@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 {2016b-PetFraDipRiz,
	title = {Decentralized Motion Control for Cooperative Manipulation with a Team of Networked Mobile Manipulators},
	booktitle = {2016 IEEE Int. Conf. on Robotics and Automation},
	year = {2016},
	month = {05/2016},
	pages = {441-446},
	address = {Stockholm, Sweden},
	abstract = { In this paper we consider the cooperative control of the manipulation of a load on a plane by a team of mobile robots. We propose two different novel solutions. The first is a controller which ensures exact tracking of the load twist. This controller is partially decentralized since, locally, it does not rely on the state of all the robots but needs only to know the system parameters and load twist. Then we propose a fully decentralized controller that differs from the first one for the use of i) a decentralized estimation of the parameters and twist of the load based only on local measurements of the velocity of the contact points and ii) a discontinuous robustification term in the control law. The second controller ensures a practical stabilization of the twist in presence of estimation errors. The theoretical results are finally corroborated with a simulation campaign evaluating different manipulation settings.},
	keywords = {Calibration of ground robots, Motion control of multiple robots},
	attachments = {https://homepages.laas.fr/afranchi/robotics/sites/default/files/2016b-PetFraDipRiz-preprint.pdf , https://homepages.laas.fr/afranchi/robotics/sites/default/files/2016b-PetFraDipRiz.mp4},
	author = {Antonio Petitti and Antonio Franchi and Donato Di Paola and Alessandro Rizzo}
}
@conference {2013d-SecFraBueRob,
	title = {Bilateral Control of the Degree of Connectivity in Multiple Mobile-robot Teleoperation},
	booktitle = {2013 IEEE Int. Conf. on Robotics and Automation},
	year = {2013},
	month = {05/2013},
	address = {Karlsruhe, Germany},
	abstract = {This paper presents a novel bilateral controller that allows to stably teleoperate the degree of connectivity in the mutual interaction between a remote group of mobile robots considered as the slave-side.
A distributed leader-follower scheme allows the human operator to command the overall group motion. The group autonomously maintains the connectivity of the interaction graph by using a decentralized gradient descent approach applied to the Fiedler eigenvalue of a properly weighted Laplacian matrix. 
The degree of connectivity, and then the flexibility, of the interaction graph can be finely tuned by the human operator through an additional bilateral teleoperation channel. Passivity of the overall system is theoretically proven and  extensive human/hardware in-the-loop simulations are presented to empirically validate the theoretical analysis.},
	keywords = {Bilateral Shared Control of Mobile Robots, Connectivity maintenance},
	attachments = {https://homepages.laas.fr/afranchi/robotics/sites/default/files/2013d-SecFraBueRob.pdf , https://homepages.laas.fr/afranchi/robotics/sites/default/files/2013d-SecFraBueRob.mp4},
	author = {Cristian Secchi and Antonio Franchi and Heinrich H. B{\"u}lthoff and Paolo Robuffo Giordano}
}
@booklet {2013l-NesRobFra,
	title = {Human-assisted Parallel Multi-target Visiting in a Connected Topology},
	howpublished = {6th Int. Work. on Human-Friendly Robotics},
	year = {2013},
	month = {10/2012},
	address = {Rome, Italy},
	keywords = {Bilateral Shared Control of Mobile Robots, Connectivity maintenance, Motion control of multiple robots},
	author = {Thomas Nestmeyer and Paolo Robuffo Giordano and Antonio Franchi}
}
@booklet {2013h-NesRieLaeHarBotRobFra,
	title = {Interactive Demo: Haptic Remote Control of Multiple UAVs with Autonomous Cohesive Behavior},
	howpublished = {Int. Work. on Towards Fully Decentralized Multi-Robot Systems: Hardware, Software and Integration, at 2013 IEEE Int. Conf. on Robotics and Automation},
	year = {2013},
	month = {05/2013},
	address = {Karlsruhe, Germany},
	keywords = {Bilateral Shared Control of Mobile Robots, Connectivity maintenance, Middleware for robotics, UAV hardware platforms},
	url = {http://icra2013mrs.tuebingen.mpg.de/},
	author = {Thomas Nestmeyer and Martin Riedel and Johannes L{\"a}chele and Simon Hartmann and Fiete Botschen and Paolo Robuffo Giordano and Antonio Franchi}
}
@booklet {2012f-NesRobFra,
	title = {Multi-target Simultaneous Exploration with Continual Connectivity},
	howpublished = {2th Int. Work. on Crossing the Reality Gap - From Single to Multi- to Many Robot Systems, at 2013 IEEE Int. Conf. on Robotics and Automation},
	year = {2013},
	month = {05/2013},
	address = {Karlsruhe, Germany},
	keywords = {Connectivity maintenance, Exploration, Motion control of multiple robots},
	author = {Thomas Nestmeyer and Paolo Robuffo Giordano and Antonio Franchi}
}
@article {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}
}
@article {2013i-CenFraMarOri,
	title = {Simultaneous Calibration of Odometry  and Sensor Parameters for Mobile Robots},
	journal = {IEEE Transaction on Robotics},
	volume = {29},
	year = {2013},
	month = {04/2013},
	pages = {475-492},
	abstract = {Consider a differential-drive mobile robot equipped with an on-board exteroceptive sensor that can estimate its own motion, e.g., a range-finder. Calibration of this robot involves estimating six parameters: three for the odometry (radii and distance between the wheels), and three for the pose of the sensor with respect to the robot. After analyzing the observability of this problem, this paper describes a method for calibrating all parameters at the same time, without the need for external sensors or devices, using only the measurement of the wheels velocities and the data from the exteroceptive sensor. The method does not require the robot to move along particular trajectories. Simultaneous calibration is formulated as a maximum-likelihood problem and the solution is found in a closed form. Experimental results show that the accuracy of the proposed calibration method is very close to the attainable limit given by the Cram{\`e}r{\textendash}Rao bound.},
	keywords = {Calibration, Calibration of ground robots, Estimation},
	attachments = {https://homepages.laas.fr/afranchi/robotics/sites/default/files/2013i-CenFraMarOri.pdf},
	author = {Andrea Censi and Antonio Franchi and Luca Marchionni and Giuseppe Oriolo}
}
@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 {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 {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}
}
@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 {2009b-FraFreOriVen,
	title = {The Sensor-based Random Graph Method for Cooperative Robot Exploration},
	journal = {IEEE/ASME Transaction on Mechatronics},
	volume = {14},
	number = {2},
	year = {2009},
	note = {Winner of the IEEE RAS ICYA Best Paper Award 2010 <a href="http://homepages.laas.fr/afranchi//robotics/?q=node/64">link</a></p>},
	month = {04/2009},
	pages = {163-175},
	abstract = {We present a decentralized cooperative exploration strategy for a team of mobile robots equipped with range finders. A roadmap of the explored area, with the associate safe region, is built in the form of a Sensor-based Random Graph (SRG). This is expanded by the robots by using a randomized local planner which automatically realizes a trade-off between information gain and navigation cost. The nodes of the SRG represent view configurations that have been visited by at least one robot, and are connected by arcs that represent safe paths. These paths have been actually traveled by the robots or added to the SRG to improve its connectivity. Decentralized cooperation and coordination mechanisms are used so as to guarantee exploration efficiency and avoid conflicts. Simulations and experiments are presented to show the performance of the proposed technique.},
	keywords = {Coverage, Distributed algorithms, Exploration, Multi-robot systems},
	attachments = {https://homepages.laas.fr/afranchi/robotics/sites/default/files/2009b-FraFreOriVen.pdf},
	author = {Antonio Franchi and Luigi Freda and Giuseppe Oriolo and Marilena Vendittelli}
}
@conference {2008a-FraFreMarOriVen,
	title = {Decentralized cooperative exploration: Implementation and experiments},
	booktitle = {10th Int. Conf. on Intelligent Autonomous Systems},
	year = {2008},
	month = {07/2008},
	pages = {348-355},
	address = {Baden-Baden, Germany},
	keywords = {Coverage, Distributed algorithms, Multi-robot systems},
	attachments = {https://homepages.laas.fr/afranchi/robotics/sites/default/files/2008a-FraFreMarOriVen.pdf},
	author = {Antonio Franchi and Luigi Freda and Luca Marchionni and Giuseppe Oriolo and Marilena Vendittelli}
}
@conference {2007b-FraFreOriVen,
	title = {A decentralized strategy for cooperative robot exploration},
	booktitle = {ACM International Conference Proceeding Series, Proceedings of the 1st international conference on Robot communication and coordination},
	volume = {318},
	number = {7},
	year = {2007},
	month = {11/2007},
	address = {Athens, Greece},
	keywords = {Coverage, Distributed algorithms, Multi-robot systems},
	attachments = {https://homepages.laas.fr/afranchi/robotics/sites/default/files/2007b-FraFreOriVen.pdf},
	author = {Antonio Franchi and Luigi Freda and Giuseppe Oriolo and Marilena Vendittelli}
}
@conference {2007a-FraFreOriVen,
	title = {A Randomized Strategy for Cooperative Robot Exploration},
	booktitle = {2007 IEEE Int. Conf. on Robotics and Automation},
	year = {2007},
	month = {04/2007},
	pages = {768-774},
	address = {Rome, Italy},
	keywords = {Coverage, Decentralized control, Distributed algorithms, Multi-robot systems},
	attachments = {https://homepages.laas.fr/afranchi/robotics/sites/default/files/2007a-FraFreOriVen.pdf},
	author = {Antonio Franchi and Luigi Freda and Giuseppe Oriolo and Marilena Vendittelli}
}
