Ocean Currents Compensation-Based IAILOS-ROESOs Guidance and Adaptive Sliding Mode Path Following Control for Unmanned Surface Vehicles

This article studies the problem of path following for unmanned surface vehicles (USVs) with ocean currents and input saturation and proposes an ocean currents compensation-based improved adaptive integral line-of-sight with reduced-order expanded state observers (IAILOS-ROESOs) guidance and adaptive integral sliding mode control (AISMC) compound guidance-control method. In the guidance module, an IAILOS-ROESOs guidance law is presented to estimate ocean currents of varying strengths, compensating for the effects of ocean currents at the kinematics level. Then, the AISMC law with the RBF neural network and parameter update law are introduced to approximate the lumped disturbances and estimate their bounds of the estimation error in the control module. Meanwhile, integrating nonlinear differential estimators and improved auxiliary dynamic systems with a smoothly switching function, achieves the differential signal filtering and input saturation, and the hyperbolic tangent saturation function with adjustable parameters is further used to improve the robustness of the system. Theoretical analysis indicates that all errors converge to zero. Finally, the effectiveness of the control strategy is verified through comparative simulations.