Evaluation of a Bionic Cable-driven Ankle Exoskeleton System for Human Walking Assistance

In order to further explore the performance of assistive exoskeleton, we tested and evaluated a bionic cable-driven ankle exoskeleton system for human walking assistance in this paper. A bionic ankle exoskeleton was used as an end-effector to provide many different patterns of assistance. Assistive forces were transmitted by a flexible Bowden cable which attached fewer moments of inertia to the wearer and minimized the impact of wearable devices on the wearer’s natural movements. We preset the assistive torque trajectory according to biological ankle moment during walking and used a torque control method of proportional control with damping injection compensated by adaptive iterative learning to achieve high-performance torque control. We evaluated the kinematics and biological efforts of one subject with predefined assistance patterns. Assistance during walking on a treadmill reduced the metabolic cost by 10.34% compared with normal shoes. The root mean square (RMS) of the soleus muscle activity decreased by 52.2%, and ankle joint moment reduced by 40.4% with the same pattern. The experimental results show that the device is capable of improving walking economy.