Flexion-synergy is a stereotypical movement pattern that inhibits independent joint control for those who have been affected by stroke; this abnormal co-activation of elbow flexors with shoulder abductors significantly reduces range of motion when reaching against gravity. It is possible to decouple this synergy by supporting the arm against gravity, alleviating the shoulder muscles. Passively-actuated devices, such as exoskeletons or orthoses, offer suitable, portable solutions towards this goal. Passive devices offer advantages over their active counterparts relating to portability, weight, and complexity. 

We seek to further investigate these advantages through the design and development of wearable ortheses based around compliant mechanisms; while such devices have been shown to accurately compensate for the arm’s weight at the shoulder, it is unclear if accurate compensation can also be achieved while minimizing device bulk. To study the possible tradeoff between device functionality and portability, we have developed a novel, multi-objective simulation-optimization framework towards the goal of designing practical gravity-balancing orthoses for the upper-limb.

Publications on this topic

H. A. Chishty, F. Sergi, “A Multi-objective Simulation-Optimization Framework for the Design of a Compliant Gravity Balancing Orthosis”, doi: 10.1101/2024.02.16.580745, 2024, pre-print.