Adaptive Tracking Controller for Rigid-Link Elastic-Joint Robots with Link Acceleration Estimation

This paper presents a adaptive switching control scheme for elastic joint robot manipulators. The characteristics of both flexible and rigid subsystems are assumed unknown except the joint stiffness. An adaptive estimator compensates the uncertainty due to the unknown robot characteristics. The actuators and links position, velocity and an estimation of the link acceleration are used as feedback to the control law. A filter is designed to estimate the links acceleration and its accuracy is insured by the linear control theory. Lyapunov theory is used to verify the asymptotic stability of the control law. The performance of the proposed control method is tested using a simulated planar robot with two rotational degrees of freedom for high and low joint stiffness.