Mechanical design and impedance compensation of SUBAR (Sogang University’s Biomedical Assist Robot)

SUBAR (Sogang Universitypsilas biomedical assistive robot), an advanced version of the EXPOS, is a wearable robot developed for assisting physically impaired people. It provides a human with assistive forces controlled by the human intention. Since it applies geared DC motors, however, the control efforts are used mainly to overcome the resistive forces caused by the friction, the damping and the inertia in the actuator. In this paper, such undesired properties are rejected by applying a flexible transmission. With the proposed method, it is intended that an actuator exhibits zero impedance without friction and generates the desired torques precisely. Since the actuation system of SUBAR has a large model variation due to human-robot interaction, a control algorithm for the flexible transmission is designed based on robust control theory. In this paper, the mechanical design of SUBAR including the flexible transmission and its associated control algorithm are discussed. They are also verified by experiments.