Design of virtual reality systems integrated with the lower-limb exoskeleton for rehabilitation purpose

Abstract

In this paper present the lower limb exoskeleton (LLE) is designed with the proportion of the lower limbs of the human body and established the torque model of each joint. The structure strength of LLE is optimized to make the mechanism safe and stable. In order to reach a high torque, the Maxon motor is combined with harmonic drive (HD) under reduction ratio 1:100 to enhance the torque up to 93%. According to the actual movement of the human gait, the infrared photography technology with the reflective ball is used to photograph and analyse the walking gait. The motor control system is installed in the LLE. Four servo motors are installed in the left and right sides of the hips and knees, respectively. The controller design is based on Field-oriented control (FOC) principle to issue commands through the motor, and then the proportional-integral-derivative controller (PID controller) is applied to assist and handle the motor feedback. This study develops a virtual reality (VR) images which is combined with the exoskeleton to make the rehabilitation more interesting. This VR images are built based on the Unity (game engine) including uphill, downhill and irregular terrains for users to experience different walking modes.