Non-smooth 3D Modeling of a Snake Robot with External Obstacles

In this paper we extend a non-smooth 3D mathematical model of a snake robot to also include external obstacles to enable obstacle aided locomotion. The model is based on the framework of non-smooth dynamics and convex analysis. This framework enables us to systematically and easily incorporate unilateral contact forces (from the obstacles and the ground) and isotropic friction forces based on Coulomb´s law. The obstacles are shaped as vertical cylinders and we describe the contact between a link of the snake robot and an obstacle with a single, moving contact point. Hence, the effect of the link touching the obstacle is accurately described. Simulation results for a 11 link snake robot moving by the serpentine motion pattern ´lateral undulation´ while pushing against obstacles are given.