  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.
