Passive joint control of a snake robot by rolling motion

Snake robots are capable of adapting to difficult situations, such as cluttered environments, using its many degrees of freedom. However, if one of the joints gets passive, it is generally very difficult to achieve ordinary performance. In this paper, control of a passive joint using rolling motion is considered, with the use of crawler gait in mind. Crawler gait is a state-of-the-art motion pattern for snake robots that is capable of moving on uneven terrain, but if there is a passive joint, the motion can be interrupted by freely moving part of the robot itself. As a key to solving this difficulty, this paper proposes to use the rolling motion, which has not been used in controlling a passive joint. A simplified model is proposed to consider the control, and based on this, one simple controller is adopted. The validity of the idea of using rolling motion is tested by numerical simulations.