A Novel High-Torque Bioinspired Knee Exoskeleton Based on the Gear Structure

This paper proposes a novel bioinspired knee joint structure characterized by high torque efficiency. After analyzing the experiment data of the knee joint, we found that there was the linear relationship between the angular variations induced by relative rolling and sliding in femur and tibia. Based on the conclusion, a compound motion of planetary gear mechanism and three-stage gear transmission mechanism is designed to simulate the motion characteristics of the knee joint in the sagittal plane. The high efficiency of the gears and the reduction ratio of approximately 6.8 allow this structure to be applied in scenarios requiring high torque when driven directly by a motor. Subsequently, the joint simulation between the human knee joint and the exoskeleton is constructed and executed using Simulink in MATLAB. Results indicate that during the flexion-extension process of the knee joint, the maximum displacement between the exoskeleton shank strap and the human body is 5mm, and the angular deviation is floating from -3 degree to +3 degree. Hence, the structure can follow the movement of knee and enhance wearable comfort of patients.