The objective of this study is to develop a method of designing dynamic gainsof biped and quadruped walking robot. The current trend of the gait of a walking robot is dynamic one for fast walking speed. However, any systematic procedure of designing a dynamic gait is not developed yet.
The main problem in designing a dynamic gait is the stability of the gait. A dynamic gait must be designed not to turn over during walking. So, it is very important to design a robust gait with respect to external disturbance. In this study, the design method of a robust dynamic gait of a biped robot and a quadruped walking robot is developed. A computational technique for designing a physically realizable robust gait for a planar biped robot is developed. Firstly, conditions for the continuous walking is derived. Secondly, a feasible set of gaits were constructed to satisfy the conditions by using an optimization technique. Then the concept of dynamic stability margin is introduced based on the robustness of a gait with respect to the external disturbances. Using that margin, we can assess the robustness of each dynamic gait in the feasible set. It is found that the parameter, called foot strike time margine, representing the readiness of the foot strike on the ground has a close positive correlation with the dynamic stability margin. We obtain a robust gait with respect to the external disturbance by maximizing the foot strike time margin. The robustness of the optimal gait is confirmed by the behavior of the gait after application of linear impulse as well as by the examination of the largest eigenvalue at the perturbed state.
Similarly, the conditions for a continuous dynamic gait of a quadruped walking robot is proposed and a feasible set of dynamic gaits is designed using optimization technique. Simulation algorithm for the three dimensional four legged dynamic gait is derived considering impact, slip and stiction between foot and ground. The contact between foot and ground is modeled by uni-lateral spherical joint. It is found that the design of a dynamic gait by the optimization technique is systematic and efficient. The effects of some design factors to the robustness of the four legged dynamic gait is studied by the parametric study using Taguchi's orthogonal array and ANOVA (analysis of variance) method. It is found that the height of mass center of body and the width between right leg and left leg has a great influence on the robustness of the gait.
