Long-term Multiple Time-Constant Model of a Spring Roll Dielectric Elastomer Actuator under Dynamic Loading*

Abstract

Dielectric elastomers are electro-mechanically coupled transducers that display a nonlinear viscoelastic stress-strain relationship. Modeling and controlling such nonlinear materials and actuators are of great challenge. A spring roll dielectric elastomer actuator is a linear actuator composed of a spring and sheets of wrapped dielectric elastomers. Since its shape and actuation performance resemble a human muscle, its application as an artificial muscle is investigated. To verify its applicability, the actuator’s controllability and time-dependent actuation behavior are examined. In this paper, we derive a multiple time-constant model specifying the response of a long-term dynamic loading of the spring roll dielectric elastomer actuator. Our modeling approach is based on multiple viscoelastic elements, having different time responses, superposed into one rheological model. In addition to viscoelasticity, the model includes the effects of the spring core, external mechanical load, the internal stress of the elastomer, and the applied dynamic voltage signal, so that it can be applied in various working conditions. Experiments and simulations are conducted to confirm the applicability and accuracy of the proposed long-term multiple time-constant model.