Superimpose Nichols chart on Nichols plot
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 the corresponding value of the closed-loop frequency response assuming unit negative feedback is
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.
ngrid returns a warning if the current axis does not contain a SISO
Nichols frequency response.
ngrid('new') clears the current axes first and sets
ngrid( plots the grid on
UIAxes object in the current figure with
AX. Use this syntax when creating apps with
ngrid in the App Designer.
Nichols Response with Nichols Grid Lines
Plot the Nichols response with Nichols grid lines for the following system:
H = tf([-4 48 -18 250 600],[1 30 282 525 60]); nichols(H) ngrid
The context menu for Nichols charts includes the Tight option under Zoom. You can use this option to clip unbounded branches of the Nichols chart.
AX — Object handle
Axes object |
Object handle, specified as an
AX to create apps with
ngrid in the