A Computer Controlled FES System Combining Multiple Modulation Techniques Simultaneously

This paper describes a multichannel electrical stimulation system for restoring functional movements in SCI and AVC people as well as for therapeutic activities, and motor control investigation. This voltage-controlled source system has 16 independent channels and 8 analog monitoring inputs, is computer controlled via USB interface, using Human Interface Device (HID) protocol, to simplify the development of software or drivers for use with control tools, such as MATLAB (MathWorks Inc). It can control pulse width (from 30 to 400µs), pulse frequency (from 3 Hz to 7 kHz), pulse interval (from 30 µs to 320 ms), burst frequency (from 1 to 1 kHz), number of pulses per burst (it depends on the burst frequency) and the stimulating amplitude (from 0 to 250 V), combining pulse modulation techniques in amplitude (PAM), width (PWM) and frequency (PFM). Its 8 inputs allow the implementation of applications in closed loop control for functional movements as gait and pedaling, for instance. Electrogoniometry and electromyogram (MMG) sensors has been tested for joints angular control and fatigue detection events, respectively.