User`s guide

tf
11-226
• s = tf('s') to specify a TF model using a rational function in the Laplace
variable,
s.
•
z = tf('z',Ts) to specify a TF 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 TF 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 Transfer Function
tfsys = tf(sys) converts an arbitrary SS or ZPK LTI model sys to transfer
function form. The output
tfsys (TF object) is the transfer function of sys.By
default,
tf useszero to computethenumeratorswhenconvertingastate-space
model to transfer function form. Alternatively,
tfsys = tf(sys,'inv')
uses inversion formulas for state-space models to derive the numerators. This
algorithm is faster but less accurate for high-order models with low gain at
.
Examples Example 1
Create the two-output/one-input transfer f unction
with input
current and o utputs torque and ang velocity.
s 0
=
Hp()
p 1+
p
2
2p 2++
-----------------------------
1
p
---
=