Go Back   Forums > General Forum > AnyBody Modeling System


Thread Tools Display Modes
Old 04-28-2018, 09:45 PM
amin_ucf2002 amin_ucf2002 is offline
Junior Member
Join Date: Jan 2015
Posts: 25
Default SpineFixationWithForceDependentKinematics Model

Hello AnyBody,

I am trying to understand how FDK feature is added in SpineFixationWithForceDependentKinematics Model(AMMR1.6.3). I read the following example in tutoral:

AnyRevoluteJoint KneeJoint = {
AnyRefFrame &Shank = .Shank.KneeCenter;
AnyRefFrame &Thigh = .Thigh.KneeCenter;
// Prepare the joint for FDK: Define the reaction types in x and y
// directions to be FDK-dependent. These reaction forces must then
// be switched off and provided by some elastic element that we
// define explicitly below.
Constraints = {
CType = {ForceDep, ForceDep, Hard, Hard, Hard};
// Define springs in the knee, simulating the effect of cartilage
// and ligaments.
AnyForce KneeStiffness = {
AnyKinLinear &lin = Main.MyModel.KneeJoint.Linear;
F = {-1000*lin.Pos[0], -5000*lin.Pos[1], 0};

However, I am trying to find the translational stiffness defined in SpineFixation model. I cannot find them. What I can find is the following codes:
// define joints, which have force-dependent behaviour
AnySphericalJoint &jntt12l1 = .refJoints.T12L1Jnt;
AnySphericalJoint &jnt12 = .refJoints.L1L2Jnt;
AnySphericalJoint &jnt23 = .refJoints.L2L3Jnt;
AnySphericalJoint &jnt34 = .refJoints.L3L4Jnt;
AnySphericalJoint &jnt45 = .refJoints.L4L5Jnt;
//AnySphericalJoint &jnt5sacrum = .refJoints.L5SacrumJnt; // this joint is commented to avoid over-constrained situation

// constraints type has to be set ForceDep for the force-dependent
// degrees of freedom of the joint
CType = {
ForceDep, ForceDep,ForceDep,
ForceDep, ForceDep,ForceDep,
ForceDep, ForceDep,ForceDep,
ForceDep, ForceDep,ForceDep,
ForceDep, ForceDep,ForceDep
//ForceDep, ForceDep,ForceDep // commented joint

Reaction.Type = {
//Off,Off,Off // commented joint

So I have one questions. 1. the FDK feature defined in SpineFixation model is for 3 ration dofs or 3 translational dofs ? 2. If it is translational FDK feature, where I can check stiffness?


Reply With Quote
Old 04-30-2018, 10:12 AM
pgalibarov's Avatar
pgalibarov pgalibarov is offline
Senior Member
Join Date: Oct 2010
Posts: 940

Hi Amin,

In this example it is a rotational dof. The idea was to find the curvature of the spine. But yes, you could also subject translational dof to the FDK analysis.

I believe some of the customers have tried to do this - maybe start looking at this publication.

Kind regards,
Reply With Quote

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump

All times are GMT +2. The time now is 12:07 PM.