National Instruments Xmath Interactive Control Design Module ICDM - Manual (Page 28)

Chapter 2 Introduction to SISO Design
© National Instruments Corporation 2-13 Xmath Interactive Control Design Module
poles and zeros are (and indeed, the only way on a black-and-white display)
is to use data-viewing.
As a general rule: To find out the meaning, purpose, or value of an object
(pole, zero, curve, and so on.) in an ICDM plot, use data-viewing.
Most objects in the ICDM Plot windows support data-viewing.
Interactive Plot Re-ranging
The range for any plot can be set in the appropriate Ranges window.
Alternatively, the ranges for plots can be interactively changed by grabbing
and dragging the axes of the plots. To make the plot range smaller, grab and
drag the appropriate axis to the desired location. A dashed line shows what
the new plot range will be. To make the plot range larger, click the left
mouse
button on the appropriate axis and, while holding the button down,
move the cursor away from the plot axis. In this case you will not see a
dashed line showing the new plot range. Instead, a small box will appear
that tells you what the new range will be. The new range is given by
extrapolation of the cursor position. You can move the cursor over other
plots, and even out of the plotting window, while increasing the range of
a plot.
If a plot range is symmetric, then the new range also will be symmetric.
That is, for a symmetric plot range the minimum and maximum values for
X or Y are the same except for sign. Changing the maximum will also
change the minimum.
These changes will be exported to the Ranges window.
Graphically Manipulating Poles and Zeros
In many of the ICDM windows, the user can grab and drag poles and zeros
graphically. The paradigm of grabbing and dragging poles and zeros is
uniform across windows. Remember that you cannot always grab and drag
every pole or zero you see in an ICDM plot—for example, in the Root
Locus window, you can grab and drag any controller pole or zero, but you
cannot grab or drag a plant pole or zero.
Editing Poles and Zeros
If there is a push button labeled Edit near the plotting area, you can use it
to edit poles and zeros. If you click the Edit button, the cursor will become
a pencil symbol. Select a pole or zero by clicking the left mouse
button with
the cursor positioned at the desired pole or zero. A dialog box will open that