Design of Parameter Estimation Method of Fuzzy FES Controller: Computer Simulation Test in Wrist Joint Control

Functional Electrical Stimulation (FES) is an effective technology for assisting or restoring paralyzed limbs of people with motor paralysis, which can be used for activities of daily living and in rehabilitation training. However, it takes a proper control method to achieve the desired functional movement repetitively. In this study, we developed a modified fuzzy controller along with a parameter estimation method for FES applications. The fuzzy controller was considered to realize the FES controller because of its simplicity and flexibility in its design. However, one of the challenges faced is how to determine the parameter values of the fuzzy controller for each individual considering that the response characteristics of the stimulated musculoskeletal system vary from one individual to another. Therefore, the parameter estimation method was developed to overcome the above problem by utilizing information from the input-output (electrical stimulation-joint angle) relationship of each individual. Computer simulation tests were accomplished to examine the fuzzy controller in controlling the 1-DOF movement of the wrist joint (palmar flexion) by stimulating the flexor carpi radialis (FCR) muscle. The control results showed that the fuzzy controller was able to track the target movement trajectory with acceptable tracking error and its parameter could be determined easier and faster using the parameter estimation method. Based on the results, we suggested that the modified fuzzy controller along with the parameter estimation method can be useful for practical FES applications.