ngrid (Function Reference)

Superimpose a Nichols chart on a 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 to , where is any complex number. For SISO systems, when is a point on the open-loop frequency response, then

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.

Example

Plot the Nichols response with Nichols grid lines for the system.

Type

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

MATLAB returns

Transfer function:
- 4 s^4 + 48 s^3 - 18 s^2 + 250 s + 600
---------------------------------------
  s^4 + 30 s^3 + 282 s^2 + 525 s + 60

Type

```
nichols(H)
ngrid
```

See Also
nichols Nichols plots

ndims nichols