Symbolic Equations

Simbody is useful for internal coordinate and coarse grained molecule modeling, large scale mechanical models like skeletons, and anything else that can be modeled as bodies interconnected by joints, acted upon by forces, and restricted by constraints.
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Adam Spiers
Posts: 3
Joined: Wed Jun 18, 2008 4:28 am

Symbolic Equations

Post by Adam Spiers » Tue Jul 15, 2008 8:53 am

Hello,

I'm trying to get to grips with understanding the differences between SimBody and SDFast as a engine for OpenSim. In particular I'm interested in the opportunity to extract equations of motion symbolically.

I understand that as SD-Fast is a general purpose multibody engine one is able to pass a system to it and it generates a file (the 'd' file) containing a series of C functions with the equations of motion.

Does Simbody work in a similar way? i.e. Am I able to open and examine the generated C code after passing it a model (either created by me or in OpenSim)?

Many Thanks,

Adam
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Michael Sherman
Posts: 804
Joined: Fri Apr 01, 2005 6:05 pm

RE: Symbolic Equations

Post by Michael Sherman » Tue Jul 15, 2008 11:25 am

Hi, Adam. Like SD/FAST, Simbody is a fully general multibody code. Unlike SD/FAST, it achieves that numerically rather than symbolically so there is no generated source code to look at, and therefore no compile step either. However, also unlike SD/FAST Simbody is open source so you can see all the code there is by downloading it from SimTK (although you probably won't need to do so to use it). If you must have generated problem-specific source code you would have to keep using SD/FAST, although I would suggest that you rethink your approach to see whether that is really necessary.

Best regards,
Sherm
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