Haptic teleoperation under variable delay and actuator saturation

In this paper, a novel control scheme is proposed to guarantee global asymptotic stability of bilateral teleoperation systems that are subject to time-varying time delays in their communication channel and 'sandwich linearity' in their actuators. This extends prior art concerning control of nonlinear bilateral teleoperation systems under time-varying time delays to the case where the local and the remote robots' control signals pass through saturation or similar nonlinearities that belong to a class of systems we name sandwich linear systems. We call the proposed method nonlinear proportional plus damping (nP+ D). The asymptotic stability of the closed-loop system is established using a Lyapunov-Krasovskii functional under conditions on the controller parameters, the actuator saturation characteristics, and the maximum values of the time-varying time delays. The controller is experimentally validated on a pair of 3-DOF PHANToM Premium 1.5A robots, which have limited actuation capacity, that form a teleoperation system with a varying-delay communication channel.