Design for walking rehabilitation of a lower limb exoskeleton based on interaction torque

In this research, an adaptive lower limb exoskeleton (AEXO) has been designed and constructed as a rehabilitation device. It is important during the rehabilitation that a user obtains assistance from the exoskeleton in an adaptive manner, as the user may improve his/her walking during rehabilitation. The assistance from the machine will be less or more according to the current situation of the user during the use of the exoskeleton. The question then arises as to how the exoskeleton can provide adaptive adjustment. It was decided that a tangible design was to measure the user status such as the user interaction force during walking. In this design, force sensors are installed on each link of exoskeleton to record the user walking effort during walking. By measuring this force, the control computer of the exoskeleton will understand for each cycle what the status of the user is and predict an adaptive torque according to measured force. In order to generate a suitable torque, the compliant motion control, which is a combination of impedance and admittance control is used. Walking experiments of a healthy person to wear the AEXO have been carried out in the lab. The first experiment verified the propose algorithm by using a predefined reference trajectory for the user and giving an adjustment to the reference trajectory based on the interaction torque. The second experiment verified that even without the predefined gait trajectory to the user, the exoskeleton can move in compliance to the user under various walking speeds. For the future development, the method will be expanded and tested for people who suffer from stroke or other walking impairment.