Chapter 2
Introduction to SISO Design
Xmath Interactive Control Design Module
2-8
ni.com
window. Thus, the Root Locus Synthesis window can be used to
interactively tweak or model-reduce a controller designed by another
method such as LQG.
•
The Pole Place window accepts any controller with the same number
of poles as the plant, or one more pole than the plant if it has integral
action. In particular, the Pole Place window can accept any LQG or H
∞
controller with or without integral action. This allows the user to
manually tune the closed-loop poles in a design that was originally
LQG or H
∞
.
•
The LQG window only accepts controllers that were generated by the
LQG synthesis window.
•
The H
∞
Synthesis window only accepts controllers that were generated
by the H
∞
Synthesis window.
•
The History window, which can be considered as a synthesis window
since it exports a controller to the ICDM Main window, is compatible
with all controllers. If the current controller has been saved on the
history list, then the History window opens, with the current controller
the active controller on the history list. If the current controller has not
been saved on the history list, it is first automatically saved on the
history list, then the History window opens with the current controller
active.
These restrictions are important when you select a new synthesis window
or read a controller from Xmath into ICDM. If the controller is not
compatible with the synthesis window, the user is warned and given several
options about how to proceed. In general, these restrictions on controllers
and synthesis windows should be transparent to the user. ICDM is designed
to do something sensible whenever a conflict can arise, and to warn the user
before any damaging actions are taken.
When the new controller and synthesis window will be compatible, the new
synthesis window is initialized with the controller. The user can simply
start designing, using the new synthesis window, from the current design.
Roughly speaking, ICDM tries to keep the current controller when you
select a new synthesis window.
As an example, suppose the LQG
window is used to design an LQG
controller. The user then can open the Pole Place window, which will be
initialized with the LQG controller, and continue the design by dragging the
closed-loop poles to new locations. At this point, the user cannot expect to
import the current controller back into the LQG Synthesis window because
the controller is no longer an LQG controller. The user can, however, open
the Root Locus window, which will be initialized with the current
