1.4 Frequency response

Frequency response palette:

The VIs in this sub-palette that are used most frequently are CD Bode, CD Nyquist, and CD Gain and PhaseMargins. These VIs are frequently used in Chapter 6, and are also polymorphic.

Cd bode.vi:

This VI gives the Bode Magnitude and Phase plots of a system, and the input is the open loop model.

The output terminals that are of interest are the ones for plotting the Magnitude and Phase graphs. These can beplotted by creating indicators for the respective terminals. The magnitude plot is shown here.

Cd nyquist.vi:

This VI gives the Nyquist plot of a system.

Remember to right-click on the output terminal of CD Nyquist and select Create»Indicator to create the Nyquist Plot indicator.

Cd gain and phase margin.vi:

This VI gives the Gain and Phase Margins of a system, along with the Magnitude and Phase graph indicating theposition where the Gain and Phase Margins occur.

The Gain and Phase margins are shown in a numeric indicator as shown.

The Magnitude graph obtained from the Block Diagram above is shown below. The zero crossing of the magnitude isindicated in the plot.