Multiobjective optimization using aspen plus

Hi. I'm trying to optimize a distillation column in aspen plus by matlab. For that I am using the Optimization Toolbox with the gamultiobj algorithm. The objectives are to minimize the cost functions (TAC) for both fixed costs (TAC (1)) and for variable costs (TAC (2)). The cost calculation for the column, the referrer and the reboiler is included in the code. However, when the optimization starts, the following message appears: "struct contents reference from a non-struct array object". Can someone help me?

function TAC = Objective(x)  

global Aspen 
 
Aspen = actxserver('Apwn.Document.36.0'); 
    [~,mess]=fileattrib; 
    Aspen.invoke('InitFromArchive2',[mess.Name '\SimulationACRYL2.bkp']);
    Aspen.Visible = 1;
    Aspen.SuppressDialogs = 1;
    Aspen.Engine.Run2(1);
    while Aspen.Engine.IsRunning == 1
        pause(0.5);
    end
    
Stages = round(x(1) + 2);
Pressure = x(2);
Feed_Stage = round((Stages-2)*x(3) + 1);

Aspen.Tree.FindNode("\Data\Blocks\B2\Input\NSTAGE").Value = Stages;
Aspen.Tree.FindNode("\Data\Blocks\B2\Subobjects\Column Internals\INT-1\Input\CA_STAGE2\INT-1\CS-1").Value = Stages - 1;
Aspen.Tree.FindNode("\Data\Blocks\B2\Input\PRES1").Value = Pressure;
Aspen.Tree.FindNode("\Data\Blocks\B2\Input\FEED_STAGE\S50").Value = Feed_Stage;


    Aspen.Reinit; % Reinit simulation
    Aspen.Engine.Run2(1); %Run the simulation. (1) ---> Matlab isnt busy; (0) Matlab is Busy;
    time = 1;
    Error = 0;
    while Aspen.Engine.IsRunning == 1 % 1 --> If Aspen is running; 0 ---> If Aspen stop.
        pause(0.5);
        time = time+1;
        if time==40 % Control of simulation time.
            Aspen.Engine.Stop;
            Error = 1;
        end
    end
         % column cost
        Lang_F = 4.74;
        Diameter = Aspen.Tree.FindNode("\Data\Blocks\B2\Subobjects\Column Internals\INT-1\Input\CA_DIAM\INT-1\CS-1").Value;
        Number_trays = double(Aspen.Tree.FindNode("\Data\Blocks\B2\Input\NSTAGE").Value - 2);
        height_Column = 0.5*(Number_trays)+2;
        heat_reboiler = (Aspen.Tree.FindNode("\Data\Blocks\B2\Output\REB_DUTY").Value)*4.1868;
        Presure_project = 441.3;
        Tension = 108000;
        Column_thickness = ((Presure_project*Diameter)/((2*Tension*0.85)-(1.2*Presure_project))) + 0.003;
        Density_carbon_steel = 7861.1;
        Column_side_volume = 3.14*Column_thickness*height_Column*Diameter;
        Column_side_mass = (Column_side_volume*Density_carbon_steel)*2.205;
        External_radius = (Diameter + 2*Column_thickness)/2;
        Cover_volume = 4*3.14*(External_radius^2)*Column_thickness*2;
        Cover_mass = (Cover_volume*Density_carbon_steel)*2.205;
        total_mass =  Column_side_mass + Cover_mass;
        Cv = exp((7.2756 + 0.18255*(log(total_mass))) + (0.02297*((log(total_mass))^2)));
        Diameterft = Diameter*3.281;
        height_Columnft = height_Column*3.281;
        Cpl = 300.9*((Diameterft)^0.63316)*(height_Columnft^0.80161);
        Factor_material_column = 1;
        FNT = 1;
        FTT = 1;
        FTM = 1; 
        CBT = 468*exp(0.1739*Diameterft);
        CT = CBT*FTM*FTT*FNT*Number_trays;
        CP = Factor_material_column*Cv + Cpl;
        Cost_column = CP + CT;
        
        % condenser cost
        Temp_out_fluid_cold = 20;
        Temp_in_fluid_cold = 5;
        Temp_in_fluid_hot = Aspen.Tree.FindNode("\Data\Streams\S4\Output\TEMP_OUT\MIXED").Value; 
        Temp_out_fluid_hot = Aspen.Tree.FindNode("\Data\Streams\S4\Output\TEMP_OUT\MIXED").Value;
        Temperature_exchange_termic = ((Temp_in_fluid_hot - Temp_out_fluid_cold) - (Temp_out_fluid_hot - Temp_in_fluid_cold))/log((Temp_in_fluid_hot - Temp_out_fluid_cold)/(Temp_out_fluid_hot - Temp_in_fluid_cold)); 
        Factor_exchange_termic = 0.85;
        coefficient_exchange_termic = 850;
        Heat_condenser = (Aspen.Tree.FindNode("\Data\Blocks\B2\Output\COND_DUTY").Value)*4.1868;
        Area_condenser = ((Heat_condenser)/(Temperature_exchange_termic*coefficient_exchange_termic*Factor_exchange_termic))*10.76;
        Cost_condenser = exp(11.0545 - 0.9228*(log(Area_condenser)) + 0.09861*(log(Area_condenser)^2)); 
        Pipe_length = 1;
        Type_Material_Condenser = 1;
        pressure_condenser = 1;
        Condenser_total_cost = Cost_condenser*Pipe_length*Type_Material_Condenser*pressure_condenser;
        
        %Reboiler cost
        Temp_in_fluid_hot_reboiler = 127.5;
        Temp_out_fluid_hot_reboiler = 127.5;    
        Temp_out_fluid_cold_reboiler = Aspen.Tree.FindNode("\Data\Streams\12\Output\TEMP_OUT\MIXED").Value;
        Temp_in_fluid_cold_reboiler = Aspen.Tree.FindNode("\Data\Streams\12\Output\TEMP_OUT\MIXED").Value;
        Temperature_exchange_termic_reboiler = ((Temp_in_fluid_hot_reboiler - Temp_out_fluid_cold_reboiler) - (Temp_out_fluid_hot_reboiler - Temp_in_fluid_cold_reboiler))/log((Temp_in_fluid_hot_reboiler - Temp_out_fluid_cold_reboiler)/(Temp_out_fluid_hot_reboiler - Temp_in_fluid_cold_reboiler)); 
        Factor_exchange_termic_reboiler = 0.85;
        coefficient_exchange_termic_reboiler = 1560;
        Area_reboiler = ((heat_reboiler)/(Temperature_exchange_termic_reboiler*coefficient_exchange_termic_reboiler*Factor_exchange_termic_reboiler))*10.76;
        Cost_reboiler = exp(11.967 - 0.8709*(log(Area_reboiler)) + 0.09005*(log(Area_reboiler)^2)); 
        Pipe_length_reboiler = 1;
        Type_Material_reboiler = 1;
        pressure_reboiler = 1;
        Reboiler_total_cost = Cost_reboiler*Pipe_length_reboiler*Type_Material_reboiler*pressure_reboiler;

        % cost of utilities
        Chilled_water_cost = ((Aspen.Tree.FindNode("\Data\Blocks\B2\Output\COND_DUTY").Value)*4.1868)*31536000*0.0000000009258;
        Steam_Cost = ((Aspen.Tree.FindNode("\Data\Blocks\B2\Output\REB_DUTY").Value)*4.1868)*0.000000004607*31536000;
        
    
Conv = Aspen.Tree.FindNode("\Data\Results Summary\Run-Status\Output\PER_ERROR").Value; 
    if Error == 0 && Conv == 1
       
        TAC(1) = (Cost_column + Condenser_total_cost + Reboiler_total_cost)*Lang_F*1.14*1.1906/10;
        TAC(2) = Steam_Cost + Chilled_water_cost;
          
    else
        TAC(1) = 2e8;
        TAC(2) = 2e8;
        
    end
    
end

[Walter Roberson]

I suggest you try

dbstop if warning

[Eduardo Braga]

Thanks for the answer. I'm a new user, where would I write this code?

[Walter Roberson]

in the command line. Then run the code. It will stop where the warning is generated. You might need to use

dbup

one or more times to determine which line led to the problem

[Eduardo Braga]

the following messages appeared:

Warning from rankAndDistance>globaloptim\private\rankAndDistance (line 22) warning('globaloptim:rankAndDistance:complexScore',msg)

warning('optim:optimtool:DeprecationMsg',deprecation_msg)

[Walter Roberson]

Those are warnings and would not cause the code to stop running in themselves.

You want to run until you get the struct contents reference from a non-struct array object error you mentioned before, and then examine to see which line of code triggered it.

[Eduardo Braga]

[Ataklti Kahsay]

Please contact me on [e-mail] i can share you some files and i am working on optimization too

[PREETHI SRIDHAR]

Hi I am running an optimization problem quite similar. I have used statemnet for checcking covergence as :

Conv = Aspen.Tree.FindNode("\Data\Results Summary\Run-Status\Output\PER_ERROR").Value;

I am getting an error suddenly after certain interations ( sometimes 1/5/20 iterations) that dot indexing not supported in the statement above. When I go and check the aspen file it just shows required input complete, but does not run. At the start I have reinit the code and I do run the engine, but it still shows required input complete, and the simulation does not run. Does anyone face a similar problem like this?

[zhizhang]

I have the same problem like you, so how do you deal with it？