Different ressults for the same parameters in MotionView and Inspire

Carlos Fondevila
Carlos Fondevila Altair Community Member
in Community Q&A

Hi all,

I'm triying to modeling a simple dinamic mechanical model with Motionsolve and Inspire, and I find different ressults.

Inspire.mp4
MotionView.avi

In Motionview model, the plug jumps and dissappear, and in Inspire, the model runs apparently more correctly.

The parameters of contact are exactly the same, and the rest of the constrains, speed of the motor etc.

What is the reason of this difference? Wich should we take as valid?

Thanks.

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Answers

  • Christopher_Fadanelli
    Christopher_Fadanelli
    Altair Employee

    Hello Carlos,

    When you run the model in both softwares, what are the units used? By default MotionView will use MMKS, in Inspire the units are MKS. Another could be the step size and integrator tolerance.

    Was the model made in both Inspire and MotionView? Or was the model sent from Inspire.

    Best,

    Christopher Fadanelli

  • Carlos Fondevila
    Carlos Fondevila Altair Community Member

    Hi @Christopher_Fadanelli ,

    The units that I use in Inspire are:

    image.png

    In MotionView I can't find the units in the preferences menu, but I supose that are the same because in a contact properties for example, I can see the next units:

    image.png

    The model saw created in a CAD software and export independent to Inspire and Motionview.

    I try to adjuts the Maximum Step size at the same value in Inspire and MotionView, (0,0001sec) and the results are the same.

  • Carlos Fondevila
    Carlos Fondevila Altair Community Member

    Ok, now I solved the problem.

    I haven't clicked this 2 options in the contact options of MotionView:

    image.png

    When I activate this two selectables, the model run correctly. Almost, in the same form that inspire.

    I think that almos the contact simulation are very sensitive to the parameters and options that you use, I don't know if the complexity is excessive in this way, when you want to do quick mechanical simulations.

    It takes a long time to adjust correctly all the parameters, and you are not sure if the simulation that you are runing is reallistic, because small variations in parameters can lead to big phisical variations in your model, as I'm seeing.

  • Orestis_YB
    Orestis_YB
    Altair Employee

    Hello @Carlos Fondevila,

    in MotionView units can be seen in model browser under Units data set. The default are the MMKS so the same that you are using in Inspire as you showed.

    image.png
    image.png

    First of all, as @Christopher_Fadanelli mentioned already, are these two different models (one created in Inspire and the other in MotionView) or you exported the Inspire model to MotionView?

    In the MotionView video I see that the cyan rod at some point fully penetrates the gray cylinder. Is there a contact defined between this two graphics?
    You can double check the contacts defined between two bodies by checking the highlight contact side in the contact entity editor. Both surfaces should be red. If not then double click on graphics and select the material inside option to revert the orientation of the surface.

    image.png
    image.png

    Best regards,
    Orestes

  • Christopher_Fadanelli
    Christopher_Fadanelli
    Altair Employee

    Hi @Carlos Fondevila ,

    Thank you for the information. Regarding the units for MotionView, there is a dataset called Solver Units. There you will be able to update the units (if needed).

    An important tip. This should be done the first thing when you start a new model. If the length was updated from millimeter to meter. All entities will not convert their values. If a point was at (1,1,1) mm. It will now be assumed to be (1,1,1) meter.

    Regarding the model, the mesh can play a factor as well. I am adding a link : https://help.altair.com/hwsolvers/ms/topics/solvers/ms/best_practices_for_modeling_3d_contacts_ms.htm.

    Please go over this to ensure the mesh is adequate. In addition we do have some values that can be used for material based contact. Please observe them here:

    https://help.altair.com/hwsolvers/ms/topics/solvers/ms/xml-format_57.htm?zoom_highlight=Contact

    Hope this helps!

    Best,

    Christopher Fadanelli

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