Chapter 2
Introduction to SISO Design
Xmath Interactive Control Design Module
2-12
ni.com
window has an autoscale feature, which can be invoked by selecting
Autoscale
on the
View
or
Plot
menu of the window. When you invoke
Autoscale, ICDM tries to assign some reasonable values to the slider and
plot scales.
Zooming
You can enlarge any portion of an ICDM plot using plot zooming. Clicking
the middle mouse button with the cursor anywhere in the plot creates a
small box containing a magnified version of the plot near the cursor. The
middle mouse button can be held down and dragged, which creates an
effect similar to dragging a magnifying glass across the plot.
Pressing <Ctrl> along with the middle mouse
button (on UNIX) increases
the size of the magnified box. Clicking with the middle mouse
button
increases the zoom factor. Pressing <Shift-Ctrl> along with middle mouse
button yields a large zoom box with a large magnification factor.
Zooming is a good way to read text in ICDM plots—for example, titles,
axis labels, and so on. These were intentionally made small because
zooming is easy.
Data-Viewing Plots
Pointing at or near plotted information within the ICDM windows and
clicking the right mouse button causes a small window to appear that
identifies the plot and gives the coordinates of the nearest data point
(for example, Loop Gain, L(10.1Hz) |=+11.2dB), along with its index.
This feature is called data-viewing.
If the right mouse button is clicked and dragged, the selected plot is tracked,
even if another plot comes close.
Pressing <Shift> along with the right mouse button allows the user to get
values on the piecewise linear plot that interpolates the data values. In this
case, index = 45.7 means that the selected plot point is between the 45th and
46th X-coordinate entries.
Because all ICDM plots have extensive data-viewing features, the number
of labels used to identify plots are minimal. For example, the Root Locus
plot has red and black poles and zeros shown, but no indication or label in
the plot saying what these colors mean. On a black-and-white display, you
cannot distinguish between the red and black poles/zeros. You can read in
the Help file message that the red ones correspond to the plant, and the
black ones to the controller. However, the easiest way to find out what the
