An incipient technology for actuation with physical and dynamic characteristics similar to natural muscles has been studied since early 90's. However, the control of such systems is not a trivial task, due to actuator non-linearities. This work presents a proposal for non-linear control of force in artificial muscles based on the VHB4905 acrylic polymer. Mathematical models of the tested actuator are developed. Experiments are performed on a especially developed test bench with a force transducer and the artificial muscle actuated by a high voltage circuit (10kV maximum). A maximum force error of 1% is obtained when comparing the model that characterizes the material and the experiment that measures force versus electric stimulus. It is shown that the proposed non-linear controller results in a better step response when compared to a standard PID controller. The standard PID does not take into account the system non-linearities, therefore it cannot avoid oscillations in the step response when subjected to high voltages, close to the dielectric breakdown of the polymer. The effectiveness of the proposed control technique is proven experimentally.
Artificial Muscles; Dielectric Polymers; Force Control
