# Modeling and Parameter Calibration of Morchella Seed Based on Discrete Element Method
## 3 Results and Discussion
### Steepest Ascent Test  
Using the three significant parameters identified from the Plackett-Burman experiment, a steepest ascent experiment was conducted [37], with five groups of tests designed to quickly approach the optimal parameter values. Within the range of significant contact parameters, increments of 0.05, 0.015, and 0.07 were applied to the respective parameters, while the other parameters were maintained at their mid-levels. In the simulation, the following settings were used for the other parameters: seed-to-seed restitution coefficient was set at 0.4, seed-to-seed static friction coefficient at 0.45, seed-to-steel restitution coefficient at 0.4, and seed-to-steel static friction coefficient at 0.6. The steepest ascent experiment calculated the relative error between the simulated repose angle and the actual repose angle. The test plan and results are shown in Table 5, and the formula for calculating the relative error (\(N\), %) is provided in Equation (4).  
\[N=\frac{|\sigma-\theta|}{\theta}\times 100\% \tag{6}\]  
where \(\sigma\) is the repose angle (\({}^{\circ}\)) of the simulation test.  
As shown in Table 5, with the incremental increase in the significant parameter values, the simulated repose angle gradually increased, while the relative error initially decreased and then increased. In the second group of tests, the simulated repose angle was closest to the repose angle from the physical experiment, with the smallest relative error. This indicates that the optimal values for the significant parameters are likely near those used in the second group of tests.  
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Test Serial** & **Parameters** & **Effects** & **Mean Square** & **Influence** & **Significance** \\
**Number** & & & & & **Rate/\%** & **Ranking** \\ \hline
1 & \(A\) & \(-\)0.208 & 0.130 & 0.018 & 7 \\
2 & \(B\) & 2.182 & 14.279 & 2.005 & 6 \\
3 & \(C\) & 12.522 & 470.376 & 66.039 & 1 \\
4 & \(D\) & 4.552 & 62.153 & 8.726 & 3 \\
5 & \(E\) & 2.368 & 16.827 & 2.362 & 4 \\
6 & \(F\) & 2.228 & 14.896 & 2.091 & 5 \\
7 & \(G\) & 4.925 & 72.767 & 10.216 & 2 \\ \hline \hline \end{tabular}
\end{table}
Table 4: Analysis of significance parameters in Plackett–Burman experiment.  
\begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline
**Test Serial** & & & **Factors** & & & **Repose** \\ \cline{2-8}
**Number** & \(A\) & \(B\) & \(C\) & \(D\) & \(E\) & \(F\) & \(G\) & **Angle/(\({}^{\circ}\))** \\ \hline
1 & 0.50 & 0.20 & 0.05 & 0.01 & 0.50 & 0.50 & 0.50 & 35.84 \\
2 & 0.50 & 0.70 & 0.05 & 0.10 & 0.50 & 0.70 & 0.05 & 43.15 \\
3 & 0.50 & 0.70 & 0.05 & 0.01 & 0.30 & 0.70 & 0.05 & 34.56 \\
4 & 0.30 & 0.20 & 0.05 & 0.01 & 0.30 & 0.50 & 0.05 & 31.41 \\
5 & 0.30 & 0.20 & 0.40 & 0.01 & 0.50 & 0.70 & 0.05 & 48.37 \\
6 & 0.50 & 0.20 & 0.40 & 0.10 & 0.50 & 0.50 & 0.05 & 52.59 \\
7 & 0.30 & 0.70 & 0.05 & 0.10 & 0.50 & 0.50 & 0.50 & 44.66 \\
8 & 0.30 & 0.70 & 0.40 & 0.01 & 0.50 & 0.70 & 0.50 & 55.36 \\
9 & 0.30 & 0.20 & 0.05 & 0.10 & 0.30 & 0.70 & 0.50 & 45.68 \\
10 & 0.50 & 0.70 & 0.40 & 0.01 & 0.30 & 0.50 & 0.50 & 53.67 \\
11 & 0.30 & 0.70 & 0.40 & 0.10 & 0.30 & 0.50 & 0.05 & 48.01 \\
12 & 0.50 & 0.20 & 0.40 & 0.10 & 0.30 & 0.70 & 0.50 & 52.43 \\ \hline \hline \end{tabular}
\end{table}
Table 3: Results of Plackett–Burman Design (P-BD) test.