User`s guide

1 Data Processing
Filtering Frequency-Domain or Frequency-Response Data in
the GUI
For frequency-domain and frequency-response data, filtering is equ ivalent to
selecting sp ecificdataranges.
To select a range of data in frequency-domain or fre quency -response data:
1 Import data into the System Identification Tool G UI, as described in
“Representing Data in the GUI” on page 1-13.
2 Drag the data set you want you want to filter to the Working Data are a.
3 Select <–Preprocess > S elect range. This selection displays one of the
following plots:
• Frequency-domain data — Plot shows the absolute of the squares of the
input and output spectra.
• Frequency-response data — Top ax es show the frequency response
magnitude equivalent to the ratio of the output to the input, and the
bottom axes show the ratio of the input signal to itself, which has the
value of
1 at all frequencies.
4 If your data contains multiple input/output channels, in the Chan nel
menu, select the channel pair you want to view. Although you view only
one channel pair at a time, the filter applies to all input/output channels
in this data set.
5 Select the data of interest using one of the following w ay s:
• Graphically — Draw a rectangle with the mouse on either the
input-signal or the output-s ignal plot to sele ct the d es ired frequency
interval. Your selection is displayed on both plots reg a rdless of the plot
on which you draw the rectangle. The Range fi eld is updated to match
the selected region.
If you need to clear your selection, right-click the plot.
• Specify the Range — Edit the beginning and the end frequency values.
For example:
8.5 20.0 (rad/s).
1-110