Feedback control of tri-layer polymer actuators to improve their positioning ability and speed of response

Improving positioning ability of electroactive polymer actuators typified by polypyrrole (PPy) through feedback control of their position has been considered. The actuators operate in air, as opposed to their predecessors. One of the problems associated with the actuators is the forward relaxation/creep or drift, which occurs after the full reduction and oxidation processes are completed. A high-resolution laser displacement sensor was used to detect the position of the cantilever-type polymer actuators and the classical, yet effective, Proportional, Integral and Derivative (PID) control method has been employed to generate the appropriate control input in order to make sure that no drift occurs in the user-specified position of the actuators. A set of experimental results with and without feedbacking the position data are presented to demonstrate the efficacy of the control method for improving the positioning ability and the speed of response. The rise time is reduced by more than 500 times and the position tracking error is less than 10% for a time-varying user-specified position command.