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kl avatar image
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kl asked kl commented

About tutorial TASK 4.2 - AGVS USING PROCESS FLOW

Hi! After I tried this tutorial, I encountered two problems:

  1. I have 4 drop off points, however, all the AGVs will always drop off at DropOff4.
  2. I have no idea why after the AGVs transport all of the items the last AGV will not return to ParkPoint5.

Hope to get some help figure these problems, thanks!!

my file: 4.2.fsm

FlexSim 21.2.4
advanced agvdropoffparking points
42.fsm (155.5 KiB)
5 |100000

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Felix Möhlmann avatar image
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Felix Möhlmann answered kl commented

1. The fact that all AGVs use the same dropoff is normal. The previous AGV has already unloaded when the next arrives at the control point that is connected to the loading dock. So all points are available to the next AGV.

Which point gets chosen is controlled by the query in the activity marked below. There is actually a mistake in the template in this version. The ORDER BY distance clause is supposed to have the token pull the point that is closest to the destination object (by straight line distance). However, the puller is incorrectly set to the token. Since the token does not have a location in the 3d space, the coordinates that are used for the distance calculation are all 0, meaning the control that is closest to the origin point of the model's coordinate system is chosen. The puller should be set to token.destination.

1688538176778.png

If you want all dropoff points to be used, you can remove the ordering by distance alltogether. This would result in a 'Round Robin if Free' type of logic.

2. In your model the deallocation behaviour was changed to "When Center Passes Current Point".

1688538544234.png

This causes a timing issue in the AGV template which assumes that the deallocation happens after the item was loaded. Due to this, the token doesn't get released from the activity marked below when the AGV continues as it should. The first nine tokens eventually get released when the next AGV drives past the pickup point (firing the deallocation event). But the last token will be stuck in the activity indefinitely, since no more AGVs pass the point after the tenth.

1688538805711.png

This means that the content of the Active Items zone stays at one, making the logic think that there is still a pending item and keep the last AGV running.

The quickest fix would be to add a small distance offset (0.01 or even less) to the deallocation behaviour to have the events happen in the 'correct' order.


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kl avatar image kl commented ·
Thanks~~~



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