Modern Control Engineering

Problems 155

Actuating error signal

Flapper

Nozzle

e

a

b

k

X + x

R

Orifice III

Ps

Pb + pb

Pc + pc

Figure 4–47

Pneumatic controller.

Actuating error signal

Flapper

Nozzle

e

a

b

k

X + x

R 2

III

R 1

Orifice

Ps

Pb + pb

Pc + pc

Figure 4–48

Pneumatic controller.

B–4–6.Figure 4–47 shows a pneumatic controller. The sig-
naleis the input and the change in the control pressure
is the output. Obtain the transfer function.
Assume that the pneumatic relay has the characteristics that
pc=Kpb ,whereK>0.

Pc(s)E(s)

pc

B–4–7.Consider the pneumatic controller shown in

Figure 4–48. What control action does this controller pro-

duce? Assume that the pneumatic relay has the character-

istics that pc=Kpb ,where K>0.