A Biologically-inspired Soft Exosuit for Knee Extension Assistance during Stair Ascent

Stair ascending is laborious, which imposes very high load on human knee, leading to high risks of knee injuries. Therefore, in this paper, a biologically-inspired soft exosuit for knee extension assistance during stair ascent was designed and the assistant effect of proposed exosuit was evaluated. We placed Bowden cables in front of thigh and shank to mimic quadriceps muscle, generating knee extension moments by length contraction. A force-based position control was implemented to deliver a knee assistant moment profile, which was based on biological knee moment during normal stair ascent. Biomechanical parameters of three experimental conditions (without exosuit, with unpowered exosuit, with powered exosuit) were compared. Experimental results showed that with powered exosuit lower-limb joint kinematics exhibited minimal changes, while net (muscles plus cables) knee moment decreased by 10.92% and net knee power decreased by 30.1% as compared to without exosuit condition.