OpenSim model for inverse dynamics analysis

Chunxia Li · Post by **Chunxia Li** » Tue Mar 13, 2012 8:26 am

Hi everyone,

I want to do inverse dynamic analysis in OpenSim. In the OpenSim, I have no muscle for the skeleton model. Is this ok?

Chunxia

Ayman Habib · Post by **Ayman Habib** » Tue Mar 13, 2012 10:29 am

Hi Chunxia,

Yes it's perfectly ok to not have any muscles since Inverse Dynamics do not use muscles, it works only on the multibody system (bodies and joints) and computes forces/torques necessary to produce a specific motion. You have to have mass properties specified, however, otherwise the problem is not well defined.

Hope this helps,
-Ayman

Chunxia Li · Post by **Chunxia Li** » Sat Mar 17, 2012 1:26 pm

Hi, Ayman,

Thank you. But how to define mass properties?

Chunxia

Chunxia Li · Post by **Chunxia Li** » Sun Mar 18, 2012 7:44 am

Hi Ayman,

Is the following specifying mass properties?

<Body name="pelvis">
<mass> 7.93070000 </mass>
<mass_center> -0.07000000 -0.00880000 0.00000000 </mass_center>
<inertia_xx> 0.06530000 </inertia_xx>
<inertia_yy> 0.05950000 </inertia_yy>
<inertia_zz> 0.05250000 </inertia_zz>
<inertia_xy> 0.00000000 </inertia_xy>
<inertia_xz> 0.00000000 </inertia_xz>
<inertia_yz> 0.00000000 </inertia_yz>

Thanks,

Chunxia

Ayman Habib · Post by **Ayman Habib** » Wed Mar 21, 2012 1:59 pm

Yes, indeed these values specify the mass properties for bodies.

Good luck,
-Ayman

OpenSim model for inverse dynamics analysis

OpenSim model for inverse dynamics analysis

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Re: OpenSim model for inverse dynamics analysis

Re: OpenSim model for inverse dynamics analysis

Re: OpenSim model for inverse dynamics analysis