: sgrid
: sgrid on
: sgrid off
: sgrid (z, w)
: sgrid (hax, …)

Control the display of s-plane grid with :

  • - zeta lines corresponding to damping ratios and
  • - omega circles corresponding to undamped natural frequencies

The function state input may be either "on" or "off" for creating or removing the grid. If omitted, a new grid is created when it does not exist or the visibility of the current grid is toggled.

The sgrid will automatically plot the grid lines at nice values or at constant values specified by two arguments : 

sgrid (Z, W)

where Z and W are :

  • Z vector of constant zeta values to plot as lines
  • W vector of constant omega values to plot as circles

Example of usage: 

sgrid on	create the s-plane grid

sgrid off 	remove the s-plane grid

sgrid		toggle the s-plane grid visibility

sgrid ([0.3, 0.8, …], [10, 75, …])   create:
  • - 
    zeta lines for 0.3, 0.8, …
  • - 
    omega circles for 10, 75, … [rad/s] 


sgrid (hax, "on")   create the s-plane grid for the axis 
                    handle hax

See also: grid.

Demonstration 1

The following code

 clf;
 num = 1; den = [1 4 5 0];
 sys = tf(num, den);
 rlocus(sys);
 sgrid on;

Produces the following figure

Figure 1

Demonstration 2

The following code

 clf;
 num = [1 3]; den = [1 5 20 16 0];
 sys = tf(num, den);
 rlocus(sys);
 hfig = get(0, "currentfigure");
 hax = get(hfig, "currentaxes");
 sgrid(hax, "on");

Produces the following figure

Figure 1

Demonstration 3

The following code

 clf;
 num = 1; den = [1 4 5 0];
 sys = tf(num, den);
 rlocus(sys);
 sgrid([0.5 0.7 0.89], [1 1.66 2.23]);

Produces the following figure

Figure 1

Package: control