Proposal of helical wave propagate motion for a snake robot to across a branch on a pipe

Hyper redundant snake robots have a possibility of utilizing in many fields, although there are control complexity problems when it is applied to complicated environment. For example, helical rolling motion have been used to climb a pipe. By using the helical rolling motion, a snake robot can move along the inside or the outside of a pipe. However, this motion has limitation when it moves in a pipe with a high gap or a branch point. In this study, we propose a motion of a snake robot, which wraps around the outside of a pipe, to overcome a branch point on a pipe. The new motion uses a hyperbolic function to make a helical wave curve. The helical wave curve is propagated by changing the parameter of hyperbolic function. Then, the joint angles of a snake robot is derived by calculating curvature and torsion of the curve based on the formula of continuous curve model. Finally, the result of simulational experiment on ROS and Gazebo are shown to validate the effectiveness of the new motion.