Kinematic parameter analysis failed

Main Forum
1

Hi,

I am doing a kinematics analysis based on C3D motion capture data.
The human model consists of head, thorax, right arm, and pelvis.

For the last my analysis, the motion capture data have markers only on right arm and thorax. And I could get a quiet satisfying result.

This time, I used markers on head additionally and did same operation.
However, I saw a message as following when I was on the motion and optimization analysis process.

  1. Calculating a new search direction (Operation: Main.Studies.KinematicStudyForParameterIdentification.Kinematics):
    Kinematic parameter analysis failed : there are 14 design variables but only 13 independent associated optimality conditions

It did not stopped by any errors, and the analysis result text files were created successfully. But I don’t think that the kinematic analysis result is reliable with those messages.

In my script, additional driver of 3 dof for pelvis was integrated in order to compensate missing dofs due to absence of pelvic markers. And the pelvis is located on a proper position by entering its coordinate manually.

Thanks.

2

Hi,

Clearly from the error message you have too much design variables, on too much.

I think it comes from the trunk. You optimize the trunk height but because STRN and C7 marker are also optimized on Y direction the height may not be properly defined by the markers. Try to fix the STRN marker location to solve it.

Best regards, Sylvain.

3

Hi, Sylvain,

I didn’t realize that those optimization options affects on the kinematic constraints.
I found that the pelvis was dangling because it has no marker on it but was set to be optimized.
Thank you. :slight_smile: