Back-drivability recovery of a full lower extremity assistive robot

Recently, walking assistance robots are receiving a great attention according to the increase of elderly population. Such systems are required to generate precise and large assistive torques to effectively assist human motions. Moreover, the assistive robots should be light and compact for the comfort and safety issues. In this paper we designed full lower extremity assistive robot with compact rotary series elastic actuators(cRSEAs) that are designed considering these factors. A worm gear is installed to amplify the motor torque in the limited space. Also, to generate assistive torque as desired, a torsional spring is used between the motor and the human joint. The device generates large assistive torques by utilizing worm gear, but the large friction introduced by the worm gear makes the controller design challenging. In this paper, a feedback control algorithm is proposed to compensate for such undesired disturbances. The proposed method is verified by experiments.