Compression force on the centeral plane of the disc

[parisa]

Dear Anybody team,
I am working with AMMRv.2.3. with Mocap simple gait. I know that the proximal-distal force in the output of the study is compression force on the frame of the lower endplate of each joint, but I want to project the forces to the central plane of the disk. In other words, I want to get the compression force on the central plane of the disc(mean inclination of the upper and lower vertebrae.) I wrote this code for this purpose:
AnyForceMomentMeasure L5={
AnyForceBase &Ref1=Main.HumanModel.BodyModel.Trunk.JointsLumbar.L4L5Jnt.Constraints.Reaction;
AnyRefNode &SRef = Main.HumanModel.BodyModel.Trunk.SegmentsLumbar.L5Seg.L4L5JntNode;
AnyVector F1 =.L5.F*Main.HumanModel.BodyModel.Trunk.SegmentsLumbar.L5Seg.L4L5JntNode.Axes;
};
Is it correct?
How can I achieve this goal?Thanks for your help.

[parisa]

Hello Anybody,
I used AnyForceMomentMeasure for calculating the compression force in the central plane of the disc. I think its output (F) is defined in the global frame. When I project it in its axes, the output would be as same as the output forces of the Anybody( proximal-distal,.. ). I wonder if the F( the output of AnyForceMomentMeasure) is the compression force in the central plane and not in the plane that is defined end of the endplate?
In addition, I got confused about its direction..the direction of the segment axes is different from the global axes, and that is because the direction of my lab is different from the direction of the reference frame in Anybody, so when I used my own C3d the global reference changes to my lab direction, but the frame axes of the segment does not change. I hesitate whether the F( the output of AnyForceMomentMeasure) shows the forces in the global frame, since I added this code in the main file. I really appreciate it if someone can give me pieces of advice.
Thanks,
Parisa

[toerholm (Søren Tørholm)]

Hi Parisa,

Please see this wiki page on the topic

AnyBody/support - Measure the reaction force in a joint in a certain coordinate system

The reaction force reported is in the joint location, you can visualize it's location by finding it's associated nodes and select "ViewFrame" and press F11 this will display the coordinate system.

The forcemoment measure will always report in global reference system, then you will transform it using the Axes property of the frame you would like to have it in.

If you are in doubt about such things, I would always recommend to make a small model with a single segment a joint and a driver. In such a model you can know results and you can test the code works as you would like it to.

Best regards
Søren