• nebbione
In summary: Sorry for the repetition."In summary, the conversation discusses the process of plotting Nyquist diagrams and the lack of clear explanations or resources on how to do so. Some suggested references are provided, but the main concept is to plot the complex function G(jω) on a polar plot, with the magnitude and phase represented by r and θ, respectively. The domain for plotting is from 0 Hz to ∞ Hz, with the number of points and spacing left to the individual's discretion."
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

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

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

Last edited by a moderator:
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 I am 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.

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 ?

The domain goes from f=0 Hz to f=∞ Hz, you make your own judgement on how many points to plot and their spacing.

http://www.facstaff.bucknell.edu/mastascu/econtrolhtml/Freq/Freq6.html

1. What are Nyquist diagrams and how are they used in science?

Nyquist diagrams are a graphical representation of the frequency response of a system. They are commonly used in fields such as engineering and physics to analyze and design control systems.

2. How do I interpret a Nyquist diagram?

To interpret a Nyquist diagram, you must understand the concept of complex numbers and their relationship to frequency response. The plot shows the real and imaginary parts of the complex function, and the shape of the plot can indicate stability and other characteristics of the system.

3. Can Nyquist diagrams be used for any type of system?

Yes, Nyquist diagrams can be used for any type of system that has a frequency response. This includes electronic circuits, mechanical systems, and biological systems.

4. Are there any limitations to using Nyquist diagrams?

One limitation of Nyquist diagrams is that they only represent the frequency response of a system at a single point in time. They do not show how the response may vary over time or with changing conditions.

5. How can Nyquist diagrams be helpful in scientific research?

Nyquist diagrams can be helpful in scientific research by providing a visual representation of complex systems and their behavior. They can also aid in the design and analysis of control systems, which are crucial in many scientific fields.

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