Out of range motion of the glenohumeral joint in FDK

Hi, I'm Dwan Lee.

I've tried to do FDK modeling for measuring joint contact force.

I referred to tutorials and the knee simulator model then followed the same procedure as below.

CType = {ForceDep, ForceDep, ForceDep};
Reaction.Type = {Off, Off, Off};

To define shoulder stiffness using "AnyForce" and "PressureModule"

The result is like the picture below.
error

When I run the model, the humerus goes down and gradually up.

My question is how to make the glenohumeral joint stable in FDK.

Is this a problem due to the lack of pretension? Do I need to create ligaments?

Thank you,

Best regards.

Dwan Lee

Hi Dwan Lee,

Most likely this is because the stiffness of the joint is not well defined.

You will need to have ligaments around the joint to ensure it will not dislocate.

As a pre-step before adding ligaments you could add a linear stiffness function in the joint that would try to keep the joint in place.

Then as a second step you can add ligaments surface contact etc, and then remove the linear stiffness function (or lower it significantly)

Please see this wiki page for trouble shooting tricks related to FDK

Best regards
Søren

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