An experimental PID controller for knee movement restoration with closed loop FES system

In this study a closed loop control of knee movements induced by functional electrical stimulation (FES) is presented. A discrete time PID controller working in a master-slave configuration was used where the knee angle, measured with an electrogoniometer, was controlled by another goniometer. First application with surface electrodes on a healthy subject is here considered, frequency response of the closed loop system is experimentally found and the transfer function of the stimulator-leg system is then analytically derived