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Optimization
Posted:
Nov 21, 2012 2:39 PM


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 with a Cost function that receives initial 3 parameters, reads experimental data, writes a file for parameter study in Abaqus, runs the simulation using the 3 parameters in the material model, reads the corresponding numerical result, compares it with the experimental data and returns a Cost Vector for the solver to do its job. The problem: When running, the solver does 4 function calls in the 0 iteration and doesn't move from the initial 3 parameters. Thus no gradient is calculated and he thinks that the initial point is already a minimum. Here is what he says:
Norm of Firstorder Iteration Funccount f(x) step optimality CGiterations 0 4 246.506 0
Initial point is a local minimum.
Optimization completed because the size of the gradient at the initial point is less than the default value of the function tolerance.
"Optimization running. Objective function value: 246.50561987942325 Initial point is a local minimum.
Optimization completed because the size of the gradient at the initial point is less than the default value of the function tolerance."
I would appreciate any help on this regard.
Thank you Matlab users.



