A NONLINEAR OBSERVER-BASED SLIDING-MODE CONTROL FOR PIEZOELECTRIC ACTUATOR SYSTEMS: THEORY AND EXPERIMENTS

摘要

This paper presents a nonlinear observer-based sliding-mode control for piezoelectric actuator systems (PASs). Because not all of the states of the PAS are available, an observer is required to estimate the state. The proposed scheme contains a feedback linearization with a sliding-mode controller, and a state observer to estimate the velocity and hysteresis of the PAS. The sliding-mode control possesses an equivalent control and a switching control. For tracking a sinusoidal trajectory, the reference model with desired amplitude and phase features is also designed to obtain a tracking . error model. Based on the observer and the error model, the equivalent control is designed to obtain the desired control behavior. Because the piezoceramic materials are ferroelectric, inherent nonlinearity and hysteresis always exist in the system. The tracking performance is attenuated due to the existence of the hysteresis, the modeling error and the estimation error. Therefore, the switching control is employed to improve the robust performance. The stability of the overall system is verified by the Lyapunov stability theory. Experiments of the PAS are also presented to verify the usefulness of the proposed control.