## 5 Test and Result Analysis  
To verify the feasibility of the designed levelling system and virtual leg elimination system, the safflower-picking mobile platform was tested. The designed levelling mechanism was installed on the mobile platform of the safflower picking robot for field experiments and commissioning. The test location was Hongqi Farm in Jimsar County, Changji Autonomous Prefecture, Xinjiang Uygur Autonomous Region. Figure 8 is the field test of the mobile platform. a is the overall structure diagram of the mobile platform, b is the installation position of the electric push rod, and c is the installation position of the IMU. The field test of the mobile platform is shown in Figure 9. Figure 9a shows the tilt attitude of the mobile platform before levelling, and Figure 9b shows the attitude of the mobile platform after levelling. Figure 8: Field test of the mobile platform. (**a**) The overall structure of the mobile platform. (**b**) The installation position of the electric push rod. (**c**) The installation position of the IMU. Figure 7: Virtual leg control flow chart. The levelling of the mobile platform was divided into static levelling and dynamic levelling. The \(X\)-axis and \(Y\)-axis angles when the body is tilted were displayed through the serial port assistant, and the levelling time was recorded. Static levelling manually changes the inclination of the mobile platform so that the mobile platform is in eight tilting states: front lowest, rear lowest, left lowest, right lowest, left front lowest, right front lowest, left rear lowest, and right rear lowest. Then, these eight states were automatically and manually levelled, the levelling tilt angle recorded, and the automatic levelling curve and the time required for manual and automatic levelling drawn, as shown in Figure 10. Figure 11 shows the comparison between automatic levelling time and manual levelling time. Figure 12 is the performance index diagram of the test results. The red points is the angle of \(\alpha\) and \(\beta\) after leveling the mobile platform.It can be seen that the dip angle after levelling is in the range of 0.2\({}^{\circ}\), which meets the requirements of levelling accuracy. The tilt angle of the mobile platform before and after the levelling test is shown in Table 2.  
For dynamic levelling, the automatic levelling mode is selected, and the scope of a section of the test field is delimited. The mobile platform carries out the nonadjustable parallel driving test and the driving while levelling the test at the same speed to test the inclination change and the levelling effect of the mobile platform when it passes this section of the road. The test is divided into three parts, and the recorded levelling data are shown in Figure 13a-c are the curve of the change of inclination angle in the process of three dynamic leveling respectively. After levelling, the pressure sensor detects the pressure value of each outrigger. If the pressure value of one outrigger is approximately 0, which is less than the pressure value of the other outriggers, it starts to eliminate the virtual leg until the pressure value of the four outriggers reaches a relatively average value. \begin{table}
\begin{tabular}{c c c c c c} \hline
**Tilt State** & **before Levelling** & **after Levelling** & **Levelling Time(s)** \\ \hline  & \(\alpha\) & \(\beta\) & \(\alpha\) & \(\beta\) & \\ \hline Front lowest & \(-4.806^{\circ}\) & \(0.84\) & \(-0.192^{\circ}\) & \(0.15^{\circ}\) & \(7.1\) \\ Rear lowest &  
Figure 10: Automatic levelling results under eight tilting states. (**a**) Front lowest, (**b**) Rear lowest, (**c**) Left lowest, (**d**) Right lowest, (**e**) Left front lowest, (**f**) Left rear lowest, (**g**) Right front lowest, (**h**) Right rear lowest. Figure 10 shows that both automatic levelling and manual levelling can level the mobile platform, and the levelling accuracy is 0.2\({}^{\circ}\).