Evaluation of FES control system employing adaptive and PI controllers

For the study of functional electrical stimulation (FES), a closed-loop system has been used to control a muscle contraction. The authors have applied Kitamori´s controller design method to the system. When the muscle properties are changed, this control system becomes unstable, since the controller cannot change its parameters. An adaptive control system can change the controller´s parameters but has less stability than the Kitamori controller. The authors propose a control system consisting of a hybrid PI (proportional-integral) and adaptive controller. They simulate the step responses of the system, showing that it has greater stability than an adaptive controller alone.<>