Passively-powered knee exoskeleton to reduce human effort during manual lifting

Abstract

The proposed device consists of a system of helical elastic springs bilaterally located on the shank for capturing/storing waste biomechanical energy at the knee, a cable and pulley system to transmit power from and to the knee, a pulley locking/unlocking mechanism to achieve passive control of the device operation ensures no restrictions are posed by the springs during walking and applies a pre-tension on springs to prevent slacking of the Bowden cable using a return spring. However, when the wearer performs a squatting task, the springs engage/disengage energy springs when the knee flexes over a preset angle (i.e., 60 degrees). The energy dissipated and generated at the knee joint during decent and ascent phases from biomechanical studies were recorded as 45 J and 50 J respectively for an average human [3]. Accordingly, the selected energy springs can collectively capture and return approximately 20% of biomechanical energy at the knee.