Line-of-Sight Guidance for Path Following of Marine Vehicles

This paper presents an overview of the Line-of-Sight (LOS) guidance law, which is a widely used method for generating heading reference trajectories, for path-following applications of marine vehicles. Due to the fact that these reference trajectories depend also on the form of the path, five path evaluation criteria are discussed. The guidance problem is presented in a constructive manner. First, two 2-D cases are studied, therefore it is assumed that the horizontal-plane motion and the vertical-plane motion are decoupled. The next step is to consider a 3-D pathfollowing scenario for a 5-DOF underwater vehicle where the motions are coupled. The interconnection between the LOS guidance and the heading/pitch controller is explained and a brief overview of depth control methods is given. Moreover, a short review of integral LOS methods in order to compensate for unknown external disturbances is presented and it is shown how course control can circumvent this problem.