Robust Interaction Control of a Dielectric Elastomer Actuator with Variable Stiffness

This paper presents an interaction control algorithm for a dielectric elastomer membrane actuator. The proposed method permits efficient exploitation of the controllable stiffness of the material, allowing to use the membrane as a 'programmable spring' in applications such as robotic manipulation or haptic devices. To achieve this goal, we propose a design algorithm based on robust control theory and linear matrix inequalities. The resulting controller permits to arbitrarily shape the stiffness of the elastomer, while providing robust stability and performance with respect to model nonlinearities. A self-sensing displacement estimation algorithm allows implementation of the method without the need of a deformation sensor, thus reducing cost and size of the system. The approach is validated on an experimental prototype consisting of an elastomer membrane preloaded with a bistable biasing spring.