A versatile multichannel direct-synthesized electrical stimulator for FES applications

Functional electrical stimulation (FES) has been applied to restore or maintain the muscle activity of paralyzed patients who suffer from spinal cord injuries and related neural impairments for several decades. In this paper, a direct-synthesized arbitrary waveform stimulator for multichannel FES applications is described. A novel element-envelope method is proposed for flexible waveform generation and implemented by a digital signal processor based system. We also designed an output circuit that can provide bi-phasic, voltage-controlled, constant-current outputs while keeping high-voltage compliance and wide signal bandwidth. High time-resolution and arbitrary stimulating waveforms can thus be synthesized, and more flexible closed-loop feedback controllers can be achieved. The proposed stimulator can be considered as a full-featured electrical stimulator for various FES applications with its flexibility in pattern generation and feedback processing capabilities.