[solved]Fiberlength error in forward dynamics simulation using scaled model

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Yuichiro Omura
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Joined: Thu Apr 04, 2019 10:03 pm

[solved]Fiberlength error in forward dynamics simulation using scaled model

Post by Yuichiro Omura » Mon Nov 29, 2021 8:06 pm

I apologize for keeping posting.
I'm using a model based on gait2392 like the attached file.
I tried to scale the model using experimental data and perform forward dynamics simulation.
However, simulations didn't proceed not at all because of the following error in almost all muscles:

Code: Select all

Error detected by Simbody method MuscleFixedWidthPennationModel::calcPennationAngularVelocity: Fiber length cannot be zero.
  (Required condition 'fiberLength > 0' was not met.)
When I tried simulating using not my code but in GUI, the same error happened.
I therefore think the model muscle parameters are wrong.
Before scaling, this error hasn't been seen.
I saw this post: viewtopicPhpbb.php?f=91&t=13307&p=38202&start=0&view=
however, can scaling cause this to happen?
Is there anything I need to do?

Best regards,
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Last edited by Yuichiro Omura on Wed Dec 01, 2021 11:26 pm, edited 1 time in total.

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User avatar
Yuichiro Omura
Posts: 44
Joined: Thu Apr 04, 2019 10:03 pm

Re: Fiberlength error in forward dynamics simulation using scaled model

Post by Yuichiro Omura » Wed Dec 01, 2021 11:25 pm

This problem was solved.
The reason is the inertia parameters of the platform which we uses as ground are 0.
I have no idea why these parameters lead to muscle fiber length error, but solved.
Sorry for the trouble.

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