A necessary condition for passive dynamic walking

摘要

Passive dynamic walking is a form of locomotion generated by a dynamical interaction between environments and passive legged robots. Its dynamics at foot strike are governed by impact forces. The impulsive dynamics have been modeled in several approaches, where all the approaches assume that the stance leg instantaneously loses contact with the ground at foot strike; however, it is unclear when the assumption is satisfied. This paper derives a loss-of-contact condition in closed-form as follows. A compass-like biped robot is considered in this paper. Its impulsive dynamics at foot strike are modeled by using a modeling framework for multibody dynamics with impact. Examining the validity of foot velocities and impact forces in the impulsive model provides a necessary and sufficient condition for the impulsive model to be valid in closed-form. The condition includes a loss-of-contact condition. The derived condition is also a necessary condition for smooth passive dynamic walking.