大地线航法在智能船舶上的应用

Application of geodesic sailing on intelligent ship

沿最短路径航行是建立高效和清洁航运的手段之一。大地线(又称测地线)是空间曲面上两点之间的最短路径。由于在地球椭圆体上采用大地线航法计算复杂、且航向不定,加之与恒向线相比,平均航程仅缩短了5%,导致大地线航法几乎无法应用于传统航海实践中。利用智能船舶的计算、数据获取、航向控制等能力,能最大限度地利用大地线航法路径最短这个优点。本文首先采用了一种快速且高精度的大地线正反解算法,其计算时间为微秒级;其次,利用智能船舶当前实时位置动态及终点计算所需大地线航向,并将新航向指令发送给自动舵。最后,提出不同策略下的航向变更限制机制(ACRM),避免频繁转向以降低自动舵的工作负荷。仿真结果表明,ACRM有助于在最短航程与最少转向次数之间取得平衡。

Sailing along the shortest path can help build an efficient and clean shipping. Geodesic is the shortest path between two points on the surface of space. Due to geodesic’s complicated calculation, varying course, and only shorten 5% voyage by average compared with rhumb line, the geodesic sailing(GS) is almost impossible in traditional nautical practice.The intelligent ship can maximize the advantage of the shortest geodetic path by using its calculation, data acquisition, course control, etc, In this paper, a fast and high-precision algorithm is presented to solve GS(direct/inverse) problems firstly. Then,apply the GS to the unmanned ship by calculating the course dynamically based on the current position and destination, and the new order is issued to the autopilot. Finally, alter course restriction mechanism(ACRM) with different strategies are proposed to reduce the autopilot’s work load by avoiding frequent course alternation. The simulation results show that ACRM can help to obtain a balance between the shortest path and the minimum number of alter course.