GRFs applied twice in Joint Reaction Analysis?

[Brody Hicks]

Hello everyone,

I've been performing some Joint Reaction Analyses following the workflow outlined in the webinar (https://www.youtube.com/watch?v=ly4rhOOifO0) and the online documentation (https://simtk-confluence.stanford.edu:8 ... s+Analysis). I want to make sure I'm doing this correctly.

The workflow calls for the setup files (model, kinematics, external loads, residuals) to be identical between Static Optimization and Joint Reaction Analysis. However, the Joint Reaction Analysis also calls for the _StaticOptimization_force file. The final columns of this file represent the ground reaction forces applied via the external loads setup in the Static Optimization step. But then, the Joint Reaction Analysis also calls for the external loads setup again.

I want to make sure that I'm not accidentally applying the ground reaction forces twice in the Joint Reaction Analysis, and thus skewing my results. Can anyone confirm this or provide an explanation?

Thanks,
Brody

[Mohammadreza Rezaie]

Hi, I had tested it and found that the output was identical with and without GRF columns in the _StaticOptimization_force.sto file. Only actuators forces are taken from this file, according to the descriptions:

... the forces for all actuators will be applied according to values specified in the forces_file ...

Hope this helps.
-Mohammadreza

[Brody Hicks]

Mohammadreza,

Thanks for the explanation. This makes sense. I had tried running the analysis without external loads, but I hadn't tried removing the GRF columns from static optimization like you did. I agree with you that it looks like the analysis does not consider the GRF columns in the "force_file".

Best,
Brody