Preferred Path Weight Questions

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question

Shinya O asked Apr 28, '23 Jeanette F commented May 16, '23

Preferred Path Weight Questions

Hi,

I'm trying to move the AGV to ControlPoint1 with the A* navigator in the following model, but it doesn't seem to move on the shortest path. I would expect the AGV to behave like when moving to ControlPoint2.

I have a few questions related to this.

Why travel threshold is different between ControlPoint1 and ControlPoint2?
What is a good way to determine the Default Preferred Path Weight? The weight value of 0.4 gives the expected behavior for this model.

Thanks in advance.

This is the picture of the initial state of this model:

This is the picture after moving to CP1:

This is the picture after moving to CP2:

AStar_sample.fsm

Software Version:

FlexSim 22.0.16

astar astar navigator preferred path

init.png (254.5 KiB)

cp1.png (2.0 MiB)

cp2.png (2.0 MiB)

astar-sample.fsm (35.5 KiB)

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5 |100000

Attachments: Up to 12 attachments (including images) can be used with a maximum of 23.8 MiB each and 47.7 MiB total.

Jeanette F ♦♦ commented · May 16, 2023 at 09:38 PM

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

If we haven't heard back from you within 3 business days we'll auto-accept an answer, but you can always unaccept and comment back to reopen your question.

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Answer 1 · 2023-05-08T15:14:19Z

Jordan Johnson answered May 8, '23 Shinya O edited May 11, '23

For your first question, the travel threshold depends on the position of the object relative to the grid nodes and to other barriers:

The algorithm used to generate the thresholds is sensitive to these relative positions.

For your second question, the best way to determine if the weight is correct is to try different weight values until your model behaves correctly. The weight value represents excess weight given to the path. More weight means the path is more likely to be used by travelers. There isn't a more formal method because each customer has unique requirements.

contropointpos.png (46.7 KiB)

· 5

5 |100000

Attachments: Up to 12 attachments (including images) can be used with a maximum of 23.8 MiB each and 47.7 MiB total.

Shinya O commented · May 09, 2023 at 07:08 AM

Thanks for the info. I understood most of it.

However, in this model, setting the Default Preferred Path Weight to 0.4 from 10 yields the path becomes used by travelers.

Can a Default Preferred Path Weight that is too high make the pass less likely to be used by travelers?

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Jordan Johnson ♦♦ Shinya O commented · May 09, 2023 at 05:28 PM

It looks to me like the weight of 10 is somehow an issue. It's no that it's repelling travelers. It's just changing the search algorithm for some reason. If the weight is 10, it doesn't seem to matter where I put the preferred paths. They can be very far away from the travel, and still the AGV goes to the incorrect location. If I changed the weight to 0.4 (I'm wondering if it's less than 1?) or if I deleted the Preferred Paths, the routing looks normal.

I've added this to the dev list. If it is by design, I'll get enough information to explain it. If it's a bug, we'll fix it.

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Jordan Johnson ♦♦ Jordan Johnson ♦♦ commented · May 10, 2023 at 06:25 PM

We reviewed this question as a dev team and determined that the weight for a Preferred Path should be be in the range [0, 1]. This resulted in a couple additions to the dev list:

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