User`s guide

zpk
11-240
Each pair specifies a particular LTI property of the model, for example, the
input names or the input delay time. See
set entry and the example below for
details. Note that
sys = zpk(z,p,k,'Property1',Value1,...,'PropertyN',ValueN)
is a shortcut for the following sequence of commands.
sys = zpk(z,p,k)
set(sys,'Property1',Value1,...,'PropertyN',ValueN)
Zero-Pole-Gain Models as Rational Expressions in s or z
You can also use rational expressions tocreate aZPK model. Todo so, first type
either:
•
s = zpk('s') to specifya ZPK modelusing a rational function inthe Laplace
variable,
s.
•
z = zpk('z',Ts) to specify a ZPK model with sample time Ts using a
rational function in the discrete-time variable,
z.
Once you specify either of these variables, you can specify ZPK models directly
as rational expressions in the variable
s orz by entering your transferfunction
as a rational expression in either
s or z.
Conversion to Zero-Pole-Gain Form
zsys = zpk(sys) converts an arbitrary LTI model sys to zero-pole-gain form.
Theoutput
zsys isaZPKobject.By default, zpk useszero to computethe zeros
when converting from state-space to zero-pole-gain. Alternatively,
zsys = zpk(sys,'inv')
uses inversion formulas for state-space models to compute the zeros. This
algorithm is faster but less accurate for high-order models with low gain at
.
Variable
Selection
As for transfer functions, you can specify which variable to use in the display
of zero-pole-gain models. Available choices include (default) and for
continuous-time models, and (default), , or for discrete-time
models. Reassign the
'Variable' property to override the defaults. Changing
the variable affects only the display of zero-pole-gain mod els.
s 0
=
s
p
z
z
1
–
qz
1
–
=