A Computer Simulation of Tuned Pid and Continuous Sliding Mode Fes Control

Functional Electrical Stimulation can restore movement in certain paralyzed individuals. Electric current pulses excite the intact peripheral nerves, cause the muscles to contract and generate joint movements. Since this physiological and biomechanical system is highly nonlinear and time-varying, feedback control is necessary for satisfactory FES control of the joint angles. In this study, a continuous computer model of a human knee was developed, and was used to compare the performance of widely used PID controller, with a newly developed sliding mode control strategy. Both strategies did compensate for the muscle fatigue effect, but the reference knee angle trajectory tracking of the tuned PID controller was poor compared to the sliding mode controller. The simulation results confirm that the sliding mode control might prove a very good candidate for precise trajectory tracking of the FES induced movements.