Open OpenSim Model Version 3.3 in 4.4

[Nima Heidari]

Hello everyone,

I tried to open the following model:

https://simtk.org/frs/index.php?group_i ... kage_id610

In OpenSim 4.4, but I faced the following error:
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Could not construct a model from C:\OpenSim 4.4\Models\Neck\VasavadaNeckModel_3dof.osim. Possible reasons: syntax error or unsupported format.
Details: Component 'supmult-C4/5-C2' of type Schutte1993Muscle_Deprecated contains invalid characters of: '\*+
/'.
Thrown at Component.cpp:201 in finalizeFromProperties().
========================================

Can someone help me with what I should do?

[John Davis]

Based on the error message, it looks like some of the muscles have invalid names because they include a slash (which can also denote folder paths, which is probably why they're invalid to use in a muscle name).

I took a look at the file and there are three invalid patterns in the muscle names: "C4/5", "C5/6", and "C6/7". I did a quick find-and-replace in a text editor to convert the slashes to underscores (so C4/5 becomes C4_5) and the model opens for me in OpenSim 4.3. See attached for the renamed version.

However I noticed two things you should look into before using the model: first, the geometry files aren't included, so I wasn't able to get all of the bones to display. I suspect earlier releases/other models on SimTK have the appropriate geometry .vtp files you'll need.

Second, it looks like the pitch, roll, and yaw coordinates are getting interpreted as being in degrees, when almost surely they are in radians: the max roll angle, for example, is 0.698 which happens to be exactly 40 degrees. Right now that's being interpreted literally, i.e. max roll of 0.698 degrees. You will need to go into the .osim file and manually convert the joint ranges to be in degrees.

[Nima Heidari]

Thank you so much, John, and sorry for my late response,

I am a beginner in OpenSim and am in the learning process. Because of that, it is a little bit time-consuming for me.

I was wondering and wanted to ask you a question,

Is it possible to obtain the muscle force displacements or mechanical properties that OpenSim considers during simulation?

I am using MSC ADAMS, so I wanted to know whether it is possible to use the properties of muscles from a validated OpenSim model in my ADAMS model.

I really appreciate any help you can provide.