Ligament Calibration

Hi,

I would like to implement ligaments using the Ligament model implemented in Anybody. The problem is the calibration that requires to “drive” the model into the position the respective ligament is slack in. If I implement multiple ligaments I would have to calibrate the different ligaments in their corresponding slack position, additionally I’m not so sure at what position which ligament is at its slack length - neither strained nor slack.
Are you planning on implementing a model where L0 is defined by a reference length, that could be measured for all ligaments in one determined position, and a reference strain, that one could implement using data from literature? Calibration to just reference lenght would make it much easier to deal with…
Thanks!
Kat

Hey Kat!

I implemented exactly the type of model you are looking for in a couple of knee models. I have attached the code with an example ligament (with random numbers though) defined. The ligament model included in the zip file assumes the ligament to be polynomial at low strains and linear at higher strains. If you need other characteristics, I hope this will give you some inspiration on how to implement it.

Best regards
Michael Skipper Andersen
Associate Professor
The AnyBody Research Group

Thanks Michael!
I have actually been working with your model already!
Only problem is that I would like to calibrate the reference length e.g. when I adjust the model to a different person etc.
I was just wondering if an easy way to do that was on the way or not!
Best regards,
Kat

Hi Kat!

I think the easiest way to do this is to create a separate model that drives the model into the reference position and saves the resulting reference ligament lengths to a file. Your other models should then refer to these files for reference length values.

Best regards
Michael Skipper Andersen
Associate Professor
The AnyBody Research Group