inverse dynamic with open cap data and external force data

[Daniel Sitte]

Hello everyone,
I have recorded a volleyball spike jump with OpenCap. The proband also jumped off on a force plate.
Now I transformed the force data into the coordinate system of Opencap and wrote a .mot file with the external force data.
When the proband does not touch the force plate (during the run-up and during the flight phase) I set the force to 0.
Now, when I run an inverse dynamic on OpenSim using the .mot file from OpenCap (kinematics data) and my .mot file (external forces), I don't get any useful results. (Looks like an earthquake signal or something).
The external force data is correct, when I display it on OpenSim while the motion simulation everything fits.

Where could be the error?

inverse dynamics results (each column is plot against the time)
https://drive.google.com/file/d/1XcxtZ_ ... p=drivesdk

[Feras Kiki]

Hi,
I didn't use OpenCap before, but I used another camera based pose estimation and inverse kinematics and it works fine for me. I don't know what these graphs represent, but I am assuming they represent markers data. I suggest you to do filtering as a first step, and to do simpler motion so you can diagnose the data much better. If your motion is fine, doing inverse dynamics is not going to be very hard.

Can you show what markers are you using (on the body), what do these graphs represent?

[Neha Sahu]

hi, i am also doing the same using opencap for marker data and using single force plate for ground reaction force. but i am unable to fix the force on opensim model . for cop appear on the ground . can anyone help to to resolve this problem. i have followed all the step as mention for ID . i have edited external force xml file. my external force mot file have position vector for copx and copz . what to edit if i want to give it for any for the foot.