Reference Joint Trajectories Generation of CUHK-EXO Exoskeleton for System Balance in Walking Assistance

This paper introduces a wearable exoskeleton suit CUHK-EXO that can help paraplegic patients regain their mobility to stand up, sit down, and walk. An offline design and online modification (ODOM) algorithm is proposed for the exoskeleton to generate reference joint trajectories during walking assistance. First, reference trajectories of CUHK-EXO are designed offline based on motion capture data considering leg geometry constraints. Then the human-exoskeleton system (HES) including a pair of crutches is modeled as an eight-link system for analysis. Since the relative position of system center of pressure (COP) is an important factor to indicate system balance during walking, it is estimated in real-time and monitored for exoskeleton control. Based on the system COP position, this paper further proposes the reference trajectories online modification method for CUHK-EXO to counteract disturbances applied to the HES, and hence stabilize system balance in the walking assistance. Finally, walking tests are performed in both healthy subjects and a paraplegic patient to validate the effectiveness of the proposed ODOM algorithm. Testing results demonstrate that knowing the COP desired areas of the wearer, the exoskeleton CUHK-EXO can counteract perturbations and decrease the wearer's efforts, so as to maintain system balance with the ODOM algorithm.