Nonlinear displacement control of magnetic material actuators

Magnetic polymer composites (MPCs) are soft material actuators capable of large deformation and fast response. They are wirelessly actuated and do not require onboard electronics or a power supply. Despite MPCs potential, the accuracy and reliability of controlling material displacement is unknown. This paper investigates the performance of three controllers for MPC position tracking: open-loop, fixed gain proportional-integral-derivative (PID) and gain scheduled PID. A systematic workflow, from plant identification to controller gain tuning, is presented, as well as a comprehensive experimental analysis of each controller. Due to observed nonlinear behavior, open-loop and fixed gain PID control were inadequate for fast, accurate position tracking. Gain scheduled PID presented a viable and efficient option for closed-loop displacement control. (paper)