Humerus coordinate system - Second option of ISB recommandations

Hi guys,

I want to simulate the humerus coordinate system of the ISB recommandation using the second option. In this second option, the coordinate system is defined as follows:

Origin : The origin coincident with GH.
Y-axis : The line connecting GH and the midpoint of EL and EM, pointing to GH.
Z-axis : The line perpendicular to the plane formed by Yh2 and Yf, pointing to the right.
X-axis : The common line perpendicular to the Z-axis and Y-axis, pointing forward.

The Yf is the axis from the Ulna styloid node to the midpoint of EL and EM.

To do that, I proceeded in the following way:

AnySeg HumerusWu2ndOption = {
Mass = 0;
Jii = {0,0,0};
r0 =.Humerus.r0;
Axes0 = .Humerus.Axes0;
//AnyDrawRefFrame drw = {ScaleXYZ={1,1,1}*0.1;RGB={0,1,0};};
AnyRefNode Node = {
sRel = {0,0,-0.1};
//AnyDrawNode drw = {ScaleXYZ={1,1,1}*0.01;};
};

AnyRefNode RotNode2 = {
ARel = RotMat(pi/2,y);
AnyDrawRefFrame drw = {ScaleXYZ={1,1,1}*0.1;RGB={0,0,1};};
};

};

AnyRevoluteJoint HumerusWu2ndOptionJnt = {
AnySeg &ref0 = …Seg.Humerus;
AnySeg &ref1 = …Seg.HumerusWu2ndOption;
Axis=y;
};

AnyKinEq HumerusWu2ndOptionCon = {
AnyKinMeasureOrg linX = {
AnyKinLinear lin = {
AnyRefNode &ref0 = …Seg.HumerusWu2ndOption.Node;
AnyRefNode &ref1 = …Seg.Ulna.us;
Ref = 0;
};
MeasureOrganizer = {0};
};
};

Does it sounds correct to you ? Do I have to set the reaction force to Off in order to avoid the force to be absorbed by the constraint ?

Regards.

Pierre

Hi Pierre,

It sounds ok for the kinematic part. About the reaction force of the driver i think it should be turned off, because it is linked to another segment (ulna), it could add a moment into the elbow joint.

So the more secure way is switch the joint reaction Off and add a reaction force between the Humerus and HumerusWu2ndOption segments.

Best regards, Sylvain.