## 4 Results and Discussion  
### Test Parameters  
The physical prototype made by using the above design method is shown in Figure 12. In order to verify the rationality of the design, related field experiments were carried out. The experimental site was the Nantong Civic Forest Farm, China, and the picked winter jujube variety is Zhanhua Dongzao. The height of this variety of jujube trees is about 3 m, and the planting interval of jujube trees is about 5 m. The terrain in the field is relatively small; there are no weeds between the main roads, and there is no wind during the test. For comparison, two kinds of picking methods are adopted. The device designed in this paper is used for mechanized picking, and the second is manual picking. The manual picking is beating winter dates using bamboo poles, so that the jujubes fall. The main test parameters include acquisition rate, collection rate, damage rate, miscellaneous rate, and misclassification rate.  
The acquisition rate refers to the ratio between the number of fallen winter jujubes and the total number of winter jujubes to be harvested. After the vibration is over, the unexplidated winter jujubes are knocked off the trees by the measure of human beating, and the corresponding number is recorded. The acquisition rate can be obtained by Equation (25).  
\[P_{r}=100\frac{N_{r}}{N_{r}+N_{u}} \tag{25}\]  
where, \(P_{r}\) is acquisition rate, %; \(N_{r}\) is the number of fallen winter jujubes by vibration; \(N_{u}\) is the number of fallen winter jujubes by artificial beating.  
Due to the adjustable vibration frequency, the amplitude of jujube trees may be too large at some time, resulting that some of the winter jujubes fall outside the umbrella collection mechanism.  
The collection rate refers to the ratio between the number of winter jujubes that fall into the boxes and the number of winter jujubes that fall in vibration, which can be obtained by Equation (26).  
\[P_{c}=100\frac{N_{c}}{N_{r}} \tag{26}\]  
Figure 12: The prototype of winter jujube harvesting and sorting device.  
where, \(P_{c}\) is the collection rate, %; \(N_{c}\) is the number of winter jujubes falling into the boxes.  
Some winter jujubes may cause surface damage when they fall outside the collecting mechanism. The damage rate refers to the ratio between the number of winter jujubes with surface damage and the number of winter jujubes that fall in vibration, and it can be obtained by Equation (27).  
\[P_{d}=100\frac{N_{d}}{N_{r}} \tag{27}\]  
where, \(P_{d}\) is the damage rate, %. \(N_{d}\) is the number of winter jujubes with surface damage.  
The miscellaneous rate refers to the ratio of the mass of jujube leaves in the jujube box to the mass of jujube and jujube leaves, which reflects the negative performance of the device, expressed in \(P_{t}\):  
\[P_{t}=100\frac{m_{y}}{m_{y}+m_{z}} \tag{28}\]  
where, \(P_{t}\) is the miscellaneous rate, %; \(m_{y}\) is the mass of the jujube leaf in the jujube box, kg; \(m_{z}\) is the mass of the jujube in the jujube box, kg.  
When classifying the winter jujubes, the large jujubes cannot be transferred into the small jujube storage box through the screening holes. However, due to excessive accumulation on the screening plate, the small juibes cannot fall into the small jujube storage box in time. Instead, due to gravity, they roll into the large jujube storage box, resulting in classification error. The misclassification rate refers to the ratio of the number of mis-division jujubes to the total number of winter jujubes in the jujube box, expressed in \(P_{i}\).  
\[P_{i}=100\frac{N_{m}}{N_{c}} \tag{29}\]  
where, \(P_{i}\) is the impurity content, %; \(N_{m}\) is the number of mis-divisions.