EXPERIMENTAL COMPARISON OF SOME COMPENSATION TECHNIQUES FOR THE CONTROL OF MANIPULATORS WITH STICK-SLIP FRICTION

This paper reports the results of an experimental study, conducted on an industrial manipulator, to evaluate the performances of selected fr iction-compensation techniques. The main element of the controller is a simple PD control. First, the addition of two modified integral acti ons namely, rate-varying integral (RVI) and reset-offset integral (ROI ) to this control is examined. Next, the application of two robust non linear compensators namely, discontinuous nonlinear proportional feedb ack (DNPF) and smooth robust nonlinear feedback (SRNF) controls is eva luated. In the literature, there is little or no experimental record o f applying these techniques to an actual industrial manipulator. The e xperiments are performed on the base axis of a GCA/DK electric-driven robot which has been retrofitted as a research manipulator. The benchm ark test, comprising step and tracking experiments, allow the experime ntal comparison of the above techniques for the first time, and on the same system.