Robot design

[Matthias Kunze]

Hello,

I have a question to the design of the musculoskeletal models:

Does OpenSim regard the wobbling of the muscles?
And could we stop this while developing and using an own robot- model?
Or doesn't it matter if we develop a robot by using "motors" instead of the muscles like in example models?


Thanks for any help.

Matthias

[Ayman Habib]

Hi Matthias,

The mass in the OpenSim model is assigned to the rigid bodies. The muscle mass is assumed to have been accounted for by the body mass. The only effect of the muscles on the model is to apply forces. The muscles can be taken out completely from the model (they live under the XML tag <ForceSet>) and different actuators (e.g. CoordinateActuator that operates as a motor applied along each coordinate) can be used instead to drive a model which would be a more accurate model of the robot.

Hope this helps and please let me know if you have any questions.

Best,
-Ayman

[Matthias Kunze]

Hi Ayman,

that means several muscles and especially their mass won't be accounted for e.g. by using the inverse dynamic tool?
So, the errors of the wobbling mass won't be accounted for by human experiments?

Thank for your help.

Best,
Matthias

[Ayman Habib]

Hi Matthias,

As a modeler you have control over what you want to account for in your model and what simplifications you make. For walking, running and similar relatively slow activities, it is reasonable to ignore these effects and include the mass of the muscles with the mass of the rigid bodies they're attached to. You'll have to decide for yourself if this is good enough for your own situation.

Hope this helps,
-Ayman