# Design and Testing of a New Bionic Corn-Ear-Picking Test Device
## 3 Design of Key Components of a New Bionic Test Device for Corn Ear Picking
### Parameter Design for Key Components
#### 3.3.2 Design of Snapping Roller  
The ear-picking roller as designed for: (i) picking corn ears regardless of their growth in different directions; (ii) picking corn ears despite their different scion heights; (iii) achieving the backwards transportation of the corn straw; (iv) preventing the straw from being damaged during the process.  
Thirty MF 12 corn plants were randomly selected to measure the parameters of their actual growth, and the measurement results are shown in Table 1. According to these actual growth characteristics, the left and right snapping rollers were designed with a 30\({}^{\circ}\) adjustment range to pick corn ears with different scion directions and scion heights.  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline \multirow{2}{*}{**Parameter**} & \multicolumn{4}{c}{**Statistics**} \\ \cline{2-5}  & **Max** & **Min** & **Average** & **Standard Deviation** \\ \hline Scion height (mm) & 1526.3 & 986.3 & 1234.11 & 175.07 \\ Corn ear length (mm) & 212.1 & 169.2 & 198.18 & 12.78 \\ Corn ear root diameter (mm) & 57.9 & 44.7 & 53.13 & 4.16 \\ Top diameter of corn ear (mm) & 22.5 & 14.2 & 18.575 & 2.29 \\ Straw root diameter (mm) & 32.9 & 25.6 & 30.13 & 2.15 \\ \hline \hline \end{tabular}
\end{table}
Table 1: Growth parameters of corn plants.  
Figure 7: Clamping conveyor. 1. Belt pulley. 2. Movable tension roller. 3. Right clamping conveyor frame. 4. Fixed tension roller. 5. Left clamping conveyor frame.  
Each snapping roller was designed with spiral grooves to prevent blockages caused by the accumulation of straw during the harvesting process. More importantly, the rotational direction of a snapping roller was determined according to the geometry of its spiral groove. Thus, the corn straws can be transported backwards. Additionally, the respective speeds of the left and right snapping rollers were controlled by the application of two motors to allow different speeds to be studied. The working modes of the snapping rollers and motors are shown in Figure 8.  
Figure 9 shows a design sketch of the snapping rollers. Because their average height was 1234.11 mm, based on the measurement results, the working range between the snapping rollers and the clamping conveyor should be at least 260 mm. Additionally, the length of a snapping roller should meet the following requirements:  
\[L=\frac{a}{sin15^{\circ}} \tag{1}\]  
where \(L\) is the length of the snapping roller in mm and \(a\) is the working range in mm.  
Here, a is taken as 260 mm, so the length L of the snapping roller is roughly 1005 mm. To prevent ear picking from being performed when the corn ears enter the groove, d shall satisfy:  
\[d_{\text{jmax}}<d<d_{\text{smin}} \tag{2}\]  
where \(d_{\text{jmax}}\) is the maximum diameter of corn straw in mm and \(d_{\text{smin}}\) is the minimum diameter of the corn ear root in mm.  
According to Table 1, the maximum diameter of a corn straw was 32.9 mm, and the minimum diameter of a corn ear root was 44.7 mm. Therefore, the groove width d was selected to be 40 mm.  
Figure 8: Rotational direction of motors and snapping rollers. 1. Sprocket of right motor. 2. Right snapping roller. 3. Left snapping roller. 4. Sprocket of the left motor.  
Figure 9: Snapping roller parameters. (\(L\) is the length of a snapping roller in mm; \(d\) is the diameter of corn straw in mm; \(a\) is the working range in mm).