Wrist Joint Control by Multichannel Closed-loop FES System: System Improvement and First Clinical Test

A closed-loop FES system for surface electrode stimulation was developed using an electromagnetic 3-D position and orientation sensor to measure joint angles. Our previous goniometer-based closed-loop FES system was found to be effective through controlling wrist joint movements of neurologically intact subjects. However, the previous system could not measure angles of the forearm pronation/supination with the wrist joint angles. The new system solved this problem and was applied to a hemiplegic patient on controlling two degree-of-freedom movements of the wrist joint as the first clinical test. The PID controller proposed previously was examined in the first clinical test with this system. It was suggested that the control system would be easily applied to patients after simple parameter determination process, although good tracking control was not achieved for the patient because of the small range of motion of the wrist radial flexion.