An Experimental Study for Leg-Exchange Phenomenon of Passive Walking

A passive walker can walk down shallow slope in a natural gait and can exhibit a stable limit cycle. In our earlier work, we have demonstrated the physical structure which forms the fixed point and the mechanism of its stability. A collision phenomenon is essential to the leg-exchange which is one of the important factors determined the fixed point. In general, the collision is undesirable because it causes troubles of precision sensors and instruments. In many studies, the leg-exchange is modeled by some assumptions and the validity of that is not sufficiently evaluated. In this study, the general model is qualitatively and quantitatively evaluated by the experiments. By observing actual collision phenomenon through the high-speed camera, we realized that the legs are not instantaneously exchanged and the loss of angular momentum is caused by the impact force during the collision. Based on this fact, the accurate modified leg-exchange model is proposed.