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  #1  
Old 01-30-2014, 10:30 AM
thomaz thomaz is offline
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Default amount of reaction force

Hi,

how is the amount of a reaction force of a driver with reaction.type=on determined in AB?

In the tutorials reaction.type = on is explained to be useful when a model has no muscles which could provide equilibrium. But what about using reaction.type = on in a model which HAS muscles?

Is the amount of reaction force optimized like the muscle activities to fulfill the objective for muscle recruitment?

I changed a spherical joint to a transspherical joint with zero translation and set the reaction type to "on" for the translational DoF, but the reaction force for the zero translation is very small and quite different from the corresponding of the spherical joint, but i don't know why.

Thanks,

Thomaz

Last edited by thomaz; 01-30-2014 at 11:14 AM. Reason: additional information
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  #2  
Old 01-31-2014, 05:05 PM
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mkjung9980 mkjung9980 is offline
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Hi Thomaz,

1) If there are some AnyReacForce objects in your model, then it will take all necessary forces(or torques) which are require to generate that motion. There is no limitation in the size of those AnyReacForce object.

2) There is no optimization in the calculation of AnyReacForce objects.

3) When muscles and AnyReacForce objects co-exist in your model, the muscles are very lazy so muscles will be only activated when it is necessary.

Here is my old post which may help your understanding:
http://forum.anyscript.org/showthread.php?t=2781

Best regards,
Moonki
__________________

Moon Ki Jung, Ph.D, Application Engineer, AnyBody Technology A/S.

※ AnyScript™ Reference Manual is the bible.
※ AnyScript™ wiki page is the best supplementary information(http://wiki.anyscript.org).
※ When you would upload your models, please write information about your AMS and AMMR versions.
※ If you want to get more intensive support, please update your information(profile, organization and signature).
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  #3  
Old 01-31-2014, 05:59 PM
thomaz thomaz is offline
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Hi Moonki,

thanks for your reply, but i am not absolutely satisfied

(In the moment i am not able to look at the recommended files, but i will ask anyhow. Hope, this is all right.)

Mostly i am concerned that i am not able to reproduce the same result when i replace the spherical joint by a transspherical joint. I set the translation to zero, set reaction.type = on and assumed that the reaction force should be as in the situation with spherical joints. Shouldn't it be? Or do i have to set reaction.type to off for this? But when it is set to off: Doesn't it mean that there is no reaction force?
Or to summarize all these questions: How can i reproduce a spherical joint with a transspherical?

WIth respect to laziness: This sounds as if the muscles have a choice ;-) But there is a rule, i assume. Is the reaction force as large as necessary to get the best objective value?
Would you say that it is more or less senseless to set the reaction.type to on when muscles should do the work?

Thanks again and a nice weekend,

Thomaz
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  #4  
Old 02-03-2014, 12:31 PM
thomaz thomaz is offline
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Hi Thomaz, ;-)

it is fully all right that you are not satisfied, because transpherical joints MUST and DO have the same results when the translational DoF is set to zero AND reaction.type = on (!) because in this case the transspherical joint is a spherical joint. You did a mistake somewhere else when you cannot reproduce the spherical joint with a transspherical one. (yes, correct, i made one)

Reaction.type = on (in combination with muscles that influence the reaction force) leads to the optimal reaction force in terms of the objective for muscle recruitment. Any other reaction force would lead to a higher MaxMuscleActivity.

Thanks for my reply,

Thomaz
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  #5  
Old 02-03-2014, 12:36 PM
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mkjung9980 mkjung9980 is offline
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Hi Thomaz,

It seems that you could find the solution by yourself. :-)
I agree to your sentence:
"Any other reaction force would lead to a higher MaxMuscleActivity."

Best regards,
Moonki
__________________

Moon Ki Jung, Ph.D, Application Engineer, AnyBody Technology A/S.

※ AnyScript™ Reference Manual is the bible.
※ AnyScript™ wiki page is the best supplementary information(http://wiki.anyscript.org).
※ When you would upload your models, please write information about your AMS and AMMR versions.
※ If you want to get more intensive support, please update your information(profile, organization and signature).
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  #6  
Old 02-03-2014, 12:40 PM
thomaz thomaz is offline
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Only to this sentence?
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  #7  
Old 02-05-2014, 02:15 PM
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mkjung9980 mkjung9980 is offline
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Hi Thomaz,

Could you just make two simple models which use either a spherical joint or a transspherical joint?

Then it may be easier to see whether two models will work in a same way or not.

If you made them already then we can seem them here if you can upload them.

Best regards,
Moonki
__________________

Moon Ki Jung, Ph.D, Application Engineer, AnyBody Technology A/S.

※ AnyScript™ Reference Manual is the bible.
※ AnyScript™ wiki page is the best supplementary information(http://wiki.anyscript.org).
※ When you would upload your models, please write information about your AMS and AMMR versions.
※ If you want to get more intensive support, please update your information(profile, organization and signature).
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driver, joint, muscle recruitment, objective, reaction type

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