Hi
this is srikanth kannan from university at buffalo. i am having hard
time running kinematic and inverse dynamic analysis of a jaw model. i
am trying to drive a measure using motion capture data (text file). i
am getting the following error:
“Model is kinematically indeterminate : Position analysis failed :
13 independent constraints and 14 unknowns”.
I have checked the model and it should ideally have 12 dof and 12
constraints. So it will be great if somebody can help me with
this.Please find the folder “Jawmodel” attached in the groups page
under files section.
If you run the ModelInformation you will the model have 12 dof and 12
constraints as you correctly said it should have.
First of all you got the error message because one driver is missing
in your script, but I’ll explain that in detail further down.
The reason why the system says in the error message that there are 14
unknowns (and not 12) is because the position vector contains in
reality 7 elements: 3 translations and 4 rotations. So there is an
extra rotation. This rotation comes from the Euler parameters but is
actually hidden. That mean you don’t have to care about this extra
rotation when making a model.
Now what’s wrong with the drivers? Right now in your model you are
using one driver that drives a linear measure between the upper jaw
and the global ref in two directions. First problem is that there is
a revolute joint connecting the upper jaw and the global ref that
mean only one rotation free. So you can drive the upper jaw in one
direction only (z rotation or y linear measure). Second problem is
that there is no driver for the lower jaw joint. That is why the
system says you are missing one constraint: it cannot solve the
position of the lower jaw.
So make sure to drive both the upper and lower jaw and only in the
direction corresponding to the free rotation of the revolute joint.
Best regards,
Sylvain, AnyBody Support.
— In anyscript@yahoogroups.com, “K Srikanth”
<srikanth_kannan84@…> wrote:
>
> Hi
> this is srikanth kannan from university at buffalo. i am having hard
> time running kinematic and inverse dynamic analysis of a jaw model.
i
> am trying to drive a measure using motion capture data (text file).
i
> am getting the following error:
> “Model is kinematically indeterminate : Position analysis failed :
> 13 independent constraints and 14 unknowns”.
> I have checked the model and it should ideally have 12 dof and 12
> constraints. So it will be great if somebody can help me with
> this.Please find the folder “Jawmodel” attached in the groups page
> under files section.
>
> thanks
> srikanth
>