AGV Process Flow activities function (List, Pull&Push)

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Sohee P asked Mar 20, '23 Felix Möhlmann commented Mar 22, '23

AGV Process Flow activities function (List, Pull&Push)

(I use FlexSim 20.2.3 version)

Now, I'm studing AGV Process Flow, But I don't know the function of a few activities.

① In Main Control Loop Flow Chart, I don't know why That activities put the token back in the NextLookForWork list as soon as they pull token from the next list of views.

② In ② activity, Why does the token move to the 'No' connection even though there is a control point (Parking Spot) connected to the park point?

③ In LookForWork Forwarding Sub Flow, What is Local Partitioned Load List for? In my AGV Process Flow Example, I didn't connect of LookForWork connection.

④ In Parking Flow Chart, The token doesn't have label 'requestedItems'. Is that condition wrong?

I'm sorry for having a bad English. Also I don't have much time for studying AGV Process Flow, then My question quality may not be good. But If you let me know about that, I appreciate for it.

I hope you have a nice day. Thank you.

Software Version:

FlexSim 20.2.3

agv process flow process flow lists

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Answer 1 · 2023-03-20T09:06:40Z

Felix Möhlmann answered Mar 20, '23 Felix Möhlmann commented Mar 22, '23

1. The "NextLookForWork" list is used as a lookup to know where the AGV should travel next. It is partitioned by control points. The partition for each control point contains all other points that are connected as a Next Work Point from that control point.

Because the list is essentially just a lookup table, you want all entries to be available at all times. Which is why the pulled point is pushed back immediately. This could also be done by using the "Leave Entries on List" option in the Pull activity. This option is, I believe, chosen to 'cycle' the control points on the list. If there are more than one connected control points the one that got pulled will be readded to the last in the last position, so that another point will be pulled by the next token. This makes it so that the AGVs act in "Round Robin" fashion when there are more than one connections.

2. Another AGV might already have pulled the park point and is currently travelling there. Also, because there is no activity that causes any sort of delay if the token moves downwards, it can look like it was send to the 'No' path when it actually moved all the to the bottom and then back up. But because this happens in one instant it might not be visible even when stepping through the model one event at a time.

3. Similar to the "NextLookForWork" list, the list is partitioned by control points. Each partition contains the items ('work') that are available at that control point. If there are no LookForWork connections, the item will be pushed to the partition of the control point that is connected to its current location. If there are such connections, the item will instead be pushed to all partitions of the connected points, but not the one it is actually at. This makes it so the work can be 'seen' from different points without actually having to pass by the location of the item.

4. I believe you are correct. It should use the "requestedAGVs" label that gets set in the activity prior to the Decide. Later versions, where the AGV flow was split into multiple variants with different complexity, this label is not present anymore and only the first condition is used.

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Sohee P commented · Mar 22, 2023 at 07:48 AM

I appreciate for your answer. I have a one more question.

In AGV Process Flow, AGVWork list is automatically created. It seems to me that it is Item list, but It look like task list. I don't know what function is exactly. Can I think about AGVWork list as Task List?

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Felix Möhlmann Sohee P commented · Mar 22, 2023 at 07:58 AM

It is an item list, but you can think of each item as representing a task sequence (pick up item at current location and transport to destination). The destination is written to a label on the item when you push it to the list in the Use Transport field of a fixed resource.

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