Development and Application of a Versatile FES System
The purpose of this study was to develop a versatile Functional Electrical Stimulation (FES) system and to perform clinical applications to restore the functions of decentralized and paralyzed limbs. The development of the electrical stimulator, core of the FES system, is based on the element-envelope method. A direct-synthesized arbitrary waveform is generated by a digital signal processor, and bi-phasic, voltage-controlled, constant current stimuli are provided by an analog output circuit. The pattern generators receive the commands, coming from a patient-driven input device or a closed-loop feedback sensing device, to synthesize the required waveforms and elicit the required functions. In clinical application, a pedal cycling FES system, a patient-driven hand grasping FES system with a closed-loop feedback controller and an ankle motion FES system with a neural network and fuzzy controller were tested. The results showed that the proposed stimulator could be considered as a full-featured electrical stimulator for various FES applications with its flexibility in pattern generation and feedback processing capabilities. All of the clinical applications showed satisfactory results in the restoration and control of some specific functions.