Troubles applying a purely normal external force

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Felicia Davenport
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Joined: Wed Jan 29, 2020 3:17 pm

Troubles applying a purely normal external force

Post by Felicia Davenport » Mon Mar 13, 2023 10:57 am

Hello! We are trying to model an external force being applied to a specific location on a segment relative to marker placements in OpenSim. When applying said force in the proper coordinate dimension of the segment's reference frame (in this case the femur), we also need it to be normal to the segment. However, the visualization of this external force in the GUI seems incorrect. It appears like OpenSim is still trying to apply the force with respect to the global reference frame, and I'm not sure why. Has anyone else encountered anything like this before?

Additional Information:
I'm currently using marker positions to orient where the force is placed for each participant-- these positions are represented in the global coordinate system. To challenge if this was the issue, I tried modeling the force at the femur's origin point(femoral head) while expressing the point in the femur's coordinate frame, and instead, the force was placed at the global coordinate frame origin.

ExternalForce1.png
This is the visual representation of the point force in OpenSim.
ExternalForce1.png (333.03 KiB) Viewed 168 times
OsimGUI.png
The settings I've defined for the point force.
OsimGUI.png (20.19 KiB) Viewed 168 times

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