# Center of Rotation with FDK Joint

Hello AnyBody,

I would like to know how Any Body calculates new center of rotation at every instant of motion, when a joint between two segments is defined using Force Dependent Kinematics.

Hi Rizzwan,

I’m not sure if I understood exactly your question. The COR is calculated as a result of all applied forces in the equations to get an equilibrium.

Dear Amir,

I would refer back to the tutorial of FDK (Lesson 1-3), where the stiffness is provided in the x and y directions of Knee Joint, resulting in translations/deformation between two respective nodes forming the knee joint.

During the motion, since two nodes of knee joint are not at the same position, how i can see, plot or infer, the new CoR which, as you explained, is calculated as result of all applied forces in the equations to get an equilibrium.

Hi Rizwan,
during this simplified knee bend of the tutorial the COR is not calculated as a value.
However, thinking about it it should be possible to compute the COR as the intersection point of the two axes.This requires probably some geometrical equations…
What is your target, what do you want to achieve? There might be easier solutions.

Dear Amir,

I am working on the standing model given in the repository and defined the lumbar joints using FDK. Right now i am only considering the flexion motion, during which the center of rotation changes. Therefore, any suggestions.