On Rock-and-Roll Effect of Quadruped Locomotion: From Mechanical and Control-Theoretical Viewpoints

Abstract

In this paper, we discuss body-induced motion of quadraped walking, in the presence of rolling contact between its feet and the ground. This paper is based on the authors’ previous study, where we had shown that active “rocking” of the torso from the left to the right (in the lateral plane) would induce alternative swing of the legs (in the sagittal plane), which result in autonomous forward walking. Now in this paper, we focus on the influence of the rolling contact of the feet and the ground; we point out that the forwading displacement is the sum of “walking effect” and “rolling effect”, and the rolling effect can be observed even when each pair of the fore legs and the hind legs are bound together. Moreover, in order to extract pure rolling motion, we analyze in detail the model of two hemispheres connected via a spine rod, as an extremely reduced model of quadruped locomotion.