Mechanical design of robot lower body based on four-bar linkage structure for energy efficient bipedal walking

Since the Fukushima nuclear plant disaster in Japan 2011, a lot of robot has been developed on behalf of human in the disaster. But they are not capable of coping with the disaster yet. The main reasons are the lack of bipedal walking technology on uneven terrain and short operating time due to low energy efficiency during walking. In the case of the existing bipedal walking robot which is driven by actuators in each joint, energy efficiency is poor because moment of inertia and mass are high due to heavy actuators located far from the rotational axis. To solve this problem, this paper suggests the six degree-of-freedom robot leg using the four-bar linkage mechanism with high rigidity. The actuator of the knee joint and ankle joint are positioned on the hip to reduce the leg mass and moment of inertia. Our aim is bipedal walking robot lower body design to increase the energy efficiency and walk on highspeed. To do so, we designed the robot lower body that has optimal dimension to endure external forces with minimum mass. And we simulated the result of each joint trajectory, torque and energy efficiency based on the designed model to generate a walking pattern. We will produce the actual robot lower body in detail based on the derived data, and compare to the existing robots' performance.