question

Douwe Jd avatar image
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Douwe Jd asked Jason Lightfoot edited

need help in simulating truck door assignment problem at warehouse

truck warehouse simulation.fsm

hi, for my thesis i want to simulate a truck door assignment problem. I am not very experienced in Flexsim but have got this far. After the truck comes in through the gate, it moves to a temporary parking area, and the Driver steps out and goes to the office to be assigned an available dock door. The idea is that he then goes back to his truck to travel to the assigned dockdoor and load the cargo that is ready over there. I am having difficulties with this last step, and also i am getting a little confused with all the labels and tokens in general, so i don't know if these are correct as well. For instance, i assume the 'Driver' token should actually be a child token from the truck, but i could not figure this out. Can someone take a look and help me in the right direction?

FlexSim 22.1.2
network nodestruckloading onto the truckchild tokens
truck-warehouse-simulation.fsm (64.5 KiB)
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1 Answer

Steven Hamoen avatar image
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Steven Hamoen answered Jason Lightfoot edited

@Douwe Jd

Some general remarks, if you see exceptions appear always try to solve those first before you continue because they might the reason why something is not working.

In your model I removed one of the truck travels to NN2 because if you give the end destination it will simply go there.

Then on the event driven source where you make the truck driver I put the truck on a label to know what truck to walk to and what truck to drive. I removed the list because that is not necessary here if you have always a pointer to the truck.

Then because the truck is already connected to the network (you can see the red line), don't move it from the queue into the node but simply into the model and check the box to preserve the global position

TruckLoading.fsm


truckloading.fsm (61.9 KiB)
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Douwe Jd avatar image Douwe Jd commented ·
Thank you Steven! So in this case is the Driver always linked to a specific Truck? This confuses me because the trucks and drivers are all called 'Truck1' and 'Man1'. Is there a way to give them matching numbers?

Also regarding the list, I added this because later on I intend to try out different dispatching rules to call forward certain trucks first if the yard becomes congested. In this context, do you recommend to still keep the list?

Thanks for your reply

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Jeanette F avatar image Jeanette F ♦♦ Douwe Jd commented ·

Hello @Douwe Jd,

Yes they are linked in a way.

You can set the name of the man using the custom code activity.

1655927815229.png



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Douwe Jd avatar image Douwe Jd commented ·

Sorry to bother you again, but for some reason i am not able to figure out how to get the truck loaded with the cargo flow items that i created. I have tried for a couple of hours to load them with a 'transporter', 'combiner' and 'operator', but i seem to mess up the properties or connections. Can you help me out with this?

truckloadingprocess.fsm

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truckloadingprocess.fsm (72.9 KiB)
Jeanette F avatar image Jeanette F ♦♦ Douwe Jd commented ·

For starters,

You needed to push the boxes to the list not the token.


1655932037591.png

I used the pull from list in your main flow to pull 20 boxes to the Cargo label (I chose 20 because that is what you had ass the limit on your queues). I assign the Truck Loader based on the DockDoor that was acquired. The taskSequence for Loading the truck uses a subflow so the fork lift load one box at a time into the truck. I placed basic fixed resources and connected them to the out gate and the road so the travel tasks for the truck would work.

1655934651845.png

See the model for any details I may have left out.

truckloadingprocess_autosave_1.fsm

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1655934651845.png (63.4 KiB)
truckloadingprocess-autosave-1.fsm (72.8 KiB)
Douwe Jd avatar image Douwe Jd Jeanette F ♦♦ commented ·

Hi Jeanette,

Thank you for your reply! It has been very helpful and my model has developed quite a bit in the mean time. However, I still encounter some problems with setting up the 'push to list' and 'pull from list' in the way I want it to work. I hope perhaps you (or someone else reading this reply?) can help me with this.

First, I will try to explain in detail how I would like it to work. In essence, each truck that arrives in my model is responsible for picking up a predetermined 'Shipment'. This 'Shipment' can either consist of a predetermined quantity of 'LooseCargo' (thus, one or multiple boxes) or a predetermined quantity of 'ULD's' (one or multiple pallets). Thus, upon arrival of each truck in my model, I want its corresponding Shipment to spawn in my main warehouse (this I managed). Since I want each truck to load its complete shipment, I would like the list to work at 'Shipment' level, rather than at individual boxes or pallets. Thus, complete shipments have to be pushed to the list upon arrival of Trucks in the simulation, and pulled from the list right before the Driver is assigned a DockDoor for this complete shipment. Ideally, I would also like DockDoor1 to be only dedicated to loading all the ULD's (pallets), and use all the other doors for the looseCargo shipments. After the Driver pulls its shipment from the list, and is assigned a dockdoor to load this complete shipment, the truck travels to this door, and the truckloader should pick up all the items that are included in the shipment from the main warehouse and load this onto the truck.

Currently, some of the Truckloaders also have to travel really far from the main warehouse to their dockdoor to pick up the cargo related to a shipment, so it would be even better if a complete Shipment for a truck assigned to a specific door automatically arrives at its corresponding staginglane, so the Truckloader only has to travel back and forth to that.


So basically the main issue is with having the list work at shipment level rather than individual flow item level. And that this whole shipment is moved to the stagingLane of a Dockdoor once it becomes clear which truck is assigned to that door. I hope what i am trying to explain makes sense. I apologize for the amount of text and the continuous questions, but I hope you can help me proceed! Thanks again

model_list_problems.fsm

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