## 2 Materials and Methods
### Vibratory Picker Structural Design
#### 2.2.3 Vibratory Crab Apple Picker Excitation Device  
Fruit picking operations need to be carried out outdoors. An inertial vibration device is used to generate centrifugal force by the circular motion of the eccentric block, which generates the vibration excitation force of the vibrating tree under the action of centrifugal force. Therefore, a vibration device with large excitation force, easy operation, and simple maintenance should be selected. The shapes of eccentric blocks are mainly fan-type and hammer-type blocks (semi-circular eccentric blocks are special fan-type eccentric blocks). In this section, it is shown that differences in their external structure, mass, and eccentricity lead to significant differences in the excitation force generated at the same excitation frequency. Different eccentrics in operation: hammer eccentrics generate the highest excitation force; fan eccentrics are widely used and their excitation force is second only to that of hammer eccentrics; semi-circular eccentrics have all the characteristics of fan eccentrics since they are sector eccentrics with a 180\({}^{\circ}\) center of circle, and are easier to process than sector eccentrics with other degrees of centering, and their eccentrics generate a higher excitation force. Therefore, the semicircular eccentric block was selected for processing in this paper. At the same time, it is also possible to change the structure and number of eccentric blocks, or change the speed of the eccentric blocks, so as to change the size of the excitation force and to cope with different picking operations. As shown in Figure 4, the single eccentric block generates a force Fx in the x-direction and a force Fy in the y-direction during rotation, which drives the excitation device to generate an excitation force, which is then transmitted to the trunk to vibrate it, where Fx is the longitudinal component of the excitation force and Fy is the transverse component. \begin{table}
\begin{tabular}{c c} \hline \hline
**Vibratory Picker Structure** & **Technical Indicators** \\ \hline Overall length, width, and height of the picker & 1.80 m; 0.75 m; 1.20 m \\ Picker diesel engine output & 6.60 KW \\ Vibration frequency adjustment range & 0.00 Hz-38.00 Hz \\ Maximum angle of clamping mechanism & 120.00\({}^{\circ}\) \\ Area opened by harvesting device & 21.00 m\({}^{2}\) \\ Overall weight of the picker & 300.00 kg \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Technical specifications of the vibrating crab apple picking mechanism. Figure 4: Eccentric block force analysis diagram. Figure 3: Three-dimensional drawing of the whole machine: (a) clamping device; (b) umbrella collection device; (c) fruit basket; (d) mobile device. In this paper, 45 steel was selected as the processing material. The density of the material is 7850 kg/m\({}^{3}\). For the production of the eccentric block, multiple pieces of the same semicircular eccentric block were stacked and welded. The thickness of the eccentric block was determined as 90 mm. Additionally, the speed of the eccentric block was set at 750 r/min. During the process of crab apple picking, different excitation forces and rotational speeds are utilized based on the specific fruit trees. Parameters such as the excitation force of the eccentric block can be calculated using the following formula:  
\[F=m\omega^{2}r \tag{1}\]  
In this equation, \(F\) represents the excitation force; \(m\) refers to the eccentric block mass; \(\omega\) represents the angular velocity of the eccentric block; and \(r\) represents the center of gravity. The angular velocity relation of the eccentric block is given by:  
\[\omega=\frac{2n\pi}{60} \tag{2}\]  
In this equation, \(n\) represents the eccentric wheel speed. The mass relationship of the eccentric wheel is given by:  
\[m=\rho V=\frac{\pi\rho lnR_{1}^{2}}{2} \tag{3}\]  
In this equation, \(\rho\) represents the density of materials used for eccentric wheels; \(h\) refers to the thickness of the eccentric wheel; and \(R\) represents the angular velocity of the eccentric block.