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Topic: fmincon: constraint normalization
Replies: 1   Last Post: Mar 9, 2013 5:46 AM

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 pietro Posts: 374 Registered: 1/3/09
fmincon: constraint normalization
Posted: Feb 21, 2013 5:24 AM

Hi all,

I'm using fmincon to optimize an objective function. I need to normalize all the constraints because the design variables have different units (i.e angles, lengths and torque) and I need to check the langrange multiplier otherwise they can't be compared. I normalized the objective function in this way: norm_f(x)=f(x)/f(x0), where f(x) is the objective function, f(x0) is the objective at the initial value and norm_f(x) is the normalzed one. I also normalized the constraint is this way:

Br=repmat(B,1,length(A(1,:)));
An=A./Br;
Bn=ones(length(A(:,1)),1);

where: A and B are the constraint matrices and An and Bn are the normalized one.

the not normalized problem works well, also the one with the normalized objective function and with A and B as constraint matrices. Instead the fully normalized one doesn't work well, despite the normalization seems correct to me, in other words:
isequal(A*x0-B,(An*x0-Bn).*B)

ans =

1

May you be kind to help me in understanding what's wrong with my code?

thank you

Best regards

Pietro

Date Subject Author
2/21/13 pietro
3/9/13 pietro