Express Markers and Forces in the Same Frame

Provide easy-to-use, extensible software for modeling, simulating, controlling, and analyzing the neuromusculoskeletal system.
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Josée Mallah
Posts: 19
Joined: Thu Jan 20, 2022 6:52 am

Express Markers and Forces in the Same Frame

Post by Josée Mallah » Sat Nov 30, 2024 1:17 pm

Hello
I am trying to create a frame at one of the foot markers and express the center of pressure relative to that frame - but I am having issues.
I think it is because the marker and force data are not expressed in the same frame initially (obviously the motion capture system has a different origin than the force plates). Is there a way to do that in OpenSim/scripting or else?
Or if you have any better ideas on how to do get the relative CoP - please let me know!
Thank you

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Aaron Fox
Posts: 294
Joined: Sun Aug 06, 2017 10:54 pm

Re: Express Markers and Forces in the Same Frame

Post by Aaron Fox » Wed Dec 04, 2024 3:42 pm

Hi Josee,

If you are scripting via the API (in C++, Matlab or Python) there are commands to express stations/points either in another frame or in the ground frame. Depending on what the original frame the data are expressed in will dictate which of these is more efficient (i.e. if they are in two different frames, maybe just express them both in the ground frame).

Aaron

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