Abstract
In the study of walking systems, it is very important to find some indexes for analyzing walking and deciding its control strategy, because the degree of freedom of a walking system is very high. In regard to biped locomotion systems, the angular momentum of the whole system can be considered as a good index, since it is a stable quantity, as seen from ‘the law of the conservation of angular momentum.’
Good indexes for quadruped locomotion systems have not been proposed yet. The body speed is an index of quadruped system. However, the body speed is not so good index for representing the state of the whole system since it is changed easily by the sway motion of swing legs, etc. In this paper, the authors defined a stable quantity which is not affected by the sway motion of swing legs or the movement of knee joints of supporting legs. We named this quantity ‘Quasi-Angular-Momentum’. The quasi-angular-momentum is varied only by the gravity effect and input torque at the hip joints of the supporting legs. So, this quantity can represent the state of the quadruped system as a whole. By using the quasi-angular-momentum, two kinds of dynamic walking are analyzed. One is a walking which utilizes the gravity effect skillfully and the other is a walking in which the body speed is kept constant.
