# Engine Speed Control System for Improving the Fuel Efficiency of Agricultural Tractors for
## 4 Throttle Control System
### Verification of the Control System  
To verify the control system, following operations were performed using the experimental tractor in a paddy field. A field test analyzed engine speed control performance and fuel-saving ability. To verify the control performance, a plowing operation was conducted before verifying the fuel efficiency performance. After verifying the control performance of the engine speed controller, numerous plowing operations were conducted to evaluate fuel-saving performance under various working conditions, such as transmission gear selection, driver habits, and workload. Specifications of the equipment used for the plowing operation are given in Table 3.  
The performance data collected from the tractor while using the control system included the engine speed, input shaft torque, throttle opening, and fuel consumption. These data were compared with the results taken from the tractor without using the control system to verify the overall performance of the system. Without the control system, the tillage depth, engine speed, and transmission gear selection were expected to operate according to the usual habits of the operator, and the operator was prohibited from shifting the transmission gear up or down during field operation.  
When using the control system, the same tillage depth and transmission gear selection as in the case without the system were maintained, and the engine speed control algorithm (Figure 17) was used to automatically control the throttle without considering operator behavior. The control system was also prohibited from shifting the transmission gear up or down the during field operation. The plowing depth was measured at randomly selected positions in the operation field using a ruler after each test was completed [13]. The field for the test was used \(100\times 100\) m square flat paddy field. Plowing operation was conducted in a straight path alone one side of the field. After tractor reach the end  
Figure 17: Flowchart of the control algorithm.  
\begin{table}
\begin{tabular}{c c} \hline \hline
**Item** & **Specification** \\ \cline{2-3}  & **Moldboard Flow** \\ \hline Length \(\times\) Width \(\times\) Height (mm) & \(2140\times 1805\times 1165\) \\ Type & Mounted \\ Plowing width (mm) & \(1810\) \\ Center of resistance rearward from rear axle (mm) & \(1583\) \\ \hline \hline \end{tabular}
\end{table}
Table 3: Specification of equipment used for plowing [13].  
side of the field, turned and moved to another side of the field with lifting up the plow implement. After reached to another side of the field, lifted down the plow implement and started plowing for opposite direction. If tractor reached the end side of the field, turned and moved to another side of field and started plowing along the side of tillage area before. The measurements were taken during the driving of the tractor along a straight path and for ensuring statistical significance, three paths were taken with same transmission gear step and tillage depth and performance data was averaged using three paths measurements.  
The average water content of soil was determined from randomly selected samples from the surface of the paddy field using the oven drying method [13]. The texture of soil in the experimental field was classified as loam based on the USDA definition. The soil strength was expressed in terms of the cone index from 8 to 10 randomly selected locations in the field, as shown in Table 4[13].