Hybrid control of powered orthosis and functional neuromuscular stimulation for restoring gait

The restoration of motor functions of patients with spinal cord injury (SCI) is one of important subjects for study. For this purpose, methods of functional neuromuscular stimulation (FNS) have been investigated in medical science and practice during these three decades. However, we have not achieved complete restoration of motor functions in SCI patients. On the other hand, we have achieved useful devices in human-scaled transportation by using power assist technology. Thus, applying power assist technology to the problem of restoring motor functions is one of possible solutions and sounds practical. In this paper, we propose a new hybrid system to combine power assist technology and FNS for restoring motor functions of lower extremity in SCI patients. Both powered orthosis and FNS are used to generate and control the joints moments of lower extremity in the proposed hybrid system. The main role of powered orthosis to compensate the joints moments generated by FNS and to enhance the controllability of FNS with the actuators. The proposed hybrid control system has been experimentally evaluated in gait motions by measuring the angle trajectories and generated moments around the knee and hip joints in the cases when only actuators are used and both FNS and actuators of the orthosis are used. The results prove that the control method for the hybrid system is useful to restore motor functions of lower extremity in SCI patients.