Shortest-time path planning method for autonomous sailboats considering wind-current coupling effects

Objectives To address the path planning problem for autonomous sailboats in environments characterized by coupled wind and current, a shortest-time path planning method that integrates calculations from a velocity prediction program (VPP) with an improved Theta* algorithm was proposed. Methods A sailing speed interpolation model was established using VPP calculations, enabling rapid retrieval of the maximum steady sailing speed under arbitrary wind, current, and heading conditions. The edge cost function in the Theta* algorithm was modified from geometric distance to a time-varying sailing time cost, and an hourly replanning strategy was introduced to handle the time-varying environment. Results Comparative experiments were conducted in both simulated and real-world scenario. In the simulated scenario experiment, the current-aware planning reduced the sailing time by 31.4% under against-current conditions, compared to the approach without current consideration. In experiments simulating time-varying wind and current scenarios in a real marine environment, the proposed method achieved a planning success rate of 87.5% and significantly reduced average sailing time compared to the standard A* and traditional Theta* algorithms. Conclusions The experimental results indicate that the proposed method is capable of effectively improving the long-duration path planning ability of autonomous sailboats in complex coupled wind-current environments.