Create step input signal
A step input signal has an initial value of
0 and transitions
to a specified step size value after a specified step time. When performing frequency response
estimation, 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. However, the amplitude of the
excitation decreases rapidly with increasing frequency. Therefore, step signals are best used
to identify low-order plants where the slowest poles are dominant. Step inputs are not
recommended for estimation across a wide range of frequencies.
When you use a step input signal for estimation, the frequencies returned in the estimated
frd model depend on the length and sampling time of the signal. They
are the frequencies obtained in the fast Fourier transform of the input signal (see the
Algorithm section of
For more information on input signals for frequency response estimation, see Estimation Input Signals.
Create Step Input Signal
Create a step input signal with a default sample time and the following properties:
Step time of
Step size of
Total duration of
input = frest.createStep('StepTime',5,'StepSize',0.1,'FinalTime',15)
timeseries Common Properties: Name: 'Created with frest.createStep utility' Time: [15001x1 double] TimeInfo: tsdata.timemetadata Data: [15001x1 double] DataInfo: tsdata.datametadata
Plot the step signal.
Specify optional pairs of arguments as
the argument name and
Value is the corresponding value.
Name-value arguments must appear after other arguments, but the order of the
pairs does not matter.
Before R2021a, use commas to separate each name and value, and enclose
Name in quotes.
'Ts',0.01 sets the input signal sample time to
Ts — Sample time
1e-3 (default) | positive scalar
Sample time of the input signal in seconds, specified as the comma-separated pair
'Ts', followed by a positive scalar.
StepSize — Step size
1 (default) | nonzero scalar
Step size, specified as the comma-separated pair
followed by a nonzero scalar. The input signal has value
FinalTime — Input signal duration
10 (default) | positive scalar
Input signal duration in seconds, specified as the comma-separated pair
'FinalTime' followed by a positive scalar.
FinalTime must be greater than
input — Step input signal
Step input signal for frequency response estimation, returned as a
To view a plot of your input signal, type