## 2 Methodology  
### Description  
In the battery-swapping truck transportation model for open-pit mines, multiple shovel points, crushing stations, and battery-swapping stations are involved. The battery-swapping trucks need to transport materials among these shovel points, crushing stations, and battery-swapping stations, as illustrated in Figure 1. The transportation scheduling plan for battery-swapping trucks should optimize route selection among the various shovel points, crushing stations, and battery-swapping stations, minimizing queue wait times at each point. This optimization aims to reduce transportation costs and enhance material transport efficiency. The selection of model variables determines the accuracy and computational complexity of the model. In this study, the model is developed by considering the actual operational conditions of the open-pit mine. The model assumptions are as follows:  
* It is not allowed for any mining truck to transport materials directly from one shovel point to another shovel point. * It is not allowed for any mining truck to transport materials directly from one crushing station to another crushing station. * It is not allowed for any mining truck to transport materials directly from one battery-swapping station to another battery-swapping station. * The working time for each shift in the mine is 8 h, and the trucks do not have any rest time during a single shift. * At the beginning of each shift, all trucks are fully charged. * All trucks in the scheduling model are battery-swapping trucks; battery capacity, rated load capacity, unit transportation cost per distance, and unit maintenance cost may vary. * The loading time at shovel points and the unloading time at crushing stations are the same for all battery-swapping trucks. * The scheduling environment for battery-swapping trucks reflects the actual situation over a short period. As the project progresses, the relocation and siting of charging stations will be considered in future phases. Initially, the battery-swapping stations are located near the crushing stations, with three battery-swapping stations in total, all offering the same battery-swapping time. * After arriving at a battery-swapping station, a truck leaves fully charged (100%) after swapping the battery, with no limit on the number of battery swaps during a single shift. Figure 1: Schematic diagram of the battery-swapping truck transportation model. * The maintenance costs due to truck malfunctions during a shift are determined based on the transportation distance. Considering the above model assumptions, the battery-swapping truck scheduling model is ultimately described as the following mathematical model, with the model symbols defined in Table 1.  
This parameter table covers the primary factors involved in the scheduling of battery-swapping trucks, categorized into several of the following key areas: location indices (e.g., loading points, unloading points, and battery-swapping stations), path and energy consumption (such as the number of trips between locations, energy use, and distances), cost and capacity (e.g., transportation cost per distance, truck load and battery capacity, and maximum production and consumption capacities), time (e.g., battery-swapping time, loading/unloading time, and shift duration), and environmental factors (such as the effect of ambient temperature on the battery capacity). These parameters collectively aid in optimizing the scheduling and energy management of battery-swapping trucks.