# Large-Area Coverage Path Planning Method Based on Vehicle-UAV Collaboration
## 4 Simulation and Discussion  
The proposed large-area coverage path planning method based on vehicle-UAV collaboration proposed in this work has been implemented in MATLAB language, and all the results are rendered via the MATLAB plot function tool (2024a). In the simulation experiment, the proposed vehicle-UAV collaboration method was verified in two test cases. The two test cases were used for algorithm evaluation and validation in small- and large-area scenarios, respectively. The two polygons consist of a number of vertices generated within two square areas and are simulated in the virtual 2D map. The side lengths of the two squares are 3000 m and 6000 m, respectively. The flight speed of the UAV was set to 3.5 m/s. The coverage width of the UAV path was set to 20 m, the safe endurance time of the UAV under heavy load is assumed to be 2000 s, and the maximum number of UAV flights for the coverage task in a sub-area is set to four. Thus, the single flight distance of the UAV is 7000 m, and the appropriate area for coverage in a sub-area is about 32,000 m\({}^{2}\). The polygon contour is loaded into the proposed vehicle-UAV collaboration method, and the outputs consist of UAV paths and vehicle paths, and all the data related to this simulation experiment are illustrated in Figure 9a,c. The area enclosed by the outermost contour is the workspace of the CCP problem. From the simulation results, it can be seen that the polygon is reasonably divided into multiple sub-areas, ensuring that these sub-areas have an approximately equal area, and providing the vertices within sub-areas the benefit of the shortest distance to the supply point. The supply points in the coverage polygon are rendered with green circles. In each sub-area, the contour is filled with multiple, equally spaced zigzag path lines; each zigzag line indicates a single flight of the UAV and is rendered with a color. The blue dot, the orange dot and the black dot indicate the starting point, the ending point and the switching point, respectively. These colored zigzag path lines have equal lengths, ensuring that the UAV can complete the coverage task in the current sub-area with fewer supplies. The bold red lines in the figure denote the simulated traversal path of the vehicle, providing an efficient way to traverse the supply points of all sub-areas. From the simulation experiments, it can be concluded that the effectiveness and feasibility of the proposed large-area coverage path planning method based on vehicle-UAV collaboration can be verified. In order to demonstrate the coverage efficiency advantage of the proposed vehicle-UAV collaboration method, two comparative experiments were conducted. The classic zigzag path filling algorithm, based entirely on the UAV, was implemented using MATLAB language and directly applied on the same polygons. For the fairness of the experiments, the gravity position was also selected as the supply point of the entire polygon. Based on the preset supply point and the single flight distance of the UAV, the coverage paths were generated, as shown in Figure 9b and 9d, respectively. From the figure, it can be seen that the generated coverage paths of the UAV contain a large number of switching points, which is caused by the UAV constraint of short endurance under heavy loads. The flight segments connecting these switching points and the supply points are the main factors affecting UAV coverage efficiency over large areas. The results of the total coverage path lengths in the two comparative experiments are summarized in Table 1. Through comparative analysis of the statistical results, in the coverage problem of the small area test case, the classic zigzag coverage path based on UAV only has a total length of 224,943 m, while the proposed method generates a total coverage path length of 202,626 m, which consists of a UAV flight path length of 198,603 m and a vehicle travel path length of 4023 m, and achieves a 9.92% path saving advantage.