Bandwidth characterization in the micropositioning of ionic polymer actuators

Ionic polymers are electromechanically coupled smart materials that can be used as both actuators and sensors. As flexible actuators, these materials have been known to exhibit nonlinear behavior, but the present work shows that linear control techniques can greatly improve the open-loop response. However, because material dehydration results in changing system parameters, the linear control designs only offer a stable system for a limited amount of time (approximately 30 s). This study shows that the application of integral control to ionic polymer actuators can provide precise tracking performance to a reference step input. The actuator's response to frequencies is also studied, in both the time and frequency domain. The frequency response analysis offers insight into the bandwidth of the actuators, where it was shown that the closed-loop bandwidth of the cantilever actuator is approximately 10% of its first resonance frequency. Simulations are performed with a linear empirical model of a cantilevered actuator, while both clamped-free and clamped-clamped configurations are tested in control experiments.