Thanks Søren,
I tried to make the drivers supply the movement generating moment. To do so,
I commented out the diagnostic muscle part (#include “JointMuscles.any”,
RightLegOnly/ LegNoMuscles.root.any:31) and set reaction.type={on} (#include
Drivers_NoMuscles.any, STS.main.any:70) for my knee and ankle flexion
drivers. It gave me the following warning:
- Inverse dynamic analysis…
WARNING(OBJ.MCH.DYN2) : C:\Documents and Settings\Jean-Olivier
Racine\Desktop\LIO\Anybody\Repository.6\ARep\LIO\STS Test
3\InverseDynamicsStudy.any(1) : ‘InverseDynamicsStudy’ : Model contains
redundant constraint reactions :
List of redundant reactions:
0: Main.Model.HumanModel.Right.Leg.Jnt.Knee.Constraints.Reaction[0]
1: Main.Model.HumanModel.Right.Leg.Jnt.Knee.Constraints.Reaction[1]
Everything ran well besides that warning. But when I looked at the moments,
the knee flexion moment looks more like noise than any realistic value. Not
to mention that it has a very low amplitude (moments of 10Nm?). So I figure
that the redundant knee reaction is competing for the moments, therefore
falsifying my values. Where is that other reaction come from? Too bad it’s
not specified in the warning message… I looked everywhere it seemed logical
to have it but couldn’t find it…
Since my solution didn’t work, I figured I’d try the other one, with the
diagnostic muscles. So I’ve set my reaction.type to off (#include
Drivers_Muscles.any, STS.main.any:69) again and re-added the joint muscles
(#include “JointMuscles.any”, RightLegOnly/ LegNoMuscles.root.any:31). But
both the negative and positive muscles give me zero strength! I only get
fibber length values (lm, lmt, lmdot, lmtdot)…
Clearly, I must be doing something wrong, but what?
Thanks!
Jean-Olivier
P.-S. Model uploaded to the group in case you need it (stsjoints.rar)
From: anyscript@yahoogroups.com [mailto:anyscript@yahoogroups.com] On Behalf
Of AnyBody Support
Sent: 26 avril 2007 03:17
To: anyscript@yahoogroups.com
Subject: [anyscript] Re: Classical inverse dynamic analysis
Hi Jean-Oliver
Yes you are right, if you have the reaction.type in the drivers set
to “On” the driver will carry the load and you can read out its value.
Alternatively if you are not driving all the human joints directly
and want to have them carried you can also apply a AnyReacForce to
the joint, in this way the free dof in joint will also be carried
but no motion will be supplied.
If you are using a repository model and you are using a model with
nomuscles on it will also be possible to read out the joint moments.
By default these versions supply joint torque muscles to the joints
and by reading out the forces in these joint torque muscles you have
the joint moments. As i recall it these can be found named
JointMuscles. Please notice that there is a muscle for each dirction
of the moement.
You are right about the ForceMomentMeasure it will currently not
measure the moment generated by the muscles, this will however be
possible in future versions.
Best regards
Søren, AnyBody Support
— In anyscript@yahoogrou <mailto:anyscript%40yahoogroups.com> ps.com,
Jean-Olivier Racine <jean-
olivier.racine.1@…> wrote:
>
> I just realized that there’s a Reaction.Type not only in joints,
but also in
> drivers. So I suppose that if I set this to ON, I should get the
required
> information. I’ll try that and see what happens. Sorry about that.
>
>
>
> _____
>
> From: anyscript@yahoogrou <mailto:anyscript%40yahoogroups.com> ps.com
[mailto:anyscript@yahoogrou <mailto:anyscript%40yahoogroups.com> ps.com]
On Behalf
> Of Jean-Olivier Racine
> Sent: 25 avril 2007 10:34
> To: anyscript@yahoogrou <mailto:anyscript%40yahoogroups.com> ps.com
> Subject: [anyscript] Classical inverse dynamic analysis
>
>
>
> Hi again,
>
> Is it possible to perform a classical inverse dynamic analysis on
the model?
> I would like to calculate joint torques and reaction forces at the
joints
> required to perform a certain motion. In the tutorial this step is
skipped,
> saying: “Since we have no muscles so far, kinematic analysis is
really all
> that makes sense”. But in my case there is some relevant
information I’d
> like to extract from this.
>
> I tried using an AnyForceMomentMeasure and including all muscles
that act on
> the joint, but it seems that these muscles are not considered to be
applied
> directly (am I right?), so I get a zero moment vector.
>
> I also tried looking at the Constraints.Reaction, but those are
just, as the
> name says, the constrained reaction, and therefore do not provide
the
> torques in the non-constrained degrees of freedom.
>
> How can I get the joint torque in the non-constrained degrees of
freedom of
> a joint?
>
> Thanks you,
>
> Jean-Olivier
>
> _____
>
> From: anyscript@yahoogrou <mailto:anyscript%40yahoogroups.com>
ps.com
> [mailto:anyscript@yahoogrou <mailto:anyscript%40yahoogroups.com>
ps.com] On
> Behalf
> Of AnyBody Support
> Sent: 21 avril 2007 15:12
> To: anyscript@yahoogrou <mailto:anyscript%40yahoogroups.com> ps.com
> Subject: [anyscript] Re: Contraints.Reaction.Fout
>
> Hello Jean-Olivier,
>
> Contraints.Reaction.Fout is a menber of any constraint. It is the
> force(s) in the constraint. If the constraint is a joint then
> Contraints.Reaction.Fout contains the joint reactions just as you
> anticipate.
>
> But here is the point of the story: Joint reactions are very
> different depending on whether you have muscles in the model or
not.
> Joint reaction forces in models relying only on joint torques, i.e.
> classical inverse dynamics, are hugely under estimated. If you only
> have joint torque providers in the model, then the joint reactions
> are only what the external forces produce. When you include the
> muscles, their contribution to the joint reaction is added and it
is
> often larger than what the xternal forces provide. A muscle can
only
> produce torque in a force couple with a joint reaction, so the real
> joint reactions are much larger than what you get from a model with
> pure joint torques.
>
> In other words, it is correct that you get different joint
reactions
> depending on whether you include muscles in the model or not.
>
> Best regards,
> John
>
> — In anyscript@yahoogrou <mailto:anyscript%40yahoogroups.com>
ps.com,
> Jean-Olivier Racine <jean-
> olivier.racine.1@> wrote:
> >
> > Hello all,
> >
> >
> >
> > I am wondering what are the Contraints.Reaction.Fout values. As I
> run my
> > model with and without muscles, I get different values for those.
> Therefore,
> > I conclude that these are not the Reaction Forces, as defined
when
> doing
> > classical inverse dynamics (reaction forces and moments passed
from
> one
> > joint to the other), since they should not change with or without
> muscles.
> > So my questions:
> >
> >
> >
> > 1. What are these Constraint.Reaction.Fout value?
> > 2. How can I get those reaction forces that come directly from
> the
> > classic inverse dynamics analysis?
> >
> >
> >
> > Thanks!
> >
> > Jean-Olivier
> >
> >
> >
> > [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]