Signal Description
Chirp on page 5-42 A swept-frequency signal that excites your system at a range
of frequencies, such that the input frequency changes
instantaneously. Chirp signals are useful when your system is
nearly linear in the simulation range. They are also useful
when you want to obtain a response quickly for a lot of
frequency points.
Random on page 5-33 A random input signal. Random signals are useful because
they can excite the system uniformly at all frequencies up to
the Nyquist frequency.
Step on page 5-34 A step input signal. Step inputs are quick to simulate and can
be useful as a first try when you do not have much knowledge
about the system you are trying to estimate.
Arbitrary on page 5-34 A MATLAB timeseries with which you can specify any time-
varying signal as input.In general, the estimated frequency response is related to the input and output signals as:Resp=FFTyest(t)
FFTuest(t).
Here, uest(t) is the injected input signal and yest (t) is the corresponding simulated output
signal. For more details, see the Algorithms section of frestimate.Online Estimation
For online estimation with the Frequency Response Estimator block, you can use two
types of input signals:- Sinestream on page 5-37 — A series of sinusoidal perturbations applied one after
another - Superposition on page 5-35 — A set of sinusoidal perturbations applied
simultaneously
For online estimation, using a sinestream signal can be more accurate and can
accommodate a wider range of frequencies than a superposition signal. The sinestream
mode can also be less intrusive. However, due to the sequential nature of the sinestream
perturbation, each frequency point you add increases the experiment time. Thus the5 Frequency Response Estimation