Feedforward and Repetitive Control for Machine Tool Feed Drives

A feed drive control method to improve the accuracy of periodic trajectory is described and evaluated. The method is based on the combination of feedforward control (zero phase error tracking control) and repetitive control. Adding the repetitive control compensates for the model mismatching which generally degrades feedforward control performance. Investigations on robust stability and disturbance effects reveal some tips on controller design. A repetitive controller is proposed to assure robust stability for unmodelled dynamics and dead-time while maintaining tracking performance in low frequencies. The regulation error, however, is increased in certain frequencies by adding the repetitive controller under the existence of load disturbances and measurement noise. Simulation results indicate that the proposed approach greatly decreases the tracking error.