Applying Force to a point located in fixed ref frame

Main Forum
1

Hi,
In using AnyForce3D when I choose point of attack of the force a node in fixed ref frame the answer doesn’t change but when I choose the point of attack a node in my segments the model applies external force.
How can I apply a force to a point which is define in fixed ref frame (global system)?
thank you in advance,
Mohammad Hossein Akhavanfar

2

Hi Mohammad,

  AnyForce3D <ObjectName> = 
  {
    //RefFrames = ;
    //Surfaces = ;
    //KinMeasureArr = {..Linear, ..Linear, ..Linear};
    //KinMeasureIndexArr = {0, 1, 2};
    //F = {0.000000000000000, 0.000000000000000, 0.000000000000000};
    //Flocal = {0.000000000000000, 0.000000000000000, 0.000000000000000};
    AnyRefFrame &<Insert name0> = <Insert object reference (or full object definition)>;
  };

As you can see from the template it is possible to provide either global or local values for the force. It sounds like you want to prescribe a global force - so you should be using F to define the force magnitude.

If you force vector is in a ref. frame that is not aligned with the global ref. frame - you could simply recompute it to be in global or local ref. frames by using appropriate rotations (ARel/Axes matrix of relevant objects).

Kind regards,
Pavel

3

hi again,
thank you for your response.
AnyForce3D UpperArmLoad = {

    F = {0, -35.63, 0};
    
    AnyRefNode &POA1 = ..ThoraxSegs.T12.GUpperArm;
    //AnyRefNode &POA2 = ..GlobalRef.GUpperArm; //this point is defined in      AnyFixedRefFrame
    
  };

POA1 & POA2 are two definitions for 1 point in the space. I mean why when I change commented line the force doesn’t apply?
bests

4

Hi Mohammad,

It does not make much sense if you apply a force to a fixed ref. frame, this force will invisibly result in some reaction forces or not even be considered.

However, it should have an effect when you apply it to the parts of the body, for example: GUpperArm

If that is not the case - something else is wrong, but i would need more details to help.

Pavel

5

hi,
I got it. Again thanks a lot for your answer.