Rate-dependent hysteresis modeling and compensation for fast steering mirrors

Fast steering mirrors (FSMs) driven by piezoelectric ceramics are actuators of pointing, acquiring, and tracking (PAT) systems in free space laser communications. However, the inherent hysteresis nonlinearity of the FSM significantly degrades the performance of the PAT system, especially the so called rate-dependent hysteresis in high frequency. This paper presents a systematic framework for modeling rate-dependent hysteresis. The rate-dependent hysteresis curve can be viewed as a superposition of the rate-independent hysteresis curve and the rate-dependent term. The proposed method is transformed into a control algorithm that can work in realtime for satellite optical communications. Meanwhile, the corresponding parameter identification methods are reasonably presented. Applying a feed-forward control strategy, the presented algorithm compensates for the rate-dependent hysteresis effect of the FSM at low and medium frequencies. The results demonstrate that the proposed algorithm effectively suppresses the rate-dependent hysteresis nonlinearity of the FSM. After the rate- dependent hysteresis effect of the FSM is compensated, the actual spiral scan trajectory of the FSM accurately tracks the target trajectory, which validates the effectiveness of the proposed compensation algorithm.