Characterization and Modeling of the Nonlinear Response of Ionic Polymer Actuators

Abstract

Ionic polymers are compliant, low density materials that operate under low voltage levels as transducers. They can be used as both sensors and actuators for various applications, primarily those involving flexible structures. While some debate continues over the dominant physical mechanisms of actuation, several model forms have been proposed. The majority of these existing models are linear relationships between the applied potential and the strain generated. However, nonlinear characteristics have been observed in both the electrical and mechanical response of cantilever actuators, including harmonic distortion in the sinusoidal time response and a shifting frequency response for increased input levels. Characterization results indicate that the nonlinear mechanisms are dynamic, since they have dominance at low frequencies, but are essentially negligible as the excitation frequency increases. This research uses knowledge gained from the characterization results to develop a dynamic model that can predict the observed nonlinear behavior. The empirical model is constructed from input-output data collected using a Gaussian input current signal and is validated against the measured frequency response function and single-frequency sinusoidal responses. The basic model form has a dynamic nonlinearity on the input to an underlying nonlinear system.