PI Sliding Mode Control and Vibration Suppression of a Space Robot with Elastic Base and Two Flexible Arms

Abstract

The trajectory tracking and vibration suppression of elastic base and two flexible arms for a free-floating space robot system with flexible arms and elastic base is discussed. Using singular perturbation theory of two kinds of time scale, a slow-subsystem describing the rigid motion and a fast-subsystem corresponding to vibration of base elastic and two flexible arms are obtained. For the slow-subsystem, neural network is used to approximate the two uncertainties in the dynamic model of the space robot. The integral term of proportional integral (PI) sliding mode control makes initial state of the system falls on the sliding surface, which can offset the unknown disturbance at the beginning of control and eliminate the chattering of controller output, so the robustness of the control law is enhanced. The PI sliding mode neural network controller is designed to improve the tracking performance of the rigid point-to-point movement. For the fast-subsystem, an optimal linear quadratic regulator(LQR) controller is adopted to damps out the vibration of the two flexible links and base elastic, which guarantees the stability and tracking accuracy of the system. Finally, computer simulation results show the effectiveness of the compound control method.