Specifications

2 LTI Models
2-40
Model Conversion
There are four LTI model types you can use with the Control System Toolbox:
TF,ZPK,SS,andFRD.Thissectionshowshow toconvertmodels fromone type
to the other.
Explicit Conversion
Model conversions are performed by tf, ss, zpk,andfrd. Given any TF, SS, or
ZPK model
sys, the syntax for conversion to another model type is
Notice that FRD models can’t be converted to the other model types. In
addition, you must also include a vector of frequencies (
frequency)asaninput
argument when converting to an FRD model.
For example, you can convert the state-space model
sys = ss(–2,1,1,3)
to a zero-pole-gain model by typing
zpk(sys)
to which MATLAB responds
Zero/pole/gain:
3 (s+2.333)
-----------
(s+2)
Note that the transfer function of a state-space model with data is
for continuous-time models, and
sys = tf(sys) % Conversion to TF
sys = zpk(sys) % Conversion to ZPK
sys = ss(sys) % Conversion to SS
sys = frd(sys,frequency) % Conversion to FRD
ABCD
,,,()
Hs() DCsIA–()
1–
B+=