Hi Søren,
The suggestion with adding a small amount of gravity works fine. The modell
does not stop at an early phase of the simulation.
Also the corrected GHreactions-file calculates now forces in the same
dimension as shown in the Bergmann study. Thanks a lot for that!
But i get several Warnings or Errors during some of my movements:
While a GH-flexion of 120° i get this warning message:
WARNING(OBJ.MCH.KIN7) :
Q:\Biomechanik\Projekte\018_AnyBody\Repository.6\Repository.6\BRep\Aalborg\Arm3D
\Muscle.any(584)
: ‘pectoralis_major_clavicular_part_4.SPLine’ : Penetration :
Via-point
‘Main.MyShoulder.HumanModel.Right.ShoulderArm.Seg.Humerus.I_pectoralis_major_cla
vicular_part_4’
on
‘Main.MyShoulder.HumanModel.Right.ShoulderArm.Mus.pectoralis_major_clavicular_pa
rt_4.SPLine’
is located below the wrapping surface
'Main.MyShoulder.HumanModel.Right.ShoulderArm.Seg.Scapula.coracoid_cyl2.cyl
Should i move the Viapiont? If yes, in which direction and how much? Do you
have any rule of thumb for this kind of problem? This warning appears five
times (part 1-5, some clavicular and some thoracic), shortly before the end
of the analysis.
While a GH-abduction from 0 to 90° this Warning appears:
WARNING(OBJ.MCH.KIN6) :
Q:\Biomechanik\Projekte\018_AnyBody\Repository.6\Repository.6\BRep\Aalborg\Arm3D
\Jnt.any(45)
: ‘GHRot’ : Close to singular position : Orientation close to
Gimbal Lock, i.e., first and third axis of rotation being parallel
Does this mean the axis of rotation of a different joint (Wrist or elbow?)
is parallel or are there more than one rotation axis in the GH-joint?
//Definition of GH joint
AnyKinRotational GHRot = {
AnyRefNode &scapula_gh = …Seg.Scapula.gh;
AnyRefNode &humerus_gh = …Seg.Humerus.gh;
Type = RotAxesAngles;
Axis1 = y;
Axis2 = z;
Axis3 = y; };
Could be a typing error as well: you did not define the x-axis. Which one
should that be?
I get an error during the simulation of the coffeepot-motion (pulling the
coffeepot standing on the table towards him, i only added a small friction
in x-direction). I use flexion in the GH-joint , a rotation in the elbow
and a wrist-abduction.
ERROR :
Q:\Biomechanik\Projekte\018_AnyBody\Repository.6\Repository.6\BRep\Aalborg\Arm3D
\Muscle.any(499)
: pectoralis_major_thoracic_part_4 : Unexpected exception in the
library OOSol :
OOSol exception : General factorization exception : Negative or zero
pivot
When i add a rotation in the SternoClavicularProtraction of -5°, so that
the clavicula-scapula-construct moves backwards with the arm, the error
disappears. Why can´t i drive only the GH-joint?
If you have any other suggestions, improvements or results you can hand out
relating to the Bergmann study, just tell me.
Thanks a lot.
Best regards,
Alex
Alexander Nolte
Berufsgenossenschaftliche Unfallklinik Murnau, Prof. Küntscher Str. 8,
82418 Murnau am Staffelsee
Eingetragener Verein, Amtsgericht München, Registernummer VR 4704
Geschäftsführer Direktor Dr. Peter Schmidt
|---------±--------------------------->
| | “AnyBody Support”|
| | <support@anybodyt|
| | ech.com> |
| | |
| | |
| | Gesendet von: |
| | anyscript@yahoogr|
| | oups.com |
| | |
| | |
| | 20.03.2007 10:47 |
| | Bitte antworten |
| | an anyscript |
| | |
|---------±--------------------------->
>-------------------------------------------------------------------------------
-----------------------------------------------|
|
|
| An: anyscript@yahoogroups.com
|
| Kopie: (Blindkopie: Alexander Nolte/V/BUKM/BGNET/DE)
|
| Thema: [anyscript] Re: Shoulder modelling
|
>-------------------------------------------------------------------------------
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Hi Alex
I will try to answer your questions.
The property GhReation.FTotal i measured in the global coordinate
system, you can see how it is calculated in the file
BRep/ArmShoulder/GHreactions.any, it is a summation of muscles
forces. It is a long explanation: the gh reaction is created by eight
pushing muscles which all points into the GH rotations center and
originates form the edge of the cavity of scapula. This setup ensures
that the gh reaction force will always fall within the joint cavity.
The FTotal property is a summation of these forces.
How do you drive the arm?, please make sure that you have no
reactions presents in your drivers this make take away load from the
arm and result in a gh lower reaction.
I have reviewed the file GHReactions.any, here i found a bug in the
summation of the shoulder forces, which has the effect that the
forces are too small by a certain factor, the shape and direction of
the forces are not effected. The FTotal is found as a summation of
eight forces as mentioned earlier, here the force in the muscle Ft is
multiplied on a vector, and it was this vector which was not
normalized. Since the eight vectors are all small and all have the
same length this only changes the size of the force. I will upload a
file named GHReaction.any to the file section of this group shortly.
In principle it would be possible to implement friction on the eight
pushing muslces mentioned above but i am not sure how this would work
out and what the size of the friction coefficient should be? If you
are more interested in this please look into the example named
PedelDemoConditional and look in the file JointAndDrivers.any in the
bottom of this file you can see an example on the use of the friction
element.
I can not say exactly why you get this error, here is a suggestion
that may help. Sometimes if you add a small amount of gravity to
another direction it creates a problem which are easier to solve for
the optimizer, so something like this {0.001,-9.81,0.001} could work.
About the timeshift i understand this as you would like to have
motion in one joint and then later on motion in another joint. If
this is the case it can be done with interpolation drivers as you
suggest, fourier drivers might also be an option, depending on what
kind of motion you would like to obtain.
Please ask again if you have further questions
Best regards
Søren, AnyBody Support
— In anyscript@yahoogroups.com, “noltealexander”
<alexander.nolte@…> wrote:
>
> Hi AnyBody-Team,
>
> i am working with a shoulder-model from the repository for my
diploma-
> thesis.
> I used the building block tutorial and included the files
> SpineNoMusclesRightArm.any from the BRep, because i wanted the
> computing time kept as short as possible and i´m not interested in
> the trunk- or leg-muscles.
> There is a Webcast on the 26th April with the subject Validation of
> the AnyBody ver-sion of the Dutch Shoulder Model by the in-vivo
> measurement of GH contact forces by Bergmann et al. (26 Apr).
> I read the paper and tried to simulate the motions Bergmann´s
patient
> did. For e-xample: The GHReactions (FTotal) shows a Resultant Force
> of only about 40 N while 90° abduction with a load of 20 N in the
> hand.
> Are these forces measured in the GHReactionCenterNode? How do you
> measure these forces?
> Could it be , that the fixed position of the humerus with reference
> to the scapula is the reason for the little GHReactions? So how
could
> i implement friction in the GH-joint (main reason for moment and
> additional lever arms which apply high load to the joint-surface)?
> With the simple muscle model (from ShoulderArm.root.any), the
motion
> 90° abducti-on stops after the 5th step with the error-
message „ERROR
> (OBJ1) : Q:\Biomechanik\Projekte\018_AnyBody\Repository.6
> \Repository.6\ARep\Murnau\MyShoulder\MyShoulder.Main.any
> (58) : ‘MyStudy’ : Muscle recruitment analysis fai-led,
simplex
> solver reports that solution does not satisfy all constraints.".
> Other types of motion are working fine, so what could that be?
> Another Question is, how i can activate some of the drivers time-
> shifted? Should i use the interpolation-driver or is there any
other
> alternative?
> Do you already have some ideas how to improve your shoulder-model?
> Unfortunately, my time is running out, so i would appreciate an
> answer ahead, so i don´t need to wait until the 26th April.
>
> Thank you very much,
>
> Alex
>