Computed Muscle Control

[César Flores]

Hello,

I've built a very simple dynamic model using OpenSim to better understand it. The model has only a ground and a "humerus" body with a single "deltoid" muscle and a "glenohumeral" joint with a single coordinate, "GH_z".

I attempted to run a Computed Muscle Control analysis but it fails with no error logs or messages. The openSim application merely closes.

I've attached my model's .osim file, control_tasks.xml, motion file, and reserve actuators xml file.

I made these by making adjustments from the Arm26 example files included with OpenSim's installation.

Thanks in advance for any guidance!

[César Flores]

I think my question was not very clear in my earlier post.

I want to know what I am doing wrong that my CMC analysis is crashing openSim.

I'd also like to know what is the difference between CMC and static optimization.

[Ayman Habib]

Hi Cesar,

Looking at your files, the problem is that you specified the joint name rather than the coordinate name in the CMC tasks file. Changing the "CMC_Joint" task name to "GH_z" makes CMC run to completion. Sorry about the confusion (basically CMC_Joint tracks a coordinate rather than a full Joint that has multiple coordinates, the naming is a bit out-of-date).

The difference between CMC and StaticOptimization is that StaticOptimization is a frame by frame solution to the distribution problem so it doesn't account for the the system dynamics and the results do not have any guarantees regarding continuity of muscle controls while CMC accounts for all these but is a more complicated process. The user guide has more details regarding both procedures, but please let us know if you continue to have questions so that we can improve the documentation.

Best regards,
-Ayman

[César Flores]

Thank you very much.

Indeed, my computed muscle control simulation runs now.

Thanks also for the explanation of the differences between CMC and static optimization.