## 3 Design of Main Working Parts
### Seedbed Preparation Device
#### 3.1.3 Mechanical Analysis of Shaper  
When studying the operation rule of the shaper for collecting soil on the ridge and analyzing the main influencing factors on the quality of collected soil on the ridge, it is found that the quality of collected soil on the ridge is not only related to the structural parameters and soil parameters of the shaper but also to the installation angle of the shaper. Suppose the angle between the working surface of the shaper and the moving direction of the machine is \(\alpha\) (that is, the installation angle \(\alpha\)), then the larger the installation angle \(\alpha\), the larger the operation width and the greater the resistance of the scraper, which is prone to cause the soil to be piled up [16; 17; 18]. If the installation angle \(\alpha\) is too small, it cannot meet the required width of the seedbed, that is, the installation angle \(\alpha\) should be reduced when the required width of the seedbed is met. In order to determine the mechanical conditions of soil scraping along ridges and furrows, it is assumed that there is no relative force between soil particles at the moment of sliding. There is no relative displacement between the soil particles and the working face of the shaper. Figure 6a shows the spatial mechanical analysis of the moment of slip of a single soil particle. Taking the soil particle center as the origin \(O\), the direction parallel to the seedbed as \(x\), the forward direction of the operating machine as \(y\), and the direction perpendicular to the seedbed as \(z\), the space rectangular coordinate system is established. Setting the direction of motion of a single particle at the moment of slip as \(A_{z}\), it is seen that the operation surface slip of the shaper is reciprocated by the combined effects of normal force \(F_{a}\), friction \(f\), and gravity \(G\). Decomposing the above forces into the \(xOz\) coordinate system, as shown in Figure 6b, the resultant force \(F_{x}\) of the soil particle along the \(x\)-axis is  
\[F_{x} =F_{a}\cos a+G\sin 15^{\circ}-f\cos\beta\sin a \tag{3}\]  
where the angle \(\beta\) is the included angle of \(A_{z}\) projection on the surface (\({}^{\circ}\)).  
Taking the formula of friction \(f\) into Formula (3),  
\[F_{x} =F_{a}\cos\alpha+G\sin 15^{\circ}-\mu F_{a}\cos\beta\sin a \tag{4}\]  
where:  
\(\mu\) is the friction coefficient between the soil particle and operating surface of the shaper;  
\(G\) is gravity (N).  
In Formula (4), the friction coefficient \(\mu\) between the soil particle and the operating surface of the shaper can be measured. The included angle \(\beta\) is related to the motion direction \(A_{z}\) at the moment of slip. The installation angle \(\alpha\) can be determined by artificial adjustment. Soil particles will generally move in the positive direction of the \(x\)-axis, and the mechanical condition is \(F_{x}>0\).  
Figure 5: Schematic diagram of operation process of the effective cross-section of the shaper. 1. Bull-dozing surface. 2 Scraper plane. 3. The action line of the rotary blade tip. 4 The soil-covering belt of seedlings.  
According to the requirements of agronomy, the shaper should not cause soil to be piled up greatly during its operation. When the curved form of the scraper is determined, the installation angle \(\alpha\) is the key factor for the formation of the seedbed and the soil-covering belt of seedlings. Field experiments show that the width of the seedbed can be guaranteed when the maximum installation angle \(\alpha\) of ridge and furrow soil collection is \(60^{\circ}\) and the width of the shaper is 330 mm.