User`s guide

balreal
11-17
which indicates that the last two states of sysb are weaklycoupledto the input
and output. You can then delete these states by
sysr = modred(sysb,[2 3],'del')
to obtain the following first-order approximation of the original system.
zpk(sysr)
Zero/pole/gain:
1.0001
--------
(s+4.97)
Compare the Bode responses of the original and reduced-order mode ls.
bode(sys,'-',sysr,'x')
Frequency (rad/sec)
Phase (deg); Magnitude (dB)
Bode Diagrams
−50
−40
−30
−20
−10
10
0
10
1
10
2
−100
−80
−60
−40
−20
0