Power assist control for walking aid with HAL-3 based on EMG and impedance adjustment around knee joint

This paper describes the power assist control for walking aid based on EMG and impedance adjustment with HAL-3 we have developed. Virtual torque derived from EMG is adopted as a basic control method, and the motion assist control as to operator´s intention can be realized by this method. And we suggest the impedance adjustment around knee joint for more effective power assist control. Experiments for simple motion and walking motion were performed to verify the proposed approach, with impedance parameters found by RLS (recursive least square) method. The evaluation of assisted motion was done by a calculation based on EMG in nearly proportion to the operator´s muscle force. The results showed the amplitudes of EMG were reduced significantly, the operator was able to swing the leg lighter by reducing the inertia around knee, and the strain of knee in foot-grounding could be alleviated by adding the stiffness to joint.