Adaptive Robust Control for Micropositioning of Piezoelectric Actuators with Environment Force Estimation

Piezoelectric actuators are widely used in applications of micropositioning. In the most situations, there is a contact with an environment. Existence of external forces is a challenging problem in controlling mechanical system, especially in micro scales such as piezoelectric actuators. In such a situation, dual hysteresis nonlinearity effects could disrupt the actuator micropositioning accuracy. In this paper a modified Prandtl-Ishlinskii (PI) operator and its inverse is utilized for both identification and real time compensation of the hysteresis effect. A variable structure controller is proposed for trajectory tracking of the actuator position. A sliding-based observer would estimate full states from the only measurable position trajectory. Proposing an adaptive perturbation estimation approach, the pure external forces would be observed. The stability of the controller in the presence of the estimated states and external forces is demonstrated analytically. The experimental results depict that the proposed approach is achieved in precise trajectory tracking and external force estimation.