On three-dimensional model of biped walking robot

Passive dynamic walking refers to a class of bipedal machines that are able to walk down a gentle slope with no external control or energy input. The two-dimensional passive dynamic model has been shown to been inherently stable, and the three-dimensional model introduce another problematic degree of freedom: roll. In this paper we introduce some 3D biped walking models. In these 3D models, we find that passive walking cycles exist, but the roll motion is unstable, resembling that of an inverted pendulum. At last we introduce some control laws for stabilizing this motion.