A versatile multichannel direct-synthesized electrical stimulator for FES applications

Functional electrical stimulation has been applied to restore or maintain the muscle activity of paralyzed patients who suffer spinal cord injuries and related neural impairments. A direct-synthesized arbitrary waveform stimulator for multichannel stimulation is developed in this paper. A novel “element-envelope” method is proposed and implemented by a digital signal processor to synthesize required stimulating patterns with high resolution. This method not only generates arbitrary waveforms but also reduces the memory requirements. It preserves the ability to adjust stimulation parameters dynamically. We also design an output stage that can provide bi-phasic, voltage-controlled constant-current patterns while remain high compliance and wide bandwidth. This system can be considered as a full-featured stimulator for various FES applications with its flexibility in pattern generation and feedback processing capabilities