Understanding applying Ground Reaction Force to a model

[Ratna Sambhav]

Hello,

I want to know how OpenSim applies the ground reaction forces for doing its inverse dynamics. For example in the following box,

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.

It is shown that force is applied to body 'calcn_r', and the point and force magnitude is expressed in the ground reference frame. So, is it point-to-point force, acting between points 'ground_force_px', '...py' and '...pz' and calcn_r (origin of its local coordinate frame)? Or Point Columns is an extra data which may not be used? Please explain how this force is being applied.

Thanks,
Ratna

[Thomas Uchida]

The force vector [ground_force_vx, ...] and coordinates of the point of application [ground_force_px, ...] are both expressed with respect to the ground reference frame. Please also see "How to Use the Inverse Dynamics Tool" (specifically, the "External Loads Specification" section) in the documentation: https://simtk-confluence.stanford.edu/d ... cification.