# Optimization parameter

Good morning,

I’m now studying your software and I would know something else about the software optimization parameter algorithm. Could you give me the related bibliographic references please?

Kind regards,
Roberto Di Marco

Hello Roberto,

the AnyBody Modeling System contains a study to perform a parameter optimization which is called AnyOptStudy. This study can use different optimization algorithms as described in the reference manual.
These algorithms are standard optimization algorithms which are probably described in quite a number of books about numerical optimization.

I am not sure if this answers your question. Could you be more precise on what you are looking for?

Kind regards
Daniel Nolte

Hi Daniel,

thanks for your help. The problem I have is: which objective function does the algorithm minimize? I would understand, for example, if the algortihm considers the markers as fixed points and tries to overlap these on the RefNode of a leg. If so, in which way does it?

Roberto Di Marco

Hi Roberto,

it is possible to define your own objective function in the AnyOptStudy. For this, a big toolbox of mathematical expressions is available to create a measure to do the optimization. An example how to use the AnyOptStudy can be found in the tutorials of the AnyBody Modelling System.

For the minimization of the distance of marker points to RefNodes it might also be interesting to look at the examples GaitFullBody and GaitLowerExtremity which are part of the AnyBody Managed Model Repository (AMMR) and come along with the software. A bit more background to this you can find in the publication of Anderson et al., A computational efficient optimisation-based method for a parameter identification of kinematically determinate and over-determinate biomechanical systems, 2010. This and more literature on this topic you can find on the publication list of the AnyBody website.

Best regards
Daniel Nolte

For this point, I m wondering what is exactly the objective fonction during the ParameterOptimization process in kinematic to find the length and the marker position.
I found in tutorial that is “the norm of the difference between the measured marker positions and the corresponding nodes on the segment over the entire motion”.

But is it the sum of this difference for each considering frame? Or just for the last or a mean? What is the number of considering frame? all the frame or only that used for design optimization process?

Thanks

Dear Coralie Germain,

The ParameterOptimization study will consider the sum of the differences between all the pairs of markers during the frame which are used in the design optimization process.

Best regards,
Moonki