# Engine Speed Control System for Improving the Fuel Efficiency of Agricultural Tractors for
## 5 Control System Verification  
### Verification of the Control System  
To verify the throttle control system, the engine speed adjustment performance was analyzed using performance data from one of the plowing operations. The control performance verification results are presented as percentage errors between the desired engine speed and the engine operating speed.  
Figure 18 shows the engine operating speed and desired engine speed from the plowing operation performed without the control system. Without the control system, the operating conditions of the agricultural tractor were easily affected by the behavior of the operator. Therefore, the data show a significant difference between the desired engine speed and engine operating speed. For these reasons, different drivers produce different results. The engine operating speed was only affected by the input shaft transmission torque of the agricultural tractor, as shown in Figure 19.  
\begin{table}
\begin{tabular}{c c c c c c c c c} \hline \hline \multirow{2}{*}{**Plot**} & \multirow{2}{*}{**Soil Texture**} & \multirow{2}{*}{
\begin{tabular}{c} **Average Water** \\ **Content, (\% d.b)** \\ \end{tabular} } & \multicolumn{6}{c}{**Average Cone Index by Depth (kPa)**} \\ \cline{3-8}  & & **0 mm** & **50 mm** & **100 mm** & **150 mm** & **200 mm** & **250 mm** \\ \hline PaddyField & Loam & 38.9 & 201 & 615 & 732 & 735 & 1485 & 2425 \\ \hline \hline \end{tabular}
\end{table}
Table 4: Soil properties of the paddy field.  
Figure 18: Measured engine speed and desired engine speed during plowing operation without the control system.  
Figure 20 shows the engine operating speed and the desired engine speed from the following operation using the control system. With the control system, the engine operating speed was closer to the desired engine speed than without the control system. The engine operating speed values showed a 1.17% error on average compared to the desired engine speed. Therefore, the throttle control system can be considered suitable for the purpose of maintaining and adjusting the engine operating speed close to the desired engine speed.  
Figure 21 shows the measured input shaft transmission torque using the throttle control system. The characteristics of the input shaft torque using the control system were very similar to the input shaft torque without the system. However, the engine operating speed showed significant differences. Moreover, adjusting the throttle only affected the engine operating speed and not the input shaft torque from the draft load during the following operation. In other words, this system could be used for adjusting the engine speed without affecting the results of the operation. Consequently, the engine operating speed can be controlled by the system for the desired engine speed that maximizes the fuel efficiency by using real-time input shaft torque.  
Figure 19: Measured and filtered input shaft torque during following operation without the control system.  
Figure 20: Measured engine speed and desired engine speed during during operation using the control system.  
Figure 22 shows the throttle command for engine speed control during field operation. The throttle opening was maintained within 34.6-43.5%, and it showed a similar tendency to the engine speed.  
It is concluded that the operating engine speed of an agricultural tractor can be controlled within a stable range by using the throttle control system.