Kinematics of the external load

[Caterina Passini]

Hi, I read something about that also here in the forum, but I’m sorry I’m still a little bit confused… I noticed that to create my own External Force file.xml I need a Force data file (ok, I get it with external loads,Cop, and Torque in every frame) and a kinematics for external loads file, now, I have got a Kinematics motion results, but It “show” me just the model walking on the space, but not the load moving with it! ( I loaded a Opensim file from OutPutReference “subject01_walk1_ik.mot” and it showed me a green Force moving on the time)..Now my question is, does anybody know if I need this kinematics for external loads file even if I have the Cop position in every frame, and in that case, how can I create-get that file?
I read a Ayman replay
“For visualizing forces you can use the "File->Preview Motion Data" Option in the GUI, and then synchronize the motions to see the ground reaction forces in sync. with the motion.”
I tried, But I wasn’t able to synchronize that to check if everything it’s fine because if I load the .trc file with the coordinate first, I can see marker moving, but then when I load always with the preview the .mot file (with Loads and Cops), I can’t see the force, and neither the blu marker anymore, probably it’s not everything ok… ?

Thank you very much
Caterina

[Ayman Habib]

Hi Caterina,

You can synchronize any number of motions together (using shift-select), you should be able to sync. the coordinates, markers and grf files and see everything moving in sync.

Unless running forward simulation with CMC results where the simulation can drift from CMC I believe the kinematics for external loads may not be needed.

The ik result file from OutputReference is from an old version of OpenSim that was combining multiple pieces of data together, however this functionality is not built into the IK solver in 2.4. You can accomplish it using the synchronization of motions, and we're working on making this easier in the next release.

Hope this helps and best regards,
-Ayman

[Caterina Passini]

Hi Ayman, thank you very much, I succeeded in synchronizes movement and it was very useful to check everything before plotting! Yes, effectively I didn’t use the Kinematic for external load and it seems to work

Thanks again!
Caterina