Hysteresis-observer based robust tracking control of piezoelectric actuators

In this paper, a robust control approach using a novel hysteresis observer is developed for precise tracking control of piezoelectric actuators (PEAs). The proposed control methodology considers the problems of unknown or uncertain system parameters, hysteresis nonlinearity and external load disturbances. For representing the behavior of a PEA, Bouc-Wen hysteresis model is integrated with a second-order linear dynamics. It is shown that the nonlinear response of the model due to the hysteresis effect, acts as a bounded disturbance. Based on this fact a hysteresis observer is proposed to estimate the hysteresis effect. Then for real-time compensation of the observer error, parametric uncertainties and external disturbances, the sliding mode control strategy with a perturbation estimation function is utilized. By using the proposed control approach the asymptotical stability in displacement tracking and robustness to the dynamic load disturbances can be provided. Finally, experimental results are illustrated to verify the efficiency of the proposed method for practical applications.