Nichols Plot Generator

Description| How it works| Gain and Phase Margins

This app will generate the Nichols Plot given a transfer function of the form
F(s) = (a + bs) e-ts / (g + hs).

Nichols plot shows open loop gain in decibels against open loop phase shift. It allows easy determination of robustness margins.


.xlsx file (42 KB)

How to use

The use of this app is quite straightforward, simply key in the values of a, b, g, h and t into the cells B6 through B10. Key in the frequency range into the cells B13 and B14. Note that the units of frequency is rad/time. The Nichols plot is generated.

Lets say we wish to obtain the Nichols plot of 2e-3s/(1 + 5s), from 0.01 rad/s to 100 rad/s. We have

a = 2,
b = 0,
g =1,
h = 5 and
t = 3.

Key in these values and the range. If done correctly, you should see the screen below.

Nichols Plot

Also See:

PID Loop Simulator

Laplace to Time Domain Converter

Nyquist Plot Generator

PI Control of First Order Process

PI Control of Integrating Process