Crawling and foot trajectory modification control for legged robot on uneven terrain

In this paper, we propose a crawling motion that a legged robot makes its feet and torso contact with the ground alternately. The crawling motion aims to reduce the risk of malfunction due to the impact forces caused by falling down for travelling across uneven terrain. In addition, we propose the foot trajectory modification method based on information obtained from force sensors and an attitude sensor. The control method contributes to avoiding a collision between its feet and the surface of uneven terrain. To verify the effectiveness of the proposed method, we suggested a model of uneven terrain using a dynamics simulator and conducted an experiment that a four-limbed robot gets over the modelled terrain. From the experimental results, it is confirmed that the robot can traverse uneven terrain by using the crawling motion and that the foot trajectory modification control method can improve the locomotion capability of the robot.