JOINT STICK-SLIP FRICTION COMPENSATION OF ROBOT MANIPULATORS BY USINGSMOOTH ROBUST CONTROLLERS

In this article, two new smooth robust nonlinear compensators have bee n developed, respectively, for positional regulation and trajectory tr acking of rigid robot manipulators with internal joint stick-slip fric tion. The proposed controllers can improve not only the positioning ac curacy but also the smoothness of motion. No exact knowledge of the fr iction models is required for the design of the controllers. Furthermo re, the tracking controller is also robust with respect to the uncerta in link parameters. Using Lyapunov's direct method, we can show that t he time-invariant positional regulation controller guarantees the glob al boundedness stability of the closed-loop system, while the time-var ying positional tracking controller guarantees the global asymptotic s tability of the closed-loop system. The numerical simulations of the c ontrollers on a two-link robot are presented as illustrations. (C) 199 4 John Wiley & Sons, Inc.