Design and Evaluation of a Passive Hip Exoskeleton to Reduce the Energy Cost of Human Walking

A passive exoskeleton was designed with the goal of reducing metabolic cost of human walking by augmenting moments around the hip joint. A novel approach, using leaf springs parallel to the human leg, was proposed. A kinematic model including man-machine interface compliance was optimized and results showed a maximal reduction of metabolic cost of 60%. A prototype was built and included a pelvic part, vertically fixing the leaf springs, and a thigh part, accommodating four degrees of freedom. The performance of the prototype was experimentally evaluated in treadmill trials. Muscle activity, metabolic energy and whole-body kinematics and kinetics were measured during normal walking, walking with the exoskeleton with and without springs. Walking with the active exoskeleton resulted in a negligible small increase in metabolic energy expenditure compared to the exoskeleton without springs.