Simulink Control Design™ - MathWorks

Step 2: Estimating Frequency Response Using Sinestream Input Signal

Sinestream input signal is the most reliable input signal for estimating an accurate

frequency response of a Simulink model using FRESTIMATE. It is a signal that is

composed of individual sinusoidal signals that are appended to the end of each other.

FRESTIMATE command simulates the model for each frequency in the sinestream input

signal, specified in "Frequency" parameter, for the corresponding amount of periods,

specified in "NumPeriods" parameter. After the simulation, FRESTIMATE uses the output

signal to compute the response at each frequency. Note that FRESTIMATE uses only the

periods after the system reaches to steady state for that input frequency, specified in

"SettlingPeriods" parameter. Create a sinestream signal with logarithmically-spaced

distinct frequencies between 0.1 and 10 rad/s:

in = frest.Sinestream('Frequency',logspace(-1,1,50),'Amplitude',1e-3)

The sinestream input signal:

Frequency : [0.1 0.10985 0.12068 0.13257 ...] (rad/s)

Amplitude : 0.001

SamplesPerPeriod : 40

5 Frequency Response Estimation