Development and Evaluation of Biomimetic Assist Suits *

In sagittal plane, movements of knee joints are relative motions between femur and tibia, which is a combination of sliding and rolling motion. The motion causes misalignment between the biological axis and the mechanical axis of the orthosis. We developed the semi-active knee joint (SKJ) with an adjustable reaction force mechanism, which can adjust the force applied depending on the flexion angle. The SKJ uses femur and tibia gears to mimic the motion of the knee joint. However, the existing SKJ comprises two linear motion springs arranged in series, making the mechanism larger in the vertical direction. To solve this problem, this paper reports the design and development of the SKJ type-P, achieving a reduced size and improved operability. We also report the development of a biomimetic assist suit (BAS) combined with knee and ankle aids, and the experiments performed to verify its effectiveness. The gait results obtained from the experiment did not confirm a significant decrease in muscle activity when wearing the BAS, except in a few cases. The reasons for this are that the assistive torque of SKJ is insufficient when the knee flexion angle is at its maximum during walking. On the other hand, attaching the BAS did not cause any increase in burden, which indicates the success of the proposed lightweight design.