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Topic: help in genetic algorithm
Replies: 5   Last Post: Apr 8, 2013 4:27 PM

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Alan Weiss

Posts: 1,259
Registered: 11/27/08
Re: help in genetic algorithm
Posted: Apr 8, 2013 12:55 PM
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On 4/8/2013 12:29 PM, mado wrote:
> Alan_Weiss <aweiss@mathworks.com> wrote in message
> <kjudjf$r7m$1@newscl01ah.mathworks.com>...

>> On 4/8/2013 7:02 AM, mado wrote:
>> > i want to ask about genetic algorithm , i am using it to tune pid
>> > parameters but it gives different p, i d values in every running

>> and > it?s not satisfying , need your help
>> > i don't know is this problem of ga parameters or it's the objective
>> > function

>>
>> The genetic algorithm is stochastic, it often gives different results
>> every time.
>>
>> Allow me to suggest that you use patternsearch instead of ga as your
>> solver. It is usually faster, more robust, and easier to tune. The
>> only down side is you need to supply initial points. If you have
>> finite upper and lower bounds, you can try
>>
>> x0 = lb + rand(size(lb)).*(ub - lb);
>>
>> Good luck,
>>

>
> I need to try ga , i increased generations but don't affect my problem
> is the values is small i need it to be bigger and it should be to
> minimize error being small that mean there is a big error between
> reference and output value


The most important thing to modify is the initial range.
http://www.mathworks.com/help/gads/population-diversity.html

The next most important thing is the population size.

But the best thing to do is chuck ga and use patternsearch.

Alan Weiss
MATLAB mathematical toolbox documentation



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