Design and Optimization of Singledegreeoffreedom Six bar Mechanisms for Knee Joint of Lower Extremity Exoskeleton Robot * The irregular contact surface between the femur and the tibia of the human body produces Jshaped instantaneous centers of rotation (ICR) of the knee joint. Therefore, two single degreeoffreedom (SDOF) sixbar mechanisms, which are composed of a trajectory fitting fourbar mechanism and a transmission fourbar mechanism, are used to fit the centers of the human knee joint and increase the loadbearing performance. Firstly, the displacements of ICR of the human knee joint are measured and calculated for the sake of the dimensional synthesis of the trajectory fitting fourbar mechanism. Then, two structural layouts of transmission fourbar mechanism are designed according to different selection of the driving rod in the trajectory fitting fourbar mechanism, and both the transmission fourbar mechanisms are optimized. The results show that after the two step optimization, the SDOF sixbar mechanism with the crank as the driving rod in the trajectory fitting fourbar mechanism has a better performance in smoothing the knee joint torque curve and superior transmission efficiency.

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.