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Thread: How to model car launching

  1. #1
    I'm looking for insight on how to properly model car launching via lap simulation.

    Can anyone help me get started on how to simulate the vehicle that is starting from 0 mph.

    So far my program takes into affect the vehicle torque, shifting, rpm curve, tire size, vehicle weight, etc. I'm just having a difficult time modeling the acceleration from a stop.

    Cheers

  2. #2
    Other things I suggest you add are longitudinal weight transfer and clutch slip.

    Regards, Ian

  3. #3
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    clutch slip being torque multiplication

  4. #4
    I am intending to implement longitudinal weight transfer in the near future, thanks. I just really want to get a general idea of how to model launching so I can get the ball rolling.

    I know when launching we want to rev to a certain RPM and the drop the clutch or whichever strategy works best for everyone...The problem I am facing is how to model this acceleration.

    Thanks guys!

  5. #5
    what program are you using?
    "Good judgement comes from experience. Experience comes from bad judgement."

  6. #6
    Originally posted by thewoundedsoldier:
    what program are you using?
    I'm writing the program and it is in Matlab at the moment.


    I'm probably going to be moving toward C# in the near future(for my sake) but I don't really have the time to rework it at this time. I find C# to be vastly superior, the only problem is future FSAE students at our university wont be able to use/compile it as it is not part of the regular engineering curriculum. Anyways, I digress...

    Have any links to a sensible way to model vehicle launching?

  7. #7
    Originally posted by ffrgtm:
    clutch slip being torque multiplication
    No, that only happens with a torque converter.

    Regards, Ian

  8. #8
    Originally posted by Spetsnazos:
    I know when launching we want to rev to a certain RPM and the drop the clutch or whichever strategy works best for everyone...
    Try holding constant engine revs, slipping the clutch and modulating engine / clutch torque (they are the same) according to available tyre grip.

    That's the essence of the 'launch control' strategies within the commonly used ECUs.

    When the clutch slip reaches zero, assume engagement and allow the engine revs to rise.

    I've built this exact model in Excel. However, I would stick to MATLAB rather than go to C#, or you will have to re-implement all the hundreds of handy MATLAB functions by yourself.

    Regards, Ian

  9. #9
    Originally posted by murpia:
    <BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by ffrgtm:
    clutch slip being torque multiplication
    No, that only happens with a torque converter.

    Regards, Ian </div></BLOCKQUOTE>

    Nah I think what he was saying is to model clutch slipping as torque multiplication, in that a certain percentage of clutch slip implies only a percentage of the maximum torque at that RPM.

  10. #10
    Originally posted by murpia:
    <BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Spetsnazos:
    I know when launching we want to rev to a certain RPM and the drop the clutch or whichever strategy works best for everyone...
    Try holding constant engine revs, slipping the clutch and modulating engine / clutch torque (they are the same) according to available tyre grip.

    That's the essence of the 'launch control' strategies within the commonly used ECUs.

    When the clutch slip reaches zero, assume engagement and allow the engine revs to rise.

    I've built this exact model in Excel. However, I would stick to MATLAB rather than go to C#, or you will have to re-implement all the hundreds of handy MATLAB functions by yourself.

    Regards, Ian </div></BLOCKQUOTE>

    Going to try this and read about it a little more as well. Thanks for the start!

    Cheers

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