A control-oriented model of underwater snake robots exposed to currents

This paper presents a control-oriented model of a neutrally buoyant underwater snake robot that is exposed to a constant irrotational current. The robot is assumed to move in a horizontal, fully submerged plane with a sinusoidal gait pattern and limited link angles. The intention behind the proposed model is to describe the qualitative behaviour of the robot by a simplified kinematic approach, thus neglecting some of the non-linear effects that do not significantly contribute to the overall behaviour. This results in a model with significantly less complex dynamic equations than existing models, which makes the new model well-fitted for control design and analysis. An existing, more complex model and a class of sinusoidal gait patterns are analysed, leading to several properties that serve as a basis for the simplified model. Some of the revealed properties are also valid for ground robots. Simulations that qualitatively validate the theoretical results are presented.