Hi guys! It was nice to visit you this week, Aalborg is lovely.
Thanks a lot for your help John, you gave us a new insight into how
the program works. I’m sorry I was a little out of it on Tuesday, but
that was quite possibly the worst cold I have ever picked up!
We’re unfortunately still getting bad results from the model. As you
can see from the pictures you can get here:
http://download.yousendit.com/AE1ACE896CEC256C
the study for saddle position horizontally and vertically tends to the
highest, most rearward position until it crashes, and the pedal width
tends to the widest possible setting, leading to absurd positions. I
can imagine that the pedal width issue might now be caused by the foot
being able to rotate, but the question then becomes if we can use any
of the solutions we implemented earlier this week.
Also of note is the very low activity values we’re getting now, though
as you said, John, the actual numbers themselves aren’t particularly
important.
Thanks for your continued effort with this, I hope we can sort this
model out once and for all!
Henrik
Tobias
— In anyscript@yahoogroups.com, “AnyBody Support” <support@…> wrote:
>
> Hi Henrik and Tobias
>
>
>
> If you make an objective function based on a few muscles activity,
you will
> most likely see jumps and peaks in the activity levels. It may
happen that a
> small change in the model will shift the activity from one muscle to
another
> and if one of these muscles is not part of the objective function
this will
> be seen as a “sudden” jump.
>
> So I would recommend using all the muscles for the measure.
>
>
>
> Happy new year
>
>
>
> Best regards
>
> Søren, AnyBody Support
>
>
>
> _____
>
> From: anyscript@yahoogroups.com [mailto:anyscript@yahoogroups.com]
On Behalf
> Of vtveteran
> Sent: 21 December 2007 16:16
> To: anyscript@yahoogroups.com
> Subject: [AnyScript] Re: Trouble with multi-dimensional analysis and
home
> installation
>
>
>
> Hi Søren!
>
> Yes, we are running a 3rd variable, varying the Pedalwidth, which is
> really the reason for our study because it seems nobody has done a
> study on the effect of pedal width on muscle efficiency before. The
> different levels therefore correspond to different values of
> PedalWidth. Ideally we would like each level to be an transparent,
> coloured solid to make it easier to follow each value, but our output
> file is churning out all the results so we will hopefully find a
> program that will let us plot the graph we want.
>
> We been unwilling to use the MaxMuscleActivity function simply because
> it only measures the very maximum level, but if that is what you
> recommend, we’ll switch to that. We’re unfortunately in a period of
> holidays and exams at Lund now, so we won’t be able to give it a try
> until after New Year, but we’ll definitely keep it in mind. Otherwise
> we were thinking of maybe just taking a few major muscles and
> outputting the activity of them, as I can see how taking all of the
> muscles may cloud the small variations in the ones actually doing most
> of the work.
>
> Thanks again for your efforts!
>
> Henrik
> Tobias
>
> — In anyscript@yahoogrou <mailto:anyscript%40yahoogroups.com> ps.com,
> “AnyBody Support” <support@> wrote:
> >
> > Hi Henrik and Tobias
> >
> >
> >
> > Looking at the plot I do not understand why there are more “levels”
> for each
> > combination of saddleposition and saddle height, did you run the
> parameter
> > study several times for each parameters set while changing a third
> > variable?. It looks like there are at least four levels for each
> parameter
> > set.
> >
> >
> >
> > I agree with John that using the MaxMuscleActivity output will
give you
> > another graph than using the “mean/sum? activity”, and it is likely
> to be
> > less “flat” when changing the saddlepos than the one you have now.
> >
> >
> >
> > The MaxMuscleActivity output will give you the activity of the highest
> > activated muscles in any part of the model for each time step. In
normal
> > practice for a model like this, there will be many muscles sharing
> this max
> > activity since they will try to help each other as much as they can.
> >
> >
> >
> > I hope this helps you move on, otherwise please write again
> >
> >
> >
> > Best regards
> >
> > Søren, AnyBody Support
> >
> >
> >
> >
> >
> > _____
> >
> > From: anyscript@yahoogrou <mailto:anyscript%40yahoogroups.com> ps.com
> [mailto:anyscript@yahoogrou <mailto:anyscript%40yahoogroups.com> ps.com]
> On Behalf
> > Of vtveteran
> > Sent: 18 December 2007 21:58
> > To: anyscript@yahoogrou <mailto:anyscript%40yahoogroups.com> ps.com
> > Subject: [AnyScript] Re: Trouble with multi-dimensional analysis and
> home
> > installation
> >
> >
> >
> > Hi John!
> >
> > Thanks for the reply. Sorry I didn’t explain myself better. We were
> > fully expecting the results to shoot upwards when they reached the
> > limit of the leg length. The part that troubles us is that it’s
> > pretty much just a ski slope up until that point. Today we ran a
> > couple of focussed studies to see if there was a minimum just before
> > they shot up, but even when we were raising the saddle by just 2.5mm
> > with each step, the lowest point would always be the last point
> > before the results shot skywards. We’ve tried using MaxMuscleActivity
> > before but, though the results were slightly different from the
> > Activity average, the general trend was always the same. We were
> > unwilling to use that function because we weren’t sure if it only
> > took the max activity from the single most active muscle, or if it
> > lumped together the max activity of all the muscles.
> >
> > Thanks again for all your help, though. I’m sure we’ll beat this some
> > day! 
> >
> > Henrik
> > Tobias
> >
> > — In anyscript@yahoogrou <mailto:anyscript%40yahoogroups.com>
ps.com,
> > “AnyBody Support” <support@>
> > wrote:
> > >
> > > Hello Henrik and Tobias,
> > >
> > > When I run my 2D bike model optimization, the muscle effort does
> > > indeed go up sharply when the seat approaches the position where
> > the
> > > feet can almost not reach the pedals anymore. The muscle effort I
> > am
> > > talking about here is the property “MaxMuscleActivity”, which is
> > > defined in any AnyBody model by default. Using that is much easier
> > > than extracting the activity of individual muscles as you have done.
> > >
> > > The reason why the activity rises is that the mechanism approaches
> > a
> > > singularity when the knees become fully extended. Just before full
> > > knee extension, the acceleration of the segments becomes very high,
> > > and the muscles must provide the necessary forces for this,
> > resulting
> > > in high activity.
> > >
> > > I propose using MaxMuscleActivity in the parameter study. I hope it
> > > will give you a well-defined optimum.
> > >
> > > Merry Christmas to everybody!
> > > John
> > >
> > > — In anyscript@yahoogrou <mailto:anyscript%40yahoogroups.com>
> ps.com,
> > “vtveteran” <henriksjostedt@>
> > > wrote:
> > > >
> > > > Hi John,
> > > >
> > > > You’re correct in that we were using the metabolism to generate
> > our
> > > > plots, and we have since introduced some lines of code that add
> > all
> > > > the various muscle activities together, much like how the
> > metabolism
> > > > is calculated in the tutorial. We used the function .Activity. The
> > > > results now are canted in the other direction, with the lowest
> > > muscle
> > > > effort tending toward the greatest saddle height before the
> > > connection
> > > > between foot and pedal is broken. Here is a picture (.jpg) of the
> > 3-
> > > D
> > > > graph we are getting, with SaddleHeight from 0.61m to 0.87m, and
> > > > SaddlePosition from -0.25m to -0.10m, and the different pedal
> > widths
> > > > giving the different levels on the surface.
> > > >
> > > > http://download. <http://download.
> <http://download.yousendit.com/26D6EC5738E63FEA>
> yousendit.com/26D6EC5738E63FEA>
> > yousendit.com/26D6EC5738E63FEA
> > > >
> > > > Is this the kind of result we should be expecting? We were hoping
> > > for
> > > > a convenient local minimum that would show us the optimum
> > > positioning
> > > > for the rider, such as the one found in the tutorial.
> > > >
> > > > Thanks once again for your continued support with this.
> > > >
> > > > Henrik
> > > > Tobias
> > > >
> > > > — In anyscript@yahoogrou <mailto:anyscript%40yahoogroups.com>
> ps.com,
> > “AnyBody Support” <support@>
> > > wrote:
> > > > >
> > > > > — In anyscript@yahoogrou <mailto:anyscript%40yahoogroups.com>
> > ps.com, “vtveteran” <henriksjostedt@>
> > > > > wrote:
> > > > >
> > > > > > The SaddleHeight variable still tends to the lowest
> > > > > > possible value.
> > > > >
> > > > > This sounds like what happens when you minimize metabolism or
> > > > > maximize metabolic efficiency. Is your objective function
> > similar
> > > to
> > > > > this?
> > > > >
> > > > > In this case the muscle effort does not come into the picture
> > > except
> > > > > as the system’s attempt to avoid negative muscle work. Some
> > > muscles
> > > > > will get a higher load when you lower the saddle, but the
> > > mechanical
> > > > > efficiency is not necessarily worse.
> > > > >
> > > > > Lowering the saddle will reduce what some people
> > call “internal”
> > > work
> > > > > in the bicycling process. This is the necessary muscle work to
> > > > > accelerate the inertia in the legs. When you raise the saddle
> > you
> > > > > also increase these accelerations because the mechanism
> > > approaches a
> > > > > singularity when the feet can no longer reach the pedals, and
> > > this
> > > > > causes higher acceleration.
> > > > >
> > > > > So if your objective function has anything to do with
> > efficiency
> > > or
> > > > > metabolism you might want to consider changing it. I have found
> > > that
> > > > > minimization of maximum muscle activity os a good criterion.
> > > > >
> > > > > Best regards,
> > > > > John
> > > > >
> > > >
> > >
> >
> >
> >
> >
> >
> > [Non-text portions of this message have been removed]
> >
>
>
>
>
>
> [Non-text portions of this message have been removed]
>