An improved integral light-of-sight guidance law for path following of unmanned surface vehicles

Abstract This paper proposes a path following control system for Unmanned Surface Vehicles (USVs) based on an improved integral Line-Of-Sight (LOS) guidance law. Unlike the conventional LOS guidance law, the look-ahead distance is designed as a function of the USV’s cruising speed and the cross tracking error to adapt to the different cruising speeds of USVs. Meanwhile, a reduced-order state observer is developed for online estimation of the time-varying sideslip angle caused by external disturbances such as wind, wave and current. Then, a heading controller is further designed using the dynamic surface control technique to track the desired heading angle. The guidance system and the reduced-order state observer subsystem are proved to be uniformly asymptotically stable and input-to-state stable respectively. The simulation results show that the path following control system designed in this paper can track the desired curved and straight line paths quickly and smoothly at different cruising speeds.