Ligament Models

[Anne Schmitz]

Hello Forum,

Does anybody have a plugin for ligaments?

Thanks,

Anne

[Andrea Morelli]

Did you received any answer ?
I think you can model a ligament using muscle editor and having specific parameters to simulate a ligament.
Anybody have added ligament to a model ?
Would be very helpful.

Thank you
Andrea

[Anne Schmitz]

Ajay Seth, a member of the OpenSim team, has a plugin for this. I think it is a modified muscle that doesn't have activation dynamics.

[Ayman Habib]

Anne,

I went ahead and posted some version of the source of our ligament plugin on the Wiki page at:

http://wiki.simtk.org/opensim/SamplePlugins

You can give it a try.

Note that you need to make/change your model to use <Ligament> in-addition-to/in-place-of some of your regular muscle (e.g. <Thelen2003Muscle>) for this to have any effect.

Best,
-Ayman

[Tim Dorn]

Hi all,

I went ahead and inserted a ligament into my model using the Ligament plugin. However everytime I try and use CMC, it always fails when trying to find initial conditions. When removing the ligament, CMC works fine. I am not sure if this could be a bug or if anyone has tried this before and has a way around it...

The error is below:

=============================================
rdCMC.computeInitialStates: ti=0.15
=============================================
rdCMC.computeControls: t = 0.15
WARN- small force range for my_lig_r (-0.145283 to -0.145283)
WARN- small force range for my_lig_l (-0.000873351 to -0.000873351)
SimTK Exception thrown at CFSQPOptimizer.cpp:225:
Optimizer failed: CFSQP failed with status = 1
OPTIMIZATION FAILED...


rdCMC.computeControls: WARN- The optimizer could not find a solution at time = 0.150000.
If using the fast target, try using the slow target.
Starting at a slightly different initial time may also help.

[Kang Li]

Tim,
Did you get the problem associated with CMC and ligament solved.

Thanks,

Kang