Development of bio-inspired knee joint for power assist suit

A lot of the power assist suits using the pneumatic artificial muscles for assisting the extension of the knee have been developed. But in almost all of devices their centers of rotation are fixed. The knee joint of human has a complex movement. Flexion and extension motions of knee joint consist of rolling and sliding. Moreover, there also exist rotations in front plane and horizontal plane. Therefore, we developed a new knee joint mechanism with a bio-inspired joint motion, torque adjustment mechanism, and U-shaped springs. We also evaluated the motion of the knee mechanism and the effect of the U-shaped springs. The combination of the sliding mechanism and wire-pulley mechanism fitted the subject´s flexion-extension motions. The U-shaped spring worked to reduce unexpected stress with misalignment.