Cascaded Extended State Observers-Based Fixed-Time Line-of-Sight Path Following Control for Unmanned Surface Vessels With Disturbances and Saturation

This article solves the path following problem of unmanned surface vessels, where model uncertainties, external environmental disturbances, and input saturation are considered. Specifically, the fixed-time line of sight (FXTLOS) based on fixed-time theory is used to design a guidance subsystem where the convergence time is independent of multiple initial states. Given the unavailability of velocity information, novel cascaded extended state observers have been proposed to estimate velocities and unknown disturbances to provide feedback to the controller for better performance, where only position and heading information is required. Furthermore, fast finite-time sliding mode control is used to solve the motion control problem for the USV, where a suitable auxiliary system is designed to deal with the adverse effects of input saturation and to ensure the stability of the system. The stability of the whole system is demonstrated, and the stability of the kinematic and dynamic cascade system is analyzed. Finally, a large number of comparative simulation cases are given to demonstrate the effectiveness and superior performance of the proposed scheme.