Error occurred when constructing local hip joint model and performing inverse dynamics operation (SINGULAR KKT matrix)

[Wei (张志伟)]

Hello, everyone:
I built a local hip model based on the CT data.I added some simple muscles to the model.But when the muscle count goes beyond 9, I make an error when I run the reverse motion:
Error (obj.mch.mus4) : mystudy.any (1) : mystudy.inversedynamics: Muscle recruitment solver: solver aborted due to singular KKT matrix.

I tried many things without success.
I would like to ask how to solve such problems.
thank you.
With respect.
Wei

[Bjorn (Bjørn Keller Engelund)]

Hi @Wei and welcome to the forum

Is it correctly understood that the model works if you only have 8 or below muscle elements?
When it fails, have you checked the mechanical information of the model ?
You can find that by double clicking the study in your model tree - this opens the systems description of that study. Here you can see all included degrees of freedom, constraints and reaction forces.
There might be some degree of freedom not properly addressed.

Best regards,
Bjørn
AnyBody Technology

[Wei (张志伟)]

Thank you,Bjorn.
I left out some information.Now I have solved this problem.
Best regards，
Wei