Extremum Seeking applied to Neuromuscular Electrical Stimulation

Extremum seeking (ES) methodology is applied to implement adaptive Proportional-Integral-Derivative (PID) closed-loop control for neuromuscular electrical stimulation (NMES). The proposed strategy is designed to control the patient's arm position in order to generate elbow extension/flexion movements. This method obviates the application of initial controller tests directly to patients since the tuning procedure is automatically performed in an online fashion. ES is used to tune the parameters of a PID controller so as to minimize a given cost function which is chosen to reflect the desired performance attributes. The ultimate responses obtained in the experiments with a healthy volunteer complied with the common specifications set in terms of the steady-state error, settling time, and the percentage overshoot.