Model reference adaptive control for a precision positioning system

Piezoelectric actuators having the characteristics of infinitely small displacement resolution are popularly applied as actuators in precision-positioning systems. Due to their nonlinear hysteresis effects, the tracking control accuracy of the precision positioning system is difficultly achieved. Hence, it is desirable to take hysteresis effect into consideration for improving the trajectory tracking performance. In this paper, a model reference adaptive control scheme based on hyperstability theory is developed for a moving stage system driven by a PZT actuator. It is worth emphasizing that the controller can be constructed without a nonlinear hysteresis dynamic equation to compensate the hysteresis effect. Through experimental examinations, the tracking performance was obtained as precision as ten nanometer order. The effectiveness of the proposed adaptive control scheme was validated.