User`s guide

Table Of Contents

inv

11-102

You can verify that

H * Hi

is the identity transfer f uncti on (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

s = 1.

cloop

Zero/pole/gain:

s (s–1)

-------------------

(s–1) (s^2 + s + 1)

–

IGH+()

–