Hi Sarah
I have uploaded a new version of you application to the file section
of the group it is named “SarahArmModel – Muscles_6-11-07V2” . I
have updated the InitialPosition.any file and made some changes in
the Mannequin.any file so now it loads at a reasonable position and
also run kinematically.
Concerning the MinMaxNRSimplex solver you may experience cases like
you are describing. When the tStart, tEnd or nStep are changed it
means that the analysis will calculate for different time values. If
the model is sensitive this may provoke recruitment problems like
you have experienced. This basically means that a certain or several
dof. in the model are difficult to balance with muscles forces. If
this is the case one solution is to try adding AnyReacForces to the
different dof in the model, if adding a AnyReacForce for a certain
dof in the model makes it stable, it indicates that this dof. is
causing the problem.
The recruitment problem may also occur if there are very strong
muscles present in the problem, this can make the model numerically
difficult to solve. This can be the case if you have strong pushing
muscles for generating support forces to the model, like on a
backrest or similar. So sometimes lowering the strength of these
muscles makes the model more stable.
If you add a small amount of gravity to the directions of the model
having zero gravity, it also often helps making the recruitment more
stable. So something like Gravity = {0.01, -9.81, 0.01}; usually
helps without disturbing the solution of the problem.
The next version of AnyBody will have some additional settings
available in the solver. This can sometimes help solve recruitment
problems if these are caused by numeric problems.
I tried to make your model run inverse analysis, but it seemed that
one timestep was causing problems. The reactions in the GH joint are
created with a number of pushing muscles which ensures that the
reaction force fall with the cavity of scapula. Due to the loading
conditions of this model i tried to change the directional reactions
in the glenohumeral joint back to a classic spherical joint, and it
help solve the problem. To introduce this change to your brep
please do the following changes in Arm3d/jnt.any
1: outcomment the line "#include "“ghreactions.any”
2: change the lines
AnyKinEq GHLinCon = {
AnyKinMeasure &GHLinCon = .GHLin;
Reaction.Type={Off,Off,Off};
};
to
AnyKinEq GHLinCon = {
AnyKinMeasure &GHLinCon = .GHLin;
// Reaction.Type={Off,Off,Off};
};
Best regards
Søren, AnyBody Support
— In anyscript@yahoogroups.com, “Sarah R. Sullivan” <sarsulli@…>
wrote:
>
> I have a question regarding RecruitmentSolvers, specifically the
> MinMaxNRSimplex solver (although I’m sure my question applies to
the
> other Recruitment Solvers as well). I have noticed in the past
(and
> with the current model that I am working on), that I will
occasionally
> get the following error when I am adjusting the tEnd and nStep
values:
>
> ERROR(OBJ1) : MyStudy’ : Muscle recruitment analysis failed,
> simplex solver reports that solution does not satisfy all
constraints.
>
> Depending on the tEnd and nStep values I plug in, I can often get
the
> model to run all the way through. For example, if I have a file
that
> has a kinematics time frame of 0-58, and a kinetics time frame of
> 0-116, I have noticed that changing the tEnd and nStep does not
always
> guarantee that the InverseDynamicsAnalysis will fully run through;
I
> can have the tEnd be 58/120 (to represent a 120 Hz sampling rate),
and
> the nStep be 58, and the model will compile and run fine.
However, if
> the tEnd is (arbitrarily) 30/120, and the nStep is 30, the model
will
> compile, however it won’t run to completion. And often, the length
> that the model will run before failing varies in a non-decipherable
> pattern. If my tEnd and nStep is 25, the model may run until 22
> before failing – completing nearly the entire analysis. However,
if
> my tEnd and nStep is 55, the model may run to only 9 before
failing –
> hardly completing any of the analysis.
>
> I’m sure there is a simple explanation for this which will help in
> future analyses and my determination of tEnd and nStep values.
Could
> you help me out with this? Thank you for your time!
>
> PS – I have uploaded a wheelchair model that I am trying to fully
> drive with the addition of trunk movement (right now the trunk is
> fixed to the back of the wheelchair – I wrote about two weeks ago
with
> a question about this model). It currently compiles, but I think
> there is a problem with the initial conditions because the left
side
> of the body does not mimic the right side at load time. It was
> working, and I’m not quite sure what I changed, but something seems
> amiss…(The file name is SarahArmModel – Muscles_6-11-07).
>