@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} } @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 {2012b-SecFraBueRob, title = {Bilateral Teleoperation of a Group of UAVs with Communication Delays and Switching Topology}, booktitle = {2012 IEEE Int. Conf. on Robotics and Automation}, year = {2012}, month = {05/2012}, address = {St. Paul, MN}, abstract = {In this paper, we present a passivity-based decentralized approach for bilaterally teleoperating a group of UAVs composing the slave side of the teleoperation system. In particular, we explicitly consider the presence of time delays, both among the master and slave, and within UAVs composing the group. Our focus is on analyzing suitable (passive) strategies that allow a stable teloperation of the group despite presence of delays, while still ensuring high flexibility to the group topology (e.g., possibility to autonomously split or join during the motion). The performance and soundness of the approach is validated by means of human/hardware-in-the-loop simulations (HHIL).}, keywords = {Bilateral Shared Control of Mobile Robots, Decentralized control, Distributed algorithms, Force feedback, Motion control of multiple robots, Multi-robot systems, Teleoperation}, attachments = {https://homepages.laas.fr/afranchi/robotics/sites/default/files/2012d-SecFraBueRob.pdf , https://homepages.laas.fr/afranchi/robotics/sites/default/files/2012d-SecFraBueRob.mp4}, author = {Cristian Secchi and Antonio Franchi and Heinrich H. B{\"u}lthoff and Paolo Robuffo Giordano} } @article {2012e-FraSecSonBueRob, title = {Bilateral Teleoperation of Groups of Mobile Robots with Time-Varying Topology}, journal = {IEEE Transaction on Robotics}, volume = {28}, year = {2012}, month = {10/2012}, pages = {1019 -1033}, abstract = {In this paper, a novel decentralized control strategy for bilaterally teleoperating heterogeneous groups of mobile robots from different domains (aerial, ground, marine and under- water) is proposed. By using a decentralized control architecture, the group of robots, treated as the slave-side, is made able to navigate in a cluttered environment while avoiding obstacles, inter-robot collisions and following the human motion commands. Simultaneously, the human operator acting on the master side is provided with a suitable force feedback informative of the group response and of the interaction with the surrounding environment. Using passivity based techniques, we allow the behavior of the group to be as flexible as possible with arbitrary split and join events (e.g., due to inter-robot visibility/packet losses or specific task requirements) while guaranteeing the stability of the system. We provide a rigorous analysis of the system stability and steady-state characteristics, and validate performance through human/hardware-in-the-tloop simulations by considering a heterogeneous fleet of UAVs and UGVs as case study. Finally, we also provide an experimental validation with 4 quadrotor UAV}, keywords = {Bilateral Shared Control of Mobile Robots, Decentralized control, Distributed algorithms, Force feedback, Haptics, Motion control of multiple robots, Multi-robot systems, Teleoperation}, attachments = {https://homepages.laas.fr/afranchi/robotics/sites/default/files/2012e-FraSecSonBueRob.pdf}, author = {Antonio Franchi and Cristian Secchi and Hyoung Il Son and Heinrich H. B{\"u}lthoff and Paolo Robuffo Giordano} } @article {2010f-FraPasBul, title = {On Cooperative Patrolling: Optimal Trajectories, Complexity Analysis, and Approximation Algorithms}, journal = {IEEE Transaction on Robotics}, volume = {28}, year = {2012}, month = {06/2012}, pages = {592-606}, abstract = {The subject of this work is the patrolling of an environment with the aid of a team of autonomous agents. We consider both the design of open-loop trajectories with optimal properties, and of distributed control laws converging to optimal trajectories. As performance criteria, the refresh time and the latency are considered, i.e., respectively, time gap between any two visits of the same region, and the time necessary to inform every agent about an event occurred in the environment. We associate a graph with the environment, and we study separately the case of a chain, tree, and cyclic graph. For the case of chain graph, we first describe a minimum refresh time and latency team trajectory, and we propose a polynomial time algorithm for its computation. Then, we describe a distributed procedure that steers the robots toward an optimal trajectory. For the case of tree graph, a polynomial time algorithm is developed for the minimum refresh time problem, under the technical assumption of a constant number of robots involved in the patrolling task. Finally, we show that the design of a minimum refresh time trajectory for a cyclic graph is NP-hard, and we develop a constant factor approximation algorithm.}, keywords = {Coverage, Distributed algorithms, Multi-robot systems, Patrolling / Surveillance}, attachments = {https://homepages.laas.fr/afranchi/robotics/sites/default/files/2010f-FraPasBul-preprint.pdf}, author = {Fabio Pasqualetti and Antonio Franchi and Francesco Bullo} } @conference {2012i-FraRob, title = {Decentralized Control of Parallel Rigid Formations with Direction Constraints and Bearing Measurements}, booktitle = {51th IEEE Conference on Decision and Control }, year = {2012}, month = {12/2012}, pages = {5310-5317}, address = {Maui, HI}, abstract = {In this paper we analyze the relationship between scalability, minimality and rigidity, and its application to cooperative control. As a case study, we address the problem of multi-agent formation control by proposing a distributed control strategy that stabilizes a formation described with bearing (direction) constraints, and that only requires bearing measurements and parallel rigidity of the interaction graph. We also consider the possibility of having different graphs modeling the interaction network in order to explicitly take into account the conceptual difference between sensing, communication, control, and parameters stored in the network. We then show how the information can be {\textquoteleft}moved{\textquoteright} from a graph to another making use of decentralized estimation, provided the parallel rigidity property. Finally we present simulative examples in order to show the validity of the theoretical analysis in some illustrative cases.}, keywords = {Decentralized control, Distributed algorithms, Estimation, Formation control, Motion control of multiple robots, Multi-robot systems}, attachments = {https://homepages.laas.fr/afranchi/robotics/sites/default/files/2012i-FraRob-preprint.pdf}, author = {Antonio Franchi and Paolo Robuffo Giordano} } @article {2011c-DurFraBul, title = {Distributed Pursuit-Evasion without Mapping or Global Localization via Local Frontiers}, journal = {Autonomous Robots}, volume = {32}, year = {2012}, month = {01/2012}, pages = {81-95}, abstract = {This paper addresses a visibility-based pursuit-evasion problem in which a team of mobile robots with limited sensing and communication capabilities must coordinate to detect any evaders in an unknown, multiply-connected planar environment. Our distributed algorithm to guarantee evader detection is built around maintaining complete coverage of the frontier between cleared and contaminated regions while expanding the cleared region. We detail a novel distributed method for storing and updating this frontier without building a map of the environment or requiring global localization. We demonstrate the functionality of the algorithm through simulations in realistic environments and through hardware experiments. We also compare Monte Carlo results for our algorithm to the theoretical optimum area cleared as a function of the number of robots available.}, keywords = {Coverage, Distributed algorithms, Multi-robot systems, Pursuit-evasion / Clearing}, url = {http://www.springerlink.com/content/a02pr41790ll754w/}, attachments = {https://homepages.laas.fr/afranchi/robotics/sites/default/files/2011c-DurFraBul-preprint.pdf , https://homepages.laas.fr/afranchi/robotics/sites/default/files/2011c-DurFraBul-video1.mp4}, author = {Joseph W. Durham and Antonio Franchi and Francesco Bullo} } @conference {2012h-RieFraRobBueSon, title = {Experiments on Intercontinental Haptic Control of Multiple UAVs}, booktitle = {12th Int. Conf. on Intelligent Autonomous Systems}, year = {2012}, month = {06/2012}, pages = {227-238}, address = {Jeju Island, Korea}, abstract = {In this paper we propose and experimentally validate a bilateral teleoperation framework where a group of UAVs are controlled over an unreliable network with typical intercontinental time delays and packet losses. This setting is meant to represent a realistic and challenging situation for the stability the bilateral closed-loop system. In order to increase human telepresence, the system provides the operator with both a video stream coming from the onboard cameras mounted on the UAVs, and with a suitable haptic cue, generated by a force-feedback device, informative of the UAV tracking performance and presence of impediments on the remote site. In addition to the theoretical background, we describe the hardware and software implementation of this intercontinental teleoperation: this is composed of a semi-autonomous group of multiple quadrotor UAVs, a 3-DOF haptic interface, and a network connection based on a VPN tunnel between Germany and South Korea. The whole software framework is based upon the Robotic Operating System (ROS) communication standard.}, keywords = {Bilateral Shared Control of Mobile Robots, Haptics, Middleware for robotics, Multi-robot systems, Teleoperation, UAV hardware platforms}, attachments = {https://homepages.laas.fr/afranchi/robotics/sites/default/files/2012h-RieFraRobBueSon.pdf , https://homepages.laas.fr/afranchi/robotics/sites/default/files/2012h-RieFraRobBueSon.mp4}, author = {Martin Riedel and Antonio Franchi and Heinrich H. B{\"u}lthoff and Paolo Robuffo Giordano and Hyoung Il Son} } @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} } @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 {2012l-CogSteFraOri, title = {Two Measurement Scenarios for Anonymous Mutual Localization in Multi-UAV Systems}, booktitle = {2nd IFAC Workshop on Multivehicle Systems}, year = {2012}, month = {10/2012}, address = {Espoo, Finland}, keywords = {Estimation, Localization, Localization of aerial robots, Multi-robot systems}, attachments = {https://homepages.laas.fr/afranchi/robotics/sites/default/files/2012l-CogSteFraOri-preprint.pdf}, author = {Marco Cognetti and Paolo Stegagno and Antonio Franchi and Giuseppe Oriolo} } @conference {2011e-RobFraSecBue, title = {Bilateral Teleoperation of Groups of UAVs with Decentralized Connectivity Maintenance}, booktitle = {2011 Robotics: Science and Systems Conference}, year = {2011}, month = {06/2011}, address = {Los Angeles, CA}, abstract = {In this paper, we present a decentralized passivity-based control strategy for the bilateral teleoperation of a fleet of Unmanned Aerial Vehicles (UAVs). The human operator at the master side can command the fleet motion and receive suitable force cues informative about the remote environment. By properly controlling the energy exchanged within the slave side (the UAV fleet), we guarantee that the connectivity of the fleet is preserved and we prevent inter-agent and obstacle collisions. At the same time, we allow the behavior of the UAVs to be as flexible as possible with arbitrary split and join maneuvers. The results of the paper are validated through semi-experiments.}, keywords = {Bilateral Shared Control of Mobile Robots, Connectivity maintenance, Decentralized control, Distributed algorithms, Estimation, Force feedback, Haptics, Multi-robot systems, Teleoperation}, attachments = {https://homepages.laas.fr/afranchi/robotics/sites/default/files/2011e-RobFraSecBue-preprint.pdf , https://homepages.laas.fr/afranchi/robotics/sites/default/files/2011e-RobFraSecBue-almost_preprint.pdf , https://homepages.laas.fr/afranchi/robotics/sites/default/files/2011e-RobFraSecBue.mp4}, author = {Paolo Robuffo Giordano and Antonio Franchi and Cristian Secchi and Heinrich H. B{\"u}lthoff} } @conference {2011i-FraMasBueRob, title = {Bilateral Teleoperation of Multiple UAVs with Decentralized Bearing-only Formation Control}, booktitle = {2011 IEEE/RSJ Int. Conf. on Intelligent Robots and Systems}, year = {2011}, month = {09/2011}, pages = {2215-2222}, address = {San Francisco, CA}, abstract = {We present a decentralized system for the bilateral teleoperation of groups of UAVs which only relies on relative bearing measurements, i.e., without the need of distance information or global localization. The properties of a 3D bearing-formation are analyzed, and a minimal set of bearings needed for its definition is provided. We also design a novel decentralized formation control almost globally convergent and able to maintain bounded and non-vanishing inter-distances among the agents despite the absence of direct distance measurements. Furthermore, we develop a multimaster/multi-slave teleoperation setup in order to control the overall behavior of the group and to convey to the human operator suitable force cues, while ensuring stability in presence of delays and packet losses over the master-slave communication channel. The theoretical framework is validated by means of extensive human/hardware in-the-loop simulations using two force-feedback devices and a group of quadrotors.}, keywords = {Bilateral Shared Control of Mobile Robots, Decentralized control, Force feedback, Formation control, Haptics, Motion control of multiple robots, Multi-robot systems, Teleoperation}, attachments = {https://homepages.laas.fr/afranchi/robotics/sites/default/files/2011i-FraMasBueRob-preprint.pdf , https://homepages.laas.fr/afranchi/robotics/sites/default/files/2011i-FraMasBueRob.mp4}, author = {Antonio Franchi and Carlo Masone and Heinrich H. B{\"u}lthoff and Paolo Robuffo Giordano} } @booklet {2011o-Fra, title = {Decentralized Bilateral Aerial Teleoperation of Multiple UAVs - Part I: a Top-Down Perspective}, howpublished = {RSS 2011 Workshop on 3D Exploration, Mapping, and Surveillance with Aerial Robots}, year = {2011}, month = {06/2011}, address = {Los Angeles, CA}, keywords = {Bilateral Shared Control of Mobile Robots, Decentralized control, Force feedback, Formation control, Haptics, Multi-robot systems, Teleoperation}, author = {Antonio Franchi} } @conference {2011g-FraBueRob, title = {Distributed Online Leader Selection in the Bilateral Teleoperation of Multiple UAVs}, booktitle = {50th IEEE Conference on Decision and Control }, year = {2011}, month = {12/2011}, pages = {3559-3565}, address = {Orlando, FL}, abstract = {For several applications like data collection, surveillance, search and rescue and exploration of wide areas, the use of a group of simple robots rather than a single complex robot has proven to be very effective and promising, and the problem of coordinating a group of agents has received a lot of attention over the last years. In this paper, we consider the challenge of establishing a bilateral force-feedback teleoperation channel between a human operator (the master side) and a remote multi-robot system (the slave side) where a special agent, the leader, is selected and directly controlled by the master. In particular, we study the problem of distributed online optimal leader selection, i.e., how to choose, and possibly change, the leader online in order to maximize some suitable criteria related to the tracking performance of the whole group w.r.t. the master commands. Human/hardware-in-the-loop simulation results with a group of UAVs support the theoretical claims of the paper.}, keywords = {Decentralized control, Distributed algorithms, Force feedback, Haptics, Leader selection, Multi-robot systems, Teleoperation}, attachments = {https://homepages.laas.fr/afranchi/robotics/sites/default/files/2011g-FraBueRob-preprint.pdf}, author = {Antonio Franchi and Heinrich H. B{\"u}lthoff and Paolo Robuffo Giordano} } @conference {2011d-SonKimChuFraRobLeeBue, title = {An Evaluation of Haptic Cues on the Tele-Operator{\textquoteright}s Perceptual Awareness of Multiple UAVs{\textquoteright} Environments}, booktitle = { IEEE – World Haptics Conference}, year = {2011}, month = {06/2011}, pages = {149-154}, address = {Istanbul, Turkey}, abstract = {The use of multiple unmanned aerial vehicles (UAVs) is increasingly being incorporated into a wide range of teleoperation applications. To date, relevant research has largely been focused on the development of appropriate control schemes. In this paper, we extend previous research by investigating how control performance could be improved by providing the teleoperator with haptic feedback cues. First, we describe a control scheme that allows a teleoperator to manipulate the flight of multiple UAVs in a remote environment. Next, we present three designs of haptic cue feedback that could increase the teleoperator{\textquoteright}s environmental awareness of such a remote environment. These cues are based on the UAVs{\textquoteright} i) velocity information, ii) proximity to obstacles, and iii) a combination of these two sources of information. Finally, we present an experimental evaluation of these haptic cue designs. Our evaluation is based on the teleoperator{\textquoteright}s perceptual sensitivity to the physical environment inhabited by the multiple UAVs. We conclude that a teleoperator{\textquoteright}s perceptual sensitivity is best served by haptic feedback cues that are based on the velocity information of multiple UAVs.}, keywords = {Evaluation, Force feedback, Haptics, Multi-robot systems, Psychophysics, Teleoperation}, attachments = {https://homepages.laas.fr/afranchi/robotics/sites/default/files/2011d-SonKimChuFraRobLeeBue-preprint.pdf}, author = {Hyoung Il Son and Junsuk Kim and Lewis L. Chuang and Antonio Franchi and Paolo Robuffo Giordano and Dongjun Lee and Heinrich H. B{\"u}lthoff} } @conference {2011k-RobFraSecBue, title = {Experiments of Passivity-Based Bilateral Aerial Teleoperation of a Group of UAVs with Decentralized Velocity Synchronization}, booktitle = {2011 IEEE/RSJ Int. Conf. on Intelligent Robots and Systems}, year = {2011}, month = {09/2011}, pages = {163-170}, address = {San Francisco, CA}, abstract = {In this paper, we present an experimental validation of a novel decentralized passivity-based control strategy for teleoperating a group of Unmanned Aerial Vehicles (UAVs): the slave side, consisting of the UAVs, is endowed with large group autonomy by allowing time-varying topology and interrobot/obstacle collision avoidance. The master side, represented by a human operator, controls the group motion and receives suitable force feedback cues informing her/him about the remote slave motion status. Passivity theory is exploited for guaranteeing stability of the slave side and of the overall teleoperation channel. Results of experiments involving the use of 4 quadcopters are reported and discussed, confirming the soundness of the paper theoretical claims.}, keywords = {Bilateral Shared Control of Mobile Robots, Decentralized control, Distributed algorithms, Force feedback, Haptics, Motion control of multiple robots, Multi-robot systems, Teleoperation}, attachments = {https://homepages.laas.fr/afranchi/robotics/sites/default/files/2011k-RobFraSecBue-preprint.pdf , https://homepages.laas.fr/afranchi/robotics/sites/default/files/2011k-RobFraSecBue.mp4}, author = {Paolo Robuffo Giordano and Antonio Franchi and Cristian Secchi and Heinrich H. B{\"u}lthoff} } @conference {2011b-LeeFraRobSonBue, title = {Haptic Teleoperation of Multiple Unmanned Aerial Vehicles over the Internet}, booktitle = { 2011 IEEE Int. Conf. on Robotics and Automation}, year = {2011}, month = {05/2011}, pages = {1341-1347}, address = {Shanghai, China}, abstract = {We propose a novel haptic teleoperation control framework for multiple unmanned aerial vehicles (UAVs) over the Internet, consisting of the three control layers: 1) UAV control layer, where each UAV is abstracted by, and is controlled to follow the trajectory of, its own kinematic virtual point (VP); 2) VP control layer, which modulates each VP{\textquoteright}s motion according to the teleoperation commands and local artificial potentials (for inter-VP/VP-obstacle collision avoidance and inter-VP connectivity preservation); and 3) teleoperation layer, through which a remote human user can command all (or some) of the VPs{\textquoteright} velocity while haptically perceiving the state of all (or some) of the UAVs over the Internet. Master-passivity/slave-stability and some asymptotic performance measures are proved. Semi-experiment results are presented to validate the theory.}, keywords = {Bilateral Shared Control of Mobile Robots, Decentralized control, Force feedback, Formation control, Haptics, Multi-robot systems, Teleoperation}, attachments = {https://homepages.laas.fr/afranchi/robotics/sites/default/files/2011b-LeeFraRobSonBue-preprint.pdf , https://homepages.laas.fr/afranchi/robotics/sites/default/files/2011b-LeeFraRobSonBue-low_qlty.mp4}, author = {Dongjun Lee and Antonio Franchi and Paolo Robuffo Giordano and Hyoung Il Son and Heinrich H. B{\"u}lthoff} } @conference {2011h-SonChuFraKimLeeLeeBueRob, title = {Measuring an Operator{\textquoteright}s Maneuverability Performance in the Haptic Teleoperation of Multiple Robots}, booktitle = {2011 IEEE/RSJ Int. Conf. on Intelligent Robots and Systems}, year = {2011}, month = {09/2011}, pages = {3039-3046}, address = {San Francisco, CA}, abstract = {In this paper, we investigate the maneuverability performance of human teleoperators on multi-robots. First, we propose that maneuverability performance can be assessed by a frequency response function that jointly considers the input force of the operator and the position errors of the multi-robot system that is being maneuvered. Doing so allows us to evaluate maneuverability performance in terms of the human teleoperator{\textquoteright}s interaction with the controlled system. This allowed us to effectively determine the suitability of different haptic cue algorithms in improving teleoperation maneuverability. Performance metrics based on the human teleoperator{\textquoteright}s frequency response function indicate that maneuverability performance is best supported by a haptic feedback algorithm which is based on an obstacle avoidance force.}, keywords = {Evaluation, Force feedback, Haptics, Multi-robot systems, Psychophysics, Teleoperation}, attachments = {https://homepages.laas.fr/afranchi/robotics/sites/default/files/2011h-SonChuFraKimLeeLeeBueRob-preprint.pdf}, author = {Hyoung Il Son and Lewis L. Chuang and Antonio Franchi and Junsuk Kim and Dongjun Lee and Seong-Whan Lee and Heinrich H. B{\"u}lthoff and Paolo Robuffo Giordano} } @conference {2011m-SteCogFraOri, title = {Mutual Localization using Anonymous Bearing Measurements}, booktitle = {2011 IEEE/RSJ Int. Conf. on Intelligent Robots and Systems}, year = {2011}, month = {09/2011}, pages = {469-474}, address = {San Francisco, CA}, abstract = {This paper addresses the problem of mutual localization in multi-robot systems in presence of anonymous (i.e., without the identity information) bearing-only measurements. The solution of this problem is relevant for the design and implementation of any decentralized multi-robot algorithm/control. A novel algorithm for probabilistic multiple registration of these measurements is presented, where no global localization, distances, or identity are used. With respect to more conventional solutions that could be conceived on the basis of the current literature, our method is theoretically suitable for tasks requiring frequent, many-to-many encounters among agents (e.g., formation control, cooperative exploration, multiple-view environment sensing). An extensive experimental study validates our method and compares it with the fullinformative case of bearing plus-distance measurements. The results show that the proposed localization system exhibits an accuracy commensurate to our previous method [1] which uses bearing-plus-distance information.}, keywords = {Distributed algorithms, Estimation, Localization, Multi-robot systems}, attachments = {https://homepages.laas.fr/afranchi/robotics/sites/default/files/2011m-SteCogFraOri-preprint.pdf , https://homepages.laas.fr/afranchi/robotics/sites/default/files/2011m-SteCogFraOri.mp4}, author = {Paolo Stegagno and Marco Cognetti and Antonio Franchi and Giuseppe Oriolo} } @conference {2011a-FraRobSecSonBue, title = {A Passivity-Based Decentralized Approach for the Bilateral Teleoperation of a Group of UAVs with Switching Topology}, booktitle = {2011 IEEE Int. Conf. on Robotics and Automation}, year = {2011}, month = {05/2011}, pages = {898-905}, address = {Shanghai, China}, abstract = {In this paper, a novel distributed control strategy for teleoperating a fleet of Unmanned Aerial Vehicles (UAVs) is proposed. Using passivity based techniques, we allow the behavior of the UAVs to be as flexible as possible with arbitrary split and join decisions while guaranteeing stability of the system. Furthermore, the overall teleoperation system is also made passive and, therefore, characterized by a stable behavior both in free motion and when interacting with unknown {passive} obstacles. The performance of the system is validated through semi-experiments.}, keywords = {Bilateral Shared Control of Mobile Robots, Decentralized control, Distributed algorithms, Force feedback, Haptics, Motion control of multiple robots, Multi-robot systems, Teleoperation}, attachments = {https://homepages.laas.fr/afranchi/robotics/sites/default/files/2011a-FraRobSecSonBue-preprint.pdf , https://homepages.laas.fr/afranchi/robotics/sites/default/files/2011a-FraRobSecSonBue-low_qlty.mp4}, author = {Antonio Franchi and Paolo Robuffo Giordano and Cristian Secchi and Hyoung Il Son and Heinrich H. B{\"u}lthoff} } @conference {2010b-DurFraBul, title = {Distributed Pursuit-Evasion with Limited-Visibility Sensor Via Frontier-based Exploration}, booktitle = {2010 IEEE Int. Conf. on Robotics and Automation}, year = {2010}, month = {05/2010}, pages = {3562-3568}, address = {Anchorage, AK}, abstract = {This paper addresses a novel visibility-based pursuit-evasion problem in which a team of searchers with limited range sensors must coordinate to clear any evaders from an unknown planar environment. We present a distributed algorithm built around guaranteeing complete coverage of the frontier between cleared and contaminated areas while expanding the cleared area. Our frontier-based algorithm can guarantee detection of evaders in unknown, multiply-connected planar environments which may be non-polygonal. We also detail a method for storing and updating the global frontier between cleared and contaminated areas without building a global map or requiring global localization, which enables our algorithm to be truly distributed. We demonstrate the functionality of the algorithm through Player/Stage simulations. }, keywords = {Coverage, Distributed algorithms, Multi-robot systems, Pursuit-evasion / Clearing}, attachments = {https://homepages.laas.fr/afranchi/robotics/sites/default/files/2010b-DurFraBul.pdf , https://homepages.laas.fr/afranchi/robotics/sites/default/files/ICRA10-FinalSub.mp4}, author = {Joseph W. Durham and Antonio Franchi and Francesco Bullo} } @conference {2010c-FraSteDirOri, title = {Distributed Target Localization and Encirclement with a Multi-robot System}, booktitle = {7th IFAC Symposium on Intelligent Autonomous Vehicles}, year = {2010}, month = {09/2010}, address = {Lecce, Italy}, abstract = {This paper presents a control scheme for localizing and encircling a target using a multi-robot system. The task is achieved in a distributed way, in that each robot only uses local information gathered by on-board relative-position sensors assumed to be noisy, anisotropic, and unable to detect the identity of the measured object. Communication between the robots is provided by limited-range transceivers. Experimental results with stationary and Multi-robot systems, distributed control, mutual localization, encirclement.moving targets support the theoretical analysis. }, keywords = {Decentralized control, Distributed algorithms, Estimation, Formation control, Multi-robot systems}, attachments = {https://homepages.laas.fr/afranchi/robotics/sites/default/files/2010c-FraSteDirOri-preprint.pdf}, author = {Antonio Franchi and Paolo Stegagno and Maurizio Di~Rocco and Giuseppe Oriolo} } @conference {2010e-PasFraBul, title = {On Optimal Cooperative Patrolling}, booktitle = {49th IEEE Conference on Decision and Control}, year = {2010}, month = {12/2010}, pages = {7153-7158}, address = {Atlanta, GA, USA}, abstract = {This work considers the problem of designing optimal multi-agent trajectories to patrol an environment. As performance criterion for optimal patrolling we consider the worst-case time gap between any two visits of the same region. We represent the area to be patrolled with a graph, and we characterize the computational complexity of the trajectory design (patrolling) problem with respect to the environment topology and to the number of robots employed in the patrolling task. Even though the patrolling problem is generally NP-hard, we identify particular cases that are solvable efficiently, and we describe optimal patrolling trajectories. Finally, we present a heuristic with performance guarantees, and an 8-approximation algorithm to solve the NP-hard patrolling problem.}, keywords = {Coverage, Distributed algorithms, Multi-robot systems, Patrolling / Surveillance}, attachments = {https://homepages.laas.fr/afranchi/robotics/sites/default/files/2010e-PasFraBul-preprint.pdf , https://homepages.laas.fr/afranchi/robotics/sites/default/files/2010e-PasFraBul.pdf}, author = {Fabio Pasqualetti and Antonio Franchi and Francesco Bullo} } @conference {2010d-FraOriSte, title = {Probabilistic Mutual Localization in Multi-agent Systems from Anonymous Position Measures}, booktitle = {49th IEEE Conference on Decision and Control}, year = {2010}, month = {12/2010}, pages = {6534-6540}, address = {Atlanta, GA, USA}, abstract = {Recent research on multi-agent systems has produced a plethora of decentralized controllers that implicitly assume various degrees of agent localization. However, many practical arrangements commonly taken to allow and achieve localization imply some form of centralization, from the use of physical tagging to allow the identification of the single agent to the adoption of global positioning systems based on cameras or GPS. These devices clearly decrease the system autonomy and range of applicability, and should be avoided if possible. Following this guideline, this work addresses the mutual localization problem with anonymous relative position measures, presenting a robust solution based on a probabilistic framework. The proposed localization system exhibits higher accuracy and lower complexity ($O(n^2)$) than our previous method~[bib]2009c-FraOriSte[/bib]. Moreover, with respect to more conventional solutions that could be conceived on the basis of the current literature, our method is theoretically suitable for tasks requiring frequent, many-to-many encounters among agents (e.g., formation control, cooperative exploration, multiple-view environment sensing). The proposed localization system has been validated by means of an extensive experimental study}, keywords = {Distributed algorithms, Estimation, Localization, Multi-robot systems}, attachments = {https://homepages.laas.fr/afranchi/robotics/sites/default/files/2010d-FraOriSte-preprint.pdf , https://homepages.laas.fr/afranchi/robotics/sites/default/files/2010d-FraOriSte.pdf}, author = {Antonio Franchi and Giuseppe Oriolo and Paolo Stegagno} } @conference {2010a-FraOriSte, title = {On the Solvability of the Mutual Localization Problem with Anonymous Position Measures}, booktitle = {2010 IEEE Int. Conf. on Robotics and Automation}, year = {2010}, month = {05/2010}, pages = {3193-3199}, address = {Anchorage, AK}, abstract = {This paper formulates and investigates a novel problem called Mutual Localization with Anonymous Position Measures. This is an extension of Mutual Localization with Position Measures, with the additional assumption that the identities of the measured robots are not known. A necessary and sufficient condition for the uniqueness of the solution is presented, which requires O(n^2/\log n) to be verified and is based on the notion of rotational symmetry in R^2. We also derive the relationship between the number of robots and the number of possible solutions, and classify the solutions in a number of equivalence classes which is linear in n. A control law is finally proposed that effectively breaks symmetric formations so as to guarantee unique solvability of the problem is also proposed; its performance is illustrated through simulations.}, keywords = {Estimation, Formation control, Localization, Multi-robot systems}, attachments = {https://homepages.laas.fr/afranchi/robotics/sites/default/files/2010a-FraOriSte.pdf , https://homepages.laas.fr/afranchi/robotics/sites/default/files/ICRA10-Final.mp4}, author = {Antonio Franchi and Giuseppe Oriolo and Paolo Stegagno} } @booklet {2010d-RobFraSonSecLeeBue, title = {Towards Bilateral Teleoperation of Multi-Robot Systems}, howpublished = {3rd Int. Work. on Human-Friendly Robotics}, year = {2010}, month = {10/2010}, address = {Tuebingen, Germany}, keywords = {Bilateral Shared Control of Mobile Robots, Decentralized control, Distributed algorithms, Force feedback, Haptics, Multi-robot systems, Teleoperation}, author = {Paolo Robuffo Giordano and Antonio Franchi and Hyoung Il Son and Cristian Secchi and Dongjun Lee and Heinrich H. B{\"u}lthoff} } @mastersthesis {60, title = {Decentralized Methods for Cooperative Task Execution in Multi-robot Systems}, year = {2009}, month = {12/2009}, school = {"La Sapienza" University of Rome}, type = {PhD}, keywords = {Coverage, Decentralized control, Distributed algorithms, Estimation, Exploration, Formation control, Localization of ground robots, Middleware for robotics, Motion control of multiple robots, Multi-robot systems, Patrolling / Surveillance, Pursuit-evasion / Clearing}, attachments = {https://homepages.laas.fr/afranchi/robotics/sites/default/files/2009-Franchi_PhDThesis.pdf}, author = {Antonio Franchi} } @article {2009a-FraOriSte, title = {Mutual Localization in a Multi-Robot System with Anonymous Relative Position Measures}, year = {2009}, month = {01/2009}, institution = {Department of Computer and System Sciences Antonio Ruberti}, abstract = {In this paper we formulate and solve the mutual localization problem for a multi-robot system under the assumption of anonymous relative position measures. The anonymity hypothesis can cause a combinatorial ambiguity in the inversion of the measure equation giving more than one possible solution to the problem. We propose MultiReg, an innovative algorithm aimed at obtaining sets ofpossible relative pose hypotheses, whose output is processed by a data associator and a multiple EKF to select the best hypothesis. We study the performance of the developed localization system using both simulations and real robot experiments.}, keywords = {Distributed algorithms, Estimation, Localization, Multi-robot systems}, attachments = {https://homepages.laas.fr/afranchi/robotics/sites/default/files/2009a-FraOriSte.pdf}, author = {Antonio Franchi and Giuseppe Oriolo and Paolo Stegagno} } @conference {2009c-FraOriSte, title = {Mutual Localization in a Multi-Robot System with Anonymous Relative Position Measures}, booktitle = {2009 IEEE/RSJ Int. Conf. on Intelligent Robots and Systems}, year = {2009}, month = {11/2009}, pages = {3974-3980}, address = {St. Louis, MO}, abstract = {We address the mutual localization problem for a multi-robot system, under the assumption that each robot is equipped with a sensor that provides a measure of the relative position of nearby robots without their identity. Anonymity generates a combinatorial ambiguity in the inversion of the measure equations, leading to a multiplicity of admissible relative pose hypotheses. To solve the problem, we propose a two-stage localization system based on MultiReg, an innovative algorithm that computes on-line all the possible relative pose hypotheses, whose output is processed by a data associator and a multiple EKF to isolate and refine the best estimates. The performance of the mutual localization system is analyzed through experiments, proving the effectiveness of the method and, in particular, its robustness with respect to false positives (objects that look like robots) and false negatives (robots that are not detected) of the measure process.}, keywords = {Distributed algorithms, Estimation, Localization, Multi-robot systems}, attachments = {https://homepages.laas.fr/afranchi/robotics/sites/default/files/2009c-FraOriSte.pdf , https://homepages.laas.fr/afranchi/robotics/sites/default/files/IROS09_MutualLoc.mp4}, author = {Antonio Franchi and Giuseppe Oriolo and Paolo Stegagno} } @article {2009b-FraFreOriVen, title = {The Sensor-based Random Graph Method for Cooperative Robot Exploration}, journal = {IEEE/ASME Transaction on Mechatronics}, volume = {14}, number = {2}, year = {2009}, note = {Winner of the IEEE RAS ICYA Best Paper Award 2010 link

}, month = {04/2009}, pages = {163-175}, abstract = {We present a decentralized cooperative exploration strategy for a team of mobile robots equipped with range finders. A roadmap of the explored area, with the associate safe region, is built in the form of a Sensor-based Random Graph (SRG). This is expanded by the robots by using a randomized local planner which automatically realizes a trade-off between information gain and navigation cost. The nodes of the SRG represent view configurations that have been visited by at least one robot, and are connected by arcs that represent safe paths. These paths have been actually traveled by the robots or added to the SRG to improve its connectivity. Decentralized cooperation and coordination mechanisms are used so as to guarantee exploration efficiency and avoid conflicts. Simulations and experiments are presented to show the performance of the proposed technique.}, keywords = {Coverage, Distributed algorithms, Exploration, Multi-robot systems}, attachments = {https://homepages.laas.fr/afranchi/robotics/sites/default/files/2009b-FraFreOriVen.pdf}, author = {Antonio Franchi and Luigi Freda and Giuseppe Oriolo and Marilena Vendittelli} } @conference {2008a-FraFreMarOriVen, title = {Decentralized cooperative exploration: Implementation and experiments}, booktitle = {10th Int. Conf. on Intelligent Autonomous Systems}, year = {2008}, month = {07/2008}, pages = {348-355}, address = {Baden-Baden, Germany}, keywords = {Coverage, Distributed algorithms, Multi-robot systems}, attachments = {https://homepages.laas.fr/afranchi/robotics/sites/default/files/2008a-FraFreMarOriVen.pdf}, author = {Antonio Franchi and Luigi Freda and Luca Marchionni and Giuseppe Oriolo and Marilena Vendittelli} } @conference {2007b-FraFreOriVen, title = {A decentralized strategy for cooperative robot exploration}, booktitle = {ACM International Conference Proceeding Series, Proceedings of the 1st international conference on Robot communication and coordination}, volume = {318}, number = {7}, year = {2007}, month = {11/2007}, address = {Athens, Greece}, keywords = {Coverage, Distributed algorithms, Multi-robot systems}, attachments = {https://homepages.laas.fr/afranchi/robotics/sites/default/files/2007b-FraFreOriVen.pdf}, author = {Antonio Franchi and Luigi Freda and Giuseppe Oriolo and Marilena Vendittelli} } @conference {2007a-FraFreOriVen, title = {A Randomized Strategy for Cooperative Robot Exploration}, booktitle = {2007 IEEE Int. Conf. on Robotics and Automation}, year = {2007}, month = {04/2007}, pages = {768-774}, address = {Rome, Italy}, keywords = {Coverage, Decentralized control, Distributed algorithms, Multi-robot systems}, attachments = {https://homepages.laas.fr/afranchi/robotics/sites/default/files/2007a-FraFreOriVen.pdf}, author = {Antonio Franchi and Luigi Freda and Giuseppe Oriolo and Marilena Vendittelli} }