Upper Limb Dynamic Model

[Alessia Franceschi]

Hi,
I'm using MoBL_ARMS_Upper_Limb_Model_OpenSim and I'm trying to run the Static Optimization starting from a simple motion file to reproduce pronation and supination. I can't understand why OpenSim crashes everytime I try to run the analysis: everything disappears with no message of error.
On the contrary, Inverse Dynamics works well. So I thing my input files are right.

Are there any problems in the model?

Please, help me.
Thank you!

[jimmy d]

Hi-

Sounds like its an issue with the capacity of the model to generate force. The crashing may be due to the model not being able to generate enough force. Have you added a reserve actuator at each model coordinate?

There also may be an error in the model that is hard to see. The model has been made by a member of the community so I am unsure of how it is built. It may be good to also post on the MoBL project page.

Goodluck and let us know how it goes,
-James

[Alessia Franceschi]

Thank you really much for the answer. Can I ask you what reserve actuators are? I don't know how to add them to each coordinate. Is it written anywhere?

I will also post on the page you suggest, thank you for the information!

Best regards.

[jimmy d]

Hi-

Static Opt is trying to calculate a set of activations that are required to achieve a target joint torque. Often, the muscles can not achieve these forces and the simulation will crash. We add reserve actuators at each coordinate to provide extra forces when the muscles are not enough.

In your OpenSim distribution you will see some examples of actuator files that are included in CMC simulations. You can use the same template for actuators in Static Opt.

Here is an online example of one;
https://github.com/opensim-org/opensim- ... uators.xml

Hope that helps,
-james

[Alessia Franceschi]

Really thank you for the complete explanations. I've added reserve actuators for each of the controllable coordinates of the models, but nothing changes. The warning message (before everything disappears) says that some columns in the storage object can't be found. These are the columns related with the uncontrollable coordinates of the model. So I've added in the motion file these columns, with their fixed values, but the warning message always appears.

I've written to the team that has developed the model, hoping in the answer.
If there are news, I'll write them here.

Best regards.

[Alessia Franceschi]

I have contacted a member of the team that has created the model and she says that they have used it successfully to use most of the dynamic simulation function in OpenSim. So it seems that the model hasn't issues. I can't understand where is the problem. The warning message I can read before OpenSim crashes is that some columns in the storage file can't be found. But these columns are in the motion file!
Maybe a pre-settings file is needed?

[Reno Hurol]

Is not entirely clear to me but I can not understand something because language is not mine.

[suzunosuke nagaoka]

Hi, did you get good result using regular IK/ID?

IK works fine for me but for some reason, ID doesn't generate any moments in one directions (and I end up with negative moments only when the kinematics suggests otherwise). Did you encounter similar problems?