## 3 Results  
### Analysis of Experimental Results  
Design-Expert 8.0.6 was used to perform multiple regression fitting analysis on the experimental results in Table 5, and the variance analysis of soil throwing distance and the stability of ditch depth was obtained as shown in Table 6. The quadratic regression model was highly significant [19]. It can be seen from the table: (1) For the soil throwing distance, the \(p\) value of ditching depth is 0.0014, which has the greatest influence on the soil throwing distance. For the stability of ditch depth, the \(p\) value of ditching depth is 0.0255, which is smaller than the cutter wheel speed and inclination angle. Ditching depth also has the greatest influence on the stability of ditch depth. (2) The order of the influence of \begin{table}
\begin{tabular}{c c c c} \hline \hline \multirow{2}{*}{**Code**} & **Cutter Speed** & **Inclination of Curved** & **Ditching Depth** \\  & **A/(r-min\({}^{-1}\))** & **Surface B/(\({}^{\circ}\))** & **C/(mm)** \\ \hline
1 & 100 & 20 & 25 \\
0 & 120 & 30 & 35 \\ \(-1\) & 140 & 40 & 45 \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Coding of factors and levels. Figure 6: Field experiment. each factor on the soil throwing distance is ditching depth > Inclination of curved surface > cutter speed, and the order of the influence on the stability of the ditch depth is ditching depth > cutter speed > Inclination of curved surface. \begin{table}
\begin{tabular}{c c c c c c c c c c} \hline \hline
**Category** & \multicolumn{6}{c}{**The Throwing Distance**} & \multicolumn{6}{c}{**The Stability of Ditch Depth**} \\ \hline
**Source** & **Squares** & **df** & **F** & **\(p\)** & **Significance Source** & **Squares** & **df** & **F** & **Significance** \\ \hline
**Models** & 57.08 & 9 & 12.81 & 0.0014 & **\(\ast\)** & 102.89 & 9 & 10.36 & 0.0028 & **\(\ast\)** \\ \hline
**A** &  
According to the statistical analysis of soil throwing distance \(Y_{1}\), \(p=0.0014<0.01\), while the \(p\) value of the lack of fit is 0.5572, which indicates that the regression model is extremely significant and has high fitting accuracy, where the coefficients of \(X_{1}\), \(X_{2}\), \(X_{3}\), \(X_{2}\)X\({}_{3}\), \(X_{12}\), \(X_{22}\), \(X_{32}\) are less than 0.05, indicating significant, and the rest are not significant. Similarly, according to the statistical analysis of \(Y_{2}\) stability of ditching depth, the total model \(p=0.0028<0.01\), and the \(p\) value of the lack of fit is 0.7976, which means that the regression model is extremely significant. After removing the non-significant items, the relationship between the response values and the independent variables was expressed by the quadratic polynomial regression model as follows:  
\[Y_{1}=57.26+0.67X_{1}+0.77X_{2}+1.28X_{3}-0.85X_{1}^{2}-0.85X_{2}^{2}-2.41X_{3 }^{2}\]  
\[Y_{2}=87.48-0.94X_{1}-0.91X_{2}-1.05X_{3}-2.81X_{1}^{2}-1.76X_{2}^{2}-2.34X_{3 }^{2}\]  
where \(Y_{1}\) is the throwing distance; \(Y_{2}\) is the stability of ditch depth, \(X_{1}\) Cutter speed, \(X_{2}\) is inclination of curved surface, and \(X_{3}\) is the ditching depth. At a certain ditching depth, the influence of both Inclination of curved surface and cutter speed on the throwing distance increases first and then decreases, and the trend of both influences is basically the same (Figure 7a); when the Inclination of curved surface is certain, the influence of cutter speed and ditching depth on the throwing distance increases first and then decreases, among which the influence on the throwing distance is greater when the cutter wheel speed is less than 124 r\(\cdot\)min\({}^{-1}\) and the ditching depth is less than 40 mm (Figure 7b); When the speed is certain, the influence of ditching depth and Inclination of curved surface on the throwing distance also increases first and then decreases, and has no interactive effect, so when operating, it is not advisable to use a deeper ditching depth, and the installation angle of the guide cover should not be too large (Figure 7c).