Problems with Scaling

[Markus Kurz]

Dear OpenSim-Community,

Thanks for all of your help so far.

Right now we encounter problems with/during scaling. According to the OpenSim Webinar: Tips and Tricks for Data Collection, Scaling and Inverse Kinematics in OpenSim (https://www.youtube.com/watch?v=ZG7wzvQC6eU). We modelled the foot as a shoe (projected the foot markers on the floor), weighted anatomical landmarks and virtual markers such as the hip, knee, and ankle joint center the most and gave no weight on the tracking markers (because they can be moved during the marker registration phase anyways). The scaling factors we applied using Kainz et al. 2017. What we encouter is the following:

Hip.JPG (63.7 KiB) Viewed 504 times

Our model gets a too strong pelvic tilt and we are not sure, why that is the case. We have not fully understand, if some scaling factors have an impact on the static position or how exactly this discrepancy arouses. Furthermore, we have a to strong of an ankle dorsiflexion which you can see in the following:

Foot.JPG (50.01 KiB) Viewed 504 times

Placing the heel marker higher wouldn't not make sense in my opinion, because as you can see in the attached .c3d file (in the zip folder), the generic model marker placement has the same heel/forefoot relation regarding the height. Or am I missing here something.
I further attached the .osim model, the markerfile, and the scale setup file.

Furthermore, i wanted to know if it is plausible to lock joints in the scaling process or what the benefit of that could be.

Thanks a lot for your help and I am looking forward hearing from you.

Kind regards
/Markus

[Patrick Mai]

Hello Opesim Comunity,


These are some very good questions. I'm facing the same problems. Have you found a solution yet?