Converting Scaled RajagopalLaiUhlrich2023 and Improved RRA Output Models to Hyfydy Format

[Ali Forouzanfar]

Hi everyone,

I am working with the scaled RajagopalLaiUhlrich2023 model and an improved RRA output model. I'm looking for guidance on how to represent these models in the Hyfydy format.

Specifically, I would appreciate any of the following:

Step-by-step instructions for converting these specific models to Hyfydy.

Tutorials or resources that demonstrate the conversion process for similar musculoskeletal models.

Example Hyfydy code snippets showcasing the representation of relevant model components (e.g., joints, muscles) based on the RajagopalLaiUhlrich2023 model.

Any help or insights on this matter would be greatly appreciated. Thank you!

[Thomas Geijtenbeek]

The model you mention is probably not suitable for predictive simulations with forward dynamics. It is best to use the models in the Examples and Tutorials folders as a starting point.

For more information, see:

https://scone.software/doku.php?id=doc:model

[Ali Forouzanfar]

Thank you for your reply

To clarify my question, I'm looking for a 3D OpenSim model that would be suitable for forward dynamic simulations of walking and running. I'm planning to scale the chosen model using gait data of walking and running and then implement it in the Hyfydy format.

Specifically, I'd like to know:

Of the models Gait2354, Gait2392, and Rajagopal, which would be most appropriate for my needs, you mentioned the Rajagopal model might not be suitable for forward dynamics. Could you elaborate on why that is?

If none of these models are ideal, could you recommend any other OpenSim models that include hand dynamics and are suitable for forward dynamic simulations of walking and running?

[Thomas Geijtenbeek]

If you need an OpenSim version of the model only for scaling, then please note that you can also scale any Hyfydy model directly in SCONE. The most recent release has an example scenario on how to do this:

Gait2D - GeyerHerr2010 - Scaled - Hyfydy.scone

This scaling method works with any Hyfydy model.

For most Hyfydy models, there is an OpenSim equivalent, but they are not all up-to-date. Please let me know if any model in the Examples folder is suitable for your needs.

[Ali Forouzanfar]

Thank you for your answer! Your guide to scaling in SCONE is correct, but I'm using OpenSim for both scaling and refining the model with RRA for forward dynamics analysis.

I noticed the H1922 model is similar to gait2354, and I haven't found other models that closely match its structure and my needed modifications. My plan is to modify gait2354 slightly to create an .hfd file compatible with SCONE, mainly by changing 23 degrees to 19 and muscle 54 to 22.

Do you think this is the most efficient approach, or are there other models already well-suited for this workflow? I'm open to other suggestions if you have any!

[Thomas Geijtenbeek]

The question is what you want to do with your model. If your intention is to use a reflex-based gait controller, then using the H1922 model is the right way to go, since there already is a functioning reflex controller for that model. The easiest way to create an OpenSim version is probably to take the OpenSim version of the H0918 model, and add the missing DOFs and muscles to that. You'll only need to add a hip abductor and adductor.

[Ali Forouzanfar]

Is there a tool available to convert an OpenSim4 model to the Hyfydy format in SCONE software?

If a dedicated tool doesn't exist, I'm exploring the possibility of creating a Python script for this purpose. I understand that such a script would involve extracting the necessary information from the OpenSim (.osim) file and formatting it according to the Hyfydy specification.

If anyone has already developed a script or tool for this conversion, I would be extremely grateful if you could share it. Your contribution would be incredibly valuable to my research.

[Thomas Geijtenbeek]

Yes, this is possible: open a .scone scenario that uses an OpenSim4 model, and go to Tools -> Convert to Hyfydy...

This will work only for supported elements, so you might need to manually adjust the .hfd model afterwards. For example, cylindrical wrapping surfaces are not supported in Hyfydy. It should still provide you with a useful starting point, though.