Impedance-based sliding mode control for nonlinear teleoperators under constant time delay

New technological advancements in the communication channel of time delay teleoperation systems have attracted a lot of attention, which have produced recently new control schemes, under a variety of conditions, including unknown (either constant or varying) time delay and parametric uncertainty. In this paper, a well-known model free, exact differentiator, is used to estimate the full state along with a chattering free second order sliding mode controller to guarantee robust impedance tracking under constant, but unknown, time delay of nonlinear multi-degree of freedom (n - DOF) robots. In addition, a new nominal reference is tailored in order to introduce a change of coordinates in the slave closed-loop dynamics. Experimental results, that validate the predicted behavior, are presented and discussed using the Phantom Premium 1.0 as the master robot and the Catalyst-5 virtual model as the slave robot, whose dynamics is solved online.