Jaw model

Hi Mark and Sylvain
i have created a sabertooth jaw model (except for STL files and also
simplified) using your human jaw model available in the repository. i
have only 3 muscles (temporalis, massetter, pterygoid) on each side. i
have also changed the motion capture data accordingly. i am able to
run the calibration study and kinematic analysis but having hard time
running the inverse dynamics analysis. i get the error “Muscle
recruitment analysis failed”. Please provide some suggestions to
improve the model. Please find uploaded the folder
“sabertooth_jaw.rar” having all the files (Jawmodel2.any is the main
file) under files section.Also can you please tell me why you are
using AnyMat33 to compute rotation matrix for nodes(TMJs) and how do
you ensure that global reference frame of your motion tracking system
matches with that of AnyBody (chewing_right.txt file contains 3d
co-ordinates in AnyBody’s reference frame).

thanks

Hi,

I had a quick look at your model.
The reason that you can’t run an inverse analysis is the model doesn’t
have muscles enough. I would add the lateral pterygoid and some of the
muscles responsible for opening the jaw.

The use of AnyMat33 is actually an old fashioned way of defining a
rotation matrix. Now I would use the function RotMat.

The driver is constructed in such a way that it drives the distance of
the frontal incisors relative to the midpoint between the TMJ. The
tracking coordinates is normally also the relative distance between
the skull and the mandible. Normally you take a reference measurement
with the mandible closed and then you can reset the tracking device.

Regards, Mark

— In anyscript@yahoogroups.com, “K Srikanth” <srikanth_kannan84@…>
wrote:
>
> Hi Mark and Sylvain
> i have created a sabertooth jaw model (except for STL files and also
> simplified) using your human jaw model available in the repository. i
> have only 3 muscles (temporalis, massetter, pterygoid) on each side. i
> have also changed the motion capture data accordingly. i am able to
> run the calibration study and kinematic analysis but having hard time
> running the inverse dynamics analysis. i get the error “Muscle
> recruitment analysis failed”. Please provide some suggestions to
> improve the model. Please find uploaded the folder
> “sabertooth_jaw.rar” having all the files (Jawmodel2.any is the main
> file) under files section.Also can you please tell me why you are
> using AnyMat33 to compute rotation matrix for nodes(TMJs) and how do
> you ensure that global reference frame of your motion tracking system
> matches with that of AnyBody (chewing_right.txt file contains 3d
> co-ordinates in AnyBody’s reference frame).
>
> thanks
>