AGV Loading item before item reaches Load Station

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Claire Krupp asked Jul 22, '21 Claire Krupp commented Jul 28, '21

AGV Loading item before item reaches Load Station

I have pallets in a storage system that need to be brought to a Pick-up Stand, where they will be loaded onto an AGV and taken to the production area. I have set it up so that I start the material handling to bring the pallet out of the storage rack, and at the same time, I acquire the nearest AGV and have it travel to the Pick-up Stand. The AGV is then supposed to wait until the pallet arrives at the Pick-up Stand, but instead it is loading the pallet immediately - effectively teleporting it out of the storage area!

Here is my Load activity:

Why is the AGV ignoring the Station location? (token.PickupLoc is a Queue object and works well in other situations.)

How can I solve this problem? I know I could use a list, but that seems like a lot of work to do something that this menu option should be doing already. (Each token is in a different sub-flow with the same parent, but my AGV sub-flow is used for all AGV moves throughout the plant, so I need something generic that will work in all cases.)

(The model is confidential and too large to post, but I can email to the dev team if needed.)

Thanks!

Software Version:

FlexSim 21.1.4

flexsim 21.1.4 agv load

1626964020511.png (16.0 KiB)

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Jeanette F ♦♦ commented · Jul 27, 2021 at 05:27 PM

Hi @Claire Krupp, was Eric M's answer helpful? If so, please click the red "Accept" button at the bottom of their answer. Or if you still have questions, add a comment and we'll continue the conversation.

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Answer 1 · 2021-07-22T21:50:37Z

Eric M answered Jul 22, '21 Claire Krupp commented Jul 28, '21

Hi @Claire Krupp, my understanding of the "station" in the load activity is that the operator will load the item from there regardless of whether the item is in that location or not. That's what I understand from this description in the manual. If the AGV always arrives before the pallet, a wait for event activity would work fine. If the AGV is sometimes at the location before and sometimes after, you could add a decide activity that determines whether to wait for the item to enter or not.

I've attached a simple model that uses a decide activity and should generalize to any items / locations on your label. Changing the delay time in the left will show what happens if the operator arrives before or after the item.

load station.fsm

load-station.fsm (38.3 KiB)

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Claire Krupp commented · Jul 28, 2021 at 02:21 PM

Thanks @Eric M , I will take a look at your answers, although my sub-flow is used by all AGV travel in the model, and this is the only case where I would need to put in a "wait for event" activity.

I decided for now that the time gained by having parallel moves is minimal, so I returned to doing the internal MH move first, and then calling the AGV when the pallet is ready at the PD stand.

I am disappointed with this logic behavior though. In other software (WITNESS) if you load from a location, and if the item is not there, the pulling object will automatically wait until the item arrives, so that you can be assured the behavior and timings are correct.

What is the purpose of the "Station" option, if it is not to determine where the item will be loaded from?

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