Design of a programmable flyback based FES system for restoring foot drop in stroke rehabilitation

Functional electrical stimulation (FES) is an assistive neurorehabilitation technology that utilizes low levels of electrical currents for neuromuscular stimulation of paralyzed extremities resulting from cerebral stroke or similar conditions. Optimization of the FES circuit is essential to reduce power consumption and to minimize power dissipation that can cause tissue damage. In this work, an improved foot pressure sensor based programmable, single channel, multi-pattern transcutaneous FES system was developed using power electronic systems and tested to correct foot-drop in stroke patients. The FES prototype developed herein uses a unique flyback circuit design and the electrical stimulation is tuned to achieve maximum functional response with minimal power drain. The flyback also provides galvanic isolation required by patient safety standards. The development of multi-pattern stimulation envelopes with variable intensity profile is an important contribution of this work, since this approach enables controlled and customized treatment depending upon the patient´s status and stroke type, so that the stimulation can be much safer and more effective. With slight modifications, the circuit can also be used for rehabilitation of children with spastic cerebral palsy. The prototype is non-invasive, portable, flexible, low-cost and suitable for point-of-care applications.