Joint angles and moments

[Jason Moore]

Hi,

Where can I find details about how OpenSim computes joint angles and moments (if it does that)? I'm interested in knowing which methods are used in detail and the C++ API calls that use them. I'm having trouble finding that in google searches.

Thanks,

Jason

[jimmy d]

Hi Jason,

The best place to look is in the OpenSim Doxygen pages here; https://simtk.org/api_docs/opensim/api_docs31/

The confluence pages have the broader ideas of the OpenSim functions and can help you find what you are looking for; http://simtk-confluence.stanford.edu:80 ... im+Support

cheers,
-james

[Jason Moore]

Thanks James, I've already been looking through those and haven't been able to find exactly what I'm looking for, so that's why I posted a question here. I was hoping for more precise pointers to the information I'm interested in.

[jimmy d]

Is it the Inverse Kineamatics tool (https://simtk.org/api_docs/opensim/api_ ... sTool.html) and the inverse dynamics tool (https://simtk.org/api_docs/opensim/api_ ... sTool.html) you are after?

For a peak under the hood I would read the simbody documentation which goes into further detail about how mulit-body dynamics is handled (https://simtk.org/docman/?group_id=47)

Let us know if that helps,
-james

[Jason Moore]

Thanks, those are helpful. I just saw the email conversation between you and Ton. We are searching for an exisiting open source and open platform tool that computes joint angles, rates, accelerations, and moments for a human in gait given marker and dual force plate data. Before we implement our own, we're trying to get an understanding of what may already exist and what algorithms are used to do the computations. Your email exchange with Ton gives more of the information we are after, but understanding where those algorithms are implemented in OpenSim/SimBody are of interest, so we can either use some pieces of the puzzle for our work or contribute pieces to OpenSim if the current ones available aren't appropriate for our use case.

[Michael Sherman]

If you didn't find these technical papers yet you might find them useful for understanding some of the internals:
OpenSim
Simbody
Joints
Moment arm

Regards,
Sherm

[Michael Sherman]

P.S. There is no capital "B" in "Simbody".

[Jason Moore]

Thanks.