Regressor-free adaptive impedance control of flexible-joint robots using FAT

Abstract

A regressor-free adaptive impedance controller is proposed for an n-link flexible-joint robot. The function approximation technique (FAT) is employed to transform the time-varying uncertainties into finite combinations of orthogonal basis functions. The tedious computation of the regressor matrix needed in traditional adaptive control is avoided in the new design, and the controller does not require the variation bounds of time-varying uncertainties needed in traditional robust control. In addition, the information of time derivative of external force and joint acceleration are not needed in the controller realization. Adaptive laws are derived based on the Lyapunov-like design. Computer simulations are performed to test the efficacy of the proposed control for a 2-DOF flexible-joint robot with environment constraint.