Hello, I'd like to solve the problem during the optimization using matlab and aspen hysys.

Hello, Whom.

I'm currently trying to optimize the simple compressor stage with the code as below.

The function is sum of the energy of the compressors and the variables are the pressures of the output

Objective = @(x) MyK1.EnergyValue + MyK2.EnergyValue + MyK3.EnergyValue;

global x;
x = 1:2;

MyM1.PressureValue = x(1);
MyM2.PressureValue = x(2);
   if MyM2.TemperatureValue < 30
      MyM3.TemperatureValue = MyM2.TemperatureValue;
   else
      MyM3.TemperatureValue = 30;
   end

lb = [107, 107];
ub = [4000, 4000];
A = [];
b = [];
Aeq = [];
beq = [];
x0 = [300, 1200];

disp(['Initial objective:' num2str(Objective(x))])

nonlincon = @TestCons;
opts = optimoptions(@fmincon,'Display','iter','Algorithm','sqp','FiniteDifferenceStepSize', 5);
problem = createOptimProblem('fmincon','objective',Objective,'x0',x0,'lb',lb,'ub',ub,'nonlcon',nonlincon,'options',opts);
gs = GlobalSearch('FunctionTolerance', 2e-4,'NumTrialPoints',2000)
ms = MultiStart(gs);
[x,f] = run(ms,problem,20)

disp(x)
disp(['Final objective:' num2str(Objective(x))])

But there's only one iteration and show the context:

 Iter  Func-count            Fval   Feasibility   Step Length       Norm of   First-order  
                                                                       step    optimality
    0           3   -3.329715e+02     3.991e+00     1.000e+00     0.000e+00     0.000e+00  
    1           4   -3.329715e+02     3.991e+00     7.000e-01     8.011e-17     0.000e+00  

Converged to an infeasible point.

fmincon stopped because the size of the current step is less than
the value of the step size tolerance but constraints are not
satisfied to within the value of the constraint tolerance.

<stopping criteria details>

No feasible solution found.

MultiStart called the local solver 20 times and did not find a point that satisfies the constraints
within the local solver constraint tolerance (problem.options.ConstraintTolerance).

x =

         300        1200


f =

 -332.9715

         300        1200

Final objective:-332.9715

So I've tried to change the stepsize artificially but not working.

What should I do with it?

Can somebody help me please?

[rubindan]

It seems like your initial guess violates the nonlinear constraints.

It also seems that your cost function does not depend on x

[Jiwon Choi]

Thank you for your replying:)

The cost function is related to the x, like changing the pressure(variable x) make a result of the energy(such as MyK1.EnergyValue) on Aspen HYSYS.

And how can I solve the problem for the initial guess not to violates it?

Could you tell me the way?