Underwater Asymmetric Hysteresis Modeling and Compensation of Flexible Structure Actuated by Macro Fiber Composites

Macro fiber composite (MFC) is widely used in vibration control due to its fast response and large actuating force. However, the underwater asymmetric hysteresis behavior of an flexible structure actuated by MFC actuator greatly affects the accuracy of vibration control. In this paper, to improve the control accuracy of the underwater MFC-actuated flexible structure, a hybrid hysteresis model is proposed to describe the asymmetric hysteresis behavior of the underwater MFC-actuated flexible structures. In the hybrid hysteresis model, we take full advantage of the curve-fitting capabilities of polynomial models to form a hybrid model cascading a classical Prandtl-Ishlinskii (CPI) model. The model fitting results show that the modified PI (MPI) model based on experimental input and output values has a better performance than the pure PI model having a symmetrical parallel quadrilateral structure, and the modeling error is reduced by 81%. Then, the tracking control experiment is performed to prove the effectiveness of feedforward compensation control for the underwater MFC-actuated flexible structure.