User`s guide

2 LTI Models
2-42
Model Conversion
There are four LTI model types you can use with the Control System Toolbox:
TF,ZPK,SS,andFRD.Thissection shows how toconvertmodelsfromonetype
to the other.
Explicit Conversion
Model conversions are performed b y tf, ss, zpk,andfrd. Given any T F, S S, 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 als o include a vector of f requencies (
frequency) as an input
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
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+=