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Position Control of a Square-plate Ionic Polymer Actuator Using Output Feedback

Ionic polymer materials exhibit coupling between the electrical, chemical, and mechanical domains that enables their use as both sensors and actuators. Because these materials are flexible and operate on battery-level voltages, they have received considerable attention in the recent years. While a universally accepted model for actuation is still in development, an empirical model is developed here between input current and center-point deflection of a square-plate polymer actuator that is clamped at its four corners. Characterization results show that a nonlinear model is needed due to the low frequency harmonic distortion that is present in the response. The square-plate actuator is used to demonstrate the potential that ionic polymers have in shape control applications for flexible structures, such as deformable mirrors. In this article, the authors demonstrate a tracking control concept, wherein the reference command signals are meant to correspond to focus adjustments in a lens.