# Constraint function in optimization toolbox

4 views (last 30 days)
Hussain Ja on 30 Jun 2020
Edited: Hussain Ja on 30 Jun 2020
One of the variables in my model is Measured Power which is being calculated by an external black box model connected with MATLAB. The way its calculated is below:

Show 1 older comment
Rik on 30 Jun 2020
Comment sent as email:
Can I send you an email with more details as the program is proprietary?
Rik on 30 Jun 2020
Since this isn't really my field I don't know if I can solve the actual problem. I just noticed the globals, which tend to be a bad sign.
Also, this forum is a hobby, private consultation is a job, and it isn't my job. There are plenty of people you could hire.
Hussain Ja on 30 Jun 2020
I have skipped all the lines of code to show my constraint which is "Powermeasm". I am using the same code for the main program and the constraint function. The constraint function program has just 2 additional lines declaring the two constraints; c and ceq. I would like to know if this procedure is correct? Can I caclulate "Powermeasm" in the main program and provide a constraint on it through another constraint program? If so, why isn't it working?

Alan Weiss on 30 Jun 2020
I think that you missed the step where you call the external function to calculate the nonlinear constraint.
function [c,ceq] = con_EbsOptimize4(para)
global asmInfo app oc model objects Pr Hu Pmeasm Hmeasm Power Powermeasm;
model.Simulate(errors);
Power = oc.CastToComp11(objects.Item('Generator_1'));
Powermeasm = Power.QREAL.Value;
c = Powermeasm-192000;
ceq = [];
end
There are two other things that you might want to keep in mind for this:
1. Often, the function that calculates the objective function is the same as the function that calculates the nonlinear constraint. If this is true for your function, consider using the technique in Objective and Nonlinear Constraints in the Same Function.
2. If you are using fmincon as your solver, keep in mind the problems in finite differences mentioned in Optimizing a Simulation or Ordinary Differential Equation.
Alan Weiss
MATLAB mathematical toolbox documentation

Hussain Ja on 30 Jun 2020
My concern is not the optimality of the solution. It's just that the solution that it returns clearly violates the supplied constraint by a significant margin. So I have a hunch that somehow it's not calculating the constraint violation correctly and giving it as zero when clearly the violation is much much larger
Alan Weiss on 30 Jun 2020
You didn't say before that "...it's not calculating the constraint violation correctly and giving it as zero when clearly the violation is much much larger." Can you give iterative display data showing what you mean, or something else to help me understand what might be happening? And did you try my previous suggestion, to set MaxGenerations_Data to 1e5?
Alan Weiss
MATLAB mathematical toolbox documentation
Hussain Ja on 30 Jun 2020
Thanks Mr. Weiss. I figured out the problem. The code is working fine now. I had written the wrong generator name.