Fuzzy Extended State Observer for Robust Sliding Mode Control of Piezoelectric Actuators

Piezoelectric actuators are widely used in micro and nano-positioning systems for accurate movement. However, they exhibit some nonlinearities, particularly hysteresis, which makes precise control rather challenging. Many methods are available in the literature to compensate for the hysteresis effect in piezoelectric actuators, but often a model of the actuator is required for this purpose. Identification of such a model is challenging too. In this paper, we propose using a robust observer-based controller for precise motion tracking of piezoelectric actuators without the need for a hysteresis model. The controller consists of a fuzzy extended state observer (FESO) to estimate the hysteresis and other nonlinearities, as well as model uncertainties and external disturbances. Subsequently, a robust sliding-mode controller is designed and added to the framework. Joint stability analysis guarantees the stability and tracking performance of the proposed combined controller. Simulation and experimental results confirm the performance of the proposed controller compared to some other techniques.