User`s guide

zgrid
11-236
11zgrid
Purpose Generate a z-plane grid of constant damping factors and nat ural frequencies
Syntax zgrid
zgrid(z,wn)
Description zgrid generates a grid of constant damping factors from zero t o one in steps of
0.1 and natural frequencies from zero to in steps of , and p lots the grid
over the current axis. If the current axis contains a discrete z-plane root locus
diagram or pole-zero map,
zgrid draws the grid over the plot without altering
the current axis limits.
zgrid(z,wn) plots a grid of constant damping factor and na tural frequency
lines forthe damping factorsand normalized naturalfrequencies in thevectors
z and wn, respectively. If the current axis contains a discrete z-plane root locus
diagram or pole-zero map,
zgrid(z,wn) draws the grid over the plot. The
frequency lines for unnormalized (true) frequencies can be plotte d using
zgrid(z,wn/Ts)
where Ts is the sample time.
zgrid([],[]) draws the unit circle.
Example Plot z-plane grid lines on the root locus for the system
by typing
H = tf([2 –3.4 1.5],[1 –1.6 0.8],–1)
Transfer function:
2 z^2 – 3.4 z + 1.5
-------------------
z^2 – 1.6 z + 0.8
Sampling time: unspecified
ππ
10
⁄
Hz()
2z
2
3.4z– 1.5+
z
2
1.6z– 0.8+
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