Hi Thomas,
You have to provide some artificial support because the system will almost
never be perfectly balanced. Basically you could provide this residual
wherever you want, but it is a good approach to do it on the pelvis.
If the input data (motion, forces, scaling of the bodymodel) is good there
should be only a small residual and therefore a small influence of the
results. The resultant hip force in your example (as in all the gait
examples in the repository) is a result of both the external forces and the
muscle forces. The muscles will be recruited to balance the forces and
stabilise the joints so they do contribute.
So I think from the model side your approach is the right one. Please have a
look at the input data. Please write again if you have further problems.
Best regards,
Sebastian
From: anyscript@yahoogroups.com [mailto:anyscript@yahoogroups.com] On Behalf
Of knox40
Sent: 10. december 2008 17:23
To: anyscript@yahoogroups.com
Subject: [AnyScript] Re: Ground contact forces
Hi Sebastian,
Thanks - Ok, then the model is working and the Hip Reaction Force is
realistic.
However if the model especially the pelvis is fixed and the foot is
loaded by ground reaction force, the hip resultant force is not the
result of the muscle forces. Thus, for example, the abductors are
far too low because the major force is carried by the fixed pelvis.
While I’m interested in both, the hip resultant hip force and the
appropriate muscle forces, what else can I do?
Best regards
Thomas
— In anyscript@yahoogrou <mailto:anyscript%40yahoogroups.com> ps.com,
AnyScript Support
<anyscriptsup@…> wrote:
>
> Hi Thomas,
>
> Sorry for not being precise. You have to switch everything ON.
Then the
> model runs the whole analysis.
>
> Best regards,
>
> Sebastian
>
>
>
> _____
>
> From: anyscript@yahoogrou <mailto:anyscript%40yahoogroups.com> ps.com
[mailto:anyscript@yahoogrou <mailto:anyscript%40yahoogroups.com> ps.com]
On Behalf
> Of knox40
> Sent: 10. december 2008 12:31
> To: anyscript@yahoogrou <mailto:anyscript%40yahoogroups.com> ps.com
> Subject: [AnyScript] Re: Ground contact forces
>
>
>
> Hi Sebastian,
>
> ok, so the reaction force in the pelvis can be switched to on, but
> the values should be as low as possible, right?
>
> But if I run the model with the GRF on the right foot, which you
can
> find under files: Thomas_Upstair:GRF.zip, it aborts with the
message:
>
> Muscle recruitment analysis failed, simplex solver reports that
> solution does not satisfy all constraints.
>
> Even if I switch the pelvis y-reaction force to On, this message
> appears.
>
> What can I do to improve my model and make it run?
>
> Best regards,
>
> Thomas
>
> — In anyscript@yahoogrou <mailto:anyscript%40yahoogroups.com>
ps.com,
> AnyScript Support
> <anyscriptsup@> wrote:
> >
> > Hi Thomas,
> >
> > I’m pretty sure that even the lateral reaction modifies your
GRL.
> The value
> > of these forces appears to be quite significant in your first
> model.
> >
> > But of course it’s very good to use the experimental force data.
> And you are
> > right in order to balance the system you will need to hook the
> system up to
> > a “hand of god”.
> >
> > See e.g. the GaitUniMiami model, there is also a Reactionforce
on
> the Pelvis
> > which grounds the residuals which will occur. (Of course these
> residuals
> > should be resonable low.)
> >
> > Best regards,
> >
> > Sebastian
> >
> >
> >
> > _____
> >
> > From: anyscript@yahoogrou <mailto:anyscript%40yahoogroups.com>
ps.com
> [mailto:anyscript@yahoogrou <mailto:anyscript%40yahoogroups.com>
ps.com]
> On Behalf
> > Of knox40
> > Sent: 9. december 2008 15:03
> > To: anyscript@yahoogrou <mailto:anyscript%40yahoogroups.com>
ps.com
> > Subject: [AnyScript] Re: Ground contact forces
> >
> >
> >
> > Hi Sebastian,
> >
> > thank you so far for your help.
> >
> > Ok, by doing so, the total contact forces are not so much “off”.
> But
> > as I have only the lateral reaction of the pelvis “On”, the
> contact
> > should be at least the value of body weight even if the dynamic
> > forces are neglected?
> > How can I balance my model if I want to turn the lateral pelvis
> > support to “OFF”? How is it managed within other models with
large
> > movements?
> >
> > As this upstair model is based on the measurements by Bergmann
> from
> > the CD “HIP98”, there are also some ground reaction forces
> > available.
> >
> > So I want to enhance my model by this ground reaction forces.
> > Therefore I have chosen the same procedure as for the Gait3D
> model,
> > using the zero-mass segment linked to the BodyModel.
> >
> > So far I have done it for the right foot - I have switched of
the
> > Conditional Contact for the right foot and it should be
supported
> by
> > the ground reaction forces. However everything is working fine
> until
> > step 5, when the left foot looses contact and the model is only
> > supported by the right foot.
> >
> > Pleas have a look at the model Thomas_Upstair_GRF.zip
> > by using again the Aalborg.zip file for scaling with the
> Repository
> > 6.2.
> >
> > I think the problem is about equilibrium, thus when the left
foot
> > leaves ground and the right foot is the only support, there must
> be
> > equilibrium between the GRF and the BodyModel.
> > But there is never 100% equilibrium for measured data, so how
can
> I
> > handle this?
> >
> > Thank you.
> >
> > Best regards
> >
> > Thomas
> >
> > — In anyscript@yahoogrou <mailto:anyscript%40yahoogroups.com>
> ps.com,
> > AnyScript Support
> > <anyscriptsup@> wrote:
> > >
> > > Hi Thomas,
> > >
> > > I had a look at your model and it appears to be not so
much “off”
> > >
> > > When you just include these lines in the study folder:
> > >
> > > AnyFloat RightForce =
> > >
> >
>
Main.Model.ModelEnvironmentConnection.Drivers.ConditionalContact.ToeM
> > edialCo
> > > ntactNodeRight.Push.NormalForceVec
> > >
> > > +
> > >
> >
>
Main.Model.ModelEnvironmentConnection.Drivers.ConditionalContact.ToeL
> > ateralC
> > > ontactNodeRight.Push.NormalForceVec
> > >
> > > +
> > >
> >
>
Main.Model.ModelEnvironmentConnection.Drivers.ConditionalContact.Heel
> > Support
> > > Right.Push.NormalForceVec;
> > >
> > >
> > >
> > > And further put these lines in the ContactSurfaceLinPush.any
> file:
> > >
> > > //resultann force given in global ref system
> > >
> > > AnyVec3 NormalForceVec =
> > > DrawNormalForce.Vec/
> > (.ScaleFactor*.DrawRef.DrawSettingsSupport.Lin.ScaleFact
> > > or);
> > >
> > > AnyVar NormalForceScalar =
> > > (NormalForceVec[0]^2+NormalForceVec[1]^2+NormalForceVec[2]^2)
> ^0.5;
> > >
> > >
> > >
> > > Then you can analyse the total contact forces which look not
so
> > bad. But of
> > > course I expect the turned on reaction in the hip to carry
some
> of
> > the load.
> > >
> > >
> > > What were your results for the Contact forces?
> > >
> > > Best regards,
> > >
> > > Sebastian
> > >
> > > _____
> > >
> > > From: anyscript@yahoogrou <mailto:anyscript%40yahoogroups.com>
> ps.com
> > [mailto:anyscript@yahoogrou <mailto:anyscript%40yahoogroups.com>
> ps.com]
> > On Behalf
> > > Of knox40
> > > Sent: 8. december 2008 12:23
> > > To: anyscript@yahoogrou <mailto:anyscript%40yahoogroups.com>
> ps.com
> > > Subject: [AnyScript] Ground contact forces
> > >
> > >
> > >
> > > Hi,
> > >
> > > I have used dummy muscles to simulate the ground reaction
forces
> > as
> > > they are unknown in my model. After calculating and looking in
> the
> > > ModelEnvironmentConnection Folder, the magnitude of the ground
> > > contact forces (in Conditional Contact) of my upstair model
> seems
> > > too low.
> > > Even if I controll the pelvis still in the x and z direction
to
> > keep
> > > balance as it is difficult to do it otherwise, the forces in
the
> > one
> > > legged stance phase must be regular something about the body
> > weight
> > > of the person (860N).
> > >
> > > However the hip reaction forces are reasonable 3-4 times body
> > weight
> > > as measured by Bergmann etc.
> > >
> > > I have upload the model as Thomas_Upstair in the file folder.
> > >
> > > Best regards
> > >
> > > Thomas
> > >
> > >
> > >
> > >
> > >
> > > [Non-text portions of this message have been removed]
> > >
> >
> >
> >
> >
> >
> > [Non-text portions of this message have been removed]
> >
>
>
>
>
>
> [Non-text portions of this message have been removed]
>
[Non-text portions of this message have been removed]