# Development and Field Testing of a Suspended Mulberry Branch Harvesting and Stubble Cutting Machine
## 4 Prototype Field Test
### Field Test
#### 4.2.2 Single-Factor Experiment Results and Analysis  
In the operation of the disc saw, the primary forces acting on it are radial force and tangential force, with the axial force fluctuations being relatively small. Specifically, the tangential force arises from the resistance encountered by the saw teeth when cutting the material, while the radial force is mainly generated by the impact forces during the cutting process. The axial force primarily originates from the pressure applied during the cutting operation and the effect of the mulberry stripping operation.  
Through a detailed analysis of Figure 13a, it can be observed that, when the cutting speed is in a lower range, the feed rate per tooth is relatively large, which leads to a significant increase in frictional resistance. In this situation, the energy consumption gradually decreases as the cutting speed increases. However, when the cutting speed becomes too high, the disc saw tends to experience vibration, significantly reducing its operational stability and causing an increase in energy consumption. It is worth noting that a moderate increase in the cutting speed has a positive effect on improving the cutting quality. However, as the cutting speed continues to increase, it leads to corresponding increases in feed speed and mulberry stripping speed, ultimately resulting in a decline in cutting quality. Experimental studies have shown that when the disc saw's line speed reaches 70 m/s, the cutting energy consumption achieves its lowest point, while the cutting quality reaches its highest level. At this point, the cutting performance is optimal.  
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Factor** & & & **Level** & \\ \hline The linear velocity of the circular saw (m/s) & 50 & 60 & 70 & 80 & 90 \\ Cutting speed ratio & 60 & 80 & 100 & 120 & 140 \\ The height of the star wheel above the ground (mm) & 630 & 680 & 730 & 780 & 830 \\ \hline \hline \end{tabular}
\end{table}
Table 2: Single factor experiment in field test.  
\begin{table}
\begin{tabular}{c c c c} \hline \hline \multirow{2}{*}{**Number**} & \multicolumn{4}{c}{**Factor Level**} \\ \cline{2-4}  & **The Linear Velocity of the** & **Cutting Speed Ratio** & **The Height of the Star Wheel** \\  & **Circular Saw (m/s)** & **Cutting Speed Ratio** & **Above the Ground (mm)** \\ \hline  
\hline \hline \end{tabular}
\end{table}
Table 3: Factors and levels of the central composite experiment.  
Further observation, as shown in Figure 13b, reveals that, as the cutting speed ratio increases, the feed rate continues to decrease, while the energy consumption initially decreases and then increases. Although an increase in the cutting speed ratio leads to a decline in cutting quality, a moderate increase in feed rate under lower feed speed conditions helps to improve the mulberry stripping effect. Repeated experiments confirm that when the cutting speed ratio is set to 100, the energy consumption is minimized, and the cutting quality reaches its best level.  
From Figure 13c, it can be seen that, under the action of the mulberry stripping star wheel, the cutting energy consumption initially decreases and then increases, while the cutting quality score first rises and then falls. When the height of the mulberry stripping star wheel from the ground is adjusted to 730 mm, the best cutting effect is achieved.  
Figure 13: Influence of different factors on cutting performance. (**a**) The influence of the linear velocity change of the circular saw on the sawing performance. (**b**) The influence of cutting speed ratio changes on sawing performance. (**c**) The impact of the change in the height of the grain—divider above the ground on the sawing performance.  
In summary, by precisely adjusting the relevant parameters to specific values, the dual optimization goals of minimizing cutting energy consumption and maximizing cutting quality can be achieved for the disc saw.