Novel Motorfree Passive Walkassisting Knee Exoskeleton In this paper, we present the design of a novel quasipassive motorfree orthosis that realizing the compensation of knee joint supporting force during the weight acceptance phase and almost free motion during the swing phase. We explain that the normal knee landing motion is approximately a linear spring through the motion curve, so a suitable linear spring for the knee joint in parallel can achieve an approximate natural response. We show a compound mechanism based on ratchet and cam, which makes springs with different stiffness parallel in support and swing phases, and explain how to design mechanism parameters in switching process. This mechanism is a passive motorfree exoskeleton with automatic switching spring stiffness. It is lightweight and has no energy consumption.

Development of Adjustable Knee Assist Device for Wearable Robot based on Linkage and Rolling Joint This paper presents an adjustable knee joint for a wearable robot for the elderly, to provide physical gait assistance. In order to compensate for the translational and rotational movements of the knee in the sagittal plane as well as aligning the frontal plane, the proposed knee joint is implemented with a rolling joint, two aligning passive joints, fourbar linkage, and a sliding mechanism. Because the sliding mechanism, fourbar linkage, and rolling joint exist between the actuator and the joint mechanism, the rotation angle of the actuator and the flexion angle of the rolling joint do not change equally due to the kinematic characteristics. In order to define the flexion angle change of the rolling joint with respect to the change to the actuator angle in the flexionextension motion of knee, the design parameters and flexion model are proposed in this paper. The proposed artificial knee joint effectively delivers the torque required for assistance while adapting to the joint motion of the wearer. This paper describes the mechanical design of this knee mechanism and its implementation on a wearable robot and in preliminary experiments. The performance of the proposed mechanism was verified by simulations and experiments. Finally, preliminary experiments were performed to demonstrate the possibility of reducing the metabolic cost of using a knee assist.