sgrid

Arguments

zeta

array of damping factors. Only values in [0 1] are taken into account. The default value is [0 0.16 0.34 0.5 0.64 0.76 0.86 0.94 0.985 1] .

wn

array of natural frequencies in Hz. only positive values are taken into account. If not given it is computed by the program to fit with the boundaries of the plot.

colors

a scalar or an 2 element array with integer values (color index).

Description

Plots selected curves of constant damping ratio (selection given by zeta) and constant natural frequency (selection given by wn).

The colors argument may be used to assign a color for constant damping ratio curves (colors(2)) and for constant natural frequency curves (colors(1)).

The sgrid function is often used to draw a grid for evens root locus of continuous time linear systems. In such a case the sgrid function should be called after the call to evans. For discrete time linear systems one should use zgrid function instead.

The optional argument 'new' can be used to erase the graphic window before plotting the grid.

Examples

//sgrid
clf();sgrid(0:0.2:1,[0.2 0.6 1 1.7 2])

H=syslin('c',352*poly(-5,'s')/poly([0,0,2000,200,25,1],'s','c'));
clf();evans(H,100);sgrid()

See also

• evans — Evans root locus
• zgrid — zgrid plot
• datatips — Tool for placing and editing tips along the plotted curves.