Improved contouring control for multi-axis system with two-degrees-of-freedom structure

This paper represents a position controller with a disturbance observer for a multi-axis servo system. The overall control system consists of three parts: the position controller; the disturbance observer with free parameters; and the cross-coupled controller which enhances contouring performance by reducing errors. Using two-degrees-of freedom conception, the authors design the command input response and the closed loop characteristics independently. The servo system can improve the closed loop characteristics without affecting the command input response. The characteristics of the closed loop system is improved by suppressing disturbance torque effectively with the disturbance observer. Moreover, the cross-coupled controller enhances tracking performance. Thus position control performance is improved. Finally, the performance of the proposed controller shows that it improves the contouring performance along with reference trajectory in the XY-table