Shoulder joint angle sequence


I am still having trouble with shoulder joint angle sequence so have attached my model to see if you can help me out. I have removed all the muscles so there are just two bones - a scapula and a humerus. I have an anyinclude3 file which has in it kinematics determined from vicon data. These kinematics are in the angle sequence yzy. The shoulder joint is also defined in the same way. When I drive the model using the kinematics I get the following error:

WARNING(OBJ.MCH.KIN6) : E:/AnyBody_Monique/T…s/06.24/TwoBones.any : GHRot : Close to singular position : Orientation close to Gimbal Lock, i.e., first and third axis of rotation being parallel

Is there any way I can define the glenohumeral joint as it is in the Bergmann model i.e. yzy and then also drive with data that has the same angle sequence?

Thanks for the help


Hi Monique,

What you get is not an error, but just a warning. It meas you are close to gimbal lock but don’t reach it yet. So the study can run normaly as long as you don’t reach the lock.
And this happens at the initial conditions, so you can remove the warning by giving a small initial angle to the humerus using the Axes0 property.
Aside of this your definition of the yzy sequence driver seems fine.

Best regards, Sylvain.

Hi Sylvain

Many thanks for the reply - your solution of adjusting the position at load time (i.e. Axes0) worked as expected. Sorry about what now seems like a silly question - things are a lot clearer now. I always thought it should be possible to drive the model in this way so I am glad it is now working.