trying to loop for transfer function plots into single figure

Parameters========================

Km1 = 0.01;

Km2 = 0.02257;

Km3 = 0.04;

Rm = 2.093;

b = 0.0000262;

t = 0.069;

T=0:0.0001:4;

========================================

something I tried, but It didnt work

for i :1:3

K(i) = Km(i)/(Rm*b+Km(i)^2);

oltf(i)=tf([K(i)],[t,(i)]);

step(i)=step(oltf(i),T);

plot(T, step(i),'r');

end

trying to fit all three plots into one figure

Thank you!!

[VINAYAK LUHA]

The "hold on" command may help, find its documentation in the following link https://in.mathworks.com/help/matlab/ref/hold.html

Answer 1

[Dyuman Joshi]

%Do not name variables dynamically
%defining them in an array and using indexing is a much better option
Km = [0.01 0.02257 0.04];
Rm = 2.093;
b = 0.0000262;
t = 0.069;
T = 0:0.0001:4;

%Defining K via vectorization
K = Km./(Rm.*b+Km.^2);

%Initialise a figure and use hold on to retain plots on the same axes
figure
hold on

for i =1:3
oltf = tf([K(i)],[t,(i)]);
step(oltf,T)

%%It's not a good idea to use function names as variables names
%step(i)=step(oltf(i),T);

%%No need to use the plot command, as the step command itself outputs a plot
%plot(T, st(i),'r')
end
hold off

[Young Lee]

There is a problem with this solution that the K (aplitude is not reflecting to the actual) eg

K@(0.02257) = Km./(Rm.*b+Km.^2) = 0.02257 / (2.093 *0.0000262 + 0.02257^2 ) = 40 ( but on the actual response from the plot the gain is at only half of it (20)

can you see the problem>?

[Sam Chak]

Hi @Young Lee

@Dyuman Joshi didn't make any mistakes in the code because he merely duplicated the transfer function from your original code. However, based on your screenshot, I would like to suggest that the correct transfer function should be:

It's perfectly fine to notify him about the issue you had.

Km1 = 0.01;
Km2 = 0.02257;
Km3 = 0.04;
Km  = [Km1 Km2 Km3];

Rm  = 2.093;
b   = 0.0000262;
t   = 0.069;
T   = 0:0.0001:4;

for i = 1:3
    K    = Km(i)/(Rm*b + Km(i)^2);
    den  = [t, 1];                  % <-- fix denominator here
    oltf = tf(K, den);
    step(oltf, T), hold on
end
grid on
hold off

[Young Lee]

thanks for your kind help

[Sam Chak]

@Young Lee, You are welcome!