Pipetting Model: muscle recruitment

Main Forum
1

Hi AnyBody,

I still continue the pipetting model that I posted yesterday. But, this time, it’s a muscle recruitment problem. Therefore, I start a new thread.

The model runs kinematically and also works in calibration to adjust tendon length. But, it fails in inverse dynamic analysis. The error message is KKT matrix singularity. I think it is likely due to improper definition of some muscles. But, I cannot find the problem. Probably someone can help me.
Thanks,

John

2

Hello John,

I had a quick look at your model and I found some things that seem not perfect. Please change

AnyKinEqSimpleDriver RotDrv1={
AnyKinRotational &ref1= .Rot1;
DriverPos={0,0,0};
DriverVel={0,0,0};
Reaction.Type={Off,Off,Off};
};

into

AnyKinEqSimpleDriver RotDrv1={
AnyKinRotational &ref1= .Rot1;
DriverPos={0,0,0};
DriverVel={0,0,0};
Reaction.Type={On,On,On};
};

That will make the model start. I also think that the forces may be applied in the wrong reference frame. Please have a look if F or Flocal should be used.

I hope that helps and you get the model running, it seems very nice and useful!!

3

Amir:

Thank you very much for your help. You pointed out exactly what caused problem. The model runs now, after including the suggested modification.

John