Programmable Multichannel Neuromuscular Electrostimulation System: A Universal Platform for Functional Electrical Stimulation

This work presents an Electrical Stimulator (ES) system able to connect to different external sensors and to perform different stimulation strategies that would meet the current research needs on FES-assisted activities, including cycling and walking. An ES with a 3-channel architecture was first developed and later evolved into an 8 and 12-channel system. Each of these channels can generate different pulse waveforms, biphasic or not, achieving pulse amplitude of 100 mA and pulse width up to 1000 \(\upmu \)s at a maximum frequency 100 Hz. To enable protocols involving different stimulation arrangements for a specific muscle, an electrode multiplexing circuit was developed. Data obtained from the functional activity can be exchanged by a wireless interface with an external platform for later offline processing. Inertial Measurement Units (IMU) can be used to calculate the joint angles of the moving limbs. This paper aims to present a brief description of the hardware and the results obtained as the platform configured as a Foot Drop Stimulator. Gait phases were detected through mechanical and inertial sensors. The identification results were compared with data obtained from a gold-standard Qualisys/AMTI system. The developed system evidences its applicability in contexts such as walking, cycling and can also be used for clinical rehabilitation purposes.