Adaptive Force/Motion Control of Constrained Robots

Abstract

The problem of controlling the robot’s motion and force on a constraint surface subject to the constraint force in both normal and tangential directions is studied in this paper. An adaptive control algorithm is proposed and the algorithm is based on the non-linear coordinate transformation of McClamroch and Wang [1], The passivity based control scheme of Slotine and Li [2] is adopted, where the sliding surface is expanded to include the contact force error, to guarantee the asymptotical stability of the closed-loop system.In the proposed scheme, the unknown parameters are adapted using the recursive least squares method. It is shown that the implementation of the parameter adaptation and the control law requires only the measurement of the joint positions, velocities and the contact force. The global convergence of the proposed adaptive control algorithm is also established. A two-link elbow direct-drive robot performing a contour following task is simulated to demonstrate the applicability of this approach.