Gait emergence by discrete leg motion period control using contact signals and CPGs

Abstract

Most living organisms need locomotion to achieve a series of goals, such as eating, escaping, and breeding. In short, locomotion refers to the periodic activities of various parts of the body and their coordination mechanisms, such as walking, jumping, etc. Each locomotion is characterized by the animal’s body and its surroundings. The common of almost all locomotion is motion of the body center such as the trunk. Therefore, we believe that the periodic movement of the central part of the body is important for achieving movement. In this study, we focused on walking with limbs. We believe that the trunk movement using limbs is a combination of periodic movements of each limb. A central pattern generator (CPG) is used for generating periodic motion. We make robot generate gait to show that walk is the motion of a center part of a body. We propose a discrete control method of leg periodic motion using a ground signal to generate gait. In the periodic adjustment of the proposed method, the leg’s motion period is changed according to the CPG phase when the grounding state of the leg is switched. We use a modular legged robot to verify the proposed control method. We did experiments and simulations using a real robot and a physics engine. It is confirmed that although the initial stage of each leg movement is random, specific gait will be generated over time. Some gaits are gaits that are shown by animals, such as Tripod and Direct Wave.