AnyReacForce

Dear AnyBodies,

the standing model contains 7 lumbar joints for 8 segments (T12, L1,
L2, L3, L4, L5, Sacrum, and Pelvis) coupled by the spine rythm, but
only two of them (the outermost, i.e. T12L1 and SacrumPelvis) have an
additional reference (T12L1JntReac and SacrumPelvisReaction) which is
used by AnyReacForce.

Although i read the manual for AnyReacForce i don’t understand its
meaning. It is clear to me that the spherical joints generate forces
to accomplish the constraints, but AnyReacForce generates moments
(according to AnyMechOutputFileForceExport). Commenting these two
AnyReacForce folders out changes the results of the analysis.

Can SomeOne please explain to me, what AnyReacForce in the present
combination with the reference to a spherical joint does and what it
physically represents?

Thanks,

Thomas

Hello Thomas,

The AnyReacForce basically provides all forces and moments that are
necessary. The AnyRecForce behaves just like normal forces in AnyBody and
takes the form of the kinematic measure, so a linear measure results in a
force and a rotational measure results in a moment.

Applying the AnyReacForce to a Spherical Joint will therefore result in
moments to carry the rotational degrees of freedom.

In your mentioned cases this is necessary because there are no muscles that
can support the Sacrum/Pelvis connection, so the AnyReacForce has to provide
the forces. In the T12L1 joint the reaction force is also in some cases
necessary, in others it may work without. It appears in some applications
that the muscles are simply not enough to balance the system.

Best regards,

Sebastian


From: anyscript@yahoogroups.com [mailto:anyscript@yahoogroups.com] On Behalf
Of zandfub1
Sent: 8. oktober 2008 14:22
To: anyscript@yahoogroups.com
Subject: [AnyScript] AnyReacForce

Dear AnyBodies,

the standing model contains 7 lumbar joints for 8 segments (T12, L1,
L2, L3, L4, L5, Sacrum, and Pelvis) coupled by the spine rythm, but
only two of them (the outermost, i.e. T12L1 and SacrumPelvis) have an
additional reference (T12L1JntReac and SacrumPelvisReaction) which is
used by AnyReacForce.

Although i read the manual for AnyReacForce i don’t understand its
meaning. It is clear to me that the spherical joints generate forces
to accomplish the constraints, but AnyReacForce generates moments
(according to AnyMechOutputFileForceExport). Commenting these two
AnyReacForce folders out changes the results of the analysis.

Can SomeOne please explain to me, what AnyReacForce in the present
combination with the reference to a spherical joint does and what it
physically represents?

Thanks,

Thomas

[Non-text portions of this message have been removed]

Hi Thomas,

Just as a follow-up to Sebastian’s message: The reason why the muscles
do not adequately balance the T12L1 joint is that the thorax part of the
spine is not modeled. So the muscles that would normally be present in
the thorax section are not included in our model and therefore the joint
adjacent to the thoracic section cannot be balanced without the
additional reaction force.

Best regards,

John


John Rasmussen,
Professor, PhD, The AnyBody Group, Dept. of Mech. Eng.
Aalborg University
www.ime.aau.dk/~jr, jr@ime.aau.dk <mailto:jr@ime.aau.dk>
Mobile: +45 2089 8350. Phone: +45 9940 9307 (New number!)


From: anyscript@yahoogroups.com [mailto:anyscript@yahoogroups.com] On
Behalf Of Sebastian Dendorfer
Sent: 10. oktober 2008 09:44
To: anyscript@yahoogroups.com
Subject: RE: [AnyScript] AnyReacForce

Hello Thomas,

The AnyReacForce basically provides all forces and moments that are
necessary. The AnyRecForce behaves just like normal forces in AnyBody
and
takes the form of the kinematic measure, so a linear measure results in
a
force and a rotational measure results in a moment.

Applying the AnyReacForce to a Spherical Joint will therefore result in
moments to carry the rotational degrees of freedom.

In your mentioned cases this is necessary because there are no muscles
that
can support the Sacrum/Pelvis connection, so the AnyReacForce has to
provide
the forces. In the T12L1 joint the reaction force is also in some cases
necessary, in others it may work without. It appears in some
applications
that the muscles are simply not enough to balance the system.

Best regards,

Sebastian


From: anyscript@yahoogroups.com <mailto:anyscript%40yahoogroups.com>
[mailto:anyscript@yahoogroups.com <mailto:anyscript%40yahoogroups.com> ]
On Behalf
Of zandfub1
Sent: 8. oktober 2008 14:22
To: anyscript@yahoogroups.com <mailto:anyscript%40yahoogroups.com>
Subject: [AnyScript] AnyReacForce

Dear AnyBodies,

the standing model contains 7 lumbar joints for 8 segments (T12, L1,
L2, L3, L4, L5, Sacrum, and Pelvis) coupled by the spine rythm, but
only two of them (the outermost, i.e. T12L1 and SacrumPelvis) have an
additional reference (T12L1JntReac and SacrumPelvisReaction) which is
used by AnyReacForce.

Although i read the manual for AnyReacForce i don’t understand its
meaning. It is clear to me that the spherical joints generate forces
to accomplish the constraints, but AnyReacForce generates moments
(according to AnyMechOutputFileForceExport). Commenting these two
AnyReacForce folders out changes the results of the analysis.

Can SomeOne please explain to me, what AnyReacForce in the present
combination with the reference to a spherical joint does and what it
physically represents?

Thanks,

Thomas

[Non-text portions of this message have been removed]

[Non-text portions of this message have been removed]

Hello John and Sebastian,

thanks for your answers. Step by step i understand more of the model, but i
have still a more basical question: What does the command
AnyReacForce T12L1JntReac={AnySphericalJoint &ref=.T12L1Jnt;};
cause? The command consists of nothing else than that single line, it refers
to a joint that is defined few lines above, and the joint already generates
forces itself, so what does AnyReacForce do additionally to what the
spherical joint does?

Sebastian, you wrote, “AnyReacForce basically provides all forces and moments
that are necessary”. Necessary to do what? What or where is the measure, you
mentioned?
When a model works without T12L1JntReac and SacrumPelvisReaction why are the
results different with and without these AnyReacForces (the rotations of the
lumbar segments are the same but the muscle forces are different)?

John, when i understood you correctly, you wrote, that if the thorax had
muscles integrated, the reaction force (moment) would not be necessary. But
how can the thorax transfer moments when the disc can be represented by
spherical joints?

Thank you for your helpfulness,

regards, Thomas

John wrote:

> Just as a follow-up to Sebastian’s message: The reason why the muscles
> do not adequately balance the T12L1 joint is that the thorax part of the
> spine is not modeled. So the muscles that would normally be present in
> the thorax section are not included in our model and therefore the joint
> adjacent to the thoracic section cannot be balanced without the
> additional reaction force.
>

Sebastian wrote:

>
> The AnyReacForce basically provides all forces and moments that are
> necessary. The AnyRecForce behaves just like normal forces in AnyBody
> and takes the form of the kinematic measure, so a linear measure results in
> a force and a rotational measure results in a moment.
>
> Applying the AnyReacForce to a Spherical Joint will therefore result in
> moments to carry the rotational degrees of freedom.
>
> In your mentioned cases this is necessary because there are no muscles
> that can support the Sacrum/Pelvis connection, so the AnyReacForce has to
> provide the forces. In the T12L1 joint the reaction force is also in some
> cases necessary, in others it may work without. It appears in some
> applications that the muscles are simply not enough to balance the system.
>

Thomas wrote:

>
> the standing model contains 7 lumbar joints for 8 segments (T12, L1,
> L2, L3, L4, L5, Sacrum, and Pelvis) coupled by the spine rythm, but
> only two of them (the outermost, i.e. T12L1 and SacrumPelvis) have an
> additional reference (T12L1JntReac and SacrumPelvisReaction) which is
> used by AnyReacForce.
>
> Although i read the manual for AnyReacForce i don’t understand its
> meaning. It is clear to me that the spherical joints generate forces
> to accomplish the constraints, but AnyReacForce generates moments
> (according to AnyMechOutputFileForceExport). Commenting these two
> AnyReacForce folders out changes the results of the analysis.
>
> Can SomeOne please explain to me, what AnyReacForce in the present
> combination with the reference to a spherical joint does and what it
> physically represents?

Hello Thomas,

From a kinetics point of view, the spherical joint provides three reaction:
Forces in X,Y and Z direction, whereas the three rotations are kept “open”.

With the line AnyReacForce T12L1JntReac={AnySphericalJoint &ref=.T12L1Jnt;};

full support is applied to the joint. This means also the rotational degrees
of freedom are supported with infinite strength - three moments are applied
to the rotational degrees of freedom to carry whatever the joint has to
carry.

These rotational degrees of freedom are the kinematic measure I mentioned in
my previous mail. Joints in AnyBody can be understood as kinematic measures
equipped with drivers. For instance, a spherical joint is a

distance between two points on two different segments that is driven to be
zero. So three translational measures are zero, and three rotational
measures have to be specified elsewhere.

The model may work in some cases even without the T12L1JntReac if this part
is loaded in particular. But generally speaking you are right. If the thorax
had all the muscles integrated than the AnyReacforce would not be needed
here.

The moments around the spherical joint would than be balanced by the muscle
forces, the thorax joints itself, as spherical joints cannot carry moments.

I hope this makes things a bit clearer, otherwise please ask again.

Sebastian


From: anyscript@yahoogroups.com [mailto:anyscript@yahoogroups.com] On Behalf
Of Zander, Thomas
Sent: 10. oktober 2008 15:00
To: anyscript@yahoogroups.com
Subject: Re: [AnyScript] AnyReacForce

Hello John and Sebastian,

thanks for your answers. Step by step i understand more of the model, but i
have still a more basical question: What does the command
AnyReacForce T12L1JntReac={AnySphericalJoint &ref=.T12L1Jnt;};
cause? The command consists of nothing else than that single line, it refers

to a joint that is defined few lines above, and the joint already generates
forces itself, so what does AnyReacForce do additionally to what the
spherical joint does?

Sebastian, you wrote, “AnyReacForce basically provides all forces and
moments
that are necessary”. Necessary to do what? What or where is the measure, you

mentioned?
When a model works without T12L1JntReac and SacrumPelvisReaction why are the

results different with and without these AnyReacForces (the rotations of the

lumbar segments are the same but the muscle forces are different)?

John, when i understood you correctly, you wrote, that if the thorax had
muscles integrated, the reaction force (moment) would not be necessary. But
how can the thorax transfer moments when the disc can be represented by
spherical joints?

Thank you for your helpfulness,

regards, Thomas

John wrote:

> Just as a follow-up to Sebastian’s message: The reason why the muscles
> do not adequately balance the T12L1 joint is that the thorax part of the
> spine is not modeled. So the muscles that would normally be present in
> the thorax section are not included in our model and therefore the joint
> adjacent to the thoracic section cannot be balanced without the
> additional reaction force.
>

Sebastian wrote:

>
> The AnyReacForce basically provides all forces and moments that are
> necessary. The AnyRecForce behaves just like normal forces in AnyBody
> and takes the form of the kinematic measure, so a linear measure results
in
> a force and a rotational measure results in a moment.
>
> Applying the AnyReacForce to a Spherical Joint will therefore result in
> moments to carry the rotational degrees of freedom.
>
> In your mentioned cases this is necessary because there are no muscles
> that can support the Sacrum/Pelvis connection, so the AnyReacForce has to
> provide the forces. In the T12L1 joint the reaction force is also in some
> cases necessary, in others it may work without. It appears in some
> applications that the muscles are simply not enough to balance the system.
>

Thomas wrote:

>
> the standing model contains 7 lumbar joints for 8 segments (T12, L1,
> L2, L3, L4, L5, Sacrum, and Pelvis) coupled by the spine rythm, but
> only two of them (the outermost, i.e. T12L1 and SacrumPelvis) have an
> additional reference (T12L1JntReac and SacrumPelvisReaction) which is
> used by AnyReacForce.
>
> Although i read the manual for AnyReacForce i don’t understand its
> meaning. It is clear to me that the spherical joints generate forces
> to accomplish the constraints, but AnyReacForce generates moments
> (according to AnyMechOutputFileForceExport). Commenting these two
> AnyReacForce folders out changes the results of the analysis.
>
> Can SomeOne please explain to me, what AnyReacForce in the present
> combination with the reference to a spherical joint does and what it
> physically represents?

[Non-text portions of this message have been removed]

Just a typo: Of course it should be:

The model may work in some cases even without the T12L1JntReac if this part
is NOT loaded in particular.


From: anyscript@yahoogroups.com [mailto:anyscript@yahoogroups.com] On Behalf
Of Sebastian Dendorfer
Sent: 10. oktober 2008 16:01
To: anyscript@yahoogroups.com
Subject: RE: [AnyScript] AnyReacForce

Hello Thomas,

From a kinetics point of view, the spherical joint provides three reaction:
Forces in X,Y and Z direction, whereas the three rotations are kept “open”.

With the line AnyReacForce T12L1JntReac={AnySphericalJoint &ref=.T12L1Jnt;};

full support is applied to the joint. This means also the rotational degrees
of freedom are supported with infinite strength - three moments are applied
to the rotational degrees of freedom to carry whatever the joint has to
carry.

These rotational degrees of freedom are the kinematic measure I mentioned in
my previous mail. Joints in AnyBody can be understood as kinematic measures
equipped with drivers. For instance, a spherical joint is a

distance between two points on two different segments that is driven to be
zero. So three translational measures are zero, and three rotational
measures have to be specified elsewhere.

The model may work in some cases even without the T12L1JntReac if this part
is loaded in particular. But generally speaking you are right. If the thorax
had all the muscles integrated than the AnyReacforce would not be needed
here.

The moments around the spherical joint would than be balanced by the muscle
forces, the thorax joints itself, as spherical joints cannot carry moments.

I hope this makes things a bit clearer, otherwise please ask again.

Sebastian


From: anyscript@yahoogrou <mailto:anyscript%40yahoogroups.com> ps.com
[mailto:anyscript@yahoogrou <mailto:anyscript%40yahoogroups.com> ps.com] On
Behalf
Of Zander, Thomas
Sent: 10. oktober 2008 15:00
To: anyscript@yahoogrou <mailto:anyscript%40yahoogroups.com> ps.com
Subject: Re: [AnyScript] AnyReacForce

Hello John and Sebastian,

thanks for your answers. Step by step i understand more of the model, but i
have still a more basical question: What does the command
AnyReacForce T12L1JntReac={AnySphericalJoint &ref=.T12L1Jnt;};
cause? The command consists of nothing else than that single line, it refers

to a joint that is defined few lines above, and the joint already generates
forces itself, so what does AnyReacForce do additionally to what the
spherical joint does?

Sebastian, you wrote, “AnyReacForce basically provides all forces and
moments
that are necessary”. Necessary to do what? What or where is the measure, you

mentioned?
When a model works without T12L1JntReac and SacrumPelvisReaction why are the

results different with and without these AnyReacForces (the rotations of the

lumbar segments are the same but the muscle forces are different)?

John, when i understood you correctly, you wrote, that if the thorax had
muscles integrated, the reaction force (moment) would not be necessary. But
how can the thorax transfer moments when the disc can be represented by
spherical joints?

Thank you for your helpfulness,

regards, Thomas

John wrote:

> Just as a follow-up to Sebastian’s message: The reason why the muscles
> do not adequately balance the T12L1 joint is that the thorax part of the
> spine is not modeled. So the muscles that would normally be present in
> the thorax section are not included in our model and therefore the joint
> adjacent to the thoracic section cannot be balanced without the
> additional reaction force.
>

Sebastian wrote:

>
> The AnyReacForce basically provides all forces and moments that are
> necessary. The AnyRecForce behaves just like normal forces in AnyBody
> and takes the form of the kinematic measure, so a linear measure results
in
> a force and a rotational measure results in a moment.
>
> Applying the AnyReacForce to a Spherical Joint will therefore result in
> moments to carry the rotational degrees of freedom.
>
> In your mentioned cases this is necessary because there are no muscles
> that can support the Sacrum/Pelvis connection, so the AnyReacForce has to
> provide the forces. In the T12L1 joint the reaction force is also in some
> cases necessary, in others it may work without. It appears in some
> applications that the muscles are simply not enough to balance the system.
>

Thomas wrote:

>
> the standing model contains 7 lumbar joints for 8 segments (T12, L1,
> L2, L3, L4, L5, Sacrum, and Pelvis) coupled by the spine rythm, but
> only two of them (the outermost, i.e. T12L1 and SacrumPelvis) have an
> additional reference (T12L1JntReac and SacrumPelvisReaction) which is
> used by AnyReacForce.
>
> Although i read the manual for AnyReacForce i don’t understand its
> meaning. It is clear to me that the spherical joints generate forces
> to accomplish the constraints, but AnyReacForce generates moments
> (according to AnyMechOutputFileForceExport). Commenting these two
> AnyReacForce folders out changes the results of the analysis.
>
> Can SomeOne please explain to me, what AnyReacForce in the present
> combination with the reference to a spherical joint does and what it
> physically represents?

[Non-text portions of this message have been removed]

[Non-text portions of this message have been removed]

Hi Thomas,

The thorax is one big rigid body. It does not have joints between the
thoracic vertebrae. That’s why it can transfer moment.

John


John Rasmussen,
Professor, PhD, The AnyBody Group, Dept. of Mech. Eng.
Aalborg University
www.ime.aau.dk/~jr, jr@ime.aau.dk <mailto:jr@ime.aau.dk>
Mobile: +45 2089 8350. Phone: +45 9940 9307 (New number!)


From: anyscript@yahoogroups.com [mailto:anyscript@yahoogroups.com] On
Behalf Of Zander, Thomas
Sent: 10. oktober 2008 15:00
To: anyscript@yahoogroups.com
Subject: Re: [AnyScript] AnyReacForce

Hello John and Sebastian,

thanks for your answers. Step by step i understand more of the model,
but i
have still a more basical question: What does the command
AnyReacForce T12L1JntReac={AnySphericalJoint &ref=.T12L1Jnt;};
cause? The command consists of nothing else than that single line, it
refers
to a joint that is defined few lines above, and the joint already
generates
forces itself, so what does AnyReacForce do additionally to what the
spherical joint does?

Sebastian, you wrote, “AnyReacForce basically provides all forces and
moments
that are necessary”. Necessary to do what? What or where is the measure,
you
mentioned?
When a model works without T12L1JntReac and SacrumPelvisReaction why are
the
results different with and without these AnyReacForces (the rotations of
the
lumbar segments are the same but the muscle forces are different)?

John, when i understood you correctly, you wrote, that if the thorax had

muscles integrated, the reaction force (moment) would not be necessary.
But
how can the thorax transfer moments when the disc can be represented by
spherical joints?

Thank you for your helpfulness,

regards, Thomas

John wrote:

> Just as a follow-up to Sebastian’s message: The reason why the muscles
> do not adequately balance the T12L1 joint is that the thorax part of
the
> spine is not modeled. So the muscles that would normally be present in
> the thorax section are not included in our model and therefore the
joint
> adjacent to the thoracic section cannot be balanced without the
> additional reaction force.
>

Sebastian wrote:

>
> The AnyReacForce basically provides all forces and moments that are
> necessary. The AnyRecForce behaves just like normal forces in AnyBody
> and takes the form of the kinematic measure, so a linear measure
results in
> a force and a rotational measure results in a moment.
>
> Applying the AnyReacForce to a Spherical Joint will therefore result
in
> moments to carry the rotational degrees of freedom.
>
> In your mentioned cases this is necessary because there are no muscles
> that can support the Sacrum/Pelvis connection, so the AnyReacForce has
to
> provide the forces. In the T12L1 joint the reaction force is also in
some
> cases necessary, in others it may work without. It appears in some
> applications that the muscles are simply not enough to balance the
system.
>

Thomas wrote:

>
> the standing model contains 7 lumbar joints for 8 segments (T12, L1,
> L2, L3, L4, L5, Sacrum, and Pelvis) coupled by the spine rythm, but
> only two of them (the outermost, i.e. T12L1 and SacrumPelvis) have an
> additional reference (T12L1JntReac and SacrumPelvisReaction) which is
> used by AnyReacForce.
>
> Although i read the manual for AnyReacForce i don’t understand its
> meaning. It is clear to me that the spherical joints generate forces
> to accomplish the constraints, but AnyReacForce generates moments
> (according to AnyMechOutputFileForceExport). Commenting these two
> AnyReacForce folders out changes the results of the analysis.
>
> Can SomeOne please explain to me, what AnyReacForce in the present
> combination with the reference to a spherical joint does and what it
> physically represents?

[Non-text portions of this message have been removed]

Hello Sebastian and John,

thanks for your comments, but one thing is still not clear to me, and this is
related to the statement: “… three moments are applied to the rotational
degrees of freedom to carry whatever the joint has to carry.” What is
this “whatever”, it can’t be arbitrary. Has this something to do with the
provided ThoraxPelvisExtension?

What makes me worry is, that this moment is about 5 Nm for zero degrees
extension, which is quite much if it should normally be zero. In vitro test
are seldomly with moments higher than 10 Nm. Additionally i wonder if it
depends on the amount of muscles forces. As this reaction moment is necessary
because of missing thoracic muscles, shouldn’t it be regarded like a kind of
muscle that must be part of the optimization? That’s why i would like to
understand how the amount of necessary moments is derived.

John, i didn’t mean moment transfer between the thoracic vertebrae but the
transfer between T12 and L1.

Thanks, Thomas

Sebastian wrote:
>
> From a kinetics point of view, the spherical joint provides three reaction:
> Forces in X,Y and Z direction, whereas the three rotations are kept “open”.
>
> With the line AnyReacForce T12L1JntReac={AnySphericalJoint
> &ref=.T12L1Jnt;};
>
> full support is applied to the joint. This means also the rotational
> degrees of freedom are supported with infinite strength - three moments
> are applied to the rotational degrees of freedom to carry whatever the
> joint has to carry.
>
> These rotational degrees of freedom are the kinematic measure I mentioned
> in my previous mail. Joints in AnyBody can be understood as kinematic
> measures equipped with drivers. For instance, a spherical joint is a
>
> distance between two points on two different segments that is driven to be
> zero. So three translational measures are zero, and three rotational
> measures have to be specified elsewhere.
>
> …

Thomas wrote:

>
> thanks for your answers. Step by step i understand more of the model, but i
> have still a more basical question: What does the command
> AnyReacForce T12L1JntReac={AnySphericalJoint &ref=.T12L1Jnt;};
> cause? The command consists of nothing else than that single line, it
> refers
>
> to a joint that is defined few lines above, and the joint already generates
> forces itself, so what does AnyReacForce do additionally to what the
> spherical joint does?
>
> Sebastian, you wrote, “AnyReacForce basically provides all forces and
> moments
> that are necessary”. Necessary to do what? What or where is the measure,
> you
>
> mentioned?
> When a model works without T12L1JntReac and SacrumPelvisReaction why are
> the
>
> results different with and without these AnyReacForces (the rotations of
> the
>
> lumbar segments are the same but the muscle forces are different)?
>
> John, when i understood you correctly, you wrote, that if the thorax had
> muscles integrated, the reaction force (moment) would not be necessary. But
> how can the thorax transfer moments when the disc can be represented by
> spherical joints?
>
> Thank you for your helpfulness,
>
> regards, Thomas
>
> John wrote:
> > Just as a follow-up to Sebastian’s message: The reason why the muscles
> > do not adequately balance the T12L1 joint is that the thorax part of the
> > spine is not modeled. So the muscles that would normally be present in
> > the thorax section are not included in our model and therefore the joint
> > adjacent to the thoracic section cannot be balanced without the
> > additional reaction force.
>
> Sebastian wrote:
> > The AnyReacForce basically provides all forces and moments that are
> > necessary. The AnyRecForce behaves just like normal forces in AnyBody
> > and takes the form of the kinematic measure, so a linear measure results
>
> in
>
> > a force and a rotational measure results in a moment.
> >
> > Applying the AnyReacForce to a Spherical Joint will therefore result in
> > moments to carry the rotational degrees of freedom.
> >
> > In your mentioned cases this is necessary because there are no muscles
> > that can support the Sacrum/Pelvis connection, so the AnyReacForce has to
> > provide the forces. In the T12L1 joint the reaction force is also in some
> > cases necessary, in others it may work without. It appears in some
> > applications that the muscles are simply not enough to balance the
> > system.
>
> Thomas wrote:
> > the standing model contains 7 lumbar joints for 8 segments (T12, L1,
> > L2, L3, L4, L5, Sacrum, and Pelvis) coupled by the spine rythm, but
> > only two of them (the outermost, i.e. T12L1 and SacrumPelvis) have an
> > additional reference (T12L1JntReac and SacrumPelvisReaction) which is
> > used by AnyReacForce.
> >
> > Although i read the manual for AnyReacForce i don’t understand its
> > meaning. It is clear to me that the spherical joints generate forces
> > to accomplish the constraints, but AnyReacForce generates moments
> > (according to AnyMechOutputFileForceExport). Commenting these two
> > AnyReacForce folders out changes the results of the analysis.
> >
> > Can SomeOne please explain to me, what AnyReacForce in the present
> > combination with the reference to a spherical joint does and what it
> > physically represents?
>
> [Non-text portions of this message have been removed]


Dr. Thomas Zander
Wirbelsäule
Julius Wolff Institut
Charité - Universitätsmedizin Berlin
Campus Virchow Klinikum (CVK)
Forum 4, Postfach 24
Augustenburger Platz 1
13353 Berlin

Tel.: +49(0)30 450 55 22 36
Fax: +49(0)30 450 55 99 80
thomas.zander@charite.de
www.julius-wolff-institut.de


From: anyscript@yahoogroups.com [mailto:anyscript@yahoogroups.com] On Behalf
Of Zander, Thomas
Sent: 13. oktober 2008 16:59
To: anyscript@yahoogroups.com
Subject: Re: [AnyScript] AnyReacForce

Hello Thomas,

The AnyReacForce can be used by the system without any cost in order to
reduce the overall muscle activation. So its value is basically adjusted so
that the system makes the most use of it. The values of these moments are
not suited to compare with other sources, as the AnyReacForce is of course
only a remedy for missing muscles which would compensate the moment
otherwise. But nevertheless we assume its influence to be rather minor,
especially when you analyse not the directly adjacent segments.

There are two possible solutions if you want to get rid of the
AnyReacForces. A quick solution would be do introduce moment generating
artificial muscles in the T12L1 joint with a limited strength (similar to
the body model without muscles). But of course the problem are to assign
reasonable strength values. And of course the best way is to build the full
blown model with all necessary muscles.

Best regards,

Sebastian

Hello Sebastian and John,

thanks for your comments, but one thing is still not clear to me, and this
is
related to the statement: “… three moments are applied to the rotational
degrees of freedom to carry whatever the joint has to carry.” What is
this “whatever”, it can’t be arbitrary. Has this something to do with the
provided ThoraxPelvisExtension?

What makes me worry is, that this moment is about 5 Nm for zero degrees
extension, which is quite much if it should normally be zero. In vitro test
are seldomly with moments higher than 10 Nm. Additionally i wonder if it
depends on the amount of muscles forces. As this reaction moment is
necessary
because of missing thoracic muscles, shouldn’t it be regarded like a kind of

muscle that must be part of the optimization? That’s why i would like to
understand how the amount of necessary moments is derived.

John, i didn’t mean moment transfer between the thoracic vertebrae but the
transfer between T12 and L1.

Thanks, Thomas

Sebastian wrote:
>
> From a kinetics point of view, the spherical joint provides three
reaction:
> Forces in X,Y and Z direction, whereas the three rotations are kept
“open”.
>
> With the line AnyReacForce T12L1JntReac={AnySphericalJoint
> &ref=.T12L1Jnt;};
>
> full support is applied to the joint. This means also the rotational
> degrees of freedom are supported with infinite strength - three moments
> are applied to the rotational degrees of freedom to carry whatever the
> joint has to carry.
>
> These rotational degrees of freedom are the kinematic measure I mentioned
> in my previous mail. Joints in AnyBody can be understood as kinematic
> measures equipped with drivers. For instance, a spherical joint is a
>
> distance between two points on two different segments that is driven to be
> zero. So three translational measures are zero, and three rotational
> measures have to be specified elsewhere.
>
> …

Thomas wrote:

>
> thanks for your answers. Step by step i understand more of the model, but
i
> have still a more basical question: What does the command
> AnyReacForce T12L1JntReac={AnySphericalJoint &ref=.T12L1Jnt;};
> cause? The command consists of nothing else than that single line, it
> refers
>
> to a joint that is defined few lines above, and the joint already
generates
> forces itself, so what does AnyReacForce do additionally to what the
> spherical joint does?
>
> Sebastian, you wrote, “AnyReacForce basically provides all forces and
> moments
> that are necessary”. Necessary to do what? What or where is the measure,
> you
>
> mentioned?
> When a model works without T12L1JntReac and SacrumPelvisReaction why are
> the
>
> results different with and without these AnyReacForces (the rotations of
> the
>
> lumbar segments are the same but the muscle forces are different)?
>
> John, when i understood you correctly, you wrote, that if the thorax had
> muscles integrated, the reaction force (moment) would not be necessary.
But
> how can the thorax transfer moments when the disc can be represented by
> spherical joints?
>
> Thank you for your helpfulness,
>
> regards, Thomas
>
> John wrote:
> > Just as a follow-up to Sebastian’s message: The reason why the muscles
> > do not adequately balance the T12L1 joint is that the thorax part of the
> > spine is not modeled. So the muscles that would normally be present in
> > the thorax section are not included in our model and therefore the joint
> > adjacent to the thoracic section cannot be balanced without the
> > additional reaction force.
>
> Sebastian wrote:
> > The AnyReacForce basically provides all forces and moments that are
> > necessary. The AnyRecForce behaves just like normal forces in AnyBody
> > and takes the form of the kinematic measure, so a linear measure results
>
> in
>
> > a force and a rotational measure results in a moment.
> >
> > Applying the AnyReacForce to a Spherical Joint will therefore result in
> > moments to carry the rotational degrees of freedom.
> >
> > In your mentioned cases this is necessary because there are no muscles
> > that can support the Sacrum/Pelvis connection, so the AnyReacForce has
to
> > provide the forces. In the T12L1 joint the reaction force is also in
some
> > cases necessary, in others it may work without. It appears in some
> > applications that the muscles are simply not enough to balance the
> > system.
>
> Thomas wrote:
> > the standing model contains 7 lumbar joints for 8 segments (T12, L1,
> > L2, L3, L4, L5, Sacrum, and Pelvis) coupled by the spine rythm, but
> > only two of them (the outermost, i.e. T12L1 and SacrumPelvis) have an
> > additional reference (T12L1JntReac and SacrumPelvisReaction) which is
> > used by AnyReacForce.
> >
> > Although i read the manual for AnyReacForce i don’t understand its
> > meaning. It is clear to me that the spherical joints generate forces
> > to accomplish the constraints, but AnyReacForce generates moments
> > (according to AnyMechOutputFileForceExport). Commenting these two
> > AnyReacForce folders out changes the results of the analysis.
> >
> > Can SomeOne please explain to me, what AnyReacForce in the present
> > combination with the reference to a spherical joint does and what it
> > physically represents?
>
> [Non-text portions of this message have been removed]


Dr. Thomas Zander
Wirbelsäule
Julius Wolff Institut
Charité - Universitätsmedizin Berlin
Campus Virchow Klinikum (CVK)
Forum 4, Postfach 24
Augustenburger Platz 1
13353 Berlin

Tel.: +49(0)30 450 55 22 36
Fax: +49(0)30 450 55 99 80
thomas.zander@ <mailto:thomas.zander%40charite.de> charite.de
www.julius-wolff-institut.de

[Non-text portions of this message have been removed]