Page 133 - Practical Control Engineering a Guide for Engineers, Managers, and Practitioners

108 Chapter Fonr

3r-~--.--.r--r---r==~========~~
Y (Process response)
0 -
- U (Control output)
0
2.5
2

0
0
t - -·-.- -·-. -·-·~·-·-·~"- -·-·- ~ -·-
~
0.5

0 1----'----'
0 30 40 50 60 70 80 90 tOO
Time
fiGuRE 4-34 Open-loop step response of FOWDT process (T= 10, D = 8, g = 2.5).
The magnitude is identical to that of the dead time-less first-order
model in Eq. (4-7) but the phase lag is increased by the contribution
of the dead time.
The Bode plot for the open-loop transfer function is given in Fig. 4-35.
Note the circles that indicate unity magnitude and -t80° phase.
t0 1 r-~~~~-----~~~---~~~-r---~~~~
......
QJ tOO r
"'tS
.a
:.= to-1 r .. ·;·
0.. i
0'
~ to-2 .. - - - - - '.· ... -- ; -
oO
to-Jto-J to-2 to-1 tOO 101

too
- 0
~
~-tOO
cu
f
-200 ....
-300to-J to-2 to-1 tOO 101
Frequency (Hz)

FIGURE 4-35 Bode plot for FOWDT process (T= 10, D = 8, g = 2.5).