Precision active disturbance rejection control of fast tool servo

Diamond ultra-precision turning is especially suitable for machining micro-structure functional surfaces. A fast tool servo with high performances is crucial to the cutting success. In such a machining process, the fast tool servo should actuate the cutting tool to complete desired high accuracy tracking motions with high frequency up to several kHz, while rejecting the time-varying cutting force disturbance. To solve the tracking control problems in the fast tool servo application, this paper presents the design of a precision active disturbance rejection controller by using the state space approach. Based on the known reference trajectory, both the active disturbance rejection control concept and the acceleration feed-forward strategy are used to improve the tracking and disturbance rejection performances. The proposed controller has been implemented and applied to the control of a normal stress electromagnetically driven linear actuator. The experimental results demonstrate the validity of the proposed controller.