Hi Thomas,
If you want to record the center of mass during movement you can use the
AnyKinCoM measure, similar like this:
AnyKinCoM ComMeasure= {
AnyFolder &Body = .Model;
};
This should give you the position.
Best regards,
Sebastian
From: anyscript@yahoogroups.com [mailto:anyscript@yahoogroups.com] On Behalf
Of knox40
Sent: 25. juli 2008 09:37
To: anyscript@yahoogroups.com
Subject: [AnyScript] Re: Abductor Muscles
Hi Sylvain,
Thank’s again for your help, this forum is quite a good institution
from ANYBODY.
Of course that was the reason why the muscle forces were so low. By
switching the reaction force OFF, the muscle forces are in good
agreement with anticipate values.
In the next step I want to change the balance point (COM) of the
upper body and chart the hip force against the changing COM position.
As I am not using the COM driver within the FreePostureMove model,
how can I record the center of mass during movement?
AnyKinMeasure Org xzmeasure ={
…?
…?
Or is it easier to use the COM Driver for this exercise? - if yes,
what dof’s should I suppress then?
Best regards,
Thomas
— In anyscript@yahoogrou <mailto:anyscript%40yahoogroups.com> ps.com,
“AnyBody Support” <support@…>
wrote:
>
> Hi Thomas,
>
> The fact that you have the reaction force On for the pelvis is
mainly
> the reason for the low muscle activity. The gluteus does not
balance
> the pelvis because the Reaction.Type already does it. So you have
to
> switch Off the reaction for the 3 rotations of the pelvis. I think
> you can keep on the reaction for the translation on x and z.
> This should give you much more reasonable results.
>
> Best regards,
> Sylvain, AnyBody Support.
>
>
>
> — In anyscript@yahoogrou <mailto:anyscript%40yahoogroups.com> ps.com,
“knox40” <knox40@> wrote:
> >
> > Hi John, Hi Sylvain,
> >
> > Unfortunately I have no measured ground reaction forces to drive
> the
> > model. Instead I defined three nodes (HeelContactNode,
> > ToeMedialContactNode and ToeLateralContactNode) where I have the
> feet
> > connected to. This nodes should provide the ground reaction
forces
> > similar to the PedalDemoConditional model. The foot in my changed
> > FreePostureMove model is driven by an interpolation driver.
> >
> > I have switched of the reaction force in the y direction of the
> > PelvisGroundDriver to transfer the load to the feed. In my
opinion
> > the fixed rotation of the pelvis must cause the low gluteus
muscle
> > forces, am I right?
> > In principle all these reaction forces should be off, but how can
I
> > than balance the model? Can I use a COM driver for that? Can you
> give
> > me an example how to use it and which dof’s do I have to change?
> >
> > Thanks so far.
> >
> > Best regards
> >
> > Thomas
> >
> >
> >
> > — In anyscript@yahoogrou <mailto:anyscript%40yahoogroups.com> ps.com,
“John Rasmussen” <jr@> wrote:
> > >
> > > Hi Thomas,
> > >
> > > I did not have time to download and debug your model but the
free
> > > posture model is similar to the gait models in the sense that
it
> is
> > > grounded at the pelvis rather than at the feet.
> > >
> > > This means that the muscle actions are determined mostly by the
> > > measured ground reaction forces you are aplying to the feet.
How
> > were
> > > they applied in your case and are you using actual measured
> forces
> > > that correspond exactly to the posture you have placed the
model
> in?
> > >
> > > The issue might be that because the GRFs go mostly axially
> through
> > > the leg, the model becomes rather sensitive to small deviations
> in
> > > force direction. If it deviates just a little in direction the
> > force
> > > vector can end up passing on the wrong side of a joint and
create
> a
> > > joint moment that has the wrong sign. This will of course
change
> > the
> > > muscle activations completely.
> > >
> > > I hope that might help.
> > > John
> > >
> > >
> > > — In anyscript@yahoogrou <mailto:anyscript%40yahoogroups.com>
ps.com, “knox40” <knox40@> wrote:
> > > >
> > > > Hi Sylvain,
> > > >
> > > > first of all thank you for your answer.
> > > >
> > > > You are right, the abductors are not all zero. Nevertheless
the
> > > > Gluteus Minimus 1-3, the Gluteus Medius 1 and the Tensor
> Fasciae
> > > > Latae are zero. The Gluteus Medius 2 and 3 (70, 85 N) is
quite
> > low
> > > > compared with values from literature for a one legged stance.
> > > >
> > > > Contrary the adductor muscles are comparative higher.
> > > >
> > > > Why are the abductors so different from literature and so
low?
> > They
> > > > should contribute mainly to the stability of the standing
> posture
> > > by
> > > > counterbalancing the weight of the torso!
> > > >
> > > > Hope you can help me as I don’t know how these results could
be
> > > > explained.
> > > >
> > > > Best regards
> > > >
> > > > Thomas
> > > >
> > > > Thomas Thielen
> > > >
> > > >
> > > >
> > > >
> > > > — In anyscript@yahoogrou <mailto:anyscript%40yahoogroups.com>
ps.com, “AnyBody Support”
<support@>
> > > > wrote:
> > > > >
> > > > > Hi Thomas,
> > > > >
> > > > > To the first question: yes the body mass for the Gait3D
model
> > is
> > > > 64.9
> > > > > kg. The model has been scaled to fit the subject of the
> > > experiment
> > > > > (in dimension as well as in mass). The standard mass of our
> > model
> > > > is
> > > > > 75 kg, so it is the mass of the FreePostureMove by default.
> > > > >
> > > > > Now I have run your model and it appeared that the Gluteus
> > muscle
> > > > > forces are not zero. So my guess is that you was probably
not
> > > > looking
> > > > > at the good output. Of course you have to look at the right
> > side
> > > > and
> > > > > not at the left side. But I’m more thinking about the
> different
> > > > > output in each muscle. There is several force output in
each
> > > muscle
> > > > > folder and the one you should look at are Fm, Ft and Fp.
> > > > > Fm is the force in the contractile element of the muscle.
Ft
> is
> > > the
> > > > > force in the tendon. Those two forces are different when
> using
> > > the
> > > > 3
> > > > > elements model, but as you are using the simple muscle
model
> > > there
> > > > is
> > > > > no difference between tendon or contractile element and
those
> > two
> > > > > forces are equally representing the total muscle force.
> > > > > Fp represents the force of the passive elasticity of the
> muscle
> > > and
> > > > > it is only used for the 3 elements muscle model. In the
> simple
> > > > model
> > > > > there is no passive elasticity so Fp is zero.
> > > > >
> > > > > Best regards,
> > > > > Sylvain, AnyBody Support.
> > > > >
> > > > >
> > > > >
> > > > >
> > > > > — In anyscript@yahoogrou <mailto:anyscript%40yahoogroups.com>
ps.com, “knox40” <knox40@> wrote:
> > > > > >
> > > > > > Hallo,
> > > > > > -----------------
> > > > > > first of all a short questions:
> > > > > >
> > > > > > The body mass of the whole gait3D model (legs + upper
body
> > > part)
> > > > is
> > > > > > 64,9 kg (649 N)whereas the FreePostureMove model is 75 kg
> > (750
> > > > N),
> > > > > > right?
> > > > > > -----------------
> > > > > >
> > > > > > My goal is to determin the hip resultant force and the
hip
> > > muscle
> > > > > > forces (especially the Gluteus Minimus/Medium/Maximus,
> > > Piriformis
> > > > > and
> > > > > > Tensor Fasciae Latae etc.)for different postures and
again
> if
> > > one
> > > > > > muscle will be suppressed to see the differences.
> > > > > >
> > > > > > So far I have changed the FreePostureMove model to a one
> > legged
> > > > > stance
> > > > > > model. The hip resultant force with about 2000 N is
> > reasonable
> > > > > (2000
> > > > > > N / 750 N = ~2.7 Body weight). Unfortunately by looking
at
> > the
> > > > > muscle
> > > > > > forces especially at the abductors (Gluteus Minimus 1-3
and
> > > > Medius
> > > > > 1-
> > > > > > 3) they are all about zero. How can this be as the
> abductors
> > > are
> > > > > > mainly responsible to keep the pelvis in ballance? Former
> > > studies
> > > > > > revealed that the hip joint is charged with about 5/6
Body
> > > weigth
> > > > > > (body weight minus standing leg) and a lever arm
depending
> on
> > > the
> > > > > > posture (position of the COM). The only possibility to
> > > withstand
> > > > a
> > > > > > moment on the hip joint are mainly the abductors on the
> other
> > > > side
> > > > > > with the lever arm from the greater trochanter to center
of
> > the
> > > > hip
> > > > > > joint. It is impossible that they are zero as in my
model…
> > > > > >
> > > > > > What is wrong with my model?
> > > > > >
> > > > > > I’ve attached my model in the file folder as
> > > > > >
> > > > > > OneLegStand_Model1.zip
> > > > > >
> > > > > > Maybe you can have a look at it to give me a judgement
what
> > > could
> > > > > be
> > > > > > wrong. Do I have to change the solution algorithm to
> > > > AnyMuslceModel
> > > > > > where all muscles have constant strength ?
> > > > > >
> > > > > >
> > > > > > Thank you for your help.
> > > > > >
> > > > > > Best regards
> > > > > >
> > > > > > Thomas
> > > > > >
> > > > >
> > > >
> > >
> >
>
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