User`s guide

sminreal
11-209
11sminreal
Purpose Perform model reduction based on structure
Syntax msys = sminreal(sys)
Description msys = sminreal(sys) eliminates the states of the state-space model sys that
don’t affect the input/output response. All of the states of the resulting
state-space model
msys are also states of sys and the input/output response of
msys is equivalent to that of sys.
sminreal eliminates only structurally non minimal states, i.e., states that can
be discarded by looking only at hard zero entries in the A, B,andCmatrices.
Such structurally nonminimal states arise, for example, when l inearizing a
Simulink model tha t includes some unconnected state-space or transfer
function blocks.
Remark The model resulting from sminreal(sys) is not necessarily minimal, and may
have a higher order than one resulting from
minreal(sys). However,
sminreal(sys) retains the state structure of sys,while,ingeneral,
minreal(sys) does not.
Example Suppose you concatenate two SS models, sys1 and sys2.
sys = [sys1,sys2];
This operation is depicted in the diagram below.
If you extract the subsystem
sys1 from sys,with
sys(1,1)
+
y
u
v
sys1
sys2