National Instruments Xmath Interactive Control Design Module ICDM - Manual (Page 119)

Chapter 13 Multi-Loop Synthesis
Xmath Interactive Control Design Module 13-8 ni.com
Editing and Deleting Loops
When a loop is highlighted, it can be edited, deleted, disabled, or enabled.
Here, “editing” means designing a SISO controller for the selected loop.
The editing and deleting options are accessible under the Edit pull-down
menu. Disabling or enabling a loop is done by clicking the button at the
bottom of the Multi-Loop
window. A loop that has been disabled is
represented by a dashed line in the graphical editor.
There are two choices for editing a loop: PID and Root Locus. After an
option has been selected, the regular SISO Design window opens. The only
difference with the regular SISO Synthesis window is the top part of the
window where loop, sensor and actuator name are listed. Refer to
Figure 13-5, where Root-Locus synthesis was selected. While the SISO
Synthesis window is open, it is impossible to do any kind of manipulation
in the Multi-Loop window. Only after the SISO window is closed, the
Multi-Loop window will become active again. It is therefore not possible,
for instance, to select some other loop and disable it during the SISO design
phase.
Loop Gain Magnitude and Phase
In the plot area of the main window, two plots are displayed where the loop
gain magnitude and phase of each loop that was closed. The loop gain is the
SISO transfer function
where C (i) is the transfer function of the controller of the selected loop, and
where is the SISO-equivalent plant of the ith loop. Here, i refers to
index of the loop in the scrolled list.
The loop displayed in a thick line type is the one that was selected; that is,
the one that is currently being edited. The loops are displayed in the same
line type in the loop gain magnitude and phase plots in the main window.
Whenever a loop is disabled or enabled, the corresponding loop gain
magnitude and phase plots in the main window also will change line type
from dashed to solid, or vice versa.
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