Question on the utilization of AGV elevators

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Glenson G asked Nov 6, '22 Glenson G commented Nov 8, '22

Question on the utilization of AGV elevators

I used the state bar to observe the utilization of the elevators. I observed that when there is 16 AGVs, the utilization of the elevators at Core 3 (top right) is better than when there are more AGVs (i.e. 22, 20 or 18).

16 AGVs -
Lift A - 77.14%, Lift B - 71.41%, Lift C - 71.20%
compared to
22 AGVs -
Lift A -71.81%, Lift B - 67.85%, Lift C - 69.58%

Is it a correct phenomenon, or is there something wrong with my model/chart?

Also, in the chart, there is also a percentage for "Waiting". Is it a parameter that can be adjusted like the loading/unloading of AGVs or is it a fixed parameter?

Thank you!

liftusage_221106.fsm

Software Version:

FlexSim 18.2.3

agv elevator

liftusage-221106.fsm (1.2 MiB)

Answer 1 · 2022-11-07T07:41:09Z

Felix Möhlmann answered Nov 7, '22 Glenson G commented Nov 8, '22

When I run your model I am getting errors because you are trying to read from rows in the Origin Table that do not exist. You should probably fix this first before running experiments.

The "waiting" state is set in the "Open/Close Door Delay" activities in the elevator flow.

1667806791078.png (4.3 KiB)

1667806865728.png (8.7 KiB)

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Glenson G commented · Nov 07, 2022 at 07:49 AM

Hi @Felix Möhlmann ,

I have fixed that error and have attached model here: liftusage-221106.fsm.

Still, is the phenomenon of the utilization of the lifts correct?

Got it for the "waiting" state. Thank you!

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liftusage-221106.fsm (1.1 MiB)

Felix Möhlmann Glenson G commented · Nov 07, 2022 at 08:34 AM

The error still happens. The maximum row value used when creating the tasks is 57. Currently the Origin Table only has 54 rows.

I would say the utilization values are correct. With more AGVs you more often have the case that once an elevator arrives at the ground floor another AGV will enter right away and be transported up, thus moving efficiently. With fewer AGVs, the same elevator might first travel back up empty to move another AGV down, before the next AGV arrives at the ground floor, increasing the overall travel distance and thus utilization.

As you can see below, the loaded travel distance and the loading/unloading times stay very similar, mostly just shift between the three elevators. While the travel empty duration increases, especially for lift A.

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1667810046763.png (6.6 KiB)

Glenson G Felix Möhlmann commented · Nov 07, 2022 at 01:38 PM

Hi @Felix Möhlmann , just to check with you. How did you find the maximum row value used when creating the tasks to be 57?

I understood your reply for the utilization values. Thank you very much!

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