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Optimiser returns strange values
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Hello,
I have been trying to minimse a function using the genatic algorithms (GA).
When I run the optimizer, it returns strange values.
It'd be very appreciated if someone can help me finding and solving the issue.
Note that the optimal value of V(t) should be either between ( 4 and 5) or (-1 and 0).
** Attached a file that explains the problem.
function z = costfunctiontest(x)
Vt = x;
A = [4/3, -4];
Vmax = 5; % Maximum temperature [°C]
Vhigh = 4; % High temperature [°C]
Vlow = 0; % Low temperature [°C]
Vmin = -1; % Minimum temperature [°C]
PiD = 30 ; % Discrete cost [£]
PiC = 10 ; % Continuous cost [£/h]
PiP = 50; % Penalty cost [£/h]
ContinuousTime = Vt/A(1);
TotalTime= Vt*((1/A(1))-(1/A(2)));
if ((Vt > Vhigh) & (Vt <= Vmax))
pvt = @(t) abs(Vt-Vhigh);
cost = (PiD + PiC*ContinuousTime + PiP*integral(pvt,0,TotalTime,'ArrayValued',true)) / TotalTime;
elseif ((Vt >= Vlow) & (Vt <= Vhigh))
cost = (PiD + PiC*ContinuousTime)/TotalTime;
else
pvt = @(t) abs(Vlow-Vt);
cost = (PiD + PiC*ContinuousTime + PiP*integral(pvt,0,TotalTime,'ArrayValued',true)) / TotalTime;
end
z=cost;
end
%% main code for minimising the fitness function using GA
ObjFcn = @costfunctiontest;
nvars = 1;
LB = [-1];
UB = [5];
[x,fval] = ga(ObjFcn,nvars,[],[],[],[],LB,UB)
3 Commenti
Matt J
il 20 Lug 2020
Also, ga is a bit excessive for a 1-variable problem. It would be quicker just to use fminbnd over the 2 intervals of interest:
K>> [x,fval] = fminbnd(ObjFcn,-1,0)
x =
-6.6107e-05
fval =
-4.5380e+05
K>> [x,fval] = fminbnd(ObjFcn,4,5)
x =
4.0001
fval =
15.0032
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