Asymptotically stable robust control of robot manipulators

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. However, in practice, feedback gains could be severely limited by hardware factors. Robust control schemes using low feedback gains are desirable. In this paper, we derive 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. Globally asymptotic stability of an n-link robot system with parametric model uncertainties is achieved. As an illustration, the proposed control scheme is applied to a two degrees-of-freedom direct drive robot arm. Simulations were conducted, and the results are in accordance with the theoretical analysis