Specifications

inv
16-104
H * Hi
is the identity transfer function (static gain I).
Limitations Do not use inv to model feedback connections such as
While it seems reasonable to evaluate the corresponding closed-loop transfer
function as
inv(1+g*h) * g
this typically leads to nonminimal closed-loop models. For example,
g = zpk([],1,1)
h = tf([2 1],[1 0])
cloop = inv(1+g*h) * g
yields a third-order closed-loop model with an unstable pole-zero cancellation
at
s = 1.
cloop
Zero/pole/gain:
s (s-1)
-------------------
(s-1) (s^2 + s + 1)
Use feedback toavoidsuchpitfalls.
cloop = feedback(g,h)
Zero/pole/gain:
s
-------------
(s^2 + s + 1)
-
+
G
H
IGH+
()
1–
G