Development of synchronous driving of lower limb exoskeleton system with virtual reality for gait training

Abstract

A synchronized lower limb exoskeleton (LLE) system combined with virtual reality (VR) was developed to create an innovative community gait training platform and to achieve task-specific gait training purpose. A new concept of the community-based VR gait training was proposed that can be free of distance restrictions. The coach could guide the user for the correct gait through a remote synchronization operation. In addition, the coach and user could obtain an immersive experience through VR to better training benefits and interest. The spatial environment was established with the HTC Vive device to locate the coordinates of the VR. The movement data that was calculated by kinematics was transmitted to the LLE worn by the user. The VR technology was utilized to collect data from the LLE wearer such as the gait of lifting the legs, walking, and climbing stairs. These data could then be recorded and analyzed simultaneously as a database for real-time control of the LLE multi-axis control system. To improve the adaptability of the LLE control system, a proportional-integral (PI) controller was used for the motor controller. The motor controller was designed by the zero-pole elimination method. The results of the LLE control system test combined with the VR show that according to 30°, 45°, and 60° rotation in VR, the movement angle error was within 1°. In the VR motion testing, the synchronization rate of the LLE and VR testing showed that the communication time was about 161 ms. The minimum RMSEs for LLE movements including walking, stair climbing, and lifting the leg were 25.5, 28.8, and 26.7, respectively. The operation cycle of walking, climbing stairs, and lifting the leg are recommended to be around 5, 6, and 4 s, respectively.