Forces

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1

Hi AnyBody support team,

I am trying to calculate the section forces at T12L1Jnt in global system.

I need few clarification.

Does the command,
‘‘Main.Study.Output.Model.HumanModel.Trunk.JointsLumbar.T12L1Jnt.Constraints.Rea
ction.Fout’’
represents the forces at T12L1Jnt in local coordinate system or global
system?

If they are in local system, then in standing model the following code
is correct to calculte the forces in global system?

AnySeg L1Seg = {

//initial position found as a function of pelvis pos and orientation

r0=.L2Seg.L1L2JntNode.sRel*.L2Seg.Axes0’+.L2Seg.r0-L1L2JntNode.sRel*Axes0’;

 AnyFunTransform3D &Scale =..ScalingTrunk.Lumbar.ScaleFunction;

 AnyVar MassS = ..Scaling.MassScaling.Lumbar.MassScale;

 AnyVar MassStandard = ..StandardParameters.Lumbar.Mass/5;
 Mass = MassS*MassStandard;

 Jii = {0.001,0.001,0.001};

 sCoM = Scale({0.031, 0.139, 0.000000});

 AnyRefNode L1L2JntNode = {sRel = .Scale({0.034,0.123,0.0});};

 AnyRefNode T12L1JntNode = {
   sRel = .Scale({0.022,0.154,0.0});

};
AnyFolder FromLocalToGlobal={
AnyVec3 v={10,0,0}; //local vector
AnyVec3 res1=v*.T12L1JntNode.Axes;
};
How can I know about the orientations of loacl system e.g L1? Does the
local system of L1 has different orientation than global system? If
different then how big is the difference?

with best regards

javed

2

Hi Javed,

The reaction forces of the joint are given in the local coordinate
system of the first node declared in the joint.
To have it in global coordinate you have to multiply by the
transposed orientation matrix of the local system. So the script
becomes:

AnyFolder FromLocalToGlobal={
AnyVec3 v={10,0,0}; //local vector
AnyVec3 res1=v*.T12L1JntNode.Axes’;
};

You can see posting #1824 answering a similar question.
You can also have a look at this folder in the file section of the
group: SmallExamples. There is a file explaining how to make the
coordinate transformations, please see the
file “CoordinateTransformations.any”.

The coordinate system of L1 is most probably different than the
global one. You can visualize it by drawing L1 RefFrame, or look at
L1.axes in the chartFX window.

Best regards,
Sylvain, AnyBody Support.

— In anyscript@yahoogroups.com, “javed377” <javed377@…> wrote:
>
> Hi AnyBody support team,
>
> I am trying to calculate the section forces at T12L1Jnt in global
system.
>
> I need few clarification.
>
> Does the command,
> ‘‘Main.Study.Output.Model.HumanModel.Trunk.JointsLumbar.T12L1Jnt.Con
straints.Reaction.Fout’’
> represents the forces at T12L1Jnt in local coordinate system or
global
> system?
>
> If they are in local system, then in standing model the following
code
> is correct to calculte the forces in global system?
>
> AnySeg L1Seg = {
>
> //initial position found as a function of pelvis pos and orientation
>
> r0=.L2Seg.L1L2JntNode.sRel*.L2Seg.Axes0’+.L2Seg.r0-
L1L2JntNode.sRelAxes0’;
>
> AnyFunTransform3D &Scale
=…ScalingTrunk.Lumbar.ScaleFunction;
>
> AnyVar MassS = …Scaling.MassScaling.Lumbar.MassScale;
>
> AnyVar MassStandard = …StandardParameters.Lumbar.Mass/5;
> Mass = MassSMassStandard;
>
> Jii = {0.001,0.001,0.001};
>
> sCoM = Scale({0.031, 0.139, 0.000000});
>
> AnyRefNode L1L2JntNode = {sRel = .Scale({0.034,0.123,0.0});};
>
> AnyRefNode T12L1JntNode = {
> sRel = .Scale({0.022,0.154,0.0});
>
> };
> AnyFolder FromLocalToGlobal={
> AnyVec3 v={10,0,0}; //local vector
> AnyVec3 res1=v*.T12L1JntNode.Axes;
> };
> How can I know about the orientations of loacl system e.g L1? Does
the
> local system of L1 has different orientation than global system? If
> different then how big is the difference?
>
> with best regards
>
> javed
>