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Topic: Optimization
Replies: 6   Last Post: Feb 27, 2013 10:42 AM

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Matt J

Posts: 4,996
Registered: 11/28/09
Re: Optimization
Posted: Nov 21, 2012 5:18 PM
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"Carlos Alejandro Perez Lasso" <carlosalejandro85@gmail.com> wrote in message <k8jaks$fqr$1@newscl01ah.mathworks.com>...
> Hi Matlab users,
> My purpose is to use the Optimtool to estimate material model parameters so that running the model with such parameters in Abaqus results in a predicted curve close to some experimental data.
> I am trying to solve the problem with the lsqnonlin solver


If it's a curve fitting problem, mightn't it be better to use lsqcurvefit.

> Optimization completed because the size of the gradient at the initial point
> is less than the default value of the function tolerance.


This usually occurs because you have quantizing operations like ROUND, FLOOR, CEIL, etc... in your objective function. They make the function locally flat in places, making the initial point trivially a point of zero gradient.

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