How to use interp1 command?

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Mohammed Alharbi 2021 年 9 月 26 日

I have the code to draw each of these 6 figures as follows:
ph1 = 1;
ph2 = 2;
ph3 = 3;
ph4 = 4;
ph5 = 5;
ph6 = 6;
Vi=30;
Vo=0:0.1:30;
d= Vo./Vi ;
m1= d*ph1;
m2= d*ph2;
m3= d*ph3;
m4= d*ph4;
m5= d*ph5;
m6= d*ph6;
floor1= floor(m1);
floor2= floor(m2);
floor3= floor(m3);
floor4= floor(m4);
floor5= floor(m5);
floor6= floor(m6);
Kcm1 = (1-(floor1./(ph1*d))).*(1+floor1-ph1*d)
Kcm2 = (1-(floor2./(ph2*d))).*(1+floor2-ph2*d)
Kcm3 = (1-(floor3./(ph3*d))).*(1+floor3-ph3*d)
Kcm4 = (1-(floor4./(ph4*d))).*(1+floor4-ph4*d)
Kcm5 = (1-(floor5./(ph5*d))).*(1+floor5-ph5*d)
Kcm6 = (1-(floor6./(ph6*d))).*(1+floor6-ph6*d)
figure (1)
hold on
title('for the output current ripple')
xlabel('Duty Cycle')
ylabel('Kcm')
plot(d,Kcm1)
plot(d,Kcm2)
plot(d,Kcm3)
plot(d,Kcm4)
plot(d,Kcm5)
plot(d,Kcm6)
legend('Phase1','Phase2','Phase3','Phase4','Phase5','Phase6');
grid on
hold off
What I want to do is that based on an input value (which is going to be a value on the X-axis), I want the output to choose the figures out of these 6 figures that give the minimum Y-axis value.
For example,
If I put the input value to be 0.5, which is a duty cycle value on the X-axis, then the output should display and recommend (phase-2, phase-4 and figure 6) as they give the minimum value of Y-axis (exactly 0) at this specific input value of 0.5
Another example,
If the input value is 0.25, then the recommend figure to be displayed is (phase-4 the yellow one) as this also gives the minimum value on the Y-axis, and so on.
I was told that I could use the "interp1" command for each curve and pick the minimum but I don't know how to use it.
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Stephen23 2021 年 9 月 27 日

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Stephen23 2021 年 9 月 27 日

Numbering your variables like that is a red-herring that makes this task more complex.
MATLAB is designed to work efficiently with arrays. Using arrays makes your code much simpler:
ph = 1:6;
Vi = 30;
Vo = 0:0.1:30;
d = Vo./Vi;
m = d(:).*ph; % note the orientation!
Kcm = (1-(floor(m)./m)).*(1+floor(m)-m);
figure (1)
title('for the output current ripple')
xlabel('Duty Cycle')
ylabel('Kcm')
plot(d,Kcm)
legend(sprintfc('Phase%d',ph));
grid on
Using arrays also makes your task much simpler:
inp = 0.5;
tmp = interp1(d,Kcm,inp);
idx = find(tmp==min(tmp))
idx = 1×3
2 4 6
inp = 0.75;
tmp = interp1(d,Kcm,inp);
idx = find(tmp==min(tmp))
idx = 4
Note that the orientation of the data in m is significant, because INTERP1 treats each column as its own dataset.
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Mohammed Alharbi 2021 年 10 月 4 日
Hi Stephen,
Thanks for your response.
I already did but still waiting for a help and the thought of asking you here. This is the link for the new post:
Thanks a lot!
Mohammed Alharbi 2021 年 10 月 4 日

Hi Stephen,
I sloved the previous issue by putting
m = d'*ph;
m = d(:).*ph;
But now I have another issue with using the "find" command in Simulink function block as it always returns a variable-length vector. Please have a look at this thread if you have time, I am sure you will be the one who can hlep me out with this
Mohammed

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