A Novel Back-Support Exoskeleton With a Differential Series Elastic Actuator for Lifting Assistance

Compared to conventional back-support exoskeletons (BSEs) with two motors, BSEs driven by a single motor have the advantage of light weight. However, current single-motor BSEs have problems with accommodating asynchronous hip movements, achieving precise force control and efficient force transmission, and giving autonomy to users when walking. In this article, we propose a novel BSE with a differential series elastic actuator (D-SEA) for lifting assistance. The unique differential working principle can accommodate the angular difference between the hip joints and provide the same assistive torque at both hip joints. The D-SEA achieves precise force control with a custom controller based on accurate spring deflection feedback, and drives the hip joints via an efficient cable-roller mechanism. Taking advantage of the active backdrivability of the D-SEA, we proposed an intelligent assistive strategy that automatically provides adequate support for lifting tasks and grants autonomy to users during walking. In experiments, the BSE reduced the activation level of the back muscles by up to 40% during lifting, without increasing the activation of the back and leg muscles during walking.