Improving Walking Assist Hip Exoskeleton Torque Efficiency with Decoupling Mechanism

Walking assist hip exoskeleton can aid healthy subject walking and reduce metabolic cost by providing assistance torque through both thigh bandages. Most hip exoskeleton thigh bandages are designed with direct and rigid fixation on the exoskeleton thigh links, leading to external forces/torques since the human and exoskeleton hip flexion/extension joints alignment cannot be ensured ideally. The external forces/torques reduce the walking assist hip exoskeleton torque efficiency. This paper presents design of a thigh bandage decoupling mechanism that eliminates human-exoskeleton thigh displacement deviation during walking. Human walking tests are conducted, and both thigh bandage and exoskeleton thigh link displacement during walking are measured through motion capture system. The interaction forces on the thigh bandage side are also measured by the force sensor. The results show effective tangential interaction force reduction with thigh bandage decoupling mechanism versus traditional direct and rigid fixation. Thus, the walking assist hip exoskeleton torque efficiency is improved. Meanwhile, the wearing comfort increases since external interaction force and torque are eliminated, which is proved by the subject's feedback after walking tests. The decoupling mechanism provides simple and effective solutions to higher walking assist hip exoskeleton torque-weight ratio since the torque efficiency is increased.