Modern Control Engineering

582 Chapter 8 / PID Controllers and Modified PID Controllers

Output

c(

t)

t (sec)

Unit-Step Response of Compensated System

1.4

1.2

1

0.8

0.6

0.4

0.2

0

02468101214

Figure 8–17

Unit-step response

curve.

Unit-Ramp Input and Output

c(

t)

t (sec)

Unit-Ramp Response of Compensated System

20

18

16

14

12

10

8

6

4

2

0

02468101214161820

Compensated System

Figure 8–18

Unit-ramp input and

the output curve.

The resulting unit-step response curve is shown in Figure 8–17 and the unit-

ramp response curve in Figure 8–18. Notice that the closed-loop pole at s=0.1897

and the zero at s=0.2 produce a long tail of small amplitude in the unit-step

response.

For an additional example of design of a PID controller based on the frequency-

response approach, see Problem A–8–7.

Openmirrors.com