A ZMP analysis of the passive walking machines

Stability is one of the most difficult problems in biped locomotion. Especially, in passive biped machines where there is no actuator in the system, the stability is satisfied only for some specific gaits in narrow boundaries. In this paper we analyze and give some preliminaly results of relation between passive walking dynamics and the zero moment point (ZMP). We consider the ZMP as an important factor for the motion analysis. First, we formulate the dynamic equations based upon the motion of ZMP. Then we discuss the control method for biped robots utilizing the passive dynamics.