Solver type (Min/max criterion)

Hi guys,
I’m working on my litterature review at the moment. I was
biomechanical dynamic problems. It seems that there is a bunch of
mathematical objective functions that can be used, but I think that
AnyBody use only one or maybe few of them (min/max criterion) (correct
me if i’m wrong).

I would like to know if you are working on the developement of new
optimization methods in the further versions of the software ? Take
for example a objective function that would minimize the pain for a
pathological situation like rotator cuff tear or the maximization of
velocity for very fast movement (sprint runners).

If it’s already possible to do so with AnyBody, please let me know. It
would be very useful for my “rotator cuff tear” pathological problem.

Thank you very much

kings regards

Pierre-Olivier

P.S. : I say hello to all of you from Montreal, Canada (Soeren, John,
Arne and all the others that I forget)

Hi Pierre

As you say AnyBody, in principle, has only one option, namely the Min/Max
criterion.

However, depending on the solver you can add a linear or a quadratic
penalty.

With the quadratic penalty you can in principle obtain an almost pure
quadratic objective function by a using a higher (dominating) penalty.

The quadratic objective function is very popular in the biomechanical
community; however notice that typically this criterion is applied with
upper bounds on muscle activity in order to avoid overloading the strong
muscles.

The Min/Max formulation does not need these upper bounds to avoid
possible.

Therefore, AnyBody’s solver unfortunately does not include the upper bounds.

Looking at the future, we cannot make any promises yet. New solvers and
criteria are indeed one of our focus points.

Upper bounds and a pure quadratic criterion will come in version 4.0 of
AnyBody in the spring. We expect to add more than this criterion too, but we
do not have the details yet.

Concerning the rotator cuff pain as criteria it may be possible to formulate
today, simply by lowering the strength of the muscles in pain. If lowered
enough the recruitment algorithm will try to avoid loading these muscles in
any possible way. The uncertain point is of course by how much the strength
should be lowered, for this there is no clear answer.

The sprint runner case; using the min/max formulation you will get the
muscle activation which will lower the activations as much as mathematical
possible, if you couple this with an inverse inverse approach and optimize
the motion you theoretically will get the fastest motion possible.

Hopes this clarified the matters a bit.

Best regards

Michael and SÃ¸ren, AnyBody Support

From: anyscript@yahoogroups.com [mailto:anyscript@yahoogroups.com] On Behalf
Of Pierre-Olivier Lemieux
Sent: 02 December 2008 17:17
To: anyscript@yahoogroups.com
Subject: [AnyScript] Solver type (Min/max criterion)

Hi guys,
I’m working on my litterature review at the moment. I was
biomechanical dynamic problems. It seems that there is a bunch of
mathematical objective functions that can be used, but I think that
AnyBody use only one or maybe few of them (min/max criterion) (correct
me if i’m wrong).

I would like to know if you are working on the developement of new
optimization methods in the further versions of the software ? Take
for example a objective function that would minimize the pain for a
pathological situation like rotator cuff tear or the maximization of
velocity for very fast movement (sprint runners).

If it’s already possible to do so with AnyBody, please let me know. It
would be very useful for my “rotator cuff tear” pathological problem.

Thank you very much

kings regards

Pierre-Olivier

P.S. : I say hello to all of you from Montreal, Canada (Soeren, John,
Arne and all the others that I forget)

[Non-text portions of this message have been removed]