How to wait in front of an intersection in a narrow passage

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Nanae H2 asked Jun 22, '22 Jeanette F commented Jul 6, '22

How to wait in front of an intersection in a narrow passage

Hi, I'm looking for a way to wait before the intersection.

In reality,

there are nallow and wide way, and workers wait in front of the intersection.

in this model,

I found the way limit transporter's with travel network and traffic control [ mutual exclusion ] mode.

but it seems some problem.

- When one transporter runs in a narrow passage (center), the other waits in front of the intersection.

- if they go in the same direction, transportera track other transporters.

In my model, it collides at an intersectionit.

I guess it should be use [untime traffic mode], but it seems compricate in the case near other intersection.

Is there more better way to apporopriate near real movement?.

or should I use other tool?

thank you for your kindly help.

sample.fsm

Software Version:

FlexSim 21.0.10

a star navigation traffic control travel networks

sample.jpg (69.6 KiB)

sample.fsm (46.9 KiB)

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

Ben Wilson ♦♦ commented · Jun 22, 2022 at 11:24 PM

@Felix Möhlmann is this at all similar to the model you presented a while back?

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Jeanette F ♦♦ commented · Jul 06, 2022 at 05:34 PM

Hi @Nanae H2, was Felix Möhlmann'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 · 2022-06-23T12:26:52Z

Felix Möhlmann answered Jun 23, '22 Jason Lightfoot edited Jul 1, '22

(Felix's answer was in response to Ben Wilson's comment: "Felix Möhlmann is this at all similar to the model you presented a while back? "

I assume you are referring to the 'AutoStore'-inspired model?

It was build to handle movement across a mostly open grid. The general principle could be applied to this problem in theory:

The model implements a custom version of the A* path finding algorithm. The difference to the current implementation in FlexSim is that every traveler always tries to 'allocate' the path as far ahead as possible. Each cell allocated in that way gets a time stamp of when the traveler will free it up again. This information is then used when other travelers try to allocate the cell. If the timeframes in which the travelers are at the cell question overlap, the second traveler is prevented from allocating the cell and has to wait at a previous eligible cell (without any other allocations).

This still leaves the problem of idle travelers blocking cells on the network. The test model only has rudimentary logic to try and fix this.

A similar logic could probably be build based on the travel network. It depends on whether the complete travel path can be determined at the start of the travel. I believe this might require data from the 'distanceTable' and 'nextOutPortTable' entires on nodemembers nodes in the NetworkNavigator. (I know about 'getsdtvalue()', but it doesn't work here, because those entries are not single values (?))

The traffic control in the model is missing one network, which is why the collision happens. Otherwise it does work to prevent collisions, though I do understand that it works to harsh at time.

Attached is also a version of the model that uses untimed traffic modes to allow both forklifts to travel in the same direction at once.

sample(1).fsm

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1655986978489.png (14.3 KiB)

sample1.fsm (49.3 KiB)

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

Nanae H2 commented · Jun 24, 2022 at 09:41 AM

thank you for your reply.

this is other situation, not of 'AutoStore'.

but,the detail is great help for understanding A star navigater background.

thank you very mutch.

and, thank you for your answer.

as you mention, using travel network seems compricate this situation

Is it possible make limit to one traveler could enter the pass from rule at barrier conditions?

it seems easy understanding, but I guess this way trade-off that other transporter following the same direction.

or...

If it do the same thing with the A-Star function,

should I use the travel network node suggestion from here?

thank you in advance.

sample_2.fsm

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sample2.jpg (85.2 KiB)

1656063185084.png (78.3 KiB)

Felix Möhlmann Nanae H2 commented · Jun 24, 2022 at 12:16 PM

The idea of using the dividers doesn't seem very feasible to me. Mostly because I don't think there is any event you could use to determine when a forklift enters the area between the dividers. This would be needed to then change the rule/conditions on the dividers and possibly recalculate the path of other travelers or stop them.

Network nodes with a traffic control (your original idea) offers the same functionality much more easily.

The method of using the network nodes as waypoints is more or less what I tried to describe in my previous comment. In the post you linked to, it is relatively easy, since, apart from the processor- and sink-sidings, the agvs travel in a one-way loop.

In your case you would have to extend the logic:
- You need a list of waypoints for each pair of starting and target location, so they can be acquired (could be in the form of a table, where each cell holds an array of the needed waypoint objects).

- The travel path in the narrow corridor might span multiple sections. The traveler needs to acquire all of them before he enters into the narrow corridor. Otherwise a deadlock situation would likely occur sooner or later.

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Nanae H2 Felix Möhlmann commented · Jun 27, 2022 at 02:40 PM

Thank you for your detail always.

I looked for another way, but these could not be understood exactly how to use.

therefore, I agree with your recommendation.

sometimes it has errors as follows,

it seems could not be found From/To on the table, but there are set on the table.

If possible, could you please tell me the cause of this?

sample1.fsm

--- following looks another way hint, but could not work (I will give up) ---

1,

the transporter has trigger ["on A star bridge"] in property also, but it should write the FlexSim script code.

2,

Network node pass could chouse [No Passing] from connection type on property, and it seems to prevent passing each other in the online manual.

but I could not understand exactly how to use it, because they pass each other as a sample model.

https://docs.flexsim.com/en/22.0/Reference/PropertiesPanels/TravelNetworkPanels/NetworkNode/NetworkNode.html

conection type_no passing.fsm

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error.png (6.4 KiB)

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