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2013-02-03 04:54
Submitted by:
Huseyin Celik (hsynclk)
Assigned to:
Ayman Habib (aymanh)
Matrix is singular error when using IK tool

Detailed description
I downloaded the full body model files from the ULB_Project, and started to use the version without finger DOFs, UpperLowerBodySimple.osim. I deleted everything under the pelvis segment since my interest is upper body motion. First, I tried to use Scaling tool. The model is scaled, then on the marker placement step I got the following error:

Exception in ID: SimTK Exception thrown at SmallMatrixMixed.h:878:
Error detected by Simbody method lapackInverse(Mat<>): Matrix is singular so can't be inverted (Lapack getrf info=3).
(Required condition 'info==0' was not met.)

That error is an output of OpenSim 3.0. I also tried Scaling tool on OpenSim 2.4. It took a couple hours to solve just a frame of kinematics for marker placement, and the experimental markers were far away from the virtual ones. I also used a version of the model without deleting anything but just adding virtual marker objects, same outcome.

Also, OpenSim 3.0 crashed many times when I tried to make changes on the visualization objects through GUI. Every tool I used was working remarkably slower compared to the other models I used such as Gait2354.

I added all the files that can be used to reproduce the error using Opensim 3.0. My operating system is Windows 7.

Thanks for your help.


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Date: 2013-03-20 19:46
Sender: Huseyin Celik

Hi again:

We did able make scaling and IK with a slightly different
version of the model. Then on the ID step, OpenSim did not
crash, but throw this error message:

Exception in ID: SimTK Exception thrown at

Some other user also reported the exact same error in the

Thanks a lot,


Date: 2013-02-06 21:45
Sender: Ayman Habib

Hi Huseyin,

I can run scaling in 3.0.1 with your files and the model ended up in funny configuration but there was no crash. could be an issue with the trc file format or finding initial conditions for IK. I'd use a very small measurement set and see how it works then add back the remaining measurements.


Date: 2013-02-03 08:55
Sender: Poramet Hemarachatanon

problems on me too. Errors at SimTK Exception thrown at SmallMatrixMixed.h:878

Thanks for your help.


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