@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 {2012b-SecFraBueRob,
	title = {Bilateral Teleoperation of a Group of UAVs with Communication Delays and Switching Topology},
	booktitle = {2012 IEEE Int. Conf. on Robotics and Automation},
	year = {2012},
	month = {05/2012},
	address = {St. Paul, MN},
	abstract = {In this paper, we present a passivity-based decentralized approach for bilaterally teleoperating a group of UAVs composing the slave side of the teleoperation system. In particular, we explicitly consider the presence of time delays, both among the master and slave, and within UAVs composing the group. Our focus is on analyzing suitable (passive) strategies that allow a stable teloperation of the group despite presence of delays, while still ensuring high flexibility to the group topology (e.g., possibility to autonomously split or join during the motion). The performance and soundness of the approach is validated by means of human/hardware-in-the-loop simulations (HHIL).},
	keywords = {Bilateral Shared Control of Mobile Robots, Decentralized control, Distributed algorithms, Force feedback, Motion control of multiple robots, Multi-robot systems, Teleoperation},
	attachments = {https://homepages.laas.fr/afranchi/robotics/sites/default/files/2012d-SecFraBueRob.pdf , https://homepages.laas.fr/afranchi/robotics/sites/default/files/2012d-SecFraBueRob.mp4},
	author = {Cristian Secchi and Antonio Franchi and Heinrich H. B{\"u}lthoff and Paolo Robuffo Giordano}
}
@article {2012e-FraSecSonBueRob,
	title = {Bilateral Teleoperation of Groups of Mobile Robots with Time-Varying Topology},
	journal = {IEEE Transaction on Robotics},
	volume = {28},
	year = {2012},
	month = {10/2012},
	pages = {1019	-1033},
	abstract = {In this paper, a novel decentralized control strategy for bilaterally teleoperating heterogeneous groups of mobile robots from different domains (aerial, ground, marine and under- water) is proposed. By using a decentralized control architecture, the group of robots, treated as the slave-side, is made able to navigate in a cluttered environment while avoiding obstacles, inter-robot collisions and following the human motion commands. Simultaneously, the human operator acting on the master side is provided with a suitable force feedback informative of the group response and of the interaction with the surrounding environment. Using passivity based techniques, we allow the behavior of the group to be as flexible as possible with arbitrary split and join events (e.g., due to inter-robot visibility/packet losses or specific task requirements) while guaranteeing the stability of the system. We provide a rigorous analysis of the system stability and steady-state characteristics, and validate performance through human/hardware-in-the-tloop simulations by considering a heterogeneous fleet of UAVs and UGVs as case study. Finally, we also provide an experimental validation with 4 quadrotor UAV},
	keywords = {Bilateral Shared Control of Mobile Robots, Decentralized control, Distributed algorithms, Force feedback, Haptics, Motion control of multiple robots, Multi-robot systems, Teleoperation},
	attachments = {https://homepages.laas.fr/afranchi/robotics/sites/default/files/2012e-FraSecSonBueRob.pdf},
	author = {Antonio Franchi and Cristian Secchi and Hyoung Il Son and Heinrich H. B{\"u}lthoff and Paolo Robuffo Giordano}
}
@conference {2012h-RieFraRobBueSon,
	title = {Experiments on Intercontinental Haptic Control of Multiple UAVs},
	booktitle = {12th Int. Conf. on Intelligent Autonomous Systems},
	year = {2012},
	month = {06/2012},
	pages = {227-238},
	address = {Jeju Island, Korea},
	abstract = {In this paper we propose and experimentally validate a bilateral teleoperation framework where a group of UAVs are controlled over an unreliable network with typical intercontinental time delays and packet losses. This setting is meant to represent a realistic and challenging situation for the stability the bilateral closed-loop system.
In order to increase human telepresence, the system provides the operator with both a video stream coming from the onboard cameras mounted on the UAVs, and with a suitable haptic cue, generated by a force-feedback device, informative of the UAV tracking performance and presence of impediments on the remote site.

In addition to the theoretical background, we describe the hardware and software implementation of this intercontinental teleoperation: this is composed of a semi-autonomous group of multiple quadrotor UAVs, a 3-DOF haptic interface, and a network connection based on a VPN tunnel between Germany and South Korea. The whole software framework is based upon the Robotic Operating System (ROS) communication standard.},
	keywords = {Bilateral Shared Control of Mobile Robots, Haptics, Middleware for robotics, Multi-robot systems, Teleoperation, UAV hardware platforms},
	attachments = {https://homepages.laas.fr/afranchi/robotics/sites/default/files/2012h-RieFraRobBueSon.pdf , https://homepages.laas.fr/afranchi/robotics/sites/default/files/2012h-RieFraRobBueSon.mp4},
	author = {Martin Riedel and Antonio Franchi and Heinrich H. B{\"u}lthoff and Paolo Robuffo Giordano and Hyoung Il Son}
}
@conference {2012k-MasFraBueRob,
	title = {Interactive Planning of Persistent Trajectories for Human-Assisted Navigation of Mobile Robots},
	booktitle = {2012 IEEE/RSJ Int. Conf. on Intelligent Robots and Systems},
	year = {2012},
	month = {10/2012},
	pages = {2641-2648},
	address = {Vilamoura, Portugal},
	abstract = {This work extends the framework of bilateral shared control of mobile robots with the aim of increasing the robot autonomy and decreasing the operator commitment. We consider persistent autonomous behaviors where a cyclic motion must be executed by the robot. The human operator is in charge of modifying online some geometric properties of the desired path. This is then autonomously processed by the robot in order to produce an actual path guaranteeing: i) tracking feasibility, ii) collision avoidance with obstacles, iii) closeness to the desired path set by the human operator, and iv) proximity to some points of interest. A force feedback is implemented to inform the human operator of the global deformation of the pathrather than using the classical mismatch between desired and executed motion commands. Physically-based simulations, with human/hardware-in-the-loop and a quadrotor UAV as robotic platform, demonstrate the feasibility of the method. },
	keywords = {Bilateral Shared Control of Mobile Robots, Force feedback, Haptics, Motion Planning, Optimal Trajectory Planning, Teleoperation},
	attachments = {https://homepages.laas.fr/afranchi/robotics/sites/default/files/2012k-MasFraBueRob.pdf , https://homepages.laas.fr/afranchi/robotics/sites/default/files/2012k-MasFraBueRob.mp4},
	author = {Carlo Masone and Antonio Franchi and Heinrich H. B{\"u}lthoff and Paolo Robuffo Giordano}
}
@article {2012q-FraMasGraRylBueRob,
	title = {Modeling and Control of UAV Bearing-Formations with Bilateral High-Level Steering},
	journal = {The International Journal of Robotics Research, Special Issue on 3D Exploration, Mapping, and Surveillance},
	volume = {31},
	year = {2012},
	month = {10/2012},
	pages = {1504-1525},
	abstract = {In this paper we address the problem of controlling the motion of a group of UAVs bound to keep a formation defined in terms of only relative angles (i.e., a bearing-formation). This problem can naturally arise within the context of several multi-robot applications such as, e.g., exploration, coverage, and surveillance. First, we introduce and thoroughly analyze the concept and properties of bearing-formations, and provide a class of minimally linear sets of bearings sufficient to uniquely define such formations. We then propose a bearing-only formation controller requiring only bearing measurements, converging almost globally, and maintaining bounded inter-agent distances despite the lack of direct metric information. The controller still leaves the possibility to impose group motions tangent to the current bearing-formation. These can be either autonomously chosen by the robots because of any additional task (e.g., exploration), or exploited by an assisting human co-operator. For this latter {\textquoteleft}human-in-the-loop{\textquoteright} case, we propose a multi-master/multi-slave bilateral shared control system providing the co-operator with some suitable force cues informative of the UAV performance. The proposed theoretical framework is extensively validated by means of simulations
and experiments with quadrotor UAVs equipped with onboard cameras. Practical limitations, e.g., limited field-of-view, are also considered.},
	keywords = {Bilateral Shared Control of Mobile Robots, Decentralized control, Force feedback, Formation control, Haptics, Motion control of multiple robots, Multi-robot systems, Teleoperation},
	attachments = {https://homepages.laas.fr/afranchi/robotics/sites/default/files/2012q-FraMasGraRylBueRob-preprint.pdf},
	author = {Antonio Franchi and Carlo Masone and Volker Grabe and Markus Ryll and Heinrich H. B{\"u}lthoff and Paolo Robuffo Giordano}
}
@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}
}
@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}
}
