Abstract:In order to improve tracking accuracy and robustness of fast tool servo(FTS) system in ultra-precision machining for the microstructured freeform optics components, the active disturbance rejection control(ADRC) was introduced. By modeling and analysis for the FTS, the equivalent model of inertia link and second oscillation link in series was obtained. According to the theory of low-order ADRC controlling highorder systems, a three-dimensional and secondorder state observer(ESO) was designed. It could be used to estimate and compensate observations realtime caused by unknown disturbances from all kinds of sources, and then the ADRC controller was designed. Moreover, parameter tuning rules were given. Digital simulation results show that ADRC has good controlling quality. Its application in fast tool servo system can improve the tracking performance and robustness.