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How can I make a step response graph for open Loop Ziegler-Nichols Method?

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Milon Chowdhury
Milon Chowdhury on 2 Oct 2019
Commented: David K. on 3 Oct 2019
HI,
Greetings. I am very new in MATLAB. I want to draw a step response graph for Open Loop Ziegler-Nichols Method. the equation is attached here. Actually, I can't understand, how to code the numerator and denominator. Thanks in advance.

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Answers (2)

David K.
David K. on 2 Oct 2019
When trying to do transfer functions in matlab one very nice way to do it is with
s = tf('s');
Now, s indicates it is a transfer function you can actually just type the rest of your equations as you would want.
k = k; d = d; tau = tau; % These are just saying that you should define these yourself
G = k*exp(-d*s)/(tau*s+1); % Create the transfer function
step(G); % Plot the transfer function

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Milon Chowdhury
Milon Chowdhury on 3 Oct 2019
Thanks for your reply. I have drawn a nice step response graph using your code. I am facing another problem. In Simulink code, how can I mention/put this equation? Transfer function.JPG

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David K.
David K. on 3 Oct 2019
Generally if you have a followup question you should put it in a comment on my answer, your question, an edit to your question, or a new question instead of an answer.
You can do it by putting a transfer function block with
num = [km]
den = [tau 1]
in series after a Transport Delay Block with the delay set to d. This is because an exponent in laplace domain results in a time delay of d seconds.

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