Modeling and feedforward control of a soft viscoelastic actuator with inhomogeneous deformation

Abstract

Recently, dielectric elastomer actuators (DEAs) have been popularly employed for several soft robotic applications. However, achieving effective control of their highly nonlinear deformation is a key issue. Besides material nonlinearity and electromechanical coupling which accounts for their strong nonlinear behavior, response of DEAs is also affected by their viscoelasticity and inhomogeneous deformation. In this paper, we present an analytical model that can account for all these factors in a circular DEA. Both the viscoelastic behavior and the effect due to inhomogeneous deformation of passive area are well exhibited. Algorithm to obtain the numerical solution is proposed and the simulation results show good agreement with the experimental data. In addition, a feedforward controller is designed by inverse solution of the proposed analytical model which is subsequently used to test the tracking ability of the developed controller. Given a desired displacement, control voltage is first calculated by the developed controller and applied to DEA. The measured displacement of the actuator follows well with the desired trajectory, which verifies the effectiveness of the developed controller. We hope that the effective control of DEAs may pave their way to expansive future applications of soft robots.