Problem with Inverse Dynamics

[William Thompson]

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I am a brand new OpenSim user, and I am trying to get inverse dynamics from a simple deep knee bend movement captured by our BTS system in order to get my feet wet. I am using the plug in gait marker set (from Tim's utilities) and the Full Body OpenSim Model. I have excluded our RBAK marker from the set, giving 38 markers total to match Tim's marker set. During the knee bend the LASI and RASI makers were occluded by the subject's body and clothing at the bottom of the movement, so I have disabled these two markers in the IK_Tasks file by setting them "false" and with a weight of 0.000. I can get Scaling and Inverse Kinematics to work very well.

My problem is that when I run inverse dynamics, I consistently get the same error:

"Tool Execution Failed. Check Messages window for details." A later message says "No output files were written".

That's it. And when I check the Messages window there are no further details there. Always this message, despite many, many attempts to get things working. I am essentially following the process laid out in Tutorial 3, which is a very similar exercise. And i am comparing my XML files to those in the tutorial for clues.

I have attached the OSIM, Static TRC, Moving TRC and the various XML files I am using. I would greatly appreciate any help in getting this to work.

Much thanks,

Bill

[Michala Cadova]

Hi William,
I had a same error massage – in my case the problem was that I forgot to include the mass and inertial properties of individual body parts (bones). For the scaling and IK you don’t need those, so they run with no problem, but for the dynamics you need it. But as I saw in your .osim model, you have it.

Then my other problem was that there were no muscles for some moments and forces. Just check that for every movement that occurs in the analysis there is a set of muscles (at least one muscle) that can really do that movement.

Michala

[William Thompson]

Thanks, Michala, I'll look into that.