My name is Lacey Bresnahan. I am a PhD student at Rush University in
Chicago IL. I am new to the AnyBody modeling system and I am
attempting to use it for Spinal Biomechanics Studies.
I am working with the Spine with Two arms model. I have been
successful at modifying the file to create and measure motion from
the L1 segment to the sacrum without muscles. However, when I add the
simple constant force muscles I am getting the error “Model is
kinematically indeterminate : Position analysis failed : 325
independent constraints and 329 unknowns”.
I am new to the AnyBody system and I am wondering where is the best
place to begin solving this error.
This error message means you are missing 4 constraints to drive
correctly the model. I understand you have been modifying the lumbar
spine. The error most probably comes from there. Which file did you
modify? Did you modify the drivers? If so, you might miss some drivers,
or they can be redundant and the system can’t solve it. It is a good
idea to check the changes you made, looking for redundant or missing
drivers.
Then I just want to make sure I understand well: you have been able to
run a kinematic analysis without muscles, and only when switching
from “BodyModel_NoMuscles” to “BodyModel” you got the error message, is
that right?
Thank you for giving us more details about your model, it will help us
solving the problem.
Best regards,
Sylvain, AnyBody Support.
— In anyscript@yahoogroups.com, “lebresnahan” <lebresnahan@…> wrote:
>
> My name is Lacey Bresnahan. I am a PhD student at Rush University in
> Chicago IL. I am new to the AnyBody modeling system and I am
> attempting to use it for Spinal Biomechanics Studies.
>
> I am working with the Spine with Two arms model. I have been
> successful at modifying the file to create and measure motion from
> the L1 segment to the sacrum without muscles. However, when I add the
> simple constant force muscles I am getting the error “Model is
> kinematically indeterminate : Position analysis failed : 325
> independent constraints and 329 unknowns”.
>
> I am new to the AnyBody system and I am wondering where is the best
> place to begin solving this error.
>
> Thank you,
> Lacey
>