Modeling and adaptive inverse control of hysteresis and creep in ionic polymer–metal composite actuators

Like most smart materials, such as piezoelectric materials and shape memory alloys, ion-exchange polymer–metal composite (IPMC), which is a kind of electroactive polymer material, exhibits the properties of hysteresis and creep. In this paper we explain the hysteresis and creep properties of IPMC, analyze the hysteresis using a discrete Prandtl–lshlinskii model, obtain a creep model of IPMC through modifying the creep model of piezoelectric material and present an inverse model of the hysteresis. For hysteresis and creep properties of IPMC changing with time at different rates, we applied the LMS (least mean square) algorithm to identify the hysteresis parameters online. An offline identification algorithm was used to obtain the creep parameters. An adaptive inverse strategy of control for IPMC actuators was set up on the basis of a superposition model of nonlinear hysteresis and linear creep, and we obtained good simulation and experiment results