Closed-Loop Position and Cadence Tracking Control for FES-Cycling Exploiting Pedal Force Direction With Antagonistic Biarticular Muscles

A functional electrical stimulation (FES)-based position and cadence tracking controller is developed to enable cycling by exploiting antagonistic biarticular muscles. A model of a stationary cycle and a rider is developed as a closed-chain mechanism. A strategy is then developed to switch between muscle groups based on the force direction of each muscle group. Stability of the developed controller is analyzed through Lyapunov-based methods. Experiments were conducted in seven healthy individuals and one individual with Parkinson's disease to illustrate the performance of the developed method. Specifically, the developed method was compared with voluntary tracking in terms of the position and velocity tracking errors. From the experimental results, we conclude that the proposed method can realize FES-cycling close to voluntary tracking.