Approach Angle Constrained Guidance Strategy of Autonomous Surface Vessel

Uncrewed Surface Vessels (USVs) are increasingly employed in critical marine operations, such as offshore monitoring and cargo transport, where autonomous docking is essential for mission success. In this paper, we introduce a novel approach to autonomous docking wherein the motion control algorithm guides the USV to the docking station while maintaining the orientation required to dock and reducing vehicle speed for safe docking. Control inputs for the vehicle are derived using sliding mode control within a nonlinear framework that guarantees the validity of the proposed controller even in scenarios with significant deviations. Owing to the inherent robustness of sliding mode control techniques, the proposed controller is robust against matched uncertainties. The proposed algorithm's effectiveness is validated through numerical simulations, demonstrating satisfactory performance in achieving precise docking of USV from various initial and final geometries.