Specifications

Creating LTI Models
2-9
where num and den are row vectors listing the coefficients of the polynomials
and , respectively, when these polynomials are ordered in descending
powers of s. The resulting variable
h is a TF object containing the numerator
and denominator data.
For example, you can create the transfer function by
typing
h = tf([1 0],[1 2 10])
MATLAB responds with
Transfer function:
s
--------------
s^2 + 2 s + 10
Note the customized display used for TF objects.
You can also specify transfer functions as rational expressions in the Laplace
variable s by:
1 Defining the variable s as a special TF model
s = tf('s');
2 Entering your transfer function as a rational expression in s
For example, once s is defined with tf as in 1,
H = s/(s^2 + 2*s +10);
produces the same transfer function as
h = tf([1 0],[1 2 10]);
Note You need only define the variable s as a TF model once. All of the
subsequent models you create using rational expressions of
s are specified as
TF objects, unless you convert the variable
s to ZPK. See “Model Conversion”
on page 2-40 for more information.
ns
()
ds
()
hs
()
ss
2
2s 10++
()⁄
=