Specifications

zpk
16-234
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 userational expressions to create a ZPK model. Todo so,first type
either:
•
s = zpk('s') tospecifyaZPK model using a rational function in the 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 thesevariables, you can specifyZPK 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 Zero-Pole-Gain Form
zsys = zpk(sys) converts an arbitrary LTI model sys to zero-pole-gain form.
Theoutput
zsys is aZPKobject.By default,zpk useszero to computethezeros
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 models.
Example Example 1
Specify the following zero-pole-gain model.
s 0=
sp
zz
1–
qz
1–
=