Abstract: Powered lower limb exoskeletons have traditionally used four or more powered joints to provide ambulation assistance for individuals with spinal cord injury. Exoskeletons with numerous powered joints commonly lost some excellent features of passive orthoses and further decreased utility due to added weight and increased control complexity. This work adopts joints coupling mechanism to design a powered exoskeleton to minimize the number of actuated joints and control complexity. Unlike conventional powered exoskeletons, the joint-coupled-powered exoskeleton only has a single motor-actuated joint for each exoskeleton leg in conjunction with a unique knee coupled system to enable their users to walk, sit, and stand. And two types of joint coupled systems are designed, respectively, hip-knee coupled and knee-ankle coupled. The joint-coupled-powered exoskeleton system allows a single actuator to power the hip motion, and allows activate knee motion through the coupled motions of the hip or ankle. More specifically, when the mechanical coupled system is activated, the knee joint is unlocked, resulting in synchronized hip-knee or ankle-knee flexion and extension. The coupling mechanism is switched on and off at specific phases of the gait (the stance phase and the swing phase) to generate the desired motions. The research work proves that minimal actuated robotic systems with joint coupled could achieve safe and natural walking.

Key words: Powered exoskeleton, Minimal actuation, Joint coupling, Single motor-actuated joint