Abstract
In this paper, we propose a trajectory tracking control law for snake robots on a cylindrical surface, which have passive wheels and active universal joints. It is necessary to avoid the sliding down for the robot to achieve locomotion on a cylindrical surface. Snake robots have two redundancies, one is dynamic redundancy and the other is kinematic redundancy. Dynamic redundancy means that control inputs are not determined uniquely since there are more inputs than the number of controlled variables based on dynamics. Kinematic redundancy is caused by introducing wheelless links and means that all joint velocities of the robot are not determined uniquely in order to achieve the desired velocity of the head of the snake robot. First, to consider the contact force and the frictional force between the robot and the cylindrical surface, we derive the dynamic model of the robot. Next, we indicate the conditions to achieve the avoidance of sliding down, and design the controller to satisfy the conditions by utilizing the redundancies. Simulation results demonstrate the validity of the proposed controller.
