Hello Christian,
I have spent some more time on this and I think I have it figured out. I built
a small test
model so that I could see what was going on.
I have uploaded TestModel.zip with the files. There are 2 segments connected
with a
spherical joint, 4 muscles, and 1 ligament. To make it easy on myself, the
model is
stationary, but I have also tried it while the upper segment is moving.
If the ligament force is set to -5, it creates a moment of -2.5 at the joint.
So by
commenting out the ligament and inserting this:
AnyMoment3D PassiveMoment = {
M = {0, 0, -2.5};
//Mlocal = {0, 0, 0};
AnyRefFrame &Seg1Seg2JntNode =
Main.TestModel.Segments.Segment1.Seg2JntNode;
};
it generates the same muscle forces. However, the reactions are different at
the joint
because there is no ligament force.
So going back to the standing model:
If I apply a moment at the L5-S1 joint node, will it help that joint rotate, and
help the back
muscles that act in the direction of the moment? From the results of my test
model, I
think it will, but please let me know if I’ve misunderstood anything. Also, it
seems that the
muscle activations would be accurate, but the joint reactions may not be.
Thank you,
Brent
— In anyscript@yahoogroups.com, “AnyBody Support” <support@…> wrote:
>
> Hello Brent
>
> I have been thinking a bit of your problem. Is it a static or a
> dynamic model? As I understand it you are trying to help the muscles
> by applying a force. But if the muscle are working against the force
> it doesn’t really work, right?
>
> Best regards
> Christian, AnyBody Support
>
> — In anyscript@yahoogroups.com, “blulrey” <blulrey@> wrote:
> >
> > Hello,
> > I am having difficulties applying a moment to simulate the passive
> extensor moment of the
> > torso in the standing model. I applied a positive moment to the Z
> coordinate (global ref) L5-
> > Sacrum joint node using AnyMoment3D. The muscle activities of the
> inverse dynamic
> > analysis show that the muscles are working against the added moment.
> How can I apply a
> > moment that helps the muscles? Am I applying to the wrong point?
> >
> > Brent
> >
>