Development of leg mechanism using a knee joint with variable reduction ratio adaptive to load

The realization of natural, fast and versatile motions for bipedal robots is still a challenge. As one approach to enhance the performance of bipedal robots, actuation with high backdrivability, high power-to-weight ratio as well as high torque is required. In this paper, a new mechanism of knee joint with variable reduction ratio adaptive to load is proposed to improve the capability of actuation while in light structure. The design method including simulation for the mechanism is described. A prototype of the leg robot has been developed and the basic feasibility of the mechanism is shown by experimental results.