Adaptive output feedback control with feedback-feedfoward compensator for piezoactuator-driven stages

The high precision of a piezo-electric positioning stage almost depends on whether the designed controller can effectively compensate the inherent hysteresis phenomenon. In this paper, an adaptive output feedback controller based on a radial basis function neural network (RBFNN) is proposed to eliminate the tracking errors caused by the hysteresis behavior. The observer-based RBFNN is used to online estimate the dynamic nonlinear hysteresis which is described by an uncertain first-order differential equation. The external disturbances and network´s approximation errors are further compensated by a robust control item. As a result, A combined controller with feedback and feedforward control scheme is designed to mitigate the effects of the uncertain nonlinear hysteresis. The stability analysis is given by Lyapunov theorem. Numerical simulations illustrate the effectiveness of the proposed control scheme.