AGV Simulation Issue: variables/callbackNode

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Glenson G asked Oct 9, '22 Glenson G commented Oct 21, '22

AGV Simulation Issue: variables/callbackNode

Hi there,

I have encountered an exception "Exception caught in evaluation of /Tools/ProcessFlow/TaskExecuter/Travel>variables/callbackNode" and my AGVs don't even pick up items anymore. Would appreciate any advice or guidance in resolving this issue. Thank you very much!

liftusage-2.fsm

Software Version:

FlexSim 18.2.3

agv agvnetwork agvelevator

liftusage-2.fsm (1.0 MiB)

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Glenson G commented · Oct 09, 2022 at 07:17 AM

I have managed to make the model work after unchecking "Wait Until Complete" of Travel 1 in the task executer process flow though I don't understand exactly why. Appreciate any explanation on that, thank you!

Also, only the top left elevators are not working. The AGVs seem to travel on the paths instead of the elevators. The whole model stops working after awhile as well. Appreciate any advice on that, thank you very much!

liftusage-2.fsm

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liftusage-2.fsm (1.1 MiB)

Answer 1 · 2022-10-10T06:19:09Z

Felix Möhlmann answered Oct 10, '22 Glenson G commented Oct 21, '22

There is a basic TE object called TaskExecuter2 positioned at the origin of the model coordinate system. While it is connected to the TaskExecuter process flow it is not connected to the AGV network which breaks some of the logic within the flow, leading to the errors that appear when starting the model.

Only the "Core1Lobby" evelators are connected to the elevator process flow which is why the other ones aren't used.

You should also check the entry trigger of the "Ward" queues, since the also cause errors (sending messages to 'centerObjects', despite the queues not having any centerport connections).

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Glenson G commented · Oct 10, 2022 at 07:23 AM

Hi @Felix Möhlmann , thank you for your reply.
I have deleted the basic TE object and added all the elevators into the process flow objects.

However, I still experience the following issues and I would really appreciate your advice and guidance:

1. The top left elevators are still not in used (They are travelling by the AGV paths instead)
2. At about 500s, AGVs arrive at the source to pick up items but left without loading items.
3. At about 600s, AGVs wait at ControlPoint478 and not enter to the pick up CPs to load items.
4. After unloading the items at the level, the AGVs stack up at ControlPoint291 (the elevator floor CP before leaving for the source together)
5. At about 6500s, there would be an task error occurring.

I have checked that all the "Ward" queues have the correct central ports as well.

Thank you very much for your time and patience!

liftusage-2.fsm

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liftusage-2.fsm (1.0 MiB)

Felix Möhlmann Glenson G commented · Oct 10, 2022 at 09:18 AM

1. The dispatcher is missing the connections to the elevators.

2./3. This is a timing issue. When both the travel to CP478 and the travel sequence to the loadCP are started in the same instant, the first travel is not correctly aborted because it was not "active" yet. This means the AGV will first travel to the loadCP and then continue to travel back to CP478. Placing a 0s delay ("Breathe") inbetween these should fix this.

4. Also connected to 2. and 3. The AGV that does a loop to return to CP478 has to wait because the control point after the elevators is allocated by an AGV returning from a different floor, causing the pil up.

5. Row 49 in the Destination table does not point to the actual queue but to the next cell in the table. You probably used the sampling tool on the next row to copy the value. Since the table cell is a node itself, the sampler picked that node and not the value in it. The value looks the same since only the lowest level of the path is displayed.

Use Copy/Paste instead to copy the pointer value from one row to another.

liftusage-2(1).fsm

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liftusage-21.fsm (1.0 MiB)

Glenson G Felix Möhlmann commented · Oct 10, 2022 at 03:13 PM

Thank you very much once again @Felix Möhlmann ! Your explanation is clear and I really appreciate it.

I have the following questions:
1. Is it possible to obtain the statistics for how many AGVs are queuing at the control point waiting for any elevators to be free?
2. Similar to 1, is it possible to have a "queue" for AGVs to show how many AGVs are queuing?
3. Is it possible to modify the model in a way where the elevators will wait for the AGVs to unload at the level, go back into the lift, and go back down to the basement?

Thank you very much!

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