Human-in-the-Loop Control of Robotic Leg Prostheses With Sensory Feedback

Human during walking can sense the joint angle and the contact force between the leg and the ground and uses such information as the feedback to regulate walking performance. To complete this motor control for the amputee with the leg prosthesis, human-in-the-loop control was proposed. This control method involves the restoration of the sensory feedback and the unified gait generator. By restoring the sensory feedback of the prosthesis with noninvasive Functional Electrical Stimulation (nFES), the subject can sense touch-down moment, leave-off moment, and height of small obstacles on the ground. Then, the unified gait generator converts the subject's intent into the prosthesis' motor command according to the damping and Spring-Loaded Inverted Pendulum (D-SLIP) model. When walking is slow, the prosthesis is stiff. When walking is fast, the prosthesis is compliant. Three experiments were conducted to prove the improvement of walking performance, such as the precision to sense the height of small obstacles, and the amount of increment for walking speed and frequency on level ground, S curve, or stairs. These results showed that the proposed control method can improve the motion capability of subjects greatly.