Note: This page has been translated by MathWorks. Click here to see

To view all translated materials including this page, select Country from the country navigator on the bottom of this page.

To view all translated materials including this page, select Country from the country navigator on the bottom of this page.

Frequency-response functions for modal analysis

`frf = modalfrf(x,y,fs,window)`

`frf = modalfrf(x,y,fs,window,noverlap)`

`frf = modalfrf(___,Name,Value)`

```
[frf,f,coh]
= modalfrf(___)
```

`[frf,f] = modalfrf(sys)`

`frf = modalfrf(sys,f)`

`modalfrf(___)`

estimates
a matrix of frequency response functions, `frf`

= modalfrf(`x`

,`y`

,`fs`

,`window`

)`frf`

,
from the excitation signals, `x`

, and the response
signals, `y`

, all sampled at a rate `fs`

.
The output, `frf`

, is an *H*_{1} estimate
computed using Welch’s method with `window`

to
window the signals. `x`

and `y`

must
have the same number of rows. If `x`

or `y`

is
a matrix, each column represents a signal. The frequency-response
function matrix, `frf`

, is computed in terms of
dynamic flexibility, and the system response, `y`

,
contains acceleration measurements.

specifies
options using name-value pair arguments, using any combination of
inputs from previous syntaxes. Options include the estimator, the
measurement configuration, and the type of sensor measuring the system
response.`frf`

= modalfrf(___,`Name,Value`

)

`[`

computes the frequency-response function of the identified model
`frf`

,`f`

] = modalfrf(`sys`

)`sys`

. Use estimation commands like `ssest`

, `n4sid`

, or `tfest`

to create
`sys`

from time-domain input and output signals. This
syntax allows use only of the `'Sensor'`

name-value pair
argument. You must have a System
Identification Toolbox™ license to use this syntax.

`modalfrf(___)`

with no output
arguments plots the frequency response functions in the current figure.
The plots are limited to the first four excitations and four responses.

[1] Brandt, Anders. *Noise and Vibration Analysis: Signal Analysis and
Experimental Procedures*. Chichester, UK: John Wiley & Sons,
2011.

[2] Vold, Håvard, John Crowley, and G. Thomas Rocklin. “New Ways of Estimating
Frequency Response Functions.” *Sound and Vibration*. Vol.
18, November 1984, pp. 34–38.

`modalfit`

| `modalsd`

| `n4sid`

| `tfestimate`

- Modal Analysis of Identified Models
- System Identification Overview (System Identification Toolbox)
- System Identification Workflow (System Identification Toolbox)
- Supported Continuous- and Discrete-Time Models (System Identification Toolbox)