Analyze muscle and joint forces in static and dynamic motion using the full model, without any movement data

[Narek Ginoyan]

Hello. I want to virtually simulate and analyze the forces that are created in muscles and joints with and without loads on the back while standing and walking using your full body model for my research project. I don't have any MoCap systems so I just want to simulate it without that.

For standing position using OpenSim Creator I attached foot-tripod contact sphere structure to the feet and a contact floor. When I try to simulate the model in OpenSim nothing moves since "Coordinates are locked". How can I unlock the coordinates to let the simulation run under the force of gravity for at least a second?

Also I am new to OpenSim and I am not sure how to simulate walking without MoCap data. Can I do that without any data? If I can't, are gyroscope for torso orientation and rheostats for joint angles enough to simulate walking movement in OpenSim? If yes where can I read more about it? The end goal is to be able to calculate metabolic cost during walking with and without loads on the back. (For this one https://simtk-confluence.stanford.edu:8 ... bolic+Cost will help, I guess?)
Would really appreciate if you at least gave me directions where to find answers to my questions.

[Jacob J. Banks]

Thanks for your interest in the our model.

We have not done too much with simulations. However, I know the basics. While the link you supplied is a good start, that was done prior to the new OpenSim Tool MOCO. You would be much better off using it:
https://simtk-confluence.stanford.edu:8 ... t-to-stand

My initial thought is that this model may be a bit complicated for SIMS (i.e., too many muscles controlling things), but anything can be overcome with good programming and CPU power.

It is unclear to me how you are simulating anything currently? You must just be letting it free fall? You need an objective to make it move. Otherwise, to unlock joints (and they should mostly be unlocked), you just need to go into the Coordinates window and unlock things (or go to the joints in the .osim file).

Hope this helps.
Jake Banks

[Narek Ginoyan]

I see, so I should try using a simpler model for just lower half of the body like gait2392. And for calculating metabolic cost use OpenSim MOCO, correct?
Thanks for the reply!

[Jacob J. Banks]

At the very least, I would start there as you know that model works. If you get that working in MOCO, then maybe try to get it working in our model.
Jake Banks