An approach to real-time parameter determination of the multichannel closed-loop FES controller

We have developed the multichannel closed loop FES controller using the PID control for multi-joint control and/or several degrees of freedom of movement control stimulating several muscles. Although the method was proved to be effective, it sometimes caused undesirable responses such as oscillations of joint angles because of strong nonlinearity of the input-output characteristics of electrically stimulated muscles. In this paper, a method of real-time parameter determination for the controller was examined. Controller parameters were determined based on stimulus intensities applied just before each adjustment of stimulation intensities. The method was effective in reducing undesirable oscillations during closed loop FES control without trial and error adjustment of controller parameters.