Gradual failures

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arn-k asked Jul 03 2023 at 8:19 PM Jason Lightfoot edited Sep 27 2023 at 10:20 AM

Gradual failures

Hello
In my simulation, I have a processor with one type of failure but it can happen either abruptly or gradually (it is a 50-50 percent probability). The same case can be for the machine's recovery (it can go back to initial state instantly or it takes some time to restore the performance level). I was wondering if there is any option I can have these settings? Thank you

Software Version:

FlexSim 23.0.1

breakdown failures fail repair

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Answer 1 · 2023-07-03T20:57:02Z

Natalie White answered Jul 03 2023 at 8:57 PM Jason Lightfoot edited Sep 27 2023 at 10:20 AM

Hi @arn-k,

I am not sure whether this is possible in MTBF/MTTR Properties. However, you can do this by using process flow. I am attaching a simple example model that uses decide activities to determine if there will be an immediate or gradual failure.

This example is simplified. It models a gradual failure or repair by increasing the process time for a period of time before stopping or resuming the processor. If this is too simplified, you could change the process flow to make the breakdown and repair more truly "gradual." If you have additional questions about this, please attach your model so we can better assist you.

Hope this helps!

gradualfailure.fsm

1688417643499.png (67.6 KiB)

gradualfailure.fsm (35.3 KiB)

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arn-k commented · Sep 26 2023 at 6:28 PM

Dear @Natalie White ,

hello again. I had a question about your reply after coming back to it. I am changed my model a bit. I added something called Time To Detect (TTD). In this scenario, faults/failures happen following a distribution, but it takes a while to detect them, hence TTD is introduced. During the TTD time frame, just as you mentioned, time to process would be lengthened. after detection, the machine would be stopped and repair would start.
Now my question is how can I add this TTD to my model while also using MTBF/MTTR Properties for failure distribution and machine repair. Can I add it without process flow? If not, how can I just add the TTD logic to process flow? Thank you again for your help.

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Jason Lightfoot ♦♦ arn-k commented · Sep 27 2023 at 10:19 AM

I believe this has already been answered in your other post. Please refrain from asking the same question in multiple places.

We encourage students to try to implement their own solutions and will provide guidance where they have issues.

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Answer 2 · 2023-07-08T06:28:35Z

Joerg Vogel answered Jul 08 2023 at 6:28 AM Joerg Vogel commented Jul 08 2023 at 6:32 AM

I think you can have a conditional MTTR. You can set a return value to null or any other positiv value upon an if-condition of duniform(0,1).
If you want to enlarge later on an already begun MTTR I would send a delayed message which is received a bit short hand before MTTR runs out. Then you can delay involved events of the event list or you activate a stop object resume mechanism to have a surrogate MTTR state.

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