Design and Validation of a Torque Controllable Hip Exoskeleton for Walking Assistance

Abstract

Recent technological advancements have expanded the field of human augmentation. Specifically, lower limb exoskeletons have benefited many by providing assistance to increase mobility. The proposed study aims to develop a novel bilateral hip exoskeleton that provides mechanical power assistance in both hip flexion and extension during walking. Each actuation unit employs series elastic actuator for a high fidelity closed loop torque control utilizing a ball screw transmission incorporated with a fiberglass leaf spring. The control architecture was divided into three tiers and each tier implemented different control algorithms. The device was experimentally validated with both benchtop and human testing. Benchtop testing was done to tune required control parameters in the low-level controller and to validate the torque response. We tested five able-bodied subjects walking with our device. We analyzed their kinematic and kinetic data with different levels of mechanical power assistance during walking. Our benchtop testing results showed that the low-level PID gains were tuned to achieve desired bandwidth and torque tracking. Human testing results demonstrated that the high-level controller provided an accurate information for assistance onset timing that the hip exoskeleton was able to assist the user effectively.