Asymptotically stable robust control of robot manipulators

Abstract

Most robust control methods of robot manipulators guarantee small tracking errors by applying sufficiently high feedback gains. Infinite gains are required for zero tracking errors under such controllers. However, in practice, feedback gains could be severely limited by hardware factors. Robust control schemes without using high gains are desirable. In this paper, we propose a globally asymptotically stable robust control scheme by combining integral control with a robust saturation control law. The proposed robust control method takes advantage of both saturation control and integral control techniques, while the disadvantages attributed to them are remedied by each other. Global asymptotic stability of an n-link robot system with parametric model uncertainties is achieved. The proposed control scheme has been implemented on a direct drive robot arm. Experiments were conducted to evaluate the proposed control method and to compare it with pure saturation and integral control methods, and experimental results are reported herein.