Abstract
Snake robots have the potential of contributing vastly in areas such as rescue missions, fire-fighting and maintenance where it may either be too narrow or too dangerous for personnel to operate. This thesis reports novel results within modelling and control of snake robots as steps toward developing snake robots capable of such operations. A survey of the various mathematical models and motion patterns for snake robots found in the published literature is presented. Both purely kinematic models and models including dynamics are investigated. More- over, different approaches to both biologically inspired locomotion and artificially generated motion patterns for snake robots are discussed. Snakes utilize irregularities in the terrain, such as rocks and vegetation, for faster and more efficient locomotion. This motivates the development of snake robots that actively use the terrain for locomotion, i.e. obstacle aided locomotion. In order to accurately model and understand this phenomenon, this thesis presents a novel non-smooth (hybrid) mathematical model for 2D snake robots, which allows the snake robot to push against external obstacles apart from a at ground. Subsequently, the 2D model is extended to a non-smooth 3D model. The 2D model offers an efficient platform for testing and development of planar snake robot motion patterns with obstacles, while the 3D model can be used to develop motion patterns where it is necessary to lift parts of the snake robot during locomotion. The framework of non-smooth dynamics and convex analysis is employed to be able to systematically and accurately incorporate both unilateral contact forces (from the obstacles and the ground) and spatial friction forces based on Coulomb's law using set-valued force laws. Snake robots can easily be constructed for forward motion on a flat surface by adding passive caster wheels on the underside of the snake robot body. However, the advantage of adding wheels suffers in rougher terrains. Therefore
