# Development of a Combined Orchard Harvesting Robot Navigation System
## 3 Results
### Navigation Experiments
For example, the mean value of the deviation decreased from 0.037 m to 0.034 m in the first-row trial and from 0.048 m to 0.045 m in the second-row trial, but the mean value of the deviation in the first-row trial was smaller than the deviation in the second-row trial. The standard deviation of the deviation values decreased from 0.02 m to 0.008 m, indicating a relatively smooth variation of the position deviation. Similar to the position deviation of the transport robot, the position deviation of the picking robot was more pronounced when there were one-sided apple trees in the rows. For example, on the first trial in row 1, the position deviation was 0.032 m for third stops, 0.063 m for fourth stops, and 0.02 m for fifth stops. The same situation occurred  
Figure 16: Experimental scheme for autonomous navigation of the picking and transporting robots. Figure 17: Picking and transporting robots carrying out autonomous navigation trials in an orchard. (**a**) Start turning at the head of the ground; (**b**) picking and transporting robots turn at the same time; (**c**) start of apple tree in-row navigation. successively at the first row and the next row other unilateral stopping points. Unlike the transport robot, which has a low position deviation at both ends of the fruit tree rows, the maximum value of the position deviation of the picking robot was 0.397 m at the first stop in the second row, while the minimum value was 0.011 m at the twelfth stop in the second row. For example, the maximum position deviation at the 20 th stopping point was 0.019 m, while the average deviation was 0.034 m.  
The distance between the center point of the front end of the picking robot and the fruit basket of the transport robot was measured at the stopping point, and then the error of the picking robot following the transport robot in the apple tree rows was calculated according to the safety setting threshold between the robots, where the error was taken as the absolute value of the calculated difference (cite as the following error), as shown in Tables S4 and S5 in the Supplementary Materials. The mean error value fluctuated from 0.01 m to 0.02 m, and the standard deviation of the error varied from 0.007 m to 0.013 m, indicating that the method of maintaining a fixed formation by detecting the position of the fruit basket is effective and that the system operates smoothly when the slave follows the master in the row. Unlike the phenomenon of position deviation variation from the robot, the following error of both robots also appeared to vary significantly in the section with apple trees on both sides. For example, the maximum interval value between robots was 0.007 m at the seventh stop in the first row, 0.034 m at the eighth stops, and 0.022 m at the ninth stops. The same phenomenon also occurred at the sixteenth and seventeenth stopping points in the next row. The actual walking paths of the transport robot and the picking robot in the orchard are shown in Figure 18, where the stopping points of the transport robot in this path are shown in Figure 18a and the stopping points of the picking robot in this path are shown in Figure 18b. It can be seen that the routes of the two robots almost overlap when driving between rows, and the intervals between the stopping points are almost the same, but there is a large position error when turning. To analyze the operation of the autonomous navigation system of the combined orchard harvesting robot more visually, the course deviation and lateral deviation between the two robots were calculated and plotted in Figure 18c,d. It is obvious from the figure that when driving at the head of the orchard, the heading deviation of the two robots was mostly within 0.05 m, and the lateral deviation was \(10^{\circ}\), with a small variation. While the maximum value of heading angle deviation was less than \(90^{\circ}\) and the maximum value of lateral deviation was less than 1 m when the ground head turned, and the change was drastic.