1. Jan 7, 2013

nebbione

Hi everyone! I searched all over the web and nobody/nothing gives a good explanation on how to plot nyquist diagrams... can somebody help with these ? I can't go forward in my study of control engineering without knowing these and i'm stucked...

How are nyquist diagrams plotted starting from a transfer function or from bode diagrams?

Can somebody explain in a detailed way or link me a site where it's explained step by step ?

Thank you

2. Jan 7, 2013

3. Jan 7, 2013

nebbione

Already viewed, but it doesn't help...

4. Jan 7, 2013

SteamKing

Staff Emeritus

http://mmae.iit.edu/~mpeet/Classes/MMAE443/443Lecture23.pdf [Broken]

Last edited by a moderator: May 6, 2017
5. Jan 7, 2013

Runei

A nyquist plot is simply plotting the whole function G(jω).

You have G(s) => G(jω), and then for each ω, you plot the resulting complex number in the complex plain. Normally this is done by using a polar plot, where instead of x and y (or Re and Im in the complex plain), we use r (the distance from origin to the point) and θ (the angle of the line from origin to that point, measured from the real axis of course, and counter-clockwise).

Now for a complex number, the r is simply the magnitude of the number, and θ is the phase.

So for the function G(jω), you simply plot each result as an r and θ. That is, you look at mag(G) and angle(G), and the you plot that.

6. Jan 8, 2013

nebbione

I already viewed even that link but cannot understand... ok i understand that i'm plotting G(jω) but what is the domain ? how much i havef to draw ? how can i know from which module to which module e from which fase to which fase ? Isn't there some place where this is well explained ?

7. Jan 27, 2013