# Design and Experimental Study of Potato-Soil Separation Device for Sticky Soils Condition
## 4 Separation Device Performance Test
### Orthogonal Test
#### 4.4.2 Analysis of Orthogonal Test Results  
To examine the primary and secondary sequence and the optimal lever of the respective factor, the range analysis for orthogonal test results (Table 3) was conducted, and the means graph (Figure 12) of a distinct index at the individual level of each factor was plotted. As indicated from the mentioned results: for the percentage of small soil \(\lambda\), the moisture content was the main factor because it had the maximal range value, and the higher the moisture content, the smaller the percentage of small soil would remain. The effect order of the respective factor to \(\lambda\) was as: moisture content-linear velocity of second-stage lifting chain > rotational speed of the soil-crushing mechanism> inclination angle of lifting chain. For the percentage of soil adhering to potato tuber \(\gamma\), the moisture content was the main factor since it had maximum range value, and the higher the moisture content, the bigger the percentage of soil adhering to potato tuber would be. The effect order of the respective factor to \(\gamma\) was moisture content > linear velocity of second-stage lifting chain > rotational speed of the soil-crushing mechanism> inclination angle of lifting chain. \begin{table}
\begin{tabular}{c c c c c} \hline \hline \multirow{2}{*}{**Levels**} & \multicolumn{4}{c}{**Factors**} \\ \cline{2-5}  & **A** & **B** & **C** & **D** \\ \cline{2-5}  & **Moisture Content** & **Rotational Speed of** & **Linear Velocity of** & **Inclination Angle of** & **Lifting Chain** \\  & **/\%** & **Soil-Crushing Mechanism** & **Second-Stage Lifting Chain** & **Lifting Chain** \\  & & **/r-min\({}^{-1}\)** & **/m\(\cdot\)s\({}^{-1}\)** & **/\({}^{\circ}\)** \\ \hline
1 & 18 & 70 & 0.75 & 15 \\
2 & 23 & 122 & 0.96 & 20 \\
3 & 28 & 175 & 1.23 & 25 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Coding with factors and levels. For the damage rate of potato tuber \(K\), the linear velocity of second-stage lifting chain acted as the main factor since it achieved the maximal range value. The effect order of the respective factor to \(K\) was linear velocity of second-stage lifting chain > inclination angle of lifting chain>rotational speed of the soil-crushing mechanism>moisture content. Based on the range analysis, the variance analysis was conducted to study whether the various factors exerted a statistically significant influence on each assessment index. Given the results of range analysis, the factor exerting the minimal influence on the assessment index served as a residual term during variance analysis, and the results are listed in Table 4.  
From the mentioned results: for a percentage of small soil \(\lambda\), a confidence interval that factor \(A\) significantly impacted \(\lambda\) was at 90-95%, thereby illustrating that statistically the moisture content significantly impacted the percentage of small soil, and other factors were not significant for \(\lambda\) due to a confidence interval below 80%. For the percentage of soil adhering to potato tuber \(\gamma\), a confidence interval that the factor \(A\) exerted some effects on \(\gamma\) was at 80-90%, which illustrated statistically that the moisture content had some effect on the percentage of soil adhering to potato tuber. Other factors were not significant for \(\lambda\) because of a confidence interval below 80%. For the damage rate of potato tuber \(K\), the confidence intervals that the factors significantly impacted \(K\) were +95% for C, 90-95% for \(B\), 90-95% for \(C\), respectively, which illustrated statistically that the mentioned factors significantly impacted \(K\).