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)