Observer-based robust motion control of a piezo-actuated stage under external disturbances

Piezoelectric actuators (PEAs) are frequently used in a wide variety of micromanipulation systems. However, the hysteresis non-linearity and the creep reduce their fidelity and cause difficulties in the micromanipulation control procedure. Besides, variation of temperature and external loads could change the model parameters identified for the piezo actuator. In this paper, a robust feedforward-feedback controller is proposed for precise tracking control of PEAs, under external disturbances. A Bouc-Wen hysteresis model is integrated with a second-order linear dynamic, to represent the behaviour of a PEA. Based on the Bouc-Wen model, a hysteresis observer is developed to estimate the hysteresis non-linear effect. Then, for real-time compensation of the observer error and the thermal and external load disturbances, a sliding mode control (SMC) strategy with a perturbation estimation function is utilized. To verify the efficiency of the proposed method, a comparison between the proposed approach and a classical SMC is presented.