## 2 Shoveling Experiments and Analysis
### Fuel Consumption Analysis  
The wheel loader fuel consumption per unit time, wheel loader displacement, lift cylinder displacement, and tilt cylinder displacement during the wheel loader shoveling process are shown in Figure 8.  
1. Insertion phase: The wheel loader is inserted into the pile at a certain distance with traction. In the early insertion phase, the insertion speed of the wheel loader is fast. However, as the insertion depth increases, the resistance to the bucket also increases rapidly, and the wheel loader insertion speed gradually decreases. Meanwhile, the fuel consumption per unit of time rises rapidly after the insertion of the pile and then remains in a relatively stable state. 2. Scooping phase: The wheel loader continues to keep moving forward. In the early scooping phase, the wheel loader can move forward rapidly because the material is scooped up by the bucket to provide space for the wheel loader to move forward. In the later scooping phase, the wheel loader advances at a slower speed due to resistance. It is obvious that when the lift cylinder and tilt cylinder remain unchanged, the fuel consumption per unit time remains at a relatively stable level. The fuel consumption per unit time increases rapidly when the displacement of the lift cylinder and tilt cylinder increases and then is in a stable state. 3. Stopping phase: The resistance of the wheel loader increases sharply, and the wheel loader is forced to stop moving forward. However, to prevent the wheel loader from moving backward, the wheel loader will continue to keep moving ahead and move forward for a short distance. The fuel consumption per unit time is then reduced to the lowest state during the entire shoveling operation. 4. Lifting phase: The wheel loader is subjected to inertia in the process of lifting the bucket and continues to keep moving forward. And the fuel consumption per unit time increases with the displacement of the lift cylinder and then remains stable. Figure 8: Fuel consumption during the shoveling process. **(a)** Shoveling gravel; **(b)** Shoveling sand. Figure 7: Engine speed during the shoveling process. **(a)** Shoveling gravel; **(b)** Shoveling sand. The sensor on the wheel loader is a flow sensor. The total fuel consumption needs to be obtained by the calculation formula, which is shown in Equation (3). As an example, in Figure 8, the total fuel consumption, the fuel consumption of each phase, and the percentage of the total fuel consumption by each phase are shown in Table 2.  
\[C=\frac{\sum\limits_{i=1}^{n}c_{i}}{f\cdot 3600}\cdot 1000 \tag{3}\]  
where \(C\) is the total fuel consumption, mL, \(c\) is the fuel consumption per unit time at a certain moment, L\(\cdot\)h\({}^{-1}\),\(f\) is the frequency, Hz. According to Figure 8 and Table 2. The fuel consumption in the scooping phase is the highest, and the fuel consumption in the stopping phase is the lowest. In shoveling gravel, the fuel consumption in the insertion phase is higher than that in the lifting phase. While shoveling sand, the fuel consumption in the insertion phase is less than that in the lifting phase. This is related to the material properties, as gravel is a denser and less loose material. The wheel loader needs more operation time and energy consumption when inserting the gravel pile. Sand, on the other hand, is less dense and relatively looser. The wheel loader is easier to insert from the sand pile and therefore generates less fuel consumption when inserting into the sand pile. In short, the fuel consumption of shoveling gravel is higher than that of shoveling sand with the same engine speed, which is determined by the material characteristics. From Figure 8, the lift cylinder displacement and tilt cylinder displacement within different phases all affect fuel consumption, which increases with the expansion of cylinder displacement.