National Instruments Xmath Interactive Control Design Module ICDM - Manual (Page 52)

Chapter 5 Root Locus Synthesis
Xmath Interactive Control Design Module 5-6 ni.com
All of the plots support data viewing: click the right mouse button with the
cursor positioned near a pole, zero, or one of the plots. This allows you to
find the gain associated with a particular point on a phase contour, for
example.
Slider and Plot Ranges
To change the ranges of the Gain slider or the root locus plot, select
View»Ranges or press <Ctrl-R> in the Root Locus
window.
The slider range also will be changed automatically if you type a new value
which is outside the current range in the corresponding variable edit box.
The plot also can be re-ranged interactively by grabbing and dragging the
plot axes. Refer to the discussion of plot re-ranging in section
s-plots-features.
Selecting View»Auto-scale or pressing <Ctrl-A> in the Root Locus
window will cause new ranges to be assigned to the slider and plot, based
on the current controller.
Manipulating the Parameters
The Graphically Manipulating Poles and Zeros section of Chapter 2,
Introduction to SISO Design , describes how to graphically manipulate the
controller poles and zeros.
The Root Locus window enforces a proper controller; that is, the controller
must have at least as many poles as zeros. If you attempt to add one zero or
a pair of zeros, that would result in more controller zeros than poles, a
warning is issued. Similarly, you cannot delete one or more controller
poles, if the deletion would result in an improper controller.
You can select Edit»Undo to restore the deleted pole(s) and/or zero(s),
provided you have not made any other changes since deleting. To abort a
delete operation, click the left mouse button with the skull and crossbones
cursor away from any pole or zero.