Problem with nonlinear objective function

Hello all

I have problem with running a script that written to excute a multi-objective optimization problem using the solver " gamultiobj ", the error message that appears in the commnad window is " Objective must be an OptimizationExpression or a struct containing scalar OptimizationExpressions."

The optimization problem is a problem-based type and the part of script related to the objective functions is presented below:

% The First Objective Function 
Jems = optimexpr;
for i = 0:Hp-1
    if i+k <=Ns+Hp

Jems = Jems + ((CCb./(2.*Nc_b.*Eb)).*DT.*Pb_ch(i+k))...
    +((CCb./(2.*Nc_b.*Eb)).*DT.*Pb_disch(i+k))...
    + (nfc.*((CCfc./Nh_fc) + Com_fc).*Delta_fc(i+k).*DT + Css_fc.* ASegma_fc(i+k))...
    + (nez.*((CCez./Nh_ez) + Com_ez).*Delta_ez(i+k).*DT + Css_ez.* ASegma_ez(i+k))...
    + (Bid_imp.*Pg_imp(i+k).*DT) - (Bid_exp.*Pg_exp(i+k).*DT);
    
    else
        break
    end
end
show(Jems);
prob.Objective.OF1 = Jems;
%==============================
% The Second Objective Function 
Eff = optimexpr;
for i = 0:Hp-1
    if i+k <=Ns+Hp

Eff = Eff + ((Pfc(i+k)+Pb_disch(i+k))) ./ ((Pez(i+k)+Pb_ch(i+k)));
    
    else
        break
    end
end
show(Eff)
prob.Objective.OF2 = Eff;
prob.Objective.OF2 = "max";

%========================
show(prob);

the optimization variables are presented below

Pb_ch = optimvar('Pb_ch',Nhr,'LowerBound',0,'UpperBound',nb*Pb_ch_max);
Pb_disch = optimvar('Pb_disch',Nhr,'LowerBound',0,'UpperBound',nb*Pb_disch_max);
Pg_imp = optimvar('Pg_imp',Nhr,'LowerBound',0,'UpperBound',Pg_imp_max);
Pg_exp = optimvar('Pg_exp',Nhr,'LowerBound',0,'UpperBound',Pg_exp_max);
Pfc = optimvar('Pfc',Nhr,'LowerBound',0,'UpperBound',nfc*Pfc_max);% Watch out here 
Pez = optimvar('Pez',Nhr,'LowerBound',0,'UpperBound',nez*Pez_max);% Watch out here 
SoCb = optimvar('SoCb',Nhr,'LowerBound',SoCb_min,'UpperBound',SoCb_max);
SoCH2 = optimvar('SoCH2',Nhr,'LowerBound',SoCH2_min,'UpperBound',SoCH2_max); 
Delta_fc = optimvar('Delta_fc',Nhr,'LowerBound',0,'UpperBound',1,'Type','integer');
Delta_ez = optimvar('Delta_ez',Nhr,'LowerBound',0,'UpperBound',1,'Type','integer');
Delta_b_ch = optimvar('Delta_b_ch',Nhr,'LowerBound',0,'UpperBound',1,'Type','integer');
Delta_b_disch = optimvar('Delta_b_disch',Nhr,'LowerBound',0,'UpperBound',1,'Type','integer');
Delta_g_imp = optimvar('Delta_g_imp',Nhr,'LowerBound',0,'UpperBound',1,'Type','integer');
Delta_g_exp = optimvar('Delta_g_exp',Nhr,'LowerBound',0,'UpperBound',1,'Type','integer');
Segma_fc = optimvar('Segma_fc',Nhr,'LowerBound',-1,'UpperBound',1,'Type','integer');
Segma_ez = optimvar('Segma_ez',Nhr,'LowerBound',-1,'UpperBound',1,'Type','integer');
ASegma_fc = optimvar('ASegma_fc',Nhr,'LowerBound',0,'Type','integer');
ASegma_ez = optimvar('ASegma_ez',Nhr,'LowerBound',0,'Type','integer');

Kindly, I need to know what is the wrong associated with the objective functions formulation, especially the second functions.

Thanks in advance

Answer 1

[Matt J]

prob.Objective.OF2 = "max";

"max" is just a string. There is no optimization expression that can be interpreted from it.

[Bashar]

Thanks a lot @Matt J

The problem has been solved.