Documentation

This is machine translation

Translated by Microsoft
Mouseover text to see original. Click the button below to return to the English verison of the page.

Note: This page has been translated by MathWorks. Please click here
To view all translated materals including this page, select Japan from the country navigator on the bottom of this page.

ngrid

Superimpose Nichols chart on Nichols plot

Syntax

ngrid

Description

ngrid superimposes Nichols chart grid lines over the Nichols frequency response of a SISO LTI system. The range of the Nichols grid lines is set to encompass the entire Nichols frequency response.

The chart relates the complex number H/(1 + H) to H, where H is any complex number. For SISO systems, when H is a point on the open-loop frequency response, then

H1+H

is the corresponding value of the closed-loop frequency response assuming unit negative feedback.

If the current axis is empty, ngrid generates a new Nichols chart grid in the region –40 dB to 40 dB in magnitude and –360 degrees to 0 degrees in phase. If the current axis does not contain a SISO Nichols frequency response, ngrid returns a warning.

Examples

collapse all

Plot the Nichols response with Nichols grid lines for the following system:

$$H(s) = \frac{{ - 4{s^4} + 48{s^3} - 18{s^2} + 250s + 600}}{{{s^4} +
30{s^3} + 282{s^2} + 525s + 60}}.$$

H = tf([-4 48 -18 250 600],[1 30 282 525 60]);
nichols(H)
ngrid

The right-click menu for Nichols charts includes the Tight option under Zoom. You can use this to clip unbounded branches of the Nichols chart.

See Also

Introduced before R2006a

Was this topic helpful?