Modern Control Engineering

Section 10–7 / Design of Control Systems with Observers 791

Output

y

t (sec)

Unit-Step Response of (2.2655s^2 + 40.779s + 256)/(s^5 + 18s^4 + 114s^3 + 320s^2 + 416s + 256)

0.6

0.8

1

1.2

1.4

0.4

0.2

0 012345678910

Figure 10–32
The unit-step
response of the
system shown in
Figure 10–31. (The
closed-loop poles for
pole placement are
ats=–1;j,
s=–8.The observer
poles are at s=–4,
s=–4.)

Comments. We considered two possible configurations for the closed-loop control

systems using observer controllers. As stated earlier, other configurations are possible.

The first configuration, which places the observer controller in the feedforward path, gen-

erally gives a fairly large overshoot. The second configuration, which places the observer con-

troller in the feedback path, gives a smaller overshoot. This response curve is quite similar to

that of the system designed by the pole-placement approach without using the observer con-

troller. See the unit-step response curve of the system, shown in Figure 10–33, designed by

the pole-placement approach without observer. Here the desired closed-loop poles used are

s=- 1 +j, s=- 1 - j, s=- 8