MATLAB CONTROL SYSTEM TOOLBOX 9 Specifikace stáhnout pdf (Strana 560)

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• s = tf('s') to specify a TF model using a rational function in the Laplace

variable,

•

z = tf('z',Ts) to specify a TF model with sample time Ts using a rational

function in the discrete-time variable,

Once you specify either of these variables, you can specify TF models directly

as rational expressions in the variable

s or z by entering your transfer function

as a rational expression in either

s or z.

Conversion to Transfer Function

tfsys = tf(sys) converts an arbitrary SS or ZPK LTI model sys to transfer

function form. The output

tfsys (TF object) is the transfer function of sys.By

default,

tf uses zero tocompute thenumerators whenconvertingastate-space

model to transfer function form. Alternatively,

tfsys = tf(sys,'inv')

uses inversion formulas for state-space models to derive the numerators. This

algorithm is faster but less accurate for high-order models with low gain at

Examples Example 1

Create the two-output/one-input transfer function

with input

current and outputs torque and ang velocity.

To do this, type

num = {[1 1] ; 1}

den = {[1 2 2] ; [1 0]}

H = tf(num,den,'inputn','current',...

'outputn',{'torque' 'ang. velocity'},...

'variable','p')

s 0=

()

p 1+

2p 2++

-----------------------------

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1 2 ... 555 556 557 558 559 560 561 562 563 564 565 ... 590 591

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MATLAB CONTROL SYSTEM TOOLBOX 9 Specifikace Strana 560

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