Multiple Cooperative Bilateral Teleoperation with Time-Varying Delay

Abstract

This paper deals with a passive-decomposition based control of bilateral teleoperation between a single master robot and multiple cooperative slave robots with time varying delay. First, we decompose the dynamics of multiple slave robots into two decoupled dynamics by using the passive-decomposition: the shape-system describing dynamics of the cooperative works and the locked-system representing the overall behavior of the multiple slave robots. Second, we propose a PD control method for bilateral teleoperation to guarantee asymptotic stability of the system with time varying delay. Finally, experimental results show the effectiveness of the proposed teleoperation. Teleoperation systems allow persons to extend their sense and manipulation capabilities to remote places. In general, a slave robot is controlled to do some real tasks at the remote place by controll signals that are sent from a master side. Com- munication channels are composed to connect the robots and the remote environment. In bilateral control, contact informa- tion is fed back to the master side when the salve robot interacts with the remote environment, therefore the manipulation capa- bility can be improved (1). One absolutely unsolved problem of the control of teleoperation systems is time delay in the com- munication line. In some cases, the master and the slave are coupled via a communication network (e.g Internet), the time delay is incurred in the transmission of data between the master and the slave sides. The delay may destabilize and deteriorate the transparency of the teleoperation system. Therefore, it is necessary to design a control law to guarantee stability of the system under communication delays. The time delay is not only constant but also variable in many cases. Up to now, many successful control schemes have been pro- posed for the teleoperation system with single master and sin- gle slave (SMSS). However, studies on teleoperation systems with multi robots are relatively rare. In (2)-(5) some control methods were proposed for the system with multiple master and multiple slave (MMMS). In this system, one human can control one slave robot to perform a separated operation in a coopera- tive task, thus the system may demand a large number of human operators if the task requires many slave robots. In (6)-(9) the single master and multiple slaves (SMMS) systems were con- sidered, but the control methods were proposed only for the motion coordination. Both MMMS and SMMS systems are ap- plied for the tasks which need the cooperation of many slave