Mobile Manipulation Using a Snake Robot in a Helical Gait

Snake robots have shown limited ability to perform manipulation tasks in comparison to their locomotion capabilities. In this article, we propose a mobile manipulation approach that increases the manipulation ability of snake robots by using their full-body motion. We consider a snake robot that moves along the outer surface of a pipe using the helical rolling gait. To perform a manipulation task, we extend the front links of the robot to form a manipulator-part, where the remaining links form a helical base that wraps around the pipe. In the proposed approach, the motion of the manipulator-part is combined with a rolling motion performed by the base-part. This results in enhanced rotational ability of the end-effector, without the need to install an additional rotary motor. The stability of the robot structure is also improved via the resulting tightening force between the helical base-part and the pipe. The kinematics of the proposed robot arrangement is represented considering a dynamically changing contact point between the links of the helical base and the pipe. To realize the proposed method, we introduce a two-level controller that enables the manipulator-part and the helical base to work simultaneously during manipulation. The experimental results showed the validity of the proposed method to track various trajectories and carry out manipulation tasks using a typical snake robot without extra actuators.