“Instantaneous Trucks” vs “TUM Trucks”
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In reality, trucks do not respect the TUM in an instant in time - in any one instant, the truck is either available or unavailable, not a mixture of the two. There’s a probability of whether a truck will be operating at an instant in time in the future (the TUM is the average over an extended period of time). This is the most correct way to think about trucks on an instantaneous basis, and for very short term scheduling. The TUM accounts for but does not explicitly contain, the frequency and duration of downtime events (a cyclone vs a broken bucket tooth).
APS now supports both methods to accommodate either paradigmsupports TUM trucks, and an approximation of instantaneous trucks (with Dispatch mode, explained below).
Truck Hours Calculation
Truck hours are based on the cycle time of the truck (when being loaded by the specific digger), the truck’s payload, the quantity and type of material moved, and the time usage model (TUM) which applies to the truck.
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Note that the way this is done in APS is to rotate through the trucks in a round-robin fashion. Dispatch Enabled: In each step the trucks will be used in the order specified. If in a steady steady state on a single loader a truck is exhausted, it will then go on to the next truck - and will use multiple truck types in the same instant (but it does not use the longer of the two cycle times). Dispatch Disabled: For each movement the loader does, a different truck will be used, going through the list in the order the trucks are specified in the Site Lists. In each steady state, the loader will choose a different truck from the previous steady state, thus approximating equal use while only using a single truck for each movement. |
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In each instant, APS will go through the diggers in order and assign trucks to diggers as it goes. If a specific route needs 5.2 trucks to haul at the maximum rate, and only has 2.3 left to assign, the digger will be derated. If there are no trucks available at all, the digger will be shut down.
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Dispatch Deadlocks
While this dispatch logic will work well in most circumstances, there are a few shortcomings. It is possible in some edge cases for APS to choose to do nothing even though if fully trucked it would do something. As an example, consider three diggers, EX1 on 62% Fe, EX2 mining 58% Fe, and EX3 on waste. There is also a strict Fe target of 60% on the crusher.
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