If you used the sinestream input for estimation, check both the filtered and the unfiltered
time response. You can toggle the display of filtered and unfiltered output by right-
clicking the plot and selecting Show filtered steady state output only. If both the
filtered and unfiltered response appear at steady state, then your model must be at steady
state. You can explore other possible causes in “Troubleshooting Frequency Response
Estimation” on page 5-49.
NoteIf you used the sinestream input for estimation, toggling the filtered and unfiltered
display only updates the Time Response and FFT plots. This selection does not change the
estimation results. For more information about filtering during estimation, see the
Algorithms section of frestimate.
FFT of Time Response
Use this plot to analyze the spectrum of the simulated output.
For example, you can use the spectrum to identify strong nonlinearities. When the FFT
plot shows large amplitudes at frequencies other than the input signal, your model is
operating outside of linear range. If you are interested in analyzing the linear response of
your system for small perturbations, explore possible solutions in “FFT Contains Large
Harmonics at Frequencies Other than the Input Signal Frequency” on page 5-52.
Analyze Simulated Output and FFT at Specific Frequencies
Using the Diagnostic Viewer in Linear Analysis Tool
Use the controls in the Diagnostic Viewer tab of the Linear Analysis Tool to analyze the
estimation results at specific frequencies.
1 If the Diagnostic Viewer tab is not visible, in the Plots and Results tab, select the
Diagnostic Viewer plot.
2 In the Diagnostic Viewer tab, in the Frequency Selector section, specify the
frequency range that you want to inspect. Use the frequency units used in the Bode
plot in the Diagnostic Viewer.
Analyze Estimated Frequency Response