Proxy-based impedance control of a cable-driven assistive system

In rehabilitation robotics, rehabilitation algorithms determine an appropriate magnitude and direction of assistive force, which is to help the patient perform desired motions. In this paper, proxy-based impedance control is proposed as a possible rehabilitation algorithm of a cable-driven assistive system that is designed for rehabilitation exercise of the wrist. The proposed method applies an assistive joint torque when the wrist angle deviates from the position of a proxy. A free space is assumed around the proxy such that a free motion of the wrist is allowed in a certain range. When the desired inertia of the hand is different from a nominal value, the proposed method also applies assistive torques to compensate for the inertia mismatch. The implementation of rehabilitation algorithms is challenged by actuator dynamics. The proposed algorithm is designed considering the actuator dynamics, and thus it shows the desired performance and stability in practice.