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  #1  
Old 01-06-2009
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Default How to use virtual path without overtaking of taskexecuters? Support_DoNotOvertake_TD

The following assignment needs to be solved:
Taskexecuter (operators) travel on a network and are not able to overtake each other.
The operators pick items from a rack and bring them to a sink.
At the end virtual path should be used for the path at the rack. Than if an operator picks from e.g. Bay 3 the other operators should wait at the network node for Bay 2.

I uploaded a small model which has the different scenarios to follow what I was trying to do.
Here is the link to the model (Support_DoNotOvertake_TD) in the support section:
http://www.flexsim.com/community/for...do=file&id=182

Scenario_01
Result: No overtaking so it seems to work, beside that no virtual path is used.

Scenario_02
Virtual Path for the rack.
Result: Orange operator overtakes yellow operator.

Scenario_03
Include some more network nodes which are Virtual Path.
Result: First look it seemed to work, but it is not because the operators go back to the second network node (virtual path).
I tried to make connections from the rack to every network node, but it was the same result as in Scenario_03.

Scenario_04
Include more racks and the connections. Change the logic that it is send to the right rack and always to the Bay 1.
Result: No overtaking in the virtual path section, but the orange operator is overtaking when he gets to the rack, because his target is behind the yellow operator.

Scenario_05
Set the operators to do not travel offsets and block space on networks.
Result: No overtaking, but the operators don’t do travel offset. To model a time for the travel offset could be done by give them a load and/or unload time.

Scenario_06
Include a control for the network node edges to prevent overtaking.
Result: No overtaking so it seems to work.

Has anyone a better idea how to solve it?
Because I do not like that I need so many racks, network nodes, connections and to control node edges.
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Old 01-07-2009
Anthony Timmiss Anthony Timmiss is offline
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Default Traffic Control

Tom

I tried using a Traffic control object on Scenario 2 between the 2 nodes of the virtual path and it appeared to solve the problem. It holds the second operator at the first virtual network node until the first operator has re-joined at the second virtual network node.

Out of interest, why would one operator be walking faster than the other?

Anthony
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  #3  
Old 01-07-2009
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Default

Anthony,

First of all thanks for having a look into my model, I really appreciate this.

I did not tested the Traffic Control (never used it so far) as you did, but if it works like you say (I believe you), than it helps to control the number of travelers between virtual nodes.

But then still a lot of network nodes are needed and also a traffic control for each virtual path between the nodes to control the number of travelers (only one at a time).
Keep in mind that the operators can not pass each other if another operator is at the rack.

So I guess that Scenario 7 could be similar to Scenario 6 beside controlling the network nodes not by code (Scenario 6) but with Traffic Controls.
This is at least closer to the Flexsim Standard, but more objects and connections are needed. But I still like the idea. Thanks.

Out of interest:
I made one operator walk faster to have different situations. You are right, this not really make sense. In the system it is more that if one operator is picking at a rack another one can not pass and should wait. This situation only occurs if the load time is different, depending e.g. on the item or if the operator picks several items from a pallet directly from the rack.
You are right, I did not give you all information, because I wanted do simplify the model to focus on the issue itself.
If the spacing on the network nodes would work for virtual nodes and travel offset, that would be the easiest solution, I guess.

Anyway, thanks again for your time and effort.

Maybe someone else has another good idea?
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