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Pallet Shifting and AGV Recharge Logic Coordination

Dear Felix Möhlmann,

I hope you're doing well.

First of all, I would like to mention that I am quite new to simulation.
I work in a general administrative role and have no previous experience with simulation software.
Recently, I have started working with it and I'm doing my best to learn, so I kindly ask for your understanding if my questions seem basic or if I misunderstand some concepts.

Queue 5 → Queue 4 → Queue 3 → Queue 2

When Queue 5 becomes empty, the pallets should shift forward one step like this:

  • Q4 → Q5

  • Q3 → Q4

  • Q2 → Q3

This shifting must occur even if all queues are not fully occupied — as long as Queue 5 becomes empty, the system should prioritize refilling Queue 5 first, based on the current upstream pallet availability.

Each pallet cannot pass another due to spatial blocking — interference must be strictly avoided.

Importantly, Queue 5 serves both as a loading zone for pallets and as the pickup location where another AGV retrieves them.

I have constructed the system using the logic you kindly shared.

However, when a token with Position 5 is repeatedly pushed and pulled, it keeps being re-sorted and selected again due to the list query, which prevents the shifting logic from working as intended.

When the pallet creation interval is short, the AGV's transport behavior becomes unstable and does not function as intended.


Additional AGV Recharge Logic

In addition, I would like to ask for your advice regarding AGV recharge control:

  • When an AGV becomes idle, it should go to the charging location and begin recharging.

  • However, recharging must be interrupted immediately and the AGV should resume work if either of the following happens:

    • A new pallet arrives at Queue 1

    • Queue 5 becomes empty

  • Currently I am using resetCP to manage charging control points, but if there is a more appropriate way to assign and manage the AGV’s charging control point, I would very much appreciate your suggestion.


Token Multiplication Issue

1744951010338.png

Additionally, I would like to ask why, when I add multiple AGVs to the "Attached Objects (Instances)" field of the AGV template, tokens appear to be generated multiple times — once for each AGV.
I’m curious to understand the reason behind this behavior.


Thank you very much for your time and support.


Queue Test_3.fsm

FlexSim 25.0.4
agvqueue
1744951010338.png (8.1 KiB)
queue-test-3.fsm (62.6 KiB)
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Felix Möhlmann avatar image
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Felix Möhlmann answered Zenix commented

The "Queue-Tokens" should of course wait until the Item has exited again before they pull the next one. I missed that in my previous example because it didn't come up due to the longer creation interval.

Uncheck the "Wait until Complete" box in the Dispatch TS activity to allow the AGV to be preempted at any point while travelling to the charging point. Using the reset CP for this is fine, as there is only one point anyway. If you have multiple points and multiple AGVs needed to access them, I would use a list to manage availability.

queue-test-2.fsm

queue-test-3.fsm

More tokens are created when you link another AGV because that is how Object Process Flows work. They run an instance of the flow for each linked object.

https://docs.flexsim.com/en/25.0/ModelLogic/ProcessFlowBasics/TypesOfProcessFlows/TypesOfProcessFlows.html


queue-test-2.fsm (55.4 KiB)
queue-test-3.fsm (70.5 KiB)
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Zenix avatar image Zenix commented ·

The queue-related issue has been resolved—thank you very much.

I’ll take some time to study more about handling multiple AGVs and charging points, and if I have further questions, I’ll post again in the future.

I truly appreciate your help!

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Zenix answered

@Felix Möhlmann I'd love to hear your opinion on this when you get a chance

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