# Towards Optimizing Garlic Combine Harvester Design with Logistic Regression
## 5 Results and Analysis
### Multifactor Orthogonal Test  
According to the results of a single-factor test and field harvest operation, three factors that had a significant impact on the test index were selected to carry out a three-level orthogonal test, which was carried out on three plots, and a range analysis was carried out for the orthogonal experiment results. The influence of each factor on the index can be judged by testing the range of each level of a factor. The three plots of each experiment were used to calculate the garlic damage rate. The statistical results are shown in Table 4. \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline \multirow{2}{*}{**No.**} & \multicolumn{2}{c}{**A Working Speed(\(\text{km}\cdot\text{h}^{-1}\))**} & \multicolumn{2}{c}{**B Digging Depth(\(\text{mm}\))**} & \multicolumn{2}{c}{**C Lifting Speed(\(\text{m}\cdot\text{s}^{-1}\))**} & \multicolumn{2}{c}{**Plot 1**} & \multicolumn{2}{c}{**Plot 2**} & \multicolumn{2}{c}{**Plot 3**} \\ \hline
1 & 1.05 & 80 & 0.69 & 2.16 & 5.00 & 3.46 \\
2 & 1.05 & 90 & 0.81 & 2.16 & 1.70 & 3.38 \\
3 & 1.05 & 100 & 0.93 & 2.08 & 3.00 & 1.20 \\
4 & 1.48 & 80 & 0.81 & 8.16 & 3.75 & 7.11 \\
5 & 1.48 & 90 & 0.93 & 3.83 & 5.26 & 4.68 \\
6 & 1.48 & 100 & 0.69 & 1.30 & 1.60 & 2.86 \\
7 & 1.91 & 80 & 0.93 & 8.62 & 8.02 & 6.80 \\
8 & 1.91 & 90 & 0.69 & 2.11 & 4.10 & 5.88 \\
9 & 1.91 & 100 & 0.81 & 1.30 & 2.58 & 2.90 \\ \hline \(K_{1}\) & 8.04 & 17.69 & 9.49 & & & \\ \(K_{2}\) & 12.85 & 11.03 & 11.01 & & & \\ \(K_{3}\) & 14.10 & 6.27 & 14.49 & & & \\ \(R\) & 6.06 & 11.42 & 5.00 & & & \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Range analysis of orthogonal test. Figure 11: Effect of equivalent friction on damage rate on cutting height. Note: working speed was 1.48 km\(\cdot\)h\({}^{-1}\), digging depth was 90 mm and lifting speed was 0.81 m\(\cdot\)s\({}^{-1}\). According to the analysis of the \(K\) value, the change of excavation depth on the level had the largest fluctuation on the garlic damage rate, followed by the working speed and the lifting speed, respectively. According to the analysis of the \(R\) value, the order of the influence degree of the three factors on the garlic damage rate was as follows: excavation depth, operation speed and lifting speed. In other words, the excavation depth had the greatest influence on the garlic damage rate, and the lifting speed had the smallest influence on the garlic damage rate. The variance analysis of the orthogonal test is shown in Table 5. The variance analysis results show that each factor was observed to have a significant influence on the garlic damage rate. The operation speed and the excavation depth had extremely significant effects on the garlic damage rate (\(p<0.01\)), and the lifting speed had significant effects on the garlic damage rate (\(p<0.05\)). The regression analysis of the orthogonal test results showed that:  
\[P=11.912+2.348A-0.190B+6.954C \tag{10}\]  
In the formula, \(P\) is the garlic damage rate, %. \(A\) is the operating speed, km\(\cdot\)h\({}^{-1}\), the value range is \(A\) = 1.05, 1.48, 1.91. \(B\) is the excavation depth, mm, and the range is \(B\) = 80, 90, 100. \(C\) is the lifting speed, m\(\cdot\)s\({}^{-1}\), and the value range is \(C\) = 0.69, 0.81, 0.93. According to Formula (10), when the excavation depth was 100 mm, the lifting speed was 0.69 m\(\cdot\)s\({}^{-1}\) and the operating speed was 1.05 km\(\cdot\)h\({}^{-1}\); the garlic damage rate reached the minimum, which was 0.18%. However, that stage of parameters does not appear in the orthogonal test table; therefore, additional sets of experiments are required. The linear regression analysis of the orthogonal test results is shown in Table 6. Supplementing a group of experiments, we found that the level of each factor was \(A_{1}B_{3}C_{1}\), while the measured garlic damage rate was 0.83%. The difference between the results of the linear regression analysis and orthogonal test was small, so the lowest garlic damage rate was the combination of the orthogonal test results.