MoCapModel: Squeezed upper body after MotionAndParameterOptimization

Main Forum
1

I use 17 markers for MotionAndParameterOptimization (see 1st pic):
C7 for the upper body and the rest is on the lower body.

After MotionAndParameterOptimization of the MoCapModel the upper body is unnaturally squeezed (see 2nd pic).

What could be the problem here?

2

Hi Fritz,

This is how the optimization scaled the ribcage and the rest of the spine (it turned out to be somehow optimal). I believe these markers are not enough or they are very noisy, which might also lead to this effect. Do you have more markers to control this behaviour? You could also preset size of the trunk and switch optimization off.

Regards,
Pavel

3

I’ve uploaded jpgs (the pngs were scaled down by the upload)

If you have a look at the first pic the position of the marker fits quite well before optimization.

But after optimization the C7 marker is positioned over the head. That doesn’t make sense.

4

I see only 1 time frame here. Do you optimize using a static trial? Does this marker “jump” over time?

Could it also be a definition of the C7 marker that it somehow looks up one of the head markers?

P.

5

Here is an video of the MotionAndParameterOptimization study

https://gigamove.rz.rwth-aachen.de/d/id/qsLLWwEEBqdgzw?11&id=qsLLWwEEBqdgzw

I can send you the model via PN.

6

Hi Fritz,

Yes, i would need to see the model.
But please check first that your virtual and real markers match, check that their trajectories are smooth enough, and that “irrelevant” or uncovered dimensions are not optimized.

Thanks,
Pavel

7

Switching "TrunkHeight" optimization off worked for now.

    // For LowerBody model
    #if UseUpperExtremities == 0
    OptimizeAnthropometricsOnOff OptimizeOnOff (
    PelvisWidthOnOff ="Off", 
    ThighLengthOnOff="On", 
    ShankLengthOnOff="On", 
    FootLengthOnOff="On", 
    HeadHeightOnOff="Off", 
    TrunkHeightOnOff="Off", 
    UpperArmLengthOnOff="Off",
    LowerArmLengthOnOff="Off",
    Model1=MotionAndParameterOptimizationModel, Model2= InverseDynamicModel
    ) ={};

Thank you

PS: With the two additional Acromion markers it was possible to switch the TrunkHeight optimization "On" again.