Nonlinear Adaptive Output Feedback Control of Flexible-Joint Space Robot Manipulators

Abstract

Growing research interest in space robotic systems capable of accurately performing autonomous manipulation tasks within an acceptable execution time has led to an increased demand for lightweight materials and mechanisms. As a result, joint flexibility effects become important, and represent the main limitation to achieving satisfactory trajectory tracking performance. This paper addresses the nonlinear adaptive output feedback control problem for flexible-joint space manipulators. Composite control schemes in which decentralized simple adaptive control-based adaptation mechanisms to control the quasisteady state robot subsystem are added to a linear correction term to stabilize the boundary layer subsystem, are proposed. An almost strictly passivity-based approach is adopted to guarantee closed-loop stability of the quasi-steady state subsystem. Simulation results are included to highlight the performance and robustness to parametric uncertainties and modeling errors of the proposed composite control methodologies.