"Could not associate a motion to current model" troubleshooting

[Rae Dias]

Does anyone why know why I am getting the following error when I try to load a motion for both the models GaitModel2354 and GaitModel2392?

"Could not associate a motion to current model"?

I did a bit of digging on the website to find out why this might be, but this is all I could find: "OpenSim will try to associate the loaded motion with the current model. If this association could not be done (e.g. because the motion file contains no coordinates from the model as column labels) then an error message is posted and the loading of the motion is aborted."

I don't really know what the above information means, and how to troubleshoot this to find out if this is the cause of my issue.

Thanks!

Rae.

[Ayman Habib]

Hello,

To produce an actual motion, the file should contain coordinate values that change over time. The file you are trying to open does not contain coordinate values so it will not cause any motion, accordingly the application gives an error and do not load it. Typically this happens if you try to load an mot file that has ground reaction forces (*_grf.mot) or some other data that is not a valid motion.

Hope this helps,
-Ayman

[Yuwei Liu]

Hello Ayman

Thanks for your answer, but I check my mot. file through txt. I found that my mot file columns only contain these:
time ground_force_1_vx ground_force_1_vy ground_force_1_vz
ground_force_1_px ground_force_1_py ground_force_1_pz
ground_moment_1_mx ground_moment_1_my ground_moment_1_mz

unlike the .mot File:
time, ground_force_vx, ground_force_vy, ground_force_vz,
ground_force_px, ground_force_py, ground_force_pz,
l_ground_force_vx, l_ground_force_vy, l_ground_force_vz,
l_ground_force_px, l_ground_force_py, l_ground_force_pz,
ground_torque_x, ground_torque_y, ground_torque_z,
l_ground_torque_x, l_ground_torque_y, l_ground_torque_z

How is this phenomenon caused? Is there a problem with converting C3D files in MATLAB? Is there any solution to this problem? Thank you very much!

[Ayman Habib]

Hello,

As explained earlier on this trail, to load a motion file it has to contain coordinate values and your file doesn't meet this requirement. The ground reaction force files are not motions that can be loaded independently for this reason, instead they can be "associated" with a motion to display forces along with the animation.

Hope this helps,
-Ayman