# Research on 2D Laser Automatic Navigation Control for Standardized Orchard
## 3 Results and Discussion
### Feature Map and Navigation Parameter Acquisition Accuracy Test  
In order to test the reliability of the system, this paper build a simulation experimental environment in the experimental field of the Northwest A & F University (108\({}^{\circ}\)4'30\" E, 34\({}^{\circ}\)17'28\" N). And three experiments had been carried out successively which involved navigation path fitting, parameter acquisition accuracy test, vehicle trajectory tracking test. The simulated orchards were arranged in two rows with a spacing of 2.5 m and a row spacing of 4 m, and PVC plastic pipes with a length of 1.2 m were selected to simulate the trunk. The layout of the simulated test scene was similar to the real orchard environment in terms of soil environment, trunk characteristics and trunk arrangement. As shown in Figure 16a, the absolute coordinate system \(XOY\) was established with the tree \(P\) as a reference, 2 m to the left and 2.5 m to the rear as the origin \(O\). In Figure 16b, the circumference of the simulated fruit tree trunk was measured with a tape measure at the same height as the 2D laser, and the diameter of the tree was obtained to be 0.04 m. The test platform was the hardware system described in Section 2.1. We placed the test platform statically to capture 2D laser point data at the center of the simulated orchard environment. We placed tree branches as noise disturbance in the driving area of the test platform. The method of fruit tree position information determination in Section 2.2 was used to process the laser point cloud data. According to the actual simulated environmental parameters, take the left and right three fruit trees as the target, set the distance threshold \(\rho_{max}=10\) m, \(x_{max}=2.5\) m, the number of adjacent points \(k=5\). The laser point cloud figure after distance threshold processing  
Figure 15: Simulation results test charts. (**a**) Straight path-tracking simulation results. (**b**) Curved path-tracking simulation results. (**c**) Linear path-tracking simulation error graph. (**d**) Curved path-tracking simulation error graph. was shown in Figure 17a; the laser point cloud figure after filter processing was shown in Figure 17b. As shown in Figure 17c, the red points were actual points of trunk, the black points were prediction points of trunk. The method of Section 2.3 was used to fit navigation path and obtain navigation control parameter, as show in Figure 17d. It can be seen from Figure 17b that the number of laser points on the same fruit tree after European clustering was five or six points. The density of laser points was related to the distance from the trunk to the laser and the diameter of it. In this study, laser data processing was carried out with three singles as one cycle. The distance of the furthest trunk was 7.5 m. It was within the range of laser measurement. Since the laser angle resolution was 0.25\({}^{\circ}\), the problem of missing laser data points was  
Figure 16: Actual test simulation site. (**a**) position measurement. (**b**) diameter measurement. Figure 17: Navigation path acquisition process. (**a**) laser point cloud image after distance threshold processing. (**b**) laser point cloud image after statistical filtering. (**c**) feature map of center point of fruit tree trunk. (**d**) navigation path fit results. small when locating a simulated trunk with a maximum distance of 7.5 m and a diameter of 4 cm. Therefore, it can provide enough laser points support for the extraction of trunk center feature point. In Figure 17c, the obtained center point feature map of the trunk has no interference points; the error from the actual position of trunk were 6.79 cm, 2.86 cm, 2.67 cm, 2.33 cm, 2.29 cm and 3.01 cm, from left to right and bottom to top, the average error was 3.325 cm. The results show that the method of obtaining the center point feature map of trunk meets the requirements of positioning accuracy. The linear regression fitting \(R^{2}\) of the navigation path was 0.988, which is close to 1.