Modern Control Engineering

552 Chapter 7 / Control Systems Analysis and Design by the Frequency-Response Method

Frequency (rad/sec)

Bode Diagram of Gc(s) = 9.5238(s + 3.0101)/(s + 14.3339)

0

40

30

20

10

60

50

5

Phase (deg); Magnitude (dB)

10

20

15

10 −^1100101102103

Figure 7–147

Bode diagram of

Gc(s).

The open-loop transfer function of the designed system is

MATLAB Program 7–27 will produce the Bode diagram of Gc(s)G(s), which is shown in

Figure 7–148.

=

95.238s+286.6759

s^3 +15.3339s^2 +14.3339s

Gc(s)G(s)=9.5238

s+3.0101

s+14.3339

10

s(s+ 1 )

MATLAB Program 7–27

num = [95.238 286.6759];

den = [1 15.3339 14.3339 0];

sys = tf(num,den);

w = logspace(–1,3,100);

bode(sys,w);

grid;

title('Bode Diagram of Gc(s)G(s)')

[Gm,pm,wcp,wcg] = margin(sys);

GmdB = 20*log10(Gm);

[Gmdb,pm,wcp,wcg]

ans =

Inf 49.4164 Inf 6.5686

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