An Experimental Test of Knee Joint Control by Fuzzy FES Controller Based on Cycle-to-Cycle Control

Abstract

A fuzzy controller based on the cycle-to-cycle control method for FES-induced gait was tested experimentally in controlling maximum knee extension angle with normal subjects in our previous study. Although the controller performed it well, error was increased in some trials because many cycles were needed to compensate the change of muscle response. This was considered to be caused by fixed parameter values of the controller for suppressing oscillating response. In this paper, an automatic adjustment method of maximum output value of the fuzzy controller based on the error of the previous cycle was tested. The experimental results of the maximum knee extension angle control with normal subjects showed that the automatic adjustment method was effective in reaching the target value with the small number of cycles and in controlling after reaching the target compensating changes of property of electrically stimulated muscles. The increase of error caused by the change of muscle response was not observed. However, in some trials, the maximum knee joint angle was not detected correctly for a few cycles and oscillating responses were observed. It is necessary for clinical applications to compensate oscillating response and to improve the maximum knee joint angle detection method.