## 3 Results
### Simulation Results
#### 3.1.3 Results and Analysis for Full Load of Beehives  
The variations in the roll and pitch values of the vehicle under each road condition when the loading box is fully loaded with bee frames on the \(8^{\circ}\) upslope and downslope are shown in Figure 22. It can be seen roll value of the vehicle when the loading box is fully loaded with bee frames on clayey soil and upland sandy loam can vary between \(-1\) and \(1^{\circ}\). The variation ranges of pitch angle are not considerably different between the clayey soil and upland sandy loam conditions, where the variation range of pitch angle in clayey soil is (\(-10.02\)-\(13.29^{\circ}\)) and that in upland sandy loam is (\(-10.2\)-\(16.29^{\circ}\)). The range of variation in upland sandy loam is slightly greater in the uphill phase. However, the vehicle in the dry sand road condition of overturned at the uphill stage, and the change in angle in the initial  
Figure 21: Box plot of (**a**) variation in roll values under each pavement condition when the loading box is fully loaded with bee frames and (**b**) variation in pitch values under each pavement condition when the loading box is fully loaded with bee frames. Figure 20: Variation of (**a**) roll values under each pavement condition when the loading box is fully loaded with bee frames (s-turn), (**b**) pitch values under each pavement condition when loading box is fully loaded with bee frames (s-turn). stage of the uphill drive had the same upward trend as that on clayey soil and upland sandy loam from the perspective of the pitch. At 11.8 s, the critical value of tipping was reached, and the angle was approximately 34.12\({}^{\circ}\), which exceeded the maximum uphill tipping angle of 34\({}^{\circ}\) under the beehive loading situation. For this reason, the vehicle could not be restrained from tipping. This is basically the same as the maximum uphill limit angle of the vehicle when it is fully loaded with beehives, as calculated in the previous section. At this time, the roll angle fluctuates drastically due to the tipping of the vehicle. The inability of the dry sandy ground to provide sufficient load carrying capacity for the vehicle is the main reason why the vehicle tilted its head and eventually overturned. Figure 23 shows the vehicle's driving torque and crawler stress when fully loaded with beehives on clayey soil and dry sand pavement. The vehicle's driving torque increased during the uphill process in the dry sand road condition; however, the vehicle's track force on the two pavements was nearly the same. It indicates that the cause of the tipping is unrelated to the track section. The driving torque and track force of the vehicle under clayey soil and dry sand pavement demonstrate this. Figure 22: Variation of (**a**) roll values under each pavement condition when the vehicle is fully loaded with beehives (8\({}^{\circ}\)) and (**b**) pitch values under for each pavement condition when the vehicle is fully loaded with beehives (8\({}^{\circ}\)). Figure 23: Description of the driving torque (**a**) and the bushing tension (**b**) of the vehicle when fully loaded with beehives. The variation of roll and pitch values of the vehicle under each road condition with a full load of beehives during s-turn is shown in Figure 24. First, in the s-turn transport test, all ground conditions were passed, and similar to the vehicle fully loaded with bee frames, the change in the roll value of the vehicle fully loaded with beehives did not exceed \(\pm 1^{\circ}\), and the maximum value changed between (\(-0.4-0.4^{\circ}\)). Thus, the range of change in the roll direction when the vehicle is fully loaded with beehives is tight, and there is no safety risk. In terms of the pitch angle variation of the vehicle with a full load of beehives, the angle variation is the largest in the dry sand road conditions, peaking at approximately \(6^{\circ}\), and in the subsequent runs, the angle changes in the range of (\(3.5-5^{\circ}\)).