Integral Line-of-Sight for path following of underwater snake robots

This paper considers straight line path following control of underwater snake robots in the presence of constant irrotational currents. An integral line-of-sight (LOS) guidance law is proposed, which is combined with a sinusoidal gait pattern and a directional controller that steers the robot towards and along the desired path. Integral action is introduced in the guidance law to compensate for the ocean current effect. The stability of the proposed control scheme in the presence of ocean currents is investigated. In particular, using Poincar\'{e} map analysis, we prove that the state variables of an underwater snake robot trace out an exponentially stable periodic orbit when the integral LOS path following controller is applied. Simulation results are presented to illustrate the performance of the proposed path following controller for both lateral undulation and eel-like motion.