Elbow Control using Functional Electrical Stimulation: an Experimental Comparison of Different Control Strategies

The lack of control systems for human movement based on Functional Electrical Stimulation (FES) providing satisfactory tracking performance and reduced fatigue may be one the major reasons for the limited number of such applications available today on worldwide markets. In view of this context, in this paper we present an experimental comparison of different control strategies for FES systems using discrete surface electrodes. Firstly, we have selected different algorithms for inducing and controlling joint motion, such as PID with anti-windup, adaptive PID, feedforward control, and controllers that employ muscle co-activation maps. Those control strategies were then evaluated on an experimental protocol in which elbow motion was controlled in the horizontal plane by means of stimulating the major antagonist muscles that produce elbow movement. The paper presents the preliminary results obtained from trials conducted on two healthy subjects, in which, although the overall performance was satisfactory, marked difference was observed between the participants.