FNS Control Schemes for the Upper Limb

This paper is concerned with the problems of control associated with the application of functional neuromuscular stimulation of the upper limb, concentrating on elbow flexion/extension and wrist pronation/supination. A closed-loop controller is needed in order to overcome the gain nonlinearities and plant dynamic parameter variations. Controllers were developed based on models and parameters previously established. Two controllers are discussed in detail, a thirdorder feedforward controller and a model reference adaptive controller. There were no striking differences in the performances of the thirdorder controllers. The conventional controllers, however, required a lengthy a priori identification procedure each time they were used. This was performed implicitly by the adaptive controller within a few seconds, making it a practical proposition for an FNS controller.