paper presents the design, control, and experimental validation of a novel fully{\textendash}actuated aerial robot for physically interactive tasks, named Tilt-Hex. We show how the Tilt-Hex, a tilted-propeller hexarotor is able to control the full pose (position and orientation independently) using a geometric control, and to exert a full-wrench (force and torque independently) with a rigidly attached end-effector using an admittance control paradigm. An outer loop control governs the desired admittance behavior and an inner loop based on geometric control ensures pose tracking. The interaction forces are estimated by a momentum based observer. Control and observation are made possible by a precise control and measurement of the speed of each propeller. An extensive experimental campaign shows that the Tilt-Hex is able to outperform the classical underactuated multi-rotors in terms of stability, accuracy and dexterity and represent one of the best choice at date for tasks requiring aerial physical interaction.},
	attachments = {https://homepages.laas.fr/afranchi/robotics/sites/default/files/2017e-RylMusPieCatAntCacFra-preprint.pdf , https://homepages.laas.fr/afranchi/robotics/sites/default/files/2017e-RylMusPieCatAntCacFra.mp4},
	author = {Markus Ryll and Giuseppe Muscio and Francesco Pierri and Elisabetta Cataldi and Gianluca Antonelli and Fabrizio Caccavale and Antonio Franchi}
}
@conference {2017c-FraMal,
	title = {Adaptive Closed-loop Speed Control of BLDC Motors with Applications to Multi-rotor Aerial Vehicles},
	booktitle = {2017 IEEE Int. Conf. on Robotics and Automation},
	year = {2017},
	month = {05/2017},
	address = {Singapore},
	abstract = { This paper introduces the adaptive bias and adaptive gain (ABAG) algorithm for closed-loop electronic speed control (ESC) of the brushless direct current (BLDC) motors typically used to spin the propellers in multi-rotor aerial robots. The ABAG algorithm is adaptive and robust in the sense that it does not require the knowledge of any mechanical/electrical parameter of the motor/propeller group and that neither a pre-calibration nor the knowledge of the feedforward/nominal input is needed. The ABAG algorithm is amenable to an extremely low complexity implementation. We experimentally prove that it can run in 27.5 μs on a 8 MHz microcontroller with no floating point unit and limited arithmetic capabilities allowing only 8-bit additions, subtractions and multiplications. Besides the controller implementation we present a self-contained open source software architecture that handles the entire speed control process, including clock synchronization, and over- current and blockage safeties. The excellent performance and robustness of ABAG are shown by experimental tests and aerial physical interaction experiments.},
	attachments = {https://homepages.laas.fr/afranchi/robotics/sites/default/files/2017c-FraMal-preprint.pdf},
	author = {Antonio Franchi and Anthony Mallet}
}
@conference {2017f-MicRylFra,
	title = {Control of Statically Hoverable Multi-Rotor Aerial Vehicles and Application to Rotor-Failure Robustness for Hexarotors},
	booktitle = {2017 IEEE Int. Conf. on Robotics and Automation},
	year = {2017},
	month = {05/2017},
	address = {Singapore},
	abstract = {Standard hexarotors are often mistakenly considered {\textquoteleft}by definition{\textquoteright} fail-safe multi-rotor platforms because of the two additional propellers when compared to quadrotors. However this is not true, in fact, a standard hexarotor cannot statically hover with {\textquoteleft}only{\textquoteright} five propellers. In this paper we provide a set of new general algebraic conditions to ensure static hover for any multi-rotor platform with any number of generically oriented rotors. These are elegantly formulated as the full-rankness of the control moment input matrix, and the non-orthogonality between its null-space and the row space of the control force input matrix. Input saturations and safety margins are also taken into account with an additional condition on the null-space of control moment input matrix. A deep analysis on the hoverability properties is then carried out focusing on the propeller loss in a hexarotor platform. Leveraging our general results we explain why a standard hexarotor is not robust and how it can be made robust thanks to a particular tilt of the rotors. We finally propose a novel cascaded controller based on a preferential direction in the null-space of the control moment input matrix for the large class of statically hoverable multi-rotors, which goes far beyond standard platforms, and we apply this controller to the case of failed tilted hexarotor.},
	attachments = {https://homepages.laas.fr/afranchi/robotics/sites/default/files/2017f-MicRylFra-preprint.pdf , https://homepages.laas.fr/afranchi/robotics/sites/default/files/2017f-MicRylFra.mp4},
	author = {Giulia Michieletto and Markus Ryll and Antonio Franchi}
}
@conference {2017i-MicCenZacFra,
	title = {Nonlinear Control of Multi-Rotor Aerial Vehicles Based on the Zero-Moment Direction},
	booktitle = {20th IFAC World Congress},
	year = {2017},
	month = {07/2017},
	address = {Toulouse, France},
	abstract = {A quaternion-based nonlinear control strategy is here presented to steer and keep a generic multi-rotor platform in a given reference position. Exploiting a state feedback structure, the proposed solution ensures the stabilization of the aerial vehicle so that its linear and angular velocity are zero and its attitude is constant. The main feature of the designed controller is the identification of a zero-moment direction in the feasible force space, i.e., a direction along which the control force intensity can be assigned independently of the control moment. The asymptotic convergence of the error dynamics is confirmed by simulation results on a hexarotor with tilted propellers.
},
	attachments = {https://homepages.laas.fr/afranchi/robotics/sites/default/files/2017i-MicCenZacFra-preprint.pdf},
	author = {Giulia Michieletto and Angelo Cenedese and Luca Zaccarian and Antonio Franchi}
}
@conference {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 {2016o-MicCenFra,
	title = {Bearing Rigidity Theory in SE(3)},
	booktitle = {55th IEEE Conference on Decision and Control},
	year = {2016},
	month = {12/2016},
	pages = {5950-5955},
	address = {Las Vegas, NV},
	abstract = {Rigidity theory has recently emerged as an efficient tool in the control field of coordinated multi-agent systems, such as multi-robot formations and UAVs swarms, that are characterized by sensing, communication and movement capabilities. This work aims at describing the rigidity properties for frameworks embedded in the three-dimensional Special Euclidean space SE(3) wherein each agent has 6DoF. In such scenario, it is assumed that the devices are able to gather bearing measurements w.r.t. their neighbors, expressing them into their own body frame. The goal is then to identify the framework transformations that allow to preserve such measurements maintaining it rigid. Rigidity properties are mathematically formalized in this work which differs from the previous ones as it faces the extension in three-dimensional space dealing with the 3D rotations manifold. In particular, the attention is focused on the infinitesimal SE(3)-rigidity for which a necessary and sufficient condition is provided.},
	attachments = {https://homepages.laas.fr/afranchi/robotics/sites/default/files/2016o-MicCenFra-preprint.pdf},
	author = {Giulia Michieletto and Angelo Cenedese and Antonio Franchi}
}
@conference {2016n-MohFraBarPra,
	title = {Cooperative Aerial Tele-Manipulation with Haptic Feedback},
	booktitle = {2016 IEEE/RSJ Int. Conf. on Intelligent Robots and System},
	year = {2016},
	month = {10/2016},
	pages = {5092-5098},
	address = {Daejeon, South Korea},
	abstract = {In this paper, we propose a bilateral tele-operation scheme for cooperative aerial manipulation in which a human operator drives a team of Vertical Take-Off and Landing (VTOL) aerial vehicles, that grasped an object beforehand, and receives a force feedback depending on the states of the system. For application scenarios in which dexterous manipulation by each robot is not necessary, we propose using a rigid tool attached to the vehicle through a passive spherical joint, equipped with a simple adhesive mechanism at the tool-tip that can stick to the grasped object. Having more than two robots, we use the extra degrees of freedom to find the optimal force allocation in term of minimum power and forces smoothness. The human operator commands a desired trajectory for the robot team through a haptic interface to a pose controller, and the output of the pose controller along with system constraints, e.g., VTOL limited forces and contact maintenance, defines the feasible set of forces. Then, an on-line optimization allocates forces by minimizing a cost function of forces and their variation. Finally, propeller thrusts are computed by a dedicated attitude and thrust controller in a decentralized fashion. Human/Hardware in the loop simulation study shows efficiency of the proposed scheme, and the importance of haptic feedback to achieve a better performance.},
	attachments = {https://homepages.laas.fr/afranchi/robotics/sites/default/files/2016n-MohFraBarPra-preprint.pdf , https://homepages.laas.fr/afranchi/robotics/sites/default/files/2016n-MohFraBarPra.mp4},
	author = {Mostafa Mohammadi and Antonio Franchi and Davide Barcelli and Domenico Prattichizzo}
}
@conference {2015f-YueMahSecBueFra,
	title = {Design, Identification and Experimental Testing of a Light-Weight Flexible-joint Arm for Aerial Physical Interaction},
	booktitle = {2015 IEEE Int. Conf. on Robotics and Automation},
	year = {2015},
	month = {05/2015},
	pages = {870-876},
	address = {Seattle, WA},
	abstract = {In this paper we introduce the design of a light- weight novel flexible-joint arm for light-weight unmanned aerial vehicles (UAVs), which can be used both for safe physical interaction with the environment and it represents also a preliminary step in the direction of performing quick motions for tasks such as hammering or throwing. The actuator consists of an active pulley driven by a rotational servo motor, a passive pulley which is attached to a rigid link, and the elastic connections (springs) between these two pulleys. We identify the physical parameters of the system, and use an optimal control strategy to maximize its velocity by taking advantage of elastic components. The prototype can be extended to a light-weight variable stiffness actuator. The flexible-joint arm is applied on a quadrotor, to be used in aerial physical interaction tasks, which implies that the elastic components can also be used for stable interaction absorbing the interactive disturbances which might damage the flying system and its hardware. The design is validated through several experiments, and future developments are discussed in the paper.},
	keywords = {Aerial Physical Interaction, Aerial Robotics},
	attachments = {https://homepages.laas.fr/afranchi/robotics/sites/default/files/2015f-YueMahSecBueFra-preprint_0.pdf , https://homepages.laas.fr/afranchi/robotics/sites/default/files/2015f-YueMahSecBueFra.mp4},
	author = {Burak Y{\"u}ksel and Saber Mahboubi and Cristian Secchi and Heinrich H. B{\"u}lthoff and Antonio Franchi}
}
@conference {2015c-GioMohFraPra,
	title = {A Force-based Bilateral Teleoperation Framework for Aerial Robots in Contact with the Environment},
	booktitle = {2015 IEEE Int. Conf. on Robotics and Automation},
	year = {2015},
	month = {05/2015},
	pages = {318-324},
	address = {Seattle, WA},
	keywords = {Aerial Physical Interaction, Aerial Robotics, Bilateral Shared Control of Mobile Robots},
	attachments = {https://homepages.laas.fr/afranchi/robotics/sites/default/files/2015c-GioMohFraPra-preprint.pdf , https://homepages.laas.fr/afranchi/robotics/sites/default/files/2015c-GioMohFraPra.mp4},
	author = {Guido Gioioso and Mostafa Mohammadi and Antonio Franchi and Domenico Prattichizzo}
}
@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 {2014c-MasRobBueFra,
	title = {Semi-autonomous Trajectory Generation for Mobile Robots with Integral Haptic Shared Control},
	booktitle = {2014 IEEE Int. Conf. on Robotics and Automation},
	year = {2014},
	month = {05/2014},
	pages = {6468-6475},
	address = {Hong Kong, China},
	abstract = {A new framework for semi-autonomous path plan- ning for mobile robots that extends the classical paradigm of bilateral shared control is presented. The path is represented as a B-spline and the human operator can modify its shape by controlling the motion of a finite number of control points. An autonomous algorithm corrects in real time the human directives in order to facilitate path tracking for the mobile robot and ensures i) collision avoidance, ii) path regularity, and iii) attraction to nearby points of interest. A haptic feedback algorithm processes both human{\textquoteright}s and autonomous control terms, and their integrals, to provide an information of the mismatch between the path specified by the operator and the one corrected by the autonomous algorithm. The framework is validated with extensive experiments using a quadrotor UAV and a human in the loop with two haptic interfaces.
},
	keywords = {Bilateral Shared Control of Mobile Robots},
	attachments = {https://homepages.laas.fr/afranchi/robotics/sites/default/files/2014c-MasRobBueFra-preprint.pdf , https://homepages.laas.fr/afranchi/robotics/sites/default/files/2014c-MasRobBueFra.mp4},
	author = {Carlo Masone and Paolo Robuffo Giordano and Heinrich H. B{\"u}lthoff and Antonio Franchi}
}
@article {2013i-CenFraMarOri,
	title = {Simultaneous Calibration of Odometry  and Sensor Parameters for Mobile Robots},
	journal = {IEEE Transaction on Robotics},
	volume = {29},
	year = {2013},
	month = {04/2013},
	pages = {475-492},
	abstract = {Consider a differential-drive mobile robot equipped with an on-board exteroceptive sensor that can estimate its own motion, e.g., a range-finder. Calibration of this robot involves estimating six parameters: three for the odometry (radii and distance between the wheels), and three for the pose of the sensor with respect to the robot. After analyzing the observability of this problem, this paper describes a method for calibrating all parameters at the same time, without the need for external sensors or devices, using only the measurement of the wheels velocities and the data from the exteroceptive sensor. The method does not require the robot to move along particular trajectories. Simultaneous calibration is formulated as a maximum-likelihood problem and the solution is found in a closed form. Experimental results show that the accuracy of the proposed calibration method is very close to the attainable limit given by the Cram{\`e}r{\textendash}Rao bound.},
	keywords = {Calibration, Calibration of ground robots, Estimation},
	attachments = {https://homepages.laas.fr/afranchi/robotics/sites/default/files/2013i-CenFraMarOri.pdf},
	author = {Andrea Censi and Antonio Franchi and Luca Marchionni and Giuseppe Oriolo}
}
@conference {2012k-MasFraBueRob,
	title = {Interactive Planning of Persistent Trajectories for Human-Assisted Navigation of Mobile Robots},
	booktitle = {2012 IEEE/RSJ Int. Conf. on Intelligent Robots and Systems},
	year = {2012},
	month = {10/2012},
	pages = {2641-2648},
	address = {Vilamoura, Portugal},
	abstract = {This work extends the framework of bilateral shared control of mobile robots with the aim of increasing the robot autonomy and decreasing the operator commitment. We consider persistent autonomous behaviors where a cyclic motion must be executed by the robot. The human operator is in charge of modifying online some geometric properties of the desired path. This is then autonomously processed by the robot in order to produce an actual path guaranteeing: i) tracking feasibility, ii) collision avoidance with obstacles, iii) closeness to the desired path set by the human operator, and iv) proximity to some points of interest. A force feedback is implemented to inform the human operator of the global deformation of the pathrather than using the classical mismatch between desired and executed motion commands. Physically-based simulations, with human/hardware-in-the-loop and a quadrotor UAV as robotic platform, demonstrate the feasibility of the method. },
	keywords = {Bilateral Shared Control of Mobile Robots, Force feedback, Haptics, Motion Planning, Optimal Trajectory Planning, Teleoperation},
	attachments = {https://homepages.laas.fr/afranchi/robotics/sites/default/files/2012k-MasFraBueRob.pdf , https://homepages.laas.fr/afranchi/robotics/sites/default/files/2012k-MasFraBueRob.mp4},
	author = {Carlo Masone and Antonio Franchi and Heinrich H. B{\"u}lthoff and Paolo Robuffo Giordano}
}
@article {2012q-FraMasGraRylBueRob,
	title = {Modeling and Control of UAV Bearing-Formations with Bilateral High-Level Steering},
	journal = {The International Journal of Robotics Research, Special Issue on 3D Exploration, Mapping, and Surveillance},
	volume = {31},
	year = {2012},
	month = {10/2012},
	pages = {1504-1525},
	abstract = {In this paper we address the problem of controlling the motion of a group of UAVs bound to keep a formation defined in terms of only relative angles (i.e., a bearing-formation). This problem can naturally arise within the context of several multi-robot applications such as, e.g., exploration, coverage, and surveillance. First, we introduce and thoroughly analyze the concept and properties of bearing-formations, and provide a class of minimally linear sets of bearings sufficient to uniquely define such formations. We then propose a bearing-only formation controller requiring only bearing measurements, converging almost globally, and maintaining bounded inter-agent distances despite the lack of direct metric information. The controller still leaves the possibility to impose group motions tangent to the current bearing-formation. These can be either autonomously chosen by the robots because of any additional task (e.g., exploration), or exploited by an assisting human co-operator. For this latter {\textquoteleft}human-in-the-loop{\textquoteright} case, we propose a multi-master/multi-slave bilateral shared control system providing the co-operator with some suitable force cues informative of the UAV performance. The proposed theoretical framework is extensively validated by means of simulations
and experiments with quadrotor UAVs equipped with onboard cameras. Practical limitations, e.g., limited field-of-view, are also considered.},
	keywords = {Bilateral Shared Control of Mobile Robots, Decentralized control, Force feedback, Formation control, Haptics, Motion control of multiple robots, Multi-robot systems, Teleoperation},
	attachments = {https://homepages.laas.fr/afranchi/robotics/sites/default/files/2012q-FraMasGraRylBueRob-preprint.pdf},
	author = {Antonio Franchi and Carlo Masone and Volker Grabe and Markus Ryll and Heinrich H. B{\"u}lthoff and Paolo Robuffo Giordano}
}
@booklet {2012p-MasFraBueRob,
	title = {Shared Trajectory Planning for Human-in-the-loop Navigation of Mobile Robots in Cluttered Environments},
	howpublished = {5th Int. Work. on Human-Friendly Robotics},
	year = {2012},
	month = {10/2012},
	address = {Bruxelles, Belgium},
	keywords = {Bilateral Shared Control of Mobile Robots, Optimal Trajectory Planning},
	author = {Carlo Masone and Antonio Franchi and Heinrich H. B{\"u}lthoff and Paolo Robuffo Giordano}
}
@booklet {2012o-FraMasRob,
	title = {A Synergetic High-level/Reactive Planning Framework with Application to Human-Assisted Navigation},
	howpublished = {2012 IEEE IROS Work. on Real-time Motion Planning: Online, Reactive, and in Real-time},
	year = {2012},
	month = {10/2012},
	address = {Vilamoura, Portugal},
	keywords = {Bilateral Shared Control of Mobile Robots, Optimal Trajectory Planning},
	attachments = {https://homepages.laas.fr/afranchi/robotics/sites/default/files/2012o-FraMasRob-preprint.pdf},
	author = {Antonio Franchi and Carlo Masone and Paolo Robuffo Giordano}
}
@conference {2011i-FraMasBueRob,
	title = {Bilateral Teleoperation of Multiple UAVs with Decentralized Bearing-only Formation Control},
	booktitle = {2011 IEEE/RSJ Int. Conf. on Intelligent Robots and Systems},
	year = {2011},
	month = {09/2011},
	pages = {2215-2222},
	address = {San Francisco, CA},
	abstract = {We present a decentralized system for the bilateral teleoperation of groups of UAVs which only relies
on relative bearing measurements, i.e., without the need of distance information or global localization. The properties of a 3D bearing-formation are analyzed, and a minimal set of bearings needed for its definition is provided. We also design a novel decentralized formation control almost globally convergent and able to maintain bounded and non-vanishing inter-distances among the agents despite the absence of direct distance measurements. Furthermore, we develop a multimaster/multi-slave teleoperation setup in order to control the overall behavior of the group and to convey to the human operator suitable force cues, while ensuring stability in presence of delays and packet losses over the master-slave communication channel. The theoretical framework is validated by means of extensive human/hardware in-the-loop simulations using two force-feedback devices and a group of quadrotors.},
	keywords = {Bilateral Shared Control of Mobile Robots, Decentralized control, Force feedback, Formation control, Haptics, Motion control of multiple robots, Multi-robot systems, Teleoperation},
	attachments = {https://homepages.laas.fr/afranchi/robotics/sites/default/files/2011i-FraMasBueRob-preprint.pdf , https://homepages.laas.fr/afranchi/robotics/sites/default/files/2011i-FraMasBueRob.mp4},
	author = {Antonio Franchi and Carlo Masone and Heinrich H. B{\"u}lthoff and Paolo Robuffo Giordano}
}
@conference {2008a-FraFreMarOriVen,
	title = {Decentralized cooperative exploration: Implementation and experiments},
	booktitle = {10th Int. Conf. on Intelligent Autonomous Systems},
	year = {2008},
	month = {07/2008},
	pages = {348-355},
	address = {Baden-Baden, Germany},
	keywords = {Coverage, Distributed algorithms, Multi-robot systems},
	attachments = {https://homepages.laas.fr/afranchi/robotics/sites/default/files/2008a-FraFreMarOriVen.pdf},
	author = {Antonio Franchi and Luigi Freda and Luca Marchionni and Giuseppe Oriolo and Marilena Vendittelli}
}
