What command do I use to assign a range of values or a set of specific values for K?

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Ashkhen Aristakessian
回答： Maarten van Els 2019-3-18
I first used "overlaymany"command per John Rossiter's video but the command doesn't exist in the Matlab software I am using. https://www.youtube.com/watchv=m1QxUvxij_E&list=PLs7mcKy_nInFEf4Lku9LKkXPdAj0zJCx0&index=2,
then I used feedback function along with step function as shown in the following script:
************************************************
clear all; close all;
z=0:1:100;
numG = [4];
denG = [1 4 7 0];
figure(1);
G = tf(numG,denG);
rlocus(G,z);
grid;
figure(2);
z1=G*0.6;
Gz1 = feedback(z1,1);
z2=G*2;
Gz2 = feedback(z2,1);
z3=G*4;
Gz3 = feedback(z3,1);
step(Gz1,Gz2,Gz3);
****************************************************************************
the plots were similar to the solution manual, but the amplitudes were off. I can't figure out what I am doing wrong.

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回答（2 个）

goerk
goerk 2015-10-14
编辑：goerk 2015-10-14
Please Tag your questions with homework. Please post your code in a readable way (Code).
You have an error in your transfer function
numL = [4 4*z];
denL = [1 4 3 0];
L = tf(numL,denL);
Hint: If you type don't use the semicolon the transfer function is displayed and you can compare it with the given one.
The multiplication of the factor z lead to a wrong result.
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goerk
goerk 2015-10-16
What was your modification? Look at the transfer function from your manual and compare it with the one you got. I get the same result. The step
z1=G*0.6;
from your example code is wrong. The factors have to be added to the open-loop transfer function as shown in my first response.
z=0.6;
numL = [4 4*z];
denL = [1 4 3 0];
L = tf(numL,denL);
G = L/(1+L)
figure; step(G)

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Maarten van Els
Maarten van Els 2019-3-18
I had the same problem when watching the video. Apparently it's a self written script, you can build it yourself using the following link: Modelling and control by Anthony Rossiter

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