State space modeling of ionic polymer-metal composite actuators based on electrostress diffusion coupling theory

Ionic polymer-metal composite (IPMC) actuators are expected as artificial muscles for bio-mimetic soft robots. The IPMC gel first bends quickly and then bends back slowly when a constant voltage is applied to the sample. The latter phenomenon, referred to as the stress relaxation, can be modeled by electrostress diffusion coupling theory. The theory can predict the behavior of the actuator for the different species of counterions. In order to describe the actuator dynamics as a system with inputs and outputs, this paper proposes a linear state space model based on the electrostress diffusion coupling theory. The model consists of the three systems, the electrical, the electro-mechanical, and the mechanical systems. The results of the simulation and the experiment demonstrate the validity of the model.