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

The realization of human-like dynamic motions by bipedal robots is still a challenge. One reason for this is that joints of bipedal robots are actuated with low backdrivability. In this paper, to improve backdrivability of the joints in a bipedal robot, a new mechanism of knee joint with continuously variable reduction ratio adaptive to load is proposed and a control method is also proposed according to the characteristic of the mechanism. A prototype of the bipedal robot using the designed knee joint with continuously variable reduction ratio adaptive to load has been developed. The effectiveness of the mechanism is shown by experimental results using the prototype.