The design and implementation of a cross-coupling controller for multi-link direct-drive robots

This paper presents a novel cross-coupling (CC) controller to effectively enhance the contouring accuracy for spatial contours in a multi-link direct-drive (DD) robot under gravity. A cross-coupling control (CCC) scheme based on Lyapunov theory and the recursive updating technique is proposed to reduce the contouring error by coordinating the motion of multiple axes in spite of considerable model uncertainties, disturbances, and gravitational effects. Experimental results on a three-degree-of-freedom (3DOF) DD robot also show that the proposed CCC significantly enhances the contouring accuracy in spatial contouring tasks.