Stable bilateral control of teleoperators under time-varying communication delay: Time domain passivity approach

In this paper, modified two-port time-domain passivity approach is proposed for stable bilateral control of teleoperators under time-varying communication delay. We separate input and output energy at each port of a bilateral controller, and propose a sufficient condition for satisfying the passivity of the bilateral controller including time-delay. Output energy at the master port should be less than the transmitted input energy from the slave port with time-delay, and output energy at the slave port should be less than the transmitted input energy from the master port with time-delay. For satisfying above two conditions, two passivity controllers are attached at each port of the bilateral controller. Teleoperation experiment with about 120 (msec) of time-delay each way is performed. Stable teleoperaion is achieved in free motion and hard contact as well.