## 5 Examples of Scheduling Optimization of Apron Support Vehicles
### Simulation 2: Configuration Optimization of Support Vehicle Quantity
Considering that the single aircraft and the double aircraft are under the protection of a set of support vehicles, through scheduling optimization, the total time can be controlled within 60 min with good optimization results, and the vehicle configuration can no longer be added. (1) Optimization of vehicle configuration with 3-aircraft support  
There is a limit to the further shortening of the guarantee time due to the number of refueling vehicles, and the adjustment measure is to add 1 refueling truck. According to Figure 10a, the population _fitness_ value is stable at 60 min, and the population average value is stable at 75 min. As can be seen from Table 7, after optimization, the utilization rate of the refueling truck is 100%, that of the oxygenation refilling truck is reduced from 81.8% to 75%, and that of the power van is increased from 42.9% to 54.5%. At the same time, the completion time of the three operations after optimization is 60 min, which is 30 min less than that before optimization. (2) Optimization of vehicle configuration with 4-aircraft support  
According to Table 4, the utilization rate of power van 1 is low, the working time is short, and the waiting time is long. The adjustment measure is to reduce 1 power van. It can be seen from Figure 10b that the population _fitness_ value is stable at 60 min, and the population average value is stable at 80 min. As can be seen from Table 7, the utilization rate  
Figure 11: Change of population _fitness_ value. (**a**) 3 aircraft, (**b**) 4 aircraft, (**c**) 5 aircraft, (**d**) 6 aircraft. of the optimized refueling truck and oxygenation refilling truck is 100%, and the utilization rate of the power van is increased to 72.7%. Through vehicle adjustment, the utilization rate of the power van is improved, the support resources are reduced, and the support time is kept at 60 min before and after optimization. Optimization of vehicle configuration with 5-aircraft support  
As can be seen from Table 4, the long working hours of the refueling truck and the oxygenation refilling truck limit the further shortening of the support time, and the long waiting time of the power van 1 causes a waste of resources. The measures are as follows: one more refueling truck and one more oxygenation refilling truck and one less power van. It can be seen from Figure 10c that the population _fitness_ value is stable at 65 min, and the population average value is stable at 90 min. From Table 7, it can be seen that the utilization rate of optimized refueling vehicles is 100%, and the waiting time is 0 min. After optimization, the utilization rates of the oxygenation refilling truck are 66.7% and 75%, respectively, which decrease from a numerical point of view but remain at a high level; with the optimization, the average utilization rate of the power van is increased from 75% to 76.9%, which is slightly improved, but the waste of resources is greatly reduced. Total time of the optimized three tasks is 65 min, which is 25 min shorter than the previous 90 min. Optimization of vehicle configuration with 6-aircraft support  
From Table 5, it can be seen that the working time of the oxygenation refilling truck limits the further shortening of the support time, and the utilization rate of power van 2 is low, resulting in a waste of resources. The measures are as follows: adding one oxygenation refilling truck and reducing one power van. According to Figure 10d, the population _fitness_ value is stable at 60 min, and the population average value is stable at 100 min. Table 8 shows that after optimization, the waiting time of the refueling truck disappears, and the utilization rates all returns to 100%. After optimization, the average utilization rate of the oxygenation refilling truck decreased, but all of them were above 75%. With the optimization, the average utilization rate of the power van is 54.5%, which is lower than that before optimization, but it is still at a high level.