# fmincon returns wrong length

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K0ertis on 8 Oct 2014
Commented: K0ertis on 8 Oct 2014
Hi! I have a large Simulink- Modell in which I want to optimize two PI- controllers. My variables are x_1... x_4 such as:
x = [Kp_1 Ti_1 Kp_2 Ti_2];
[x,f,eflag,output] = fmincon(@fun,x0,[],[],[],[],lb,ub,@mynlconst,opts);
In my nonlinear constrains I added 20 constrains, for example:
function [c,ceq] = mynlconst(x)
ceq = [];
set_param(char([SimName '/CF/Kp_1']), 'Gain', 'x(1)');
set_param(char([SimName '/CF/Ti_1']), 'Gain', 'x(2)');
% Same for x(3) and x(4)
opts = simset('DstWorkspace','current','SrcWorkspace','base');
sim(SimName,Tend,opts);
c(1) = max(yout(:,1)) - MaxPX;
c(2) = -min(yout(:,1)) - MinPX;
c(3) = max(yout(:,3)) - MaxTX;
c(4) = -min(yout(:,3)) - MinTX;
c(5) = max(yout(:,5)) - MaxHX;
c(6) = -min(yout(:,5)) - MinHX;
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c(20)= ...;
yout is a matrix from Simulink with the size (130,variables). As constrains I've used the max, min of the vector.
My optimazion function fun (To keep it simple I just wrote the necessary parts):
function y = fun(x)
set_param(char([SimName '/CF/Kp_1']), 'Gain', 'x(1)');
set_param(char([SimName '/CF/Ti_1']), 'Gain', 'x(2)');
% Same for x(3) and x(4)
opts = simset('DstWorkspace','current','SrcWorkspace','base');
sim(SimName,Tend,opts);
y = e'*e; % e= error, imput of controller
Somehow I get a vector x length 130, my Sample lengh :( I just want a optimized variable x legnth 4.
Any suggestions?
Thank you!

Alan Weiss on 8 Oct 2014
What is your x0 input to fmincon? The returned solution x has the same size as x0.
Alan Weiss
MATLAB mathematical toolbox documentation
K0ertis on 8 Oct 2014
Just found out that i overwrote x in my Simulink Modell. Thank you for your help!