Position command shaping control in a retrofitted milling machine

A position command shaping controller, hybrid structure of feedforward controller and cross-coupling controller, for accurate contouring in motion control is proposed in this paper. The feedforward controller can improve tracking performance of single axis and the cross-coupling controller guarantees the reduction in contour error for multi-axis motion. When compared with the conventional motion system, this new structure has the advantage that the compensators have a simpler design process than conventional ones and so does its stability analysis. The proposed compensators (or controllers) are evaluated and compared experimentally with a traditional controller on a microcomputer controlled dual-axis positioning system. The experimental results show that the new hybrid structure reduces remarkably the tracking error and contour error. In addition, this new controller can be implemented easily on a majority of motion systems in use today via reprogramming the reference position command subroutine.