## 3 Design of Essential Parts of the Seed Dispenser
### Parametric Design of Seed Box Housings  
The seed box shell is the core component that enables the transmission of the seeder, and it is also an essential structure for storing and providing seeds. Whether the seed box shell structure design is appropriate will directly affect the seed discharge performance of the seeder [26]. When designing the seed box shell, the primary consideration is the structural parameters and volume size of the seed box shell. The seed box shell structure mainly comprises two parts, region I and region II, as shown in Figure 5.  
Small cabbage planting agronomic requirements ensure that the row spacing and plant spacing are about 110 mm. The area of each acre of land is set to 667 m\({}^{2}\), according to the Formula (10), that can be obtained to plant one acre of Chinese cabbage with the required seed box volume size.  
\[N=\frac{667G_{0}}{\rho zh} \tag{10}\]  
where:  
\(N\)--seed box shell volume, m\({}^{3}\)  
\(G_{0}\)--mass of a single cabbage seed, g  
\(\rho\)--cabbage seed density, g/L\({}^{-1}\)  
\(z\)--cabbage seed planting spacing, m  
\(h\)--cabbage seed planting row spacing, m  
In accordance with the literature [23], cabbage seeds with a single grain mass of 0.00295 g and a density of 690 g/L, by the Formula (10), can be planted in one acre with a seed box volume of 0.00024 m\({}^{3}\), taking into consideration the comprehensive design of the seed box and the shell volume size of 0.00030 m\({}^{3}\).  
In the process of cabbage seeds entering the seed-filling chamber from the seed box shell, the seeds have strong mobility. If the seed box shell region I W1 width is too small,  
Figure 5: Structure of the seed box housing. (**a**) Rear view of the seed box housing, (**b**) Side view of seed box housing.  
the seeds are prone to clogging and arching phenomena when the flow occurs. According to the particle flow, a Langmaid hole critical equation can be obtained [27]:  
\[\left\{\begin{array}{c}\frac{W_{min}}{d_{v}}=1.8+0.038\left(\frac{\sigma_{s}}{ \sigma_{v}}\right)^{1.8}\\ d_{v}=\frac{\sum_{i}\theta_{in}d^{2}}{\sum_{i}\pi_{i}d^{3}}=\frac{\theta_{i}}{d }\end{array}\right. \tag{11}\]  
where:  
\(W_{min}\)--minimum width of seed box shell area I, mm  
\(d_{v}\)--seed specific surface area equivalent diameter, mm  
\(\sigma_{s}\)--seed surface area shape factor  
\(\sigma_{v}\)--seed volume shape factor  
\(n_{i}\)--number of i-th seed  
\(d\)--cabbage seed equivalent diameter, mm  
Since cabbage seeds are spherical-like particles, there are \(\sigma_{s}/\sigma_{v}\) = 6. According to Equation (11), it can be obtained as follows: \(W_{min}\) = 32.1 mm. The comprehensive parameters and process requirements of the seed box shell of the whole seed are the design of the seed box shell area I where width W1 is 40 mm, and the thickness H1 is 30 mm. To ensure that the seeds can smoothly enter the bottom of the seed box filling chamber, the angle \(\beta\) between the bottom plate of Area I and the horizontal direction should be greater than the sliding friction angle between the seeds, and between the seeds and the seed box. Combined with the literature [28], the angle \(\beta\) was determined to be 60\({}^{\circ}\). The trapezoidal table structure of area II can effectively increase the volume size of the seed box shell. The top of the seed box shell area I and the bottom of area II coincide, so the volume size of area II is the difference between the volume size of the seed box shell and the volume size of area I. According to the requirements of the volume size of the seed box shell, the set area II on the bottom of the length is 40 mm, the bottom of the length is 80 mm, height is 120 mm, thickness is 30 mm, and the distance between the top of the seed box housing and the upper bottom surface of the trapezoidal platform is 30 mm.