Helical wave propagation motion for a snake robot on a vertical pipe containing a branch

Snake robots could be utilized in many fields because of their hyper-redundant properties, although there are still control problems when they are operated in complex environments. For example, a helical rolling motion has been used to climb a pipe. By using this kind of motion, a snake robot can move along the inside or outside of a pipe. However, this motion has limitations when the robot moves along a pipe containing a high gap or a branch point. In this study, we propose a type of motion for snake robots that involves wrapping around the outside of a pipe to overcome a branch point on it. This new motion uses a hyperbolic function to make a helical wave curve, which is then propagated by shifting the shape of the hyperbolic function along the body of the snake robot. The joint angles of the snake robot are derived by calculating the curvature and torsion of the curve on the basis of the formula of the continuous curve model. Finally, the results of simulations performed using the Robot Operating System and Gazebo programs are shown to validate the effectiveness of the new motion.