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## Re: Help with rlocus appearance of initial location of poles and zeros

 From: Doug Stewart Subject: Re: Help with rlocus appearance of initial location of poles and zeros Date: Tue, 30 Jan 2018 12:25:35 -0500

On Tue, Jan 30, 2018 at 5:18 AM, Beginner1 wrote:
In fact, what is happening is the dispersión of the "O" marker for zero
locations as soon as the poles trajectories converge at the real axis:

Kp=1.5, Ki=940

<http://octave.1599824.n4.nabble.com/file/t372684/1st.jpg>

Kp=1.5, Ki=960

<http://octave.1599824.n4.nabble.com/file/t372684/2nd.jpg>

when changing the value of Ki from 940 to 960 in this code:

ki=960;

kp=1.5;

w=314.159;

num=([kp ki kp*w.^2]);

den=([1 0 w.^2]);

sis=tf(num,den);

%[RLDATA, ki] = rlocus (sis, 1, 0, 40);

%plot(rlocus(sis),"*","markersize",1)

rlocus(sis)

nr=roots(num);

dr=roots(den);

hold on

plot(nr,"co","markersize",15)

plot(dr,"rx","markersize",15)

Change to plot commands to

plot(real(nr), imag(nr),"co","markersize",15)

plot(real(dr),imag(dr),"rx","markersize",15)

hold off/

So can anybody give me advice on how to avoid this movement of the zero
marker?

Thank you

--
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-----------------------------------------
DAS 