Virtual Repulsive Force Field Guided Coordination for Multi-telerobot Collaboration Nak Young Chong, Tetsuo Kotoku, Kohtaro Ohba, and Kazuo Tanie Intelligent Systems Laboratory National Institute of Advanced Industrial Science and Technology 1-2 Namiki, Tsukuba, Japan 305-8564 Email: nychong@ieee.org Abstract The Intelligent Systems Laboratory (ISL) has been developing coordinated control technologies for multi- telerobot collaboration in a common environment re- motely controlled from multiple operators physically at a distance from each other. We have built a test bed and conducted a series of experiments, where we learned more about how the transmission delay over the network deteriorates the performance of telerobots. Previously, to overcome the problems arising from the throughput of the network such as the operator’s de- layed visual perception, we have suggested several co- ordination approaches in the local operator site. Like- wise, this paper discusses the use of virtual repulsive force field in the on-line predictive simulator to as- sist the operator to cope with the collision between telerobots in remote environments. In the test bed, the operators control their master robot to get remote telerobots to work cooperatively with the other teler- obots in a task. Specifically, the operator detects a priori the possibility of collision in the predictive sim- ulator that runs in near real-time and the use of vir- tual force field prevents the telerobots from coming into collision. We have demonstrated various tasks by two telerobots and two operators via an Ethernet Local Area Network (LAN) subject to simulated communi- cation delays and evaluated the validity of the virtual force field guided approach in Multi-Operator-Multi- Robot (MOMR) tele-collaboration. 1 Introduction The current on-site work and maintenance that usually require a lot of travel is to be substituted for remote teleoperation over the network in a cost- effective way. Thus, we expect that the collaborative multi-telerobotsystemwouldbeanalternativetosup- port the coming society in which the working popu- lation decreases. In teleoperation with time delay, re- motetelerobotmotionscontrolledfromlocaloperators would be visualized with round-trip time delays, thus the video camera image is often overlaid with graph- ics model predicted from local master control instruc- tions. However, in the MOMR tele-collaboration as showninFig. 1,thetelerobotunderthecontrolofthe counterpart operator would not be straightforwardly predictable and accordingly the telerobots are most probably exposed to the possibilities of collision in re- mote environments. This seriously affects operators’ decision-making and accordingly the performance of telerobots. Thus, to cope with the operator’s delayed visual perception arising from the throughput of the network,weneedtofeedanothersupplementaryinfor- mation locally to the operator to safely steer remote telerobots through time delay [5]. Todate,manyworkshavebeenreportedinthecon- troloftelerobotoverthenetworkandSheridanexten- sively reviewed them in [13]. In addition, Goldberg et al. [7][8]builtsystemsthatallowarobottobeteleop- eratedviatheWWW.Brady et al. [1]proposedanew method for controlling telerobots over vast distances, where communication propagation delays exist. But most of the past works were applied only to a single telerobot controlled by a single operator. Recently, some efforts have been devoted to the teleoperation of multiple telerobots [9], [14]. But, they did not con- sider communication delays between local operators with large physical separation over the network. In this work, we have built an experimental test bed to research the remote tele-collaboration through timedelaybetweentwodistantoperators. Specifically, toassisttheoperatorsufferingfromthedelayedvisual Proceedings of the 2000 IEEE International Conference on Robotics & Automation Seoul, Korea • May 21-26, 2001 0-7803-6475-9/01/$10.00© 2001 IEEE