National Instruments ICDM What the ICDM Main Window Plots Show, Controller/Synthesis Window Compatibilities

Chapter 2 Introduction to SISO Design

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