Generate z-plane grid of constant damping factors and natural frequencies
zgrid generates, for root locus and pole-zero maps, a grid of constant damping factors from zero to one in steps of 0.1 and natural frequencies from zero to π in steps of π/10, and plots 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 natural frequency lines for the damping factors and normalized natural frequencies in the vectors 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 plotted using
where Ts is the sample time.
Alternatively, you can select Grid from the right-click menu to generate the same z-plane grid.
Plot z-plane grid lines on the root locus for the system
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
To see the z-plane grid on the root locus plot, type
rlocus(H) zgrid axis('square')