Pipetting model

Main Forum
1

Hi AnyBody:
I have an user-developed model simulating the thumb action during pipetting. The model works OK kinematically. But, when I tried to calibrate the model, there was an error message “8 over-constrains”. It seems that each of DOF in the calibration driver caused a conflict of over-constrain. I did only “TendonLengthAdjustment”.
The model is attached. It runs on v3.0. It also works on v5.0, you have to change all “Transparency” to “Opacity”.
Thanks,
John Wu

2

Hi John,

Would you please let us know which version of AMMR(model repository) you have used for this model?

Best regards,
Moonki

3

Hi Moonki,

No repository was used. This is an user-developed model.

Regards, John

4

Hi John,

It will take some time to investigate your model in detail, but let me explain my guess.
Of course this may not be the reason of your problem.

When I loaded your model, I could find these warnings.

WARNING for Main.Cylinder.handle: Non-orthogonal axes were adjusted.
WARNING for Main.ThumbModel.CenterOfPressure1.button: Non-orthogonal axes were adjusted.

When I tried to run ‘InitialConditions’ operation of Calibration, I could see the error due to the over-constrained kinematic situation.

So when I looked the ‘Main.Cylinder.handle’ and ‘Main.ThumbModel.CenterOfPressure1.button’ objects in your model,

  AnyRefNode handle = {
    sRel = {0.09,0.005,0.048};
    //      ARel = RotMat(-90*pi/180, x);
    ARel = {{-1, 0, 0}, {0, 0, 1}, {0, -1, 0}};
    
//    AnyDrawSTL DrwSurf = { 
//      FileName = "handle.STL"; 
//      ScaleXYZ = {1, 1, 1}/700.0;
//      Transparency = 1.0;
//      RGB = {0.80, 0.20, 0.00};
//    };
  };

AnySeg CenterOfPressure1={
  Mass=0;
  Jii={0.0,0.0,0.0};
  AnyRefNode node={
    sRel={0.0,0.0,0};
    AnyDrawNode drw={
    ScaleXYZ={0.01,0.01,0.003}; 
    Transparency = 1;
    RGB={1.0,0,1};};
  };
  AnyRefNode button = {
      sRel = {0.01,0.01,0.075};
//      ARel = RotMat(-90*pi/180, x);
      ARel = {{-1, 0, 0}, {0, 0, 1}, {0, -1, 0}};

      AnyDrawSTL DrwSurf = { 
      FileName = "button.STL"; 
      ScaleXYZ = {1.0, 1.0, 1.0}/1000.0;
      Transparency = 1.0;
      RGB = {0.80, 0.20, 0.00};
    };};
};

The basis vectors that constructs ARel matrix are not orthogonal each other.
I guess that it would be modified like this:

ARel = {{-1, 0, 0}, {0, 0, 1}, {0, 1, 0}};

or

ARel = {{-1, 0, 0}, {0, 0, -1}, {0, -1, 0}};

Please modify these values and check whether this change can be applied to your model.

And if you can’t solve the problem again, please ask again.

Best regards,
Moonki

5

Moonki,

Thanks for the quick response. I have modified the axis. These two warnings have been eliminated. But, the problem of over-constrains in calibration is still there.

Thanks, John

6

Hi John,

If you double-click on the calibration study you will notice that you have 2 sets of drivers for your joints - 0, 1, 2 and 5, 6, 7:
Drivers:
0: Main.ThumbModel.Drivers.CMCMotion (3constr.) Segments(1): Proximal_Phalanx
1: Main.ThumbModel.Drivers.MPMotion (3constr.) Segments(2): Proximal_Phalanx Middle_Phalanx
2: Main.ThumbModel.Drivers.IPMotion (2constr.) Segments(2): Middle_Phalanx Distal_Phalanx

5: Main.CalibrationDrivers.CMCCali (3constr.) Segments(1): Proximal_Phalanx
6: Main.CalibrationDrivers.MPCali (3constr.) Segments(2): Proximal_Phalanx Middle_Phalanx
7: Main.CalibrationDrivers.IPCali (2constr.) Segments(2): Middle_Phalanx Distal_Phalanx

You should exclude 0, 1, 2 in order to run the calibration.

Best regards,
Pavel

7

Pavel:

Thanks. That is exactly what caused over-constains. I have deleted the CalibrationDrivers completely and it works now.

My problem has been resolved.

John