@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 {2021e-RylBicGiuLovFra, title = {FAST-Hex - A Morphing Hexarotor: Design, Mechanical Implementation, Control and Experimental Validation}, journal = {IEEE/ASME Transactions on Mechatronics}, year = {2021}, doi = {10.1109/TMECH.2021.3099197}, attachments = {https://homepages.laas.fr/afranchi/robotics/sites/default/files/2021e-RylBicGiuLovFra.pdf , https://homepages.laas.fr/afranchi/robotics/sites/default/files/2021e-RylBicGiuLovFra.mp4}, author = {Markus Ryll and Davide Bicego and Mattia Giurato and Marco Lovera and Antonio Franchi} } @conference {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 {2021c-BasHamBroFra, title = {A Novel Robust Hexarotor Capable of Static Hovering in Presence of Propeller Failure}, journal = {IEEE Robotics and Automation Letters}, year = {2021}, month = {03/2021}, abstract = {This paper presents a novel open source design of the Y-shaped hexarotor Unmanned Aerial Vehicle (UAV), and proves both in theory and real experiments its robustness to the failure of any of its propellers. An intuitive geometrical interpretation of UAV static hovering ability is presented, through which the robustness of different coplanar/collinear hexarotor designs is analyzed. Following the presented geometrical interpretation, we also show the conditions that allow the Star-shaped hexarotor to be robust to the failure of some of its propellers, while showing its incapability to static hover in the case of the failure of any of its propellers. Finally, the efficiency of the Y-shaped and Star-shaped hexarotors are tested experimentally, and conclusions on the advantages and disadvantages of the two designs are drawn.}, doi = {10.1109/LRA.2021.3067182}, attachments = {https://homepages.laas.fr/afranchi/robotics/sites/default/files/2021c-BasHamBroFra.pdf , https://homepages.laas.fr/afranchi/robotics/sites/default/files/2021c-BasHamBroFra.mp4}, author = {Elgiz Baskaya and Mahmoud Hamandi and Murat Bronz and Antonio Franchi} } @article {2021j-BarFraOri, title = {Towards Safe Human-Quadrotor Interaction: Mixed-Initiative Control via Real-Time NMPC}, journal = {IEEE Robotics and Automation Letters, Special Issue on Shared Autonomy for Physical Human-Robot Interaction}, volume = {6}, year = {2021}, pages = {7611-7618}, abstract = {This paper presents a novel algorithm for blending human inputs and automatic controller commands, guarantee- ing safety in mixed-initiative interactions between humans and quadrotors. The algorithm is based on nonlinear model predictive control (NMPC) and involves using the state solution to assess whether safety- and/or task-related rules are met to mix control authority. The mixing is attained through the convex combination of human and actual robot costs and is driven by a continuous function that measures the rules{\textquoteright} violation. To achieve real-time feasibility, we rely on an efficient real-time iteration (RTI) variant of a sequential quadratic programming (SQP) scheme to cast the mixed-initiative controller. We demonstrate the effectiveness of our algorithm through numerical simulations, where a second autonomous algorithm is used to emulate the behavior of pilots with different skill levels. Simulations show that our scheme provides suitable assistance to pilots, especially novices, in a workspace with obstacles while underpinning computational efficiency.}, doi = {10.1109/LRA.2021.3096502}, attachments = {https://homepages.laas.fr/afranchi/robotics/sites/default/files/2021j-BarFraOri.pdf , https://homepages.laas.fr/afranchi/robotics/sites/default/files/2021j-BarFraOri.mp4}, author = {Barbara Barros Carlos and Antonio Franchi and Giuseppe Oriolo} } @article {2020l-BicMazFarCarFra, title = {Nonlinear Model Predictive Control with Enhanced Actuator Model for Multi-Rotor Aerial Vehicles with Generic Designs}, journal = {Journal of Intelligent and Robotic Systems}, volume = {100}, year = {2020}, pages = {1213-1247}, abstract = {In this paper, we propose, discuss, and validate an online Nonlinear Model Predictive Control (NMPC) method for multi-rotor aerial systems with arbitrarily positioned and oriented rotors which simultaneously addresses the local ref- erence trajectory planning and tracking problems. This work brings into question some common modeling and control design choices that are typically adopted to guarantee ro- bustness and reliability but which may severely limit the at- tainable performance. Unlike most of state of the art works, the proposed method takes advantages of a unified nonlinear model which aims to describe the whole robot dynamics by explicitly including a realistic physical description of the ac- tuator dynamics and limitations. As a matter of fact, our so- lution does not resort to common simplifications such as: 1) linear model approximation, 2) cascaded control paradigm used to decouple the translational and the rotational dynam- ics of the rigid body, 3) use of low-level reactive trackers for the stabilization of the internal loop, and 4) unconstrained optimization resolution or use of fictitious constraints. More in detail, we consider as control inputs the derivatives of the propeller forces and propose a novel method to suit- ably identify the actuator limitations by leveraging experi- mental data. Differently from previous approaches, the con- straints of the optimization problem are defined only by the real physics of the actuators, avoiding conservative {\textendash} and often not physical {\textendash} input/state saturations which are present, e.g., in cascaded approaches. The control algorithm is im- plemented using a state-of-the-art Real Time Iteration (RTI) scheme with partial sensitivity update method. The perfor- mances of the control system are finally validated by means of real-time simulations and in real experiments, with a large spectrum of heterogeneous multi-rotor systems: an under- actuated quadrotor, a fully-actuated hexarotor, a multi-rotor with orientable propellers, and a multi-rotor with an unex- pected rotor failure. To the best of our knowledge, this is the first time that a predictive controller framework with all the valuable aforementioned features is presented and exten- sively validated in real-time experiments and simulations}, doi = {10.1007/s10846-020-01250-9}, attachments = {https://homepages.laas.fr/afranchi/robotics/sites/default/files/2020l-BicMazFarCarFra.pdf}, author = {Davide Bicego and Jacopo Mazzetto and Marcello Farina and Ruggero Carli and Antonio Franchi} } @conference {2020c-JacCorBicFra, title = {Perception-constrained and Motor-level Nonlinear MPC for both Underactuated and Tilted-propeller UAVs}, booktitle = {2020 IEEE Int. Conf. on Robotics and Automation}, year = {2020}, month = {05/2020}, address = {Paris, France}, attachments = {https://homepages.laas.fr/afranchi/robotics/sites/default/files/2020c-JacCorBicFra.mp4 , https://homepages.laas.fr/afranchi/robotics/sites/default/files/2020c-JacCorBicFra-preprint.pdf}, author = {Martin Jacquet and Gianluca Corsini and Davide Bicego and Antonio Franchi} } @article {2019h-RylMusPieCatAntCacFra, title = {6D Interaction Control with Aerial Robots: The Flying End-Effector Paradigm}, journal = {The International Journal of Robotics Research}, volume = {38}, year = {2019}, pages = {1045-1062}, doi = {10.1177/0278364919856694}, attachments = {https://homepages.laas.fr/afranchi/robotics/sites/default/files/2019h-RylMusPieCatAntCacFra-preprint.pdf , https://homepages.laas.fr/afranchi/robotics/sites/default/files/2019h-RylMusPieCatAntCacFra-1.mp4 , https://homepages.laas.fr/afranchi/robotics/sites/default/files/2019h-RylMusPieCatAntCacFra-2.mp4 , https://homepages.laas.fr/afranchi/robotics/sites/default/files/2019h-RylMusPieCatAntCacFra-3.mp4}, author = {Markus Ryll and Giuseppe Muscio and Francesco Pierri and Elisabetta Cataldi and Gianluca Antonelli and Fabrizio Caccavale and Davide Bicego and Antonio Franchi} } @article {2019b-YueSecBueFra, title = {Aerial Physical Interaction via IDA-PBC}, journal = {The International Journal of Robotics Research}, volume = {38}, year = {2019}, pages = {403{\textendash}421}, abstract = {This paper proposes the use of a novel control method based on IDA-PBC in order to address the Aerial Physical Interaction (APhI) problem for a quadrotor UAV. The apparent physical properties of the quadrotor are reshaped in order to achieve better APhI performances, while ensuring the stability of the interaction through passivity preservation. The robustness of the IDA-PBC method with respect to sensor noise is also analyzed. The direct measurement of the external wrench {\textendash} needed to implement the control method {\textendash} is compared to the use of a nonlinear Lyapunov-based wrench observer and advantages/disadvantages of both methods are discussed. The validity and practicability of the proposed APhI method is evaluated through experiments, where for the first time in the literature, a light-weight all- in-one low-cost F/T sensor is used onboard of a quadrotor. Two main scenarios are shown: a quadrotor responding external disturbances while hovering (physical human-quadrotor interaction), and the same quadrotor sliding with a rigid tool along an uneven ceiling surface (inspection/painting-like task).}, doi = {10.1177/0278364919835605}, attachments = {https://homepages.laas.fr/afranchi/robotics/sites/default/files/2019b-YueSecBueFra-preprint.pdf , https://homepages.laas.fr/afranchi/robotics/sites/default/files/2019b-YueSecBueFra.mp4}, author = {Burak Y{\"u}ksel and Cristian Secchi and Heinrich H. B{\"u}lthoff and Antonio Franchi} } @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 {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 {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} } @conference {2018o-FurBicFra, title = {Design and Input Allocation for Robots with Saturated Inputs via Genetic Algorithms}, booktitle = {12th IFAC Symposium on Robot Control}, year = {2018}, month = {08/2018}, address = {Budapest, Hungary}, abstract = {In this paper we consider fully-actuated and redundantly-actuated robots, whose saturated inputs can have high bandwidth or can be slowly varying (with dynamics). The slowly varying inputs can be considered as configurations for the system. The proposed strategy allows to find the optimal actuators{\textquoteright} configuration to optimize a cost function as the manipulability or the energy consumption. The approach allows for both a static design, which can include actuators{\textquoteright} parameters such as position, orientation, saturations, numbers of actuators, and for a dynamic design, where the configurations can be controlled by an input of the system. A generalized solution to the optimal problem is proposed with the use of genetic algorithms. The results are validated in two simulation scenarios: a reconfiguration of the actuators orientation of an redundantly-actuated planar robot for trajectory tracking and the design optimization of the orientation of the motors in a generalized hexa-rotor with arbitrary propeller orientation.}, attachments = {https://homepages.laas.fr/afranchi/robotics/sites/default/files/2018o-FurBicFra-preprint.pdf}, author = {Michele Furci and Davide Bicego and Antonio Franchi} } @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 {2018d-FraCarBicRyl, title = {Full-Pose Tracking Control for Aerial Robotic Systems with Laterally-Bounded Input Force}, journal = {IEEE Trans. on Robotics}, volume = {34}, year = {2018}, month = {04/2018}, pages = {534-541}, abstract = {A class of abstract aerial robotic systems is introduced, the Laterally Bounded Force (LBF) vehicles, in which most of the control authority is expressed along a principal thrust direction, while in the lateral directions a (smaller and possibly null) force may be exploited to achieve full-pose tracking. This class approximates platforms endowed with non-collinear rotors that can modify the orientation of the total thrust in body frame. The proposed SE(3)-based control strategy achieves, if made possible by the force constraints, the independent tracking of position-plus-orientation trajectories. The method, which is proven using a Lyapunov technique, deals seamlessly with both under- and fully-actuated platforms, and guarantees at least the position tracking in the case of an unfeasible full-pose reference trajectory. Several experimental tests are presented, that clearly shown the approach practicability and the sharp improvement with respect to state of-the-art.}, doi = {10.1109/TRO.2017.2786734}, attachments = {https://homepages.laas.fr/afranchi/robotics/sites/default/files/2018d-FraCarBicRyl.pdf , https://homepages.laas.fr/afranchi/robotics/sites/default/files/2018d-FraCarBicRyl-1.mp4 , https://homepages.laas.fr/afranchi/robotics/sites/default/files/2018d-FraCarBicRyl-2.mp4 , https://homepages.laas.fr/afranchi/robotics/sites/default/files/2018d-FraCarBicRyl-3.mp4}, author = {Antonio Franchi and Ruggero Carli and Davide Bicego and Markus Ryll} } @article {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 {2018n-RylBicFra, title = {A Truly Redundant Aerial Manipulator exploiting a Multi-directional Thrust Base}, booktitle = {12th IFAC Symposium on Robot Control}, year = {2018}, month = {08/2018}, address = {Budapest, Hungary}, abstract = {We present a novel aerial manipulator concept composed of a fully actuated hexarotor aerial vehicle and an n degree of freedom manipulator. Aiming at interaction tasks, we present a trajectory following control framework for the end-effector of the manipulator. The system is modeled in Euler-Lagrangian formalism and in Denavit-Hartenberg form. Benefiting from the redundancy of the system, we present several cost function strategies based on the projected gradient method to optimize the aerial manipulator behavior. The control framework is based on exact feedback linearization. In an advanced simulation section, we thoroughly present the robustness of the system and its limits in two typical configuration constituted by an 8 and a 10 degrees of freedom redundant aerial manipulator.}, attachments = {https://homepages.laas.fr/afranchi/robotics/sites/default/files/2018n-RylBicFra-preprint.pdf}, author = {Markus Ryll and Davide Bicego and Antonio Franchi} } @article {2017k-NesRobBueFra, title = {Decentralized Simultaneous Multi-target Exploration using a Connected Network of Multiple Robots}, journal = {Autonomous Robots}, volume = {41}, year = {2017}, month = {03/2016}, pages = {989-1011}, abstract = {This paper presents a novel decentralized control strategy for a multi-robot system that enables parallel multi-target exploration while ensuring a time-varying connected topology in cluttered 3D environments. Flexible continuous connectivity is guaranteed by building upon a recent connectivity maintenance method, in which limited range, line-of-sight visibility, and collision avoidance are taken into account at the same time. Completeness of the decentralized multi-target exploration algorithm is guaranteed by dynamically assigning the robots with different motion behaviors during the exploration task. One major group is subject to a suitable downscaling of the main traveling force based on the traveling efficiency of the current leader and the direction alignment between traveling and connectivity force. This supports the leader in always reaching its current target and, on a larger time horizon, that the whole team realizes the overall task in finite time. Extensive Monte~Carlo simulations with a group of several quadrotor UAVs show the scalability and effectiveness of the proposed method and experiments validate its practicability. }, keywords = {Connectivity maintenance, Exploration, Motion control of multiple robots, Patrolling / Surveillance}, attachments = {https://homepages.laas.fr/afranchi/robotics/sites/default/files/1505.05441v3.pdf , https://homepages.laas.fr/afranchi/robotics/sites/default/files/2016g-NesRobBueFra-exp.mp4 , https://homepages.laas.fr/afranchi/robotics/sites/default/files/2016g-NesRobBueFra-empty.mp4 , https://homepages.laas.fr/afranchi/robotics/sites/default/files/2016g-NesRobBueFra-office.mp4 , https://homepages.laas.fr/afranchi/robotics/sites/default/files/2016g-NesRobBueFra-town.mp4}, author = {Thomas Nestmeyer and Paolo Robuffo Giordano and Heinrich H. B{\"u}lthoff and Antonio Franchi} } @conference {2017g-TogYueBuoFra, title = {Dynamic Decentralized Control for Protocentric Aerial Manipulators}, booktitle = {2017 IEEE Int. Conf. on Robotics and Automation}, year = {2017}, month = {05/2017}, pages = {6375-6380}, address = {Singapore}, abstract = {We present a control methodology for underactuated aerial manipulators that is both easy to implement on real systems and able to achieve highly dynamic behaviors. The method is composed by two parts: i) a nominal input/state trajectory generator that takes into account the full-body dynamics of the system exploiting its differential flatness property; ii) a decentralized feedback controller acting on the actuated degrees of freedom that confers the needed robustness to the closed-loop system. We demonstrate that the proposed controller is able to precisely track dynamic trajectories when implemented on a standard hardware. Comparative experiments clearly show the benefit of using the nominal input/state generator.}, attachments = {https://homepages.laas.fr/afranchi/robotics/sites/default/files/2017g-TogYueBuoFra-preprint.pdf , https://homepages.laas.fr/afranchi/robotics/sites/default/files/2017g-TogYueBuoFra.mp4}, author = {Marco Tognon and Burak Y{\"u}ksel and Gabriele Buondonno and Antonio Franchi} } @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} } @inbook {2013n-SpeNotBueFra, title = {Aggressive Maneuver Regulation of a Quadrotor UAV}, booktitle = {Robotics Research, The 16th International Symposium ISRR}, volume = {114}, number = {Springer Tracts in Advanced Robotics}, year = {2016}, month = {04/2016}, pages = {95-112}, publisher = {Springer}, organization = {Springer}, abstract = {In this paper we design a nonlinear controller for aggressive maneuvering of a quadrotor. We take a maneuver regulation perspective. Differently from the classical trajectory tracking approach, maneuver regulation does not require following a timed reference state, but a geometric {\textquotedblleft}path{\textquotedblright} with a velocity (and possibly orientation) profile assigned on it. The proposed controller re- lies on three main ideas. Given a desired maneuver, i.e., a set of state trajectories equivalent under time translations, the system dynamics is decomposed into dynamics longitudinal and transverse to the maneuver. A space-dependent version of the transverse dynamics is derived, by using the longitudinal state, i.e., the arc-length of the path, as an independent variable. Then the controller is obtained as a function of the arc-length consisting of two terms: a feedforward term, being the nominal input to apply when on the path at the current arc-length, and a feedback term exponentially stabilizing the state-dependent transverse dynamics. Numerical computations are presented to prove the effectiveness of the proposed strategy. The controller performances are tested in presence of uncertainty of the model parameters and input noise and saturations. The controller is also tested in a realistic simulation environment validated against an experimental test-bed.}, keywords = {Aerial Robotics}, attachments = {https://homepages.laas.fr/afranchi/robotics/sites/default/files/2013n-SpeNotBueFra-preprint.pdf , https://homepages.laas.fr/afranchi/robotics/sites/default/files/2013n-SpeNotBueFra-1_no_sat.mp4 , https://homepages.laas.fr/afranchi/robotics/sites/default/files/2013n-SpeNotBueFra-1_no_sat_zoom.mp4 , https://homepages.laas.fr/afranchi/robotics/sites/default/files/2013n-SpeNotBueFra-2_sat_8_5.mp4 , https://homepages.laas.fr/afranchi/robotics/sites/default/files/2013n-SpeNotBueFra-2_sat_8_5_zoom.mp4 , https://homepages.laas.fr/afranchi/robotics/sites/default/files/2013n-SpeNotBueFra-2_sat_7.mp4 , https://homepages.laas.fr/afranchi/robotics/sites/default/files/2013n-SpeNotBueFra-2_sat_7_zoom.mp4}, author = {Sara Spedicato and Giuseppe Notarstefano and Heinrich H. B{\"u}lthoff and Antonio Franchi} } @conference {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 {2016k-YueBuoFra, title = {Differential Flatness and Control of Protocentric Aerial Manipulators with Any Number of Arms and Mixed Rigid-/Elastic-Joints}, booktitle = {2016 IEEE/RSJ Int. Conf. on Intelligent Robots and System}, year = {2016}, month = {10/2016}, pages = {561-566}, address = {Daejeon, South Korea}, abstract = {In this paper we introduce a particularly relevant class of aerial manipulators that we name protocentric. These robots are formed by an underactuated aerial vehicle, a planarVertical Take-Off and Landing (PVTOL), equipped with any number of different parallel manipulator arms with the only property that all the first joints are attached at the Center of Mass (CoM) of the PVTOL, while the center of actuation of the PVTOL can be anywhere. We prove that protocentric aerial manipulators (PAMs) are differentially flat systems regardless the number of joints of each arm and their kinematic and dynamic parameters. The set of flat outputs is constituted by the CoM of the PVTOL and the absolute orientation angles of all the links. The relative degree of each output is equal to four. More amazingly, we prove that PAMs are differentially flat even in the case that any number of the joints are elastic, no matter the internal distribution between elastic and rigid joints. The set of flat outputs is the same but in this case the total relative degree grows quadratically with the number of elastic joints. We validate the theory by simulating object grasping and transportation tasks with unknown mass and parameters and using a controller based on dynamic feedback linearization.}, attachments = {https://homepages.laas.fr/afranchi/robotics/sites/default/files/2016k-YueBuoFra-preprint.pdf , https://homepages.laas.fr/afranchi/robotics/sites/default/files/2016k-YueBuoFra-tech_report.pdf , https://homepages.laas.fr/afranchi/robotics/sites/default/files/2016k-YueBuoFra.mp4}, author = {Burak Y{\"u}ksel and Gabriele Buondonno and Antonio Franchi} } @article {2016h-SteCogOriBueFra, title = {Ground and Aerial Mutual Localization using Anonymous Relative-Bearing Measurements}, journal = {IEEE Transaction on Robotics}, volume = {32}, year = {2016}, month = {09/2017}, pages = {1133-1151}, abstract = {We present a decentralized algorithm for estimating mutual poses (i.e., relative positions and orientations) in a group of mobile robots. The algorithm uses only anonymous relative-bearing measurements obtainable, e.g., using onboard monocular cameras, and onboard motion measurements, such as inertial ones (acceleration and angular velocity). Onboard relative-bearing sensors supply anonymous measurements, i.e., they provide the directions along which other robots are located but each direction is not associated to any robot (identities are unknown). The issue of anonymity is often overlooked in theory but represents a real problem in practice, especially when employing onboard vision. The solution is first presented for ground robots, in SE(2), and then for aerial robots, in SE(3), in order to emphasize the difference between the two cases. The proposed method is based on a two-step approach, the first uses instantaneous geometrical arguments on the anonymous measurements in order to retrieve the most likely unscaled relative configurations together with the identities, the second uses a numeric Bayesian filtering in order to take advantage of the motion model over time and to retrieve the scale. The proposed method exhibits robustness w.r.t. false positives and negatives of the robot detector. An extensive experimental validation of the algorithm is performed using Khepera III ground mobile robots and quadrotor aerial robots.}, attachments = {https://homepages.laas.fr/afranchi/robotics/sites/default/files/2016h-SteCogOriBueFra-preprint.pdf , https://homepages.laas.fr/afranchi/robotics/sites/default/files/2016h-SteCogOriBueFra.mp4}, author = {Paolo Stegagno and Marco Cognetti and Giuseppe Oriolo and Heinrich H. B{\"u}lthoff and Antonio Franchi} } @conference {2016j-RylBicFra, title = {Modeling and Control of FAST-Hex: a Fully-Actuated by Synchronized-Tilting Hexarotor}, booktitle = {2016 IEEE/RSJ Int. Conf. on Intelligent Robots and System}, year = {2016}, month = {10/2016}, pages = {1689-1694}, address = {Daejeon, South Korea}, abstract = {We present FAST-Hex, a novel UAV concept which is able to smoothly change its configuration from underactuated to fully actuated by using only one additional motor that tilts all propellers at the same time. FAST-Hex can adapt to the task at hand by finely tuning its configuration from the efficient (but underactuated) flight (typical of coplanar multi{\textendash} rotor platforms) to the full-pose-tracking (but less efficient) flight, which is attainable by non-coplanar multi-rotors. We also introduce a novel full-pose geometric controller for generic multi-rotors (not only the FAST-Hex) that outperforms classical inverse dynamics approaches. The controller receives as input any reference pose in R^3{\texttimes}SO(3) (3D position + 3D orientation). Exact tracking is achieved if the reference pose is feasible with respect to the propeller spinning rate saturations. In case of unfeasibility a new feasible desired trajectory is generated online giving priority to the positional part. The new controller is tested with the FAST-Hex but can be used for many other multi-rotor platforms: underactuated, slightly fully-actuated and completely fully-actuated.}, attachments = {https://homepages.laas.fr/afranchi/robotics/sites/default/files/2016j-RylBicFra-preprint.pdf , https://homepages.laas.fr/afranchi/robotics/sites/default/files/2016j-RylBicFra.mp4}, author = {Markus Ryll and Davide Bicego and Antonio Franchi} } @conference {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 {2015e-RajRylBueFra, title = {Modeling, Control and Design Optimization for a Fully-actuated Hexarotor Aerial Vehicle with Tilted Propellers}, booktitle = {2015 IEEE Int. Conf. on Robotics and Automation}, year = {2015}, month = {05/2015}, pages = {4006-4013}, address = {Seattle, WA}, keywords = {Aerial Robotics, UAV hardware platforms}, attachments = {https://homepages.laas.fr/afranchi/robotics/sites/default/files/2015e-RajRylBueFra-preprint.pdf , https://homepages.laas.fr/afranchi/robotics/sites/default/files/2015e-RajRylBueFra.mp4}, author = {Sujit Rajappa and Markus Ryll and Heinrich H. B{\"u}lthoff and Antonio Franchi} } @article {2014i-ZelRobBueFra, title = {Decentralized Rigidity Maintenance Control with Range Measurements for Multi-Robot Systems}, journal = {The International Journal of Robotics Research}, volume = {34}, year = {2014}, pages = {105-128}, abstract = {This work proposes a fully decentralized strategy for maintaining the formation rigidity of a multi-robot system using only range measurements, while still allowing the graph topology to change freely over time. In this direction, a first contribution of this work is the new concept of weighted frameworks and rigidity, and of the rigidity eigenvalue, which when positive ensures the infinitesimal rigidity of a weighted framework. We then propose a distributed algorithm for estimating a common relative position reference frame amongst a team of robots with only range measurements in addition to one agent endowed with the capability of measuring the bearing to two other agents. This first estimation step is embedded into a subsequent distributed algorithm for estimating the rigidity eigenvalue associated with the weighted framework. The estimate of the rigidity eigenvalue is finally used to generate a local control action for each agent that both maintains the rigidity property and enforces additional constraints such as collision avoidance and sensing/communication range limits and occlusions. As an additional feature of our approach, the communication and sensing links among the robots are also left free to change over time while preserving rigidity of the whole framework. The proposed scheme is then experimentally validated with a robotic testbed consisting of 6 quadrotor UAVs operating in a cluttered environment.}, keywords = {Motion control of multiple robots, Rigidity mainenance}, attachments = {https://homepages.laas.fr/afranchi/robotics/sites/default/files/1309.0535v3.pdf , https://homepages.laas.fr/afranchi/robotics/sites/default/files/1309.0535v2.pdf}, author = {Daniel Zelazo and Antonio Franchi and Heinrich H. B{\"u}lthoff and Paolo Robuffo Giordano} } @booklet {2014l-GioSalFraMalSchMelRylBuePra, title = {The Flying Hand: a Teleoperation Framework for Cooperative Aerial Grasping and Transportation}, howpublished = {Automatica.it 2014, Convegno Annuale dei Docenti e Ricercatori Italiani in Automatica}, year = {2014}, month = {09/2014}, address = {Bergamo, Italy}, keywords = {workshop}, author = {Guido Gioioso and Gionata Salvietti and Antonio Franchi and Monica Malvezzi and Stefano Scheggi and L. Meli and Markus Ryll and Heinrich H. B{\"u}lthoff and Domenico Prattichizzo} } @conference {2014g-GagOriBueFra, title = {Image-based Road Network Clearing without Localization and without Maps using a Team of UAVs}, booktitle = {2014 European Control Conference}, year = {2014}, month = {06/2014}, pages = {1902-1908}, address = {Strasbourg, France}, abstract = {We address the problem of clearing an arbitrary and unknown network of roads using an organized team of Unmanned Aerial Vehicles (UAVs) equipped with a monocular down-facing camera, an altimeter, plus high-bandwidth short- range and low-bandwidth long-range communication systems. We allow the UAVs to possibly split in several subgroups. In each subgroup a leader guides the motion employing a hierarchical coordination. A feature/image-based algorithm guides the subgroup toward the unexplored region without any use of global localization or environmental mapping. At the same time all the entry-points of the the explored region are kept under control, so that any moving object that enters or exits the previously cleared area. Simulative results on real aerial images demonstrate the functionalities and the effectiveness of the proposed algorithm. }, keywords = {Aerial Robotics, Exploration, Motion control of multiple robots, Patrolling / Surveillance, Pursuit-evasion / Clearing}, attachments = {https://homepages.laas.fr/afranchi/robotics/sites/default/files/2014g-GagOriBueFra-preprint.pdf , https://homepages.laas.fr/afranchi/robotics/sites/default/files/2014g-GagOriBueFra-video.mp4}, author = {Matteo Gagliardi and Giuseppe Oriolo and Heinrich H. B{\"u}lthoff and Antonio Franchi} } @conference {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 {2014c-MasRobBueFra, title = {Semi-autonomous Trajectory Generation for Mobile Robots with Integral Haptic Shared Control}, booktitle = {2014 IEEE Int. Conf. on Robotics and Automation}, year = {2014}, month = {05/2014}, pages = {6468-6475}, address = {Hong Kong, China}, abstract = {A new framework for semi-autonomous path plan- ning for mobile robots that extends the classical paradigm of bilateral shared control is presented. The path is represented as a B-spline and the human operator can modify its shape by controlling the motion of a finite number of control points. An autonomous algorithm corrects in real time the human directives in order to facilitate path tracking for the mobile robot and ensures i) collision avoidance, ii) path regularity, and iii) attraction to nearby points of interest. A haptic feedback algorithm processes both human{\textquoteright}s and autonomous control terms, and their integrals, to provide an information of the mismatch between the path specified by the operator and the one corrected by the autonomous algorithm. The framework is validated with extensive experiments using a quadrotor UAV and a human in the loop with two haptic interfaces. }, keywords = {Bilateral Shared Control of Mobile Robots}, attachments = {https://homepages.laas.fr/afranchi/robotics/sites/default/files/2014c-MasRobBueFra-preprint.pdf , https://homepages.laas.fr/afranchi/robotics/sites/default/files/2014c-MasRobBueFra.mp4}, author = {Carlo Masone and Paolo Robuffo Giordano and Heinrich H. B{\"u}lthoff and Antonio Franchi} } @conference {2014e-SteBasBueFra, title = {A Semi-autonomous UAV Platform for Indoor Remote Operation with Visual and Haptic Feedback}, booktitle = {2014 IEEE Int. Conf. on Robotics and Automation}, year = {2014}, month = {05/2014}, pages = {3862-3869}, address = {Hong Kong, China}, abstract = {We present the development of a semi-autonomous quadrotor UAV platform for indoor teleoperation using RGB- D technology as exteroceptive sensor. The platform integrates IMU and Dense Visual Odometry pose estimation in order to stabilize the UAV velocity and track the desired velocity commanded by a remote operator though an haptic inter- face. While being commanded, the quadrotor autonomously performs a persistent pan-scanning of the surrounding area in order to extend the intrinsically limited field of view. The RGB-D sensor is used also for collision-safe navigation using a probabilistically updated local obstacle map. In the operator visual feedback, pan-scanning movement is real time compensated by an IMU-based adaptive filtering algorithm that lets the operator perform the drive experience in a oscillation- free frame. An additional sensory channel for the operator is provided by the haptic feedback, which is based on the obstacle map and velocity tracking error in order to convey information about the environment and quadrotor state. The effectiveness of the platform is validated by means of experiments performed without the aid of any external positioning system.}, keywords = {Aerial Robotics, Localization of aerial robots, UAV hardware platforms}, attachments = {https://homepages.laas.fr/afranchi/robotics/sites/default/files/2014e-SteBasBueFra-preprint.pdf , https://homepages.laas.fr/afranchi/robotics/sites/default/files/2014e-SteBasBueFra.mp4}, author = {Paolo Stegagno and Massimo Basile and Heinrich H. B{\"u}lthoff and Antonio Franchi} } @conference {2014b-GioRylPraBueFra, title = {Turning a Near-hovering Controlled Quadrotor into a 3D Force Effector}, booktitle = {2014 IEEE Int. Conf. on Robotics and Automation}, year = {2014}, month = {05/2014}, pages = {6278-6284}, address = {Hong Kong, China}, abstract = {In this paper the problem of a quadrotor that physically interacts with the surrounding environment through a rigid tool is considered. We present a theoretical design that allows to exert an arbitrary 3D force by using a standard near-hovering controller that was originally developed for contact-free flight control. This is achieved by analytically solving the nonlinear system that relates the quadrotor state, the force exerted by the rigid tool on the environment, and the near-hovering controller action at the equilibrium points, during any generic contact. Stability of the equilibria for the most relevant actions (pushing, releasing, lifting, dropping, and left-right shifting) are proven by means of numerical analysis using the indirect Lyapunov method. An experimental platform, including a suitable tool design, has been developed and used to validate the theory with preliminary experiments.}, keywords = {Aerial Physical Interaction, Aerial Robotics, UAV hardware platforms}, attachments = {https://homepages.laas.fr/afranchi/robotics/sites/default/files/2014b-GioRylPraBueFra-preprint.pdf , https://homepages.laas.fr/afranchi/robotics/sites/default/files/2014b-GioRylPraBueFra.mp4}, author = {Guido Gioioso and Markus Ryll and Domenico Prattichizzo and Heinrich H. B{\"u}lthoff and Antonio Franchi} } @conference {2013d-SecFraBueRob, title = {Bilateral Control of the Degree of Connectivity in Multiple Mobile-robot Teleoperation}, booktitle = {2013 IEEE Int. Conf. on Robotics and Automation}, year = {2013}, month = {05/2013}, address = {Karlsruhe, Germany}, abstract = {This paper presents a novel bilateral controller that allows to stably teleoperate the degree of connectivity in the mutual interaction between a remote group of mobile robots considered as the slave-side. A distributed leader-follower scheme allows the human operator to command the overall group motion. The group autonomously maintains the connectivity of the interaction graph by using a decentralized gradient descent approach applied to the Fiedler eigenvalue of a properly weighted Laplacian matrix. The degree of connectivity, and then the flexibility, of the interaction graph can be finely tuned by the human operator through an additional bilateral teleoperation channel. Passivity of the overall system is theoretically proven and extensive human/hardware in-the-loop simulations are presented to empirically validate the theoretical analysis.}, keywords = {Bilateral Shared Control of Mobile Robots, Connectivity maintenance}, attachments = {https://homepages.laas.fr/afranchi/robotics/sites/default/files/2013d-SecFraBueRob.pdf , https://homepages.laas.fr/afranchi/robotics/sites/default/files/2013d-SecFraBueRob.mp4}, author = {Cristian Secchi and Antonio Franchi and Heinrich H. B{\"u}lthoff and Paolo Robuffo Giordano} } @article {2011q-SonFraChuKimBueRob, title = {Human-Centered Design and Evaluation of Haptic Cueing for Teleoperation of Multiple Mobile Robots}, journal = {IEEE Transactions on Systems, Man, \& Cybernetics. Part B: Cybernetics}, volume = {43}, year = {2013}, month = {04/2013}, pages = {597-609}, abstract = {In this paper, we investigate the effect of haptic cueing on human operator{\textquoteright}s performance in the field of bilateral teleoperation of multiple mobile robots, in particular multiple unmanned aerial vehicles (UAVs). Two aspects of human performance are deemed important in this area, namely the maneuverability of mobile robots and perceptual sensitivity of the remote environment. We introduce metrics that allow us to address these aspects in two psychophysical studies, which are reported here. Three fundamental haptic cue types were evaluated. The Force cue conveys information on the proximity of the commanded trajectory to obstacles in the remote environment. The Velocity cue represents the mismatch between the commanded and actual velocity of the UAVs and can implicitly provide a rich amount of information regarding the actual behavior of the UAVs. Finally, the Velocity+Force cue is a linear combination of the two. Our experimental results show that while maneuverability is best supported by the Force cue feedback, perceptual sensitivity is best served by the Velocity cue feedback. In addition, we show that large gains in the haptic feedbacks do not always guarantee an enhancement in teleoperator{\textquoteright}s performance.}, keywords = {Evaluation, Force feedback, Haptics, Multi-robot systems, Psychophysical evaluation of haptic feedback, Psychophysics, Teleoperation}, attachments = {https://homepages.laas.fr/afranchi/robotics/sites/default/files/2013a-SonFraChuKimBueRob_1.pdf}, author = {Hyoung Il Son and Antonio Franchi and Lewis L. Chuang and Junsuk Kim and Heinrich H. B{\"u}lthoff and Paolo Robuffo Giordano} } @booklet {2013h-NesRieLaeHarBotRobFra, title = {Interactive Demo: Haptic Remote Control of Multiple UAVs with Autonomous Cohesive Behavior}, howpublished = {Int. Work. on Towards Fully Decentralized Multi-Robot Systems: Hardware, Software and Integration, at 2013 IEEE Int. Conf. on Robotics and Automation}, year = {2013}, month = {05/2013}, address = {Karlsruhe, Germany}, keywords = {Bilateral Shared Control of Mobile Robots, Connectivity maintenance, Middleware for robotics, UAV hardware platforms}, url = {http://icra2013mrs.tuebingen.mpg.de/}, author = {Thomas Nestmeyer and Martin Riedel and Johannes L{\"a}chele and Simon Hartmann and Fiete Botschen and Paolo Robuffo Giordano and Antonio Franchi} } @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 {2013j-GraRieBueRobFra, title = {The TeleKyb Framework for a Modular and Extendible ROS-based Quadrotor Control}, booktitle = {6th European Conference on Mobile Robots}, year = {2013}, month = {09/2013}, address = {Barcelona, Spain}, abstract = {The free and open source Tele-Operation Platform of the MPI for Biological Cybernetics (TeleKyb) is an end- to-end software framework for the development of bilateral teleoperation systems between human interfaces (e.g., haptic force feedback devices or gamepads) and groups of quadrotor Unmanned Aerial Vehicles (UAVs). Among drivers for devices and robots from various hardware manufactures, TeleKyb provides a high-level closed-loop robotic controller for mobile robots that can be extended dynamically with modules for state estimation, trajectory planning, processing, and tracking. Since all internal communication is based on the Robot Operating System (ROS), TeleKyb can be easily extended to meet future needs. The capabilities of the overall framework are demonstrated in both an experimental validation of the controller for an individual quadrotor and a complex experimental setup involving bilateral human-robot interaction and shared formation control of multiple UAVs.}, keywords = {Middleware for robotics, UAV hardware platforms}, url = {http://www.ros.org/wiki/telekyb}, attachments = {https://homepages.laas.fr/afranchi/robotics/sites/default/files/2013j-GraRieBueRobFra-preprint.pdf}, author = {Volker Grabe and Martin Riedel and Heinrich H. B{\"u}lthoff and Paolo Robuffo Giordano and Antonio Franchi} } @conference {2013p-SteBasBueFra, title = {Vision-based Autonomous Control of a Quadrotor UAV using an Onboard RGB-D Camera and its Application to Haptic Teleoperation}, booktitle = {2nd IFAC Workshop on Research, Education and Development of Unmanned Aerial Systems}, year = {2013}, month = {11/2013}, address = {Compiegne, France}, keywords = {Aerial Robotics}, attachments = {https://homepages.laas.fr/afranchi/robotics/sites/default/files/2013p-SteBasBueFra-preprint.pdf}, author = {Paolo Stegagno and Massimo Basile and Heinrich H. B{\"u}lthoff and Antonio Franchi} } @conference {2012c-CogSteFraOriBue, title = {3D Mutual Localization with Anonymous Bearing Measurements}, booktitle = {2012 IEEE Int. Conf. on Robotics and Automation}, year = {2012}, month = {05/2012}, address = {St. Paul, MN}, abstract = {We present a decentralized algorithm for estimating mutual 3-D poses in a group of mobile robots, such as a team of UAVs. Our algorithm uses bearing measurements reconstructed, e.g., by a visual sensor, and inertial measurements coming from the robot IMU. Since identification of a specific robot in a group would require visual tagging and may be cumbersome in practice, we simply assume that the bear- ing measurements are anonymous. The proposed localization method is a non-trivial extension of our previous algorithm for the 2-D case, and exhibits similar performance and robustness. An experimental validation of the algorithm has been performed using quadrotor UAVs.}, keywords = {Distributed algorithms, Estimation, Localization, Localization of aerial robots, Multi-robot systems}, attachments = {https://homepages.laas.fr/afranchi/robotics/sites/default/files/2012c-CogSteFraOriBue.pdf}, author = {Marco Cognetti and Paolo Stegagno and Antonio Franchi and Giuseppe Oriolo and Heinrich H. B{\"u}lthoff} } @conference {2012j-SpiFraOriBueRob, title = {Aerial Grasping of a Moving Target with a Quadrotor UAV}, booktitle = {2012 IEEE/RSJ Int. Conf. on Intelligent Robots and Systems}, year = {2012}, month = {10/2012}, pages = {4985-4992}, address = {Vilamoura, Portugal}, abstract = {For a quadrotor aircraft, we study the problem of planning a trajectory that connects two arbitrary states while allowing the UAV to grasp a moving target at some intermediate time. To this end, two classes of canonical grasping maneuvers are defined and characterized. A planning strategy relying on differential flatness is then proposed to concatenate one or more grasping maneuvers by means of spline-based subtrajectories, with the additional objective of minimizing the total transfer time. The proposed planning algorithm is not restricted to pure hovering-to-hovering motions and takes into account practical constraints, such as the finite duration of the grasping phase. The effectiveness of the proposed approach is shown by means of physically-based simulations.}, keywords = {Motion Planning, Optimal Trajectory Planning}, attachments = {https://homepages.laas.fr/afranchi/robotics/sites/default/files/2012j-SpiFraOriBueRob.pdf , https://homepages.laas.fr/afranchi/robotics/sites/default/files/2012j-SpiFraOriBueRob.mp4}, author = {Riccardo Spica and Antonio Franchi and Giuseppe Oriolo and Heinrich H. B{\"u}lthoff and Paolo Robuffo Giordano} } @conference {2012b-SecFraBueRob, title = {Bilateral Teleoperation of a Group of UAVs with Communication Delays and Switching Topology}, booktitle = {2012 IEEE Int. Conf. on Robotics and Automation}, year = {2012}, month = {05/2012}, address = {St. Paul, MN}, abstract = {In this paper, we present a passivity-based decentralized approach for bilaterally teleoperating a group of UAVs composing the slave side of the teleoperation system. In particular, we explicitly consider the presence of time delays, both among the master and slave, and within UAVs composing the group. Our focus is on analyzing suitable (passive) strategies that allow a stable teloperation of the group despite presence of delays, while still ensuring high flexibility to the group topology (e.g., possibility to autonomously split or join during the motion). The performance and soundness of the approach is validated by means of human/hardware-in-the-loop simulations (HHIL).}, keywords = {Bilateral Shared Control of Mobile Robots, Decentralized control, Distributed algorithms, Force feedback, Motion control of multiple robots, Multi-robot systems, Teleoperation}, attachments = {https://homepages.laas.fr/afranchi/robotics/sites/default/files/2012d-SecFraBueRob.pdf , https://homepages.laas.fr/afranchi/robotics/sites/default/files/2012d-SecFraBueRob.mp4}, author = {Cristian Secchi and Antonio Franchi and Heinrich H. B{\"u}lthoff and Paolo Robuffo Giordano} } @article {2012e-FraSecSonBueRob, title = {Bilateral Teleoperation of Groups of Mobile Robots with Time-Varying Topology}, journal = {IEEE Transaction on Robotics}, volume = {28}, year = {2012}, month = {10/2012}, pages = {1019 -1033}, abstract = {In this paper, a novel decentralized control strategy for bilaterally teleoperating heterogeneous groups of mobile robots from different domains (aerial, ground, marine and under- water) is proposed. By using a decentralized control architecture, the group of robots, treated as the slave-side, is made able to navigate in a cluttered environment while avoiding obstacles, inter-robot collisions and following the human motion commands. Simultaneously, the human operator acting on the master side is provided with a suitable force feedback informative of the group response and of the interaction with the surrounding environment. Using passivity based techniques, we allow the behavior of the group to be as flexible as possible with arbitrary split and join events (e.g., due to inter-robot visibility/packet losses or specific task requirements) while guaranteeing the stability of the system. We provide a rigorous analysis of the system stability and steady-state characteristics, and validate performance through human/hardware-in-the-tloop simulations by considering a heterogeneous fleet of UAVs and UGVs as case study. Finally, we also provide an experimental validation with 4 quadrotor UAV}, keywords = {Bilateral Shared Control of Mobile Robots, Decentralized control, Distributed algorithms, Force feedback, Haptics, Motion control of multiple robots, Multi-robot systems, Teleoperation}, attachments = {https://homepages.laas.fr/afranchi/robotics/sites/default/files/2012e-FraSecSonBueRob.pdf}, author = {Antonio Franchi and Cristian Secchi and Hyoung Il Son and Heinrich H. B{\"u}lthoff and Paolo Robuffo Giordano} } @article {2010f-FraPasBul, title = {On Cooperative Patrolling: Optimal Trajectories, Complexity Analysis, and Approximation Algorithms}, journal = {IEEE Transaction on Robotics}, volume = {28}, year = {2012}, month = {06/2012}, pages = {592-606}, abstract = {The subject of this work is the patrolling of an environment with the aid of a team of autonomous agents. We consider both the design of open-loop trajectories with optimal properties, and of distributed control laws converging to optimal trajectories. As performance criteria, the refresh time and the latency are considered, i.e., respectively, time gap between any two visits of the same region, and the time necessary to inform every agent about an event occurred in the environment. We associate a graph with the environment, and we study separately the case of a chain, tree, and cyclic graph. For the case of chain graph, we first describe a minimum refresh time and latency team trajectory, and we propose a polynomial time algorithm for its computation. Then, we describe a distributed procedure that steers the robots toward an optimal trajectory. For the case of tree graph, a polynomial time algorithm is developed for the minimum refresh time problem, under the technical assumption of a constant number of robots involved in the patrolling task. Finally, we show that the design of a minimum refresh time trajectory for a cyclic graph is NP-hard, and we develop a constant factor approximation algorithm.}, keywords = {Coverage, Distributed algorithms, Multi-robot systems, Patrolling / Surveillance}, attachments = {https://homepages.laas.fr/afranchi/robotics/sites/default/files/2010f-FraPasBul-preprint.pdf}, author = {Fabio Pasqualetti and Antonio Franchi and Francesco Bullo} } @article {2011c-DurFraBul, title = {Distributed Pursuit-Evasion without Mapping or Global Localization via Local Frontiers}, journal = {Autonomous Robots}, volume = {32}, year = {2012}, month = {01/2012}, pages = {81-95}, abstract = {This paper addresses a visibility-based pursuit-evasion problem in which a team of mobile robots with limited sensing and communication capabilities must coordinate to detect any evaders in an unknown, multiply-connected planar environment. Our distributed algorithm to guarantee evader detection is built around maintaining complete coverage of the frontier between cleared and contaminated regions while expanding the cleared region. We detail a novel distributed method for storing and updating this frontier without building a map of the environment or requiring global localization. We demonstrate the functionality of the algorithm through simulations in realistic environments and through hardware experiments. We also compare Monte Carlo results for our algorithm to the theoretical optimum area cleared as a function of the number of robots available.}, keywords = {Coverage, Distributed algorithms, Multi-robot systems, Pursuit-evasion / Clearing}, url = {http://www.springerlink.com/content/a02pr41790ll754w/}, attachments = {https://homepages.laas.fr/afranchi/robotics/sites/default/files/2011c-DurFraBul-preprint.pdf , https://homepages.laas.fr/afranchi/robotics/sites/default/files/2011c-DurFraBul-video1.mp4}, author = {Joseph W. Durham and Antonio Franchi and Francesco Bullo} } @conference {2012h-RieFraRobBueSon, title = {Experiments on Intercontinental Haptic Control of Multiple UAVs}, booktitle = {12th Int. Conf. on Intelligent Autonomous Systems}, year = {2012}, month = {06/2012}, pages = {227-238}, address = {Jeju Island, Korea}, abstract = {In this paper we propose and experimentally validate a bilateral teleoperation framework where a group of UAVs are controlled over an unreliable network with typical intercontinental time delays and packet losses. This setting is meant to represent a realistic and challenging situation for the stability the bilateral closed-loop system. In order to increase human telepresence, the system provides the operator with both a video stream coming from the onboard cameras mounted on the UAVs, and with a suitable haptic cue, generated by a force-feedback device, informative of the UAV tracking performance and presence of impediments on the remote site. In addition to the theoretical background, we describe the hardware and software implementation of this intercontinental teleoperation: this is composed of a semi-autonomous group of multiple quadrotor UAVs, a 3-DOF haptic interface, and a network connection based on a VPN tunnel between Germany and South Korea. The whole software framework is based upon the Robotic Operating System (ROS) communication standard.}, keywords = {Bilateral Shared Control of Mobile Robots, Haptics, Middleware for robotics, Multi-robot systems, Teleoperation, UAV hardware platforms}, attachments = {https://homepages.laas.fr/afranchi/robotics/sites/default/files/2012h-RieFraRobBueSon.pdf , https://homepages.laas.fr/afranchi/robotics/sites/default/files/2012h-RieFraRobBueSon.mp4}, author = {Martin Riedel and Antonio Franchi and Heinrich H. B{\"u}lthoff and Paolo Robuffo Giordano and Hyoung Il Son} } @conference {2012k-MasFraBueRob, title = {Interactive Planning of Persistent Trajectories for Human-Assisted Navigation of Mobile Robots}, booktitle = {2012 IEEE/RSJ Int. Conf. on Intelligent Robots and Systems}, year = {2012}, month = {10/2012}, pages = {2641-2648}, address = {Vilamoura, Portugal}, abstract = {This work extends the framework of bilateral shared control of mobile robots with the aim of increasing the robot autonomy and decreasing the operator commitment. We consider persistent autonomous behaviors where a cyclic motion must be executed by the robot. The human operator is in charge of modifying online some geometric properties of the desired path. This is then autonomously processed by the robot in order to produce an actual path guaranteeing: i) tracking feasibility, ii) collision avoidance with obstacles, iii) closeness to the desired path set by the human operator, and iv) proximity to some points of interest. A force feedback is implemented to inform the human operator of the global deformation of the pathrather than using the classical mismatch between desired and executed motion commands. Physically-based simulations, with human/hardware-in-the-loop and a quadrotor UAV as robotic platform, demonstrate the feasibility of the method. }, keywords = {Bilateral Shared Control of Mobile Robots, Force feedback, Haptics, Motion Planning, Optimal Trajectory Planning, Teleoperation}, attachments = {https://homepages.laas.fr/afranchi/robotics/sites/default/files/2012k-MasFraBueRob.pdf , https://homepages.laas.fr/afranchi/robotics/sites/default/files/2012k-MasFraBueRob.mp4}, author = {Carlo Masone and Antonio Franchi and Heinrich H. B{\"u}lthoff and Paolo Robuffo Giordano} } @booklet {2012q-RieFraBueRob, title = {Intercontinental Haptic Control and Advanced Supervisory Interfaces for Groups of Multiple UAVs}, howpublished = {5th Int. Work. on Human-Friendly Robotics}, year = {2012}, month = {10/2012}, address = {Bruxelles, Belgium}, keywords = {Bilateral Shared Control of Mobile Robots, Middleware for robotics, Motion control of multiple robots, UAV hardware platforms}, author = {Martin Riedel and Heinrich H. B{\"u}lthoff and Antonio Franchi and Paolo Robuffo Giordano} } @article {2012q-FraMasGraRylBueRob, title = {Modeling and Control of UAV Bearing-Formations with Bilateral High-Level Steering}, journal = {The International Journal of Robotics Research, Special Issue on 3D Exploration, Mapping, and Surveillance}, volume = {31}, year = {2012}, month = {10/2012}, pages = {1504-1525}, abstract = {In this paper we address the problem of controlling the motion of a group of UAVs bound to keep a formation defined in terms of only relative angles (i.e., a bearing-formation). This problem can naturally arise within the context of several multi-robot applications such as, e.g., exploration, coverage, and surveillance. First, we introduce and thoroughly analyze the concept and properties of bearing-formations, and provide a class of minimally linear sets of bearings sufficient to uniquely define such formations. We then propose a bearing-only formation controller requiring only bearing measurements, converging almost globally, and maintaining bounded inter-agent distances despite the lack of direct metric information. The controller still leaves the possibility to impose group motions tangent to the current bearing-formation. These can be either autonomously chosen by the robots because of any additional task (e.g., exploration), or exploited by an assisting human co-operator. For this latter {\textquoteleft}human-in-the-loop{\textquoteright} case, we propose a multi-master/multi-slave bilateral shared control system providing the co-operator with some suitable force cues informative of the UAV performance. The proposed theoretical framework is extensively validated by means of simulations and experiments with quadrotor UAVs equipped with onboard cameras. Practical limitations, e.g., limited field-of-view, are also considered.}, keywords = {Bilateral Shared Control of Mobile Robots, Decentralized control, Force feedback, Formation control, Haptics, Motion control of multiple robots, Multi-robot systems, Teleoperation}, attachments = {https://homepages.laas.fr/afranchi/robotics/sites/default/files/2012q-FraMasGraRylBueRob-preprint.pdf}, author = {Antonio Franchi and Carlo Masone and Volker Grabe and Markus Ryll and Heinrich H. B{\"u}lthoff and Paolo Robuffo Giordano} } @conference {2012g-ZelFraAlgBueRob, title = {Rigidity Maintenance Control for Multi-Robot Systems}, booktitle = {2012 Robotics: Science and Systems Conference}, year = {2012}, month = {07/2012}, address = {Sydney, Australia}, abstract = {Rigidity of formations in multi-robot systems is important for formation control, localization, and sensor fusion. This work proposes a rigidity maintenance gradient controller for a multi-agent robot team. To develop such a controller, we first provide an alternative characterization of the rigidity matrix and use that to introduce the novel concept of the rigidity eigenvalue. We provide a necessary and sufficient condition relating the positivity of the rigidity eigenvalue to the rigidity of the formation. The rigidity maintenance controller is based on the gradient of the rigidity eigenvalue with respect to each robot position. This gradient has a naturally distributed structure, and is thus amenable to a distributed implementation. Additional requirements such as obstacle and inter-agent collision avoidance, as well as typical constraints such as limited sensing/communication ranges and line-of-sight occlusions, are also explicitly considered. Finally, we present a simulation with a group of seven quadrotor UAVs to demonstrate and validate the theoretical results.}, keywords = {Decentralized control, Formation control, Motion control of multiple robots, Multi-robot systems, Rigidity mainenance}, attachments = {https://homepages.laas.fr/afranchi/robotics/sites/default/files/2012g-ZelFraAlgBueRob-preprint.pdf}, author = {Daniel Zelazo and Antonio Franchi and Frank Allg{\"o}wer and Heinrich H. B{\"u}lthoff and Paolo Robuffo Giordano} } @article {2012f-FraSecRylBueRob, title = {Shared Control: Balancing Autonomy and Human Assistance with a Group of Quadrotor UAVs.}, journal = {IEEE Robotics and Automation Magazine, Special Issue on Aerial Robotics and the Quadrotor Platform}, volume = {19}, year = {2012}, month = {09/2012}, pages = {57-68}, abstract = {In this paper, we present a complete control framework and associated experimental testbed for the bilateral shared control of a group of quadrotor UAVs. This control architecture is applicable to any task and allows to integrate: i) a decentralized topological motion control (responsible for the mutual interactions in the UAV formation), ii) a human assistance module (allowing human intervention, whenever needed, on some aspects of the UAV group behavior), and iii) a force-feedback possibility (increasing the telepresence of the human assistants by providing suitable haptic cues informative of the UAV behavior). We will show, as worked-out case studies, how to specialize the topological motion controller to the relevant cases of constant, unconstrained and connected group topologies, and how to let a human operator intervening at the level of single UAVs or of the whole group dynamics. A detailed description of the experimental testbed is also provided with emphasis on the quadrotor UAV hardware and software architectures. Finally, the versatility of the proposed framework is demonstrated by means of experiments with real UAVs. Although quadrotors are used as actual robotic platforms, the proposed framework can be straightforwardly extended to many different kinds of UAVs with similar motion characteristics.}, keywords = {Bilateral Shared Control of Mobile Robots, Decentralized control, Force feedback, Formation control, Haptics, Middleware for robotics, Motion control of multiple robots, Multi-robot systems, UAV hardware platforms}, attachments = {https://homepages.laas.fr/afranchi/robotics/sites/default/files/2012f-FraSecRylBueRob-preprint.pdf}, author = {Antonio Franchi and Cristian Secchi and Markus Ryll and Heinrich H. B{\"u}lthoff and Paolo Robuffo Giordano} } @booklet {2012p-MasFraBueRob, title = {Shared Trajectory Planning for Human-in-the-loop Navigation of Mobile Robots in Cluttered Environments}, howpublished = {5th Int. Work. on Human-Friendly Robotics}, year = {2012}, month = {10/2012}, address = {Bruxelles, Belgium}, keywords = {Bilateral Shared Control of Mobile Robots, Optimal Trajectory Planning}, author = {Carlo Masone and Antonio Franchi and Heinrich H. B{\"u}lthoff and Paolo Robuffo Giordano} } @inbook {2012m-LaeFraBueRob, title = {SwarmSimX: Real-time Simulation Environment for Multi-robot Systems}, booktitle = {3rd Int. Conf. on Simulation, Modeling, and Programming for Autonomous Robots}, year = {2012}, month = {11/2012}, address = {Tsukuba, Japan}, abstract = {In this paper we present a novel simulation environment called SwarmSimX with the ability to simulate dozens of robots in a realistic 3D environment. The software architecture of SwarmSimX allows new robots, sensors, and other libraries to be loaded at runtime, extending the functionality of the simulation environment significantly. In addition, SwarmSimX allows an easy exchange of the underlying libraries used for the visual and physical simulation to incorporate different libraries (e.g., improved or future versions). A major feature is also the possibility to perform the whole simulation in real-time allowing for human-in-the-loop or hardware-in-the-loop scenarios. SwarmSimX has been already employed in several works presenting haptic shared control of multiple mobile robots (e.g., quadrotor UAVs). Additionally, we present here two validation tests showing the physical delity and the real-time performance of SwarmSimX. For the tests we used NVIDIA PhysX and Ogre3D as physics and rendering libraries, respectively}, keywords = {Multi-robot systems, Simulators for robotics}, attachments = {https://homepages.laas.fr/afranchi/robotics/sites/default/files/2012m-LaeFraBueRob-preprint.pdf}, author = {Johannes L{\"a}chele and Antonio Franchi and Heinrich H. B{\"u}lthoff and Paolo Robuffo Giordano} } @conference {2011e-RobFraSecBue, title = {Bilateral Teleoperation of Groups of UAVs with Decentralized Connectivity Maintenance}, booktitle = {2011 Robotics: Science and Systems Conference}, year = {2011}, month = {06/2011}, address = {Los Angeles, CA}, abstract = {In this paper, we present a decentralized passivity-based control strategy for the bilateral teleoperation of a fleet of Unmanned Aerial Vehicles (UAVs). The human operator at the master side can command the fleet motion and receive suitable force cues informative about the remote environment. By properly controlling the energy exchanged within the slave side (the UAV fleet), we guarantee that the connectivity of the fleet is preserved and we prevent inter-agent and obstacle collisions. At the same time, we allow the behavior of the UAVs to be as flexible as possible with arbitrary split and join maneuvers. The results of the paper are validated through semi-experiments.}, keywords = {Bilateral Shared Control of Mobile Robots, Connectivity maintenance, Decentralized control, Distributed algorithms, Estimation, Force feedback, Haptics, Multi-robot systems, Teleoperation}, attachments = {https://homepages.laas.fr/afranchi/robotics/sites/default/files/2011e-RobFraSecBue-preprint.pdf , https://homepages.laas.fr/afranchi/robotics/sites/default/files/2011e-RobFraSecBue-almost_preprint.pdf , https://homepages.laas.fr/afranchi/robotics/sites/default/files/2011e-RobFraSecBue.mp4}, author = {Paolo Robuffo Giordano and Antonio Franchi and Cristian Secchi and Heinrich H. B{\"u}lthoff} } @conference {2011i-FraMasBueRob, title = {Bilateral Teleoperation of Multiple UAVs with Decentralized Bearing-only Formation Control}, booktitle = {2011 IEEE/RSJ Int. Conf. on Intelligent Robots and Systems}, year = {2011}, month = {09/2011}, pages = {2215-2222}, address = {San Francisco, CA}, abstract = {We present a decentralized system for the bilateral teleoperation of groups of UAVs which only relies on relative bearing measurements, i.e., without the need of distance information or global localization. The properties of a 3D bearing-formation are analyzed, and a minimal set of bearings needed for its definition is provided. We also design a novel decentralized formation control almost globally convergent and able to maintain bounded and non-vanishing inter-distances among the agents despite the absence of direct distance measurements. Furthermore, we develop a multimaster/multi-slave teleoperation setup in order to control the overall behavior of the group and to convey to the human operator suitable force cues, while ensuring stability in presence of delays and packet losses over the master-slave communication channel. The theoretical framework is validated by means of extensive human/hardware in-the-loop simulations using two force-feedback devices and a group of quadrotors.}, keywords = {Bilateral Shared Control of Mobile Robots, Decentralized control, Force feedback, Formation control, Haptics, Motion control of multiple robots, Multi-robot systems, Teleoperation}, attachments = {https://homepages.laas.fr/afranchi/robotics/sites/default/files/2011i-FraMasBueRob-preprint.pdf , https://homepages.laas.fr/afranchi/robotics/sites/default/files/2011i-FraMasBueRob.mp4}, author = {Antonio Franchi and Carlo Masone and Heinrich H. B{\"u}lthoff and Paolo Robuffo Giordano} } @conference {2011g-FraBueRob, title = {Distributed Online Leader Selection in the Bilateral Teleoperation of Multiple UAVs}, booktitle = {50th IEEE Conference on Decision and Control }, year = {2011}, month = {12/2011}, pages = {3559-3565}, address = {Orlando, FL}, abstract = {For several applications like data collection, surveillance, search and rescue and exploration of wide areas, the use of a group of simple robots rather than a single complex robot has proven to be very effective and promising, and the problem of coordinating a group of agents has received a lot of attention over the last years. In this paper, we consider the challenge of establishing a bilateral force-feedback teleoperation channel between a human operator (the master side) and a remote multi-robot system (the slave side) where a special agent, the leader, is selected and directly controlled by the master. In particular, we study the problem of distributed online optimal leader selection, i.e., how to choose, and possibly change, the leader online in order to maximize some suitable criteria related to the tracking performance of the whole group w.r.t. the master commands. Human/hardware-in-the-loop simulation results with a group of UAVs support the theoretical claims of the paper.}, keywords = {Decentralized control, Distributed algorithms, Force feedback, Haptics, Leader selection, Multi-robot systems, Teleoperation}, attachments = {https://homepages.laas.fr/afranchi/robotics/sites/default/files/2011g-FraBueRob-preprint.pdf}, author = {Antonio Franchi and Heinrich H. B{\"u}lthoff and Paolo Robuffo Giordano} } @conference {2011d-SonKimChuFraRobLeeBue, title = {An Evaluation of Haptic Cues on the Tele-Operator{\textquoteright}s Perceptual Awareness of Multiple UAVs{\textquoteright} Environments}, booktitle = { IEEE – World Haptics Conference}, year = {2011}, month = {06/2011}, pages = {149-154}, address = {Istanbul, Turkey}, abstract = {The use of multiple unmanned aerial vehicles (UAVs) is increasingly being incorporated into a wide range of teleoperation applications. To date, relevant research has largely been focused on the development of appropriate control schemes. In this paper, we extend previous research by investigating how control performance could be improved by providing the teleoperator with haptic feedback cues. First, we describe a control scheme that allows a teleoperator to manipulate the flight of multiple UAVs in a remote environment. Next, we present three designs of haptic cue feedback that could increase the teleoperator{\textquoteright}s environmental awareness of such a remote environment. These cues are based on the UAVs{\textquoteright} i) velocity information, ii) proximity to obstacles, and iii) a combination of these two sources of information. Finally, we present an experimental evaluation of these haptic cue designs. Our evaluation is based on the teleoperator{\textquoteright}s perceptual sensitivity to the physical environment inhabited by the multiple UAVs. We conclude that a teleoperator{\textquoteright}s perceptual sensitivity is best served by haptic feedback cues that are based on the velocity information of multiple UAVs.}, keywords = {Evaluation, Force feedback, Haptics, Multi-robot systems, Psychophysics, Teleoperation}, attachments = {https://homepages.laas.fr/afranchi/robotics/sites/default/files/2011d-SonKimChuFraRobLeeBue-preprint.pdf}, author = {Hyoung Il Son and Junsuk Kim and Lewis L. Chuang and Antonio Franchi and Paolo Robuffo Giordano and Dongjun Lee and Heinrich H. B{\"u}lthoff} } @conference {2011k-RobFraSecBue, title = {Experiments of Passivity-Based Bilateral Aerial Teleoperation of a Group of UAVs with Decentralized Velocity Synchronization}, booktitle = {2011 IEEE/RSJ Int. Conf. on Intelligent Robots and Systems}, year = {2011}, month = {09/2011}, pages = {163-170}, address = {San Francisco, CA}, abstract = {In this paper, we present an experimental validation of a novel decentralized passivity-based control strategy for teleoperating a group of Unmanned Aerial Vehicles (UAVs): the slave side, consisting of the UAVs, is endowed with large group autonomy by allowing time-varying topology and interrobot/obstacle collision avoidance. The master side, represented by a human operator, controls the group motion and receives suitable force feedback cues informing her/him about the remote slave motion status. Passivity theory is exploited for guaranteeing stability of the slave side and of the overall teleoperation channel. Results of experiments involving the use of 4 quadcopters are reported and discussed, confirming the soundness of the paper theoretical claims.}, keywords = {Bilateral Shared Control of Mobile Robots, Decentralized control, Distributed algorithms, Force feedback, Haptics, Motion control of multiple robots, Multi-robot systems, Teleoperation}, attachments = {https://homepages.laas.fr/afranchi/robotics/sites/default/files/2011k-RobFraSecBue-preprint.pdf , https://homepages.laas.fr/afranchi/robotics/sites/default/files/2011k-RobFraSecBue.mp4}, author = {Paolo Robuffo Giordano and Antonio Franchi and Cristian Secchi and Heinrich H. B{\"u}lthoff} } @conference {2011b-LeeFraRobSonBue, title = {Haptic Teleoperation of Multiple Unmanned Aerial Vehicles over the Internet}, booktitle = { 2011 IEEE Int. Conf. on Robotics and Automation}, year = {2011}, month = {05/2011}, pages = {1341-1347}, address = {Shanghai, China}, abstract = {We propose a novel haptic teleoperation control framework for multiple unmanned aerial vehicles (UAVs) over the Internet, consisting of the three control layers: 1) UAV control layer, where each UAV is abstracted by, and is controlled to follow the trajectory of, its own kinematic virtual point (VP); 2) VP control layer, which modulates each VP{\textquoteright}s motion according to the teleoperation commands and local artificial potentials (for inter-VP/VP-obstacle collision avoidance and inter-VP connectivity preservation); and 3) teleoperation layer, through which a remote human user can command all (or some) of the VPs{\textquoteright} velocity while haptically perceiving the state of all (or some) of the UAVs over the Internet. Master-passivity/slave-stability and some asymptotic performance measures are proved. Semi-experiment results are presented to validate the theory.}, keywords = {Bilateral Shared Control of Mobile Robots, Decentralized control, Force feedback, Formation control, Haptics, Multi-robot systems, Teleoperation}, attachments = {https://homepages.laas.fr/afranchi/robotics/sites/default/files/2011b-LeeFraRobSonBue-preprint.pdf , https://homepages.laas.fr/afranchi/robotics/sites/default/files/2011b-LeeFraRobSonBue-low_qlty.mp4}, author = {Dongjun Lee and Antonio Franchi and Paolo Robuffo Giordano and Hyoung Il Son and Heinrich H. B{\"u}lthoff} } @conference {2011h-SonChuFraKimLeeLeeBueRob, title = {Measuring an Operator{\textquoteright}s Maneuverability Performance in the Haptic Teleoperation of Multiple Robots}, booktitle = {2011 IEEE/RSJ Int. Conf. on Intelligent Robots and Systems}, year = {2011}, month = {09/2011}, pages = {3039-3046}, address = {San Francisco, CA}, abstract = {In this paper, we investigate the maneuverability performance of human teleoperators on multi-robots. First, we propose that maneuverability performance can be assessed by a frequency response function that jointly considers the input force of the operator and the position errors of the multi-robot system that is being maneuvered. Doing so allows us to evaluate maneuverability performance in terms of the human teleoperator{\textquoteright}s interaction with the controlled system. This allowed us to effectively determine the suitability of different haptic cue algorithms in improving teleoperation maneuverability. Performance metrics based on the human teleoperator{\textquoteright}s frequency response function indicate that maneuverability performance is best supported by a haptic feedback algorithm which is based on an obstacle avoidance force.}, keywords = {Evaluation, Force feedback, Haptics, Multi-robot systems, Psychophysics, Teleoperation}, attachments = {https://homepages.laas.fr/afranchi/robotics/sites/default/files/2011h-SonChuFraKimLeeLeeBueRob-preprint.pdf}, author = {Hyoung Il Son and Lewis L. Chuang and Antonio Franchi and Junsuk Kim and Dongjun Lee and Seong-Whan Lee and Heinrich H. B{\"u}lthoff and Paolo Robuffo Giordano} } @conference {2011a-FraRobSecSonBue, title = {A Passivity-Based Decentralized Approach for the Bilateral Teleoperation of a Group of UAVs with Switching Topology}, booktitle = {2011 IEEE Int. Conf. on Robotics and Automation}, year = {2011}, month = {05/2011}, pages = {898-905}, address = {Shanghai, China}, abstract = {In this paper, a novel distributed control strategy for teleoperating a fleet of Unmanned Aerial Vehicles (UAVs) is proposed. Using passivity based techniques, we allow the behavior of the UAVs to be as flexible as possible with arbitrary split and join decisions while guaranteeing stability of the system. Furthermore, the overall teleoperation system is also made passive and, therefore, characterized by a stable behavior both in free motion and when interacting with unknown {passive} obstacles. The performance of the system is validated through semi-experiments.}, keywords = {Bilateral Shared Control of Mobile Robots, Decentralized control, Distributed algorithms, Force feedback, Haptics, Motion control of multiple robots, Multi-robot systems, Teleoperation}, attachments = {https://homepages.laas.fr/afranchi/robotics/sites/default/files/2011a-FraRobSecSonBue-preprint.pdf , https://homepages.laas.fr/afranchi/robotics/sites/default/files/2011a-FraRobSecSonBue-low_qlty.mp4}, author = {Antonio Franchi and Paolo Robuffo Giordano and Cristian Secchi and Hyoung Il Son and Heinrich H. B{\"u}lthoff} } @conference {2010b-DurFraBul, title = {Distributed Pursuit-Evasion with Limited-Visibility Sensor Via Frontier-based Exploration}, booktitle = {2010 IEEE Int. Conf. on Robotics and Automation}, year = {2010}, month = {05/2010}, pages = {3562-3568}, address = {Anchorage, AK}, abstract = {This paper addresses a novel visibility-based pursuit-evasion problem in which a team of searchers with limited range sensors must coordinate to clear any evaders from an unknown planar environment. We present a distributed algorithm built around guaranteeing complete coverage of the frontier between cleared and contaminated areas while expanding the cleared area. Our frontier-based algorithm can guarantee detection of evaders in unknown, multiply-connected planar environments which may be non-polygonal. We also detail a method for storing and updating the global frontier between cleared and contaminated areas without building a global map or requiring global localization, which enables our algorithm to be truly distributed. We demonstrate the functionality of the algorithm through Player/Stage simulations. }, keywords = {Coverage, Distributed algorithms, Multi-robot systems, Pursuit-evasion / Clearing}, attachments = {https://homepages.laas.fr/afranchi/robotics/sites/default/files/2010b-DurFraBul.pdf , https://homepages.laas.fr/afranchi/robotics/sites/default/files/ICRA10-FinalSub.mp4}, author = {Joseph W. Durham and Antonio Franchi and Francesco Bullo} } @conference {2010e-PasFraBul, title = {On Optimal Cooperative Patrolling}, booktitle = {49th IEEE Conference on Decision and Control}, year = {2010}, month = {12/2010}, pages = {7153-7158}, address = {Atlanta, GA, USA}, abstract = {This work considers the problem of designing optimal multi-agent trajectories to patrol an environment. As performance criterion for optimal patrolling we consider the worst-case time gap between any two visits of the same region. We represent the area to be patrolled with a graph, and we characterize the computational complexity of the trajectory design (patrolling) problem with respect to the environment topology and to the number of robots employed in the patrolling task. Even though the patrolling problem is generally NP-hard, we identify particular cases that are solvable efficiently, and we describe optimal patrolling trajectories. Finally, we present a heuristic with performance guarantees, and an 8-approximation algorithm to solve the NP-hard patrolling problem.}, keywords = {Coverage, Distributed algorithms, Multi-robot systems, Patrolling / Surveillance}, attachments = {https://homepages.laas.fr/afranchi/robotics/sites/default/files/2010e-PasFraBul-preprint.pdf , https://homepages.laas.fr/afranchi/robotics/sites/default/files/2010e-PasFraBul.pdf}, author = {Fabio Pasqualetti and Antonio Franchi and Francesco Bullo} } @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} }