Gradient optimization problem with fmincon

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Dai Nguyen
Dai Nguyen 2021-5-19
编辑： Torsten 2021-5-20
Hi I'm currently working on an optimzation problem where I need to optimization a design dimension to minimize the ROI with Sequential Quadratic Programing with fmincon. However, I don't really know how the fmincon work and how my constrain will need to implement into the code. I'm new to matlab
Thank you for your time,
Here is my equation and constrain that I want to put in Matlab
with r is the radius and l is the length of the tank
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Dai Nguyen
Dai Nguyen 2021-5-19
my initial design is 5000 for length and 500 for radius
Dai Nguyen
Dai Nguyen 2021-5-19
yeah you are right it doesn't depends. I think in this case imma minimize the volume

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回答（1 个）

Sulaymon Eshkabilov
Here is a simple solution to your exercise. Adjust your constrains for r (radius) and l (length).
% NOTE: RL(1) is R and RL(2) is L.
ROI =@(RL) (.05*(509.7*pi(RL(1)^3+RL(1)^2*RL(2))+5.505e3*RL(1)^2)-509.7*pi*(RL(1)^3+RL(1)^2*RL(2))+5.505e3*RL(1)^2)/(509.7*pi*(RL(1)^3+RL(1)^2*RL(2))+5.505e3*RL(1)^3);
Rb = [0,0];
% NOTE: 0<=R<=5; 0<=L<=15; Thus, Rb= [0, 0]; and Lb = [5, 15];
Lb = [5, 15];
% No Other constraints are considered here
A = [];
b = [];
Aeq = [];
beq = [];
x0 = (Lb + Rb)/2;
RL = fmincon(ROI,x0,A,b,Aeq,beq,Lb,Rb);
R = RL(1);
L = RL(2);
fprintf('Found values: R = %f [ft] L = %f [ft] \n', [R, L])
Good luck.
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Dai Nguyen
Dai Nguyen 2021-5-19
Yeah I tried to put the constraints but my constraints is non linear
c(1)= L + R - 131.23; % height of tank
c(2) = 1224.303*RL(1)^2; % height of distance, fuel needed
c(3) = (RL(1)*RL(2))/(2*(RL(2)+RL(1)))- 0.25; % thickness of tank
Torsten
Torsten 2021-5-20
编辑：Torsten 2021-5-20
The first constraint is linear, the second is superfluous and the third can be put in function "nonlcon".
Read the documentation of fmincon for more details.

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