MATLAB CONTROL SYSTEM TOOLBOX 9 Dokumentacja Pobierz pdf (Strona 565)

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tfdata

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16tfdata

Purpose Quick access to transfer function data

Syntax [num,den] = tfdata(sys)

[num,den] = tfdata(sys,'v')

[num,den,Ts] = tfdata(sys)

Description [num,den] = tfdata(sys) returns the numerator(s) and denominator(s) of

the transfer function for the TF, SS or ZPK model (or LTI array of TF, SS or

ZPKmodels)

sys. For singleLTImodels,theoutputs num and den of tfdata are

cell arrays with the following characteristics:

•

num and den have as many rows as outputs and as many columns as inputs.

• The

(i,j) entries num{i,j} and den{i,j} are row vectors specifying the

numerator and denominator coefficients of the transfer function from input

j to output i. These coefficients are ordered in descending powers of or .

For arrays

sys of LTI models, num and den are multidimensional cell arrays

with the same sizes as

sys.

sys is a state-space or zero-pole-gain model, it is first converted to transfer

function form using

tf. See Table 11-15, “LTI Properties,” on page 11-194 for

more information on the format of transfer function model data.

For SISO transfer functions, the syntax

[num,den] = tfdata(sys,'v')

forcestfdata to return the numeratorand denominatordirectlyasrowvectors

rather than as cell arrays (see example below).

[num,den,Ts] = tfdata(sys) also returns the sample time Ts.

You can access the remaining LTI properties of

sys with get or by direct

referencing, for example,

sys.Ts

sys.variable

Example Given the SISO transfer function

h = tf([1 1],[1 2 5])

1 2 ... 560 561 562 563 564 565 566 567 568 569 570 ... 590 591

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