when i want to fix the rotational degrees of freedom of a spherical joint (as if it was rusty), is it all right to set the joint coordinates (e.g. to zero) and switch Reaction.Type in the Driver to {On}? (1)
And a bit more specific (2):
What is the meaning of the Reaction.Type in the SpineRythmDrv?
E. g. the last line of the SRMatrix has the meaning:
-1 * u6[2] + 0.9131695 * u7[2] = 0
When i now set the last component of the Reaction.Type of the SpineRhythmDrv to “On”, does this have a descriptive meaning like a joint moment or is this not really illustrative, more a mathematical meaning?
I would like to fix the rotational DoF of one or two intervertebral disc so that it can transfer moments. What way would this be done best (3)?
The spine rhythm defines a relationship between the thoracopelvic angle and individual angles of the lumbar spine - a sort of weight/percentage matrix for the angles.
So the options you have (1) is to exclude the spine rhythm and drive all angles individually, (2) redefine this matrix to exclude the joint of interest, and (3) use the force-dependent kinematics approach like was done in the SpineFixationWithForceDepKinematics example.
So depending on the repository that you are using there are several ways to exclude the spine rhythm:
In 1.6 you could use the BM_SPINE_RHYTHM as OFF
In previous repositories that could be done using by defining “norhythm” (check SpineFixationWithFDK example)