National Instruments Xmath Interactive Control Design Module ICDM - Manual (Page 22)

Chapter 2 Introduction to SISO Design
© National Instruments Corporation 2-7 Xmath Interactive Control Design Module
list. The current controller is the active or selected entry on the list of
saved controllers.
Only one synthesis window, or the History window, is allowed to be open
at any given time, which eliminates any possible confusion over the source
of the current controller. Remember the simple rule: If any synthesis
window, or the History window, is open, it is the source of the current
controller.
What the ICDM Main Window Plots Show
The plots in the ICDM Main window always use the plant and the current
controller. For example, the step response plot shows the step response of
the closed-loop system formed by the plant transfer function and the
current controller transfer function.
Optionally, the plots also can show the response of the alternate plant
connected with the current controller. In this case, the responses with the
plant and the alternate plant are shown in different line types or colors, and
can always be distinguished by data-viewing. Refer to the
Data-Viewing
Plots section.
Controller/Synthesis Window Compatibilities
As much as possible, ICDM allows you to switch from one synthesis
method to another while keeping the current controller the same. As an
example, suppose the LQG Synthesis window is open, so the current
controller is an LQG controller. You then can open the Root Locus
Synthesis window, which will be initialized with the current (LQG)
controller. Moreover, opening the Root Locus window will cause the LQG
synthesis window to close. You now can continue the design using the Root
Locus
window. For example, you might delete some controller poles and
zeros—that is, do some interactive controller model reduction. When you
have deleted some controller poles and zeros, the controller will no longer
be an LQG controller, so you cannot expect to be able to open the LQG
window and retain the current controller.
There are some restrictions on the controllers that each synthesis window
can accept (read):
• The PID Synthesis window can accept any PID controller. The PID
Synthesis window is intuitive enough to figure out if a given controller
has PID form and, if so, set its parameters appropriately.
• The Root Locus window accepts all controllers, so it can be opened at
any time. The current controller will be read into the Root Locus