User`s guide

tf
11-224
11tf
Purpose Specify transfer functions or convert LTI model to transfer function form
Syntax sys = tf(num,den)
sys = tf(num,den,Ts)
sys = tf(M)
sys = tf(num,den,ltisys)
sys = tf(num,den,'Property1',Value1,...,'PropertyN',ValueN)
sys = tf(num,den,Ts,'Property1',Value1,...,'PropertyN',ValueN)
sys = tf('s')
sys = tf('z')
tfsys = tf(sys)
tfsys = tf(sys,'inv') % for state-space sys only
Description tf is used to create real-valued transfer function models (TF objects) or to
convert state-space or zero-pole-gain models to transfer function form.
Creation of Transfer Functions
sys = tf(num,den) creates a continuous-time transfer function with
numerator(s) and denominator(s) specified by
num and den. The outputsys is a
TFobjectstoringthetransferfunctiondata(see“TransferFunctionModels”on
page 2- 8).
Inthe SISOcase,
num andden are thereal-valued rowvectors ofnumeratora nd
denominator coefficients ordered in descending powers of . T hese two vectors
need not have equal length and the transfer function need not be proper. For
example,
h = tf([1 0],1) specifies the pure derivative .
To create MIMO transfer functions, specify the numerator and denominator of
each SISO entry. In this case:
•
num and den are cell arrays of row vectors with as many rows as outputs and
as many columns as inputs.
• The row vectors
num{i,j} and den{i,j} specify the numerator and
denominator of the transfer functionfrom input
j to output i (with the SISO
convention).
s
hs
()
s
=