How to apply Force using curve?

TheConvolutedMind
TheConvolutedMind Altair Community Member
edited January 2023 in Community Q&A

I have a .csv file with time dependent force (time vs force column). I imported that file and generated a curve in motionview.

Now, I want to use that curve to apply force in specific direction. How can I achieve that? What should I kept as an independent variable?

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  • Sonu Manjhi_20605
    Sonu Manjhi_20605
    Altair Employee
    edited January 2023 Answer ✓

    Hi Aditya,

    You should use `time` as independent variable in Force component assuming 'time' is a column in csv file.

    image

    Please make sure that you use back quotes in time variable name otherwise you will see error.

    image

    image source: https://www.computerhope.com/jargon/b/backquot.htm

     

    Regards,
    Sonu

  • TheConvolutedMind
    TheConvolutedMind Altair Community Member
    edited January 2023
    Sonu Manjhi_20605 said:

    Hi Aditya,

    You should use `time` as independent variable in Force component assuming 'time' is a column in csv file.

    image

    Please make sure that you use back quotes in time variable name otherwise you will see error.

    image

    image source: https://www.computerhope.com/jargon/b/backquot.htm

     

    Regards,
    Sonu

    Thank you Sonu Ji. Learning is easier when there are guys like you around.

  • VKR
    VKR Altair Community Member

    Hello, I have very similar problem. I have a time-force defined curve from .csv.

    But the model gives me following error: Error evaluating Force 1-x_math under Model.

    My columns are named time and force. What do you think might be the problem? I also have a second question - if I define the Force by curve that starts from 0 to 1 on time scale but I want to activate the force by a sensor let's say 20 seconds into the simulation, would that work?

    Thank you very much!

  • GTT Adam
    GTT Adam
    Altair Employee

    Hi @VKR,

    For your first question, you have likely not change the X input to be the FILE type and it is still set to MATH:

    image.png

    For your second question, you can activate an entity using a Template. Simply run the simulation for 20 seconds, activate the force, then run for another 10 seconds using the following:

    image.png

    In this example, the force would be sharply applied when activated. A recommendation would be to smoothly engage this force if you are finding it is causing instability in the simulation.

    Additionally, you could avoid the use of a Template and instead STEP the force on at 20 seconds using the following expression:

    STEP(TIME,20,0,20.1,AKISPL(TIME,0,{crv_0.idstring}))

    Here, the interpolated value from the curve is saturated by the STEP function to be 0 until 20 seconds. Then, it is slowly ramped up to the intended value over a 0.1 second interval. This would more smoothly engage this delayed force and make for a more stable solution.

    Hope this helps!

    Adam Reid

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