A light knee exoskeleton for assisted ramp walking

Most unpowered exoskeletons use a crossed four-bar linkages for rotating the knee joint instantaneously to ensure movement comfort. Powered exoskeletons generally employ a single-degree-of-freedom hinge mechanism that provides a boost while limiting the wearer's flexibility. So we tried to use powered crossed four-bar linkages to do the job. We propose a lightweight knee exoskeleton structure design and its control method to assist the conversion of sitting and standing postures and walking uphill, helping the elderly who are weakened by age. The exoskeleton uses an embedded crossed four-link mechanism to simulate the polycentric movement of the human knee joint. The control unit can accurately distinguish the user's intention according to the user's attitude information, use different control strategies in different terrains, control the motor to generate accurate desired force, and help the knee joint to stretch and flex. We conducted a preliminary experiment of 6 volunteers, and in a controlled experiment, the assist effect of exoskeletons was assessed using the angle of the lower limb joint when walking and the muscle fatigue of the main muscle responsible for knee extension and flexion. The experimental results show that the exoskeleton worn on it walks at different speeds at different slopes does not affect the angle of the lower limb joints, and the muscle fatigue of the main muscles required for the movement of the human knee joint is reduced to varying degrees.