Page 1 of 1
OpenSim model for inverse dynamics analysis
Posted: Tue Mar 13, 2012 8:26 am
by followtime
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
Re: OpenSim model for inverse dynamics analysis
Posted: Tue Mar 13, 2012 10:29 am
by aymanh
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
Re: OpenSim model for inverse dynamics analysis
Posted: Sat Mar 17, 2012 1:26 pm
by followtime
Hi, Ayman,
Thank you. But how to define mass properties?
Chunxia
Re: OpenSim model for inverse dynamics analysis
Posted: Sun Mar 18, 2012 7:44 am
by followtime
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
Re: OpenSim model for inverse dynamics analysis
Posted: Wed Mar 21, 2012 1:59 pm
by aymanh
Yes, indeed these values specify the mass properties for bodies.
Good luck,
-Ayman