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摘要:
针对复杂真实环境下无人机三维路径规划解算速度慢的问题,提出一种基于二维连通图的快速三维路径规划方法。首先解析真实地理环境的地形特征和建筑要素,构建基于数字高程模型(DEM)的多层次等效三维数字地图;在此基础上,经过无人机可行空域到二维连通图的转化、连通图中的路径规划及路径的三维化与优化,快速获得一条可执行的三维路径。针对连通图中的全局路径规划,设计了一种基于步长地图的变步长稀疏A*算法,在保证路径质量的同时有效降低路径搜索的时间;针对连通图中的局部路径规划,提出一种基于障碍预测的随机路标图(PRM)实时路径重规划算法,以满足无人机的实时性避障需求。分别在山地环境和城市环境中进行仿真飞行,结果表明:所提方法能够有效降低三维路径规划的解算难度,在短时间内完成复杂环境下不同尺度和需求的路径规划,全局路径规划算法同比三维A*算法和基于二维连通图的二维A*算法搜索时间分别降低了99%和95%,局部路径重规划算法能够在1 s的单次采样周期内完成路径重规划,实时躲避未知障碍物,保证飞行过程的安全。
Abstract:A fast 3D path planning method based on a 2D connected graph is proposed in order to address the issue of the unmanned aerial vehicle 3D path planning problem's slow problem-solving speed in a complicated real environment. In order to create a multi-level equivalent 3D digital map based on digital elevation model, it is first necessary to analyze the topographic features and architectural components of the actual geographic environment. Based on this analysis, a 2D connected graph is transformed into a 3D connected graph, which is then transformed into and optimized in 3D. For global path planning in a connected graph, a sparse A* search algorithm with changeable steps based on a step size map is designed, which can effectively reduce the path search time while ensuring the quality of path. For local path planning in connected graphs, a real-time path replanning algorithm using probabilistic roadmap method based on obstacle prediction is proposed to meet the real-time obstacle avoidance requirements of UAVs. The simulation flight is carried out in a mountain scene and an urban scene respectively, the results show that the proposed method can effectively reduce the difficulty of solving 3D path planning and complete the path planning of different scales and requirements in a complex environment in a short time; compared with the 3D A* algorithm and the 2D A* algorithm based on 2D connected graph, global path planning algorithm reduces the search time by 99% and 95% respectively, local path replanning algorithm can complete the path replanning in a single sampling period of 1 s, avoid unknown obstacles in real-time and ensure the safety of the flight process.
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表 1 DXF文件中楼房建筑的部分组码
Table 1. Partial grouping codes of “buildings ”layer in DXF files
组码 说明 0 图元类型(网格图元MESH) 8 图层名(buildings) 100 子类标记 92 0级顶点数 10 顶点位置x 20 顶点位置y 30 顶点位置z 表 2 二维路径规划算法对比
Table 2. Comparison of 2D path planning algorithms
规划算法 参数设置 路径长度/pix 规划时间/s A*算法 步长1像素 918.1800 10.9231 Bi-RRT算法 步长20像素 1083.9088 0.0885 VORONOI算法 1122.6981 0.1100 PRM算法 采样点数200 1076.2962 4.3746 GA 种群数200,代数300 1579.1426 71.7549 本文算法 步长1~20像素 950.2214 0.3706 表 3 三维路径规划算法对比
Table 3. Comparison of 3D path planning algorithms
规划算法 修剪 路径长度/像素 规划时间
/s三维A*算法 否 223.443 329.9670 三维A*算法 是 214.4229 330.2463 本文算法 否 295.8179 0.910911 本文算法 是 205.6610 0.988584 表 4 山地场景的全局路径规划
Table 4. Global path planning in mountain scenes
路线编号 终点坐标/像素 路径长度/像素 规划时间
/s1 (630,350,270) 710.9418 1.0469 2 (140,330,300) 464.0216 1.9923 3 (630,70,250) 576.6748 0.8638 表 5 城市场景的全局路径规划
Table 5. Global path planning in urban scenes
路线编号 终点坐标/像素 路径长度/像素 规划时间/s 1 (1200,730,55) 1408.0388 5.2401 2 (530,600,95) 773.1240 1.6845 3 (145,705,160) 694.6993 0.6461 -
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