ngrid

Superimpose Nichols chart on Nichols plot

Syntax

ngrid

ngrid('new')

ngrid(AX,___)

Description

ngridsuperimposes 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 numberH/(1 +H) toH, whereHis any complex number. For SISO systems, whenH在开环f是一个点吗requency response, then the corresponding value of the closed-loop frequency response assuming unit negative feedback is

$\frac{H}{1 + H}$

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

ngrid('new')clears the current axes first and setshold on.

ngrid(AX,___)plots the grid on theAxesorUIAxesobject in the current figure with the handleAX. Use this syntax when creating apps withngridin the App Designer.

Examples

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Nichols Response with Nichols Grid Lines

Open Live Script

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

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

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

Figure contains an axes object. The axes object contains an object of type line. This object represents H.

The context menu for Nichols charts includes theTightoption underZoom. You can use this option to clip unbounded branches of the Nichols chart.

Input Arguments

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`AX`—Object handle
`Axes`object|`UIAxes`object

Object handle, specified as anAxesorUIAxesobject. UseAXto create apps withngridin the App Designer.

Version History

Introduced before R2006a