Autonomous Navigation Method for Ships in Tidal River Sections Under Special Rule Constraints

To address the issue of autonomous ship navigation under the constraints of special navigation rules in tidal river sections, a case study is conducted using the Nantong section waters, focusing on situation awareness, rule integration, and maneuvering decisions. Based on environmental characteristics and decision-making requirements, an innovative digital traffic environment model for tidal river sections is developed by incorporating channel factors and tidal conditions into the traditional digital traffic environment model. Driven by real data, this model is transformed into an information database recognizable by decision-making programs. The system reads the database to perceive the real-time status and development trends of environmental elements near the own ship, providing input for critical processes such as decision-making and control. The"Inland Waterway Collision Avoidance Rules" and good seamanship requirements are quantitatively analyzed. By integrating the channel direction and angle-on-the-bow comparison in tidal river sections, an improved model for identifying encounter situations based on angle-on-the-bow comparison is developed. An innovative model for identifying encounter situations and collision avoidance responsibilities in tidal river sections is established, clarifying the responsibilities and timing of actions during flood and non-flood tides, and converting these into computable constraint equations. Under the constraints of environment, collision avoidance responsibilities, and maneuverability, a novel autonomous navigation method is proposed to adaptively account for tidal influences and derive collision avoidance solutions. Two sets of simulation experiments and a comparative experiment are conducted in a real-data-driven general aviation environment. The simulation results demonstrate that, under different tidal conditions, the proposed method can accurately identify encounter situations, determine collision avoidance responsibilities, and calculate and execute course and speed change plans to avoid all targets. In the comparative experiment, under the inland wide waterway navigation decision-making method, the own ship alters course 5° to starboard at t = 1 s to avoid the target ship, resulting in incorrect collision avoidance responsibility judgment, with action timing and magnitude not complying with special rules and good seamanship requirements. In contrast, the proposed method, which accounts for tidal conditions and the own ship's navigation state, alters course 15° to starboard at t = 201 s, ensuring safe passage in compliance with requirements.