A study of the leg-swing motion of passive walking

In our earlier work, we showed that high stability of passive walking can be achieved by the global stabilization principle of fixed point. The principle has been established, providing that the state just after heel-strike exists at the next step. However, this condition may not always hold. The passive walker with knees can execute the leg-swing motion with no control, only by gravity effect. Unfortunately, while the walker takes a step forward, the swing leg may strike its toe on the slope at unsuitable point. Therefore, understanding of the mechanism of leg-swing motion is very important for assuring the next step. In this paper, we focus on the leg-swing motion of passive walking, and demonstrate the mechanism of the flexion and extension of knee joint of swing leg.