Line-of-sight-based global finite-time stable path following control of unmanned surface vehicles with actuator saturation

This paper focuses on the path following problem of unmanned surface vehicles (USVs) with unknown velocities, model uncertainties, and actuator saturation. To steer a USV rapidly and accurately follow the desired parameterized path, a line-of-sight (LOS)-based finite-time path following scheme is constructed in which the finite-time technique can ensure the fast error convergence, such that some intelligent operations, including patrolling, fuel supplying, and formation control, can be promptly performed. First, USV kinematic and kinetic models are established, and finite-time observers are subsequently employed to identify the unmeasured USV velocities and model uncertainties. Then, an LOS guidance law is designed to achieve the finite-time convergence of the position errors. In addition, an optimized look-ahead distance is developed using a fuzzy algorithm. Meanwhile, the control subsystem is designed at the kinetic level by combining the backstepping sliding mode method and a novel auxiliary dynamic system, where the auxiliary system is applied to address actuator saturation. Subsequently, theoretical analysis is conducted to verify that the entire system is uniformly global finite-time stable (UGFTS). Finally, the simulation studies confirms the availability of the developed method.