Integral LOS guidance for horizontal path following of underactuated autonomous underwater vehicles in the presence of vertical ocean currents

A control strategy allowing underactuated underwater vehicles to perform horizontal path following tasks in the presence of vertical irrotational ocean currents is developed. It is based on a modified three-dimensional Line-of-Sight (LOS) guidance law with integral action and three adaptive feedback controllers. The traditional LOS guidance technique is often used in the marine field for path following purposes. It is however highly susceptible to environmental disturbances such as unknown currents. The integral effect is hence successfully introduced to counteract the current and the chosen integration law is defined to reduce the risk of wind-up effects. Furthermore, a simple translation of the equations of motion is used to simplify the underactuated design problem. The closed loop stability is addressed and path following of horizontal straight-line paths is proved. Finally, simulation results are presented.