Page 162 - Practical Control Engineering a Guide for Engineers, Managers, and Practitioners

Iatric es and I igh er-0 rd e r Process I o d els l37

iii' 0
:2. . . "! · ....... ~
cu -20 ·~:. ...
]-40 . . . . . . : ... : . . . · ....
';:::! --60 •
I
6b • • • o I • I o ,r •"• I • Ito o o • \ • • \
~ -80 ........... ,,,,, .... .
-too~~~~~~~--~~~~~~--~--~~~
1~ 1~ 1~
Or-~.-~.-~.- .. -----:--~--r==m~t==~==ru====~~~
-50 ....... :-: ...... ·..::: ~ .......... - egr -o y con o
~ -100 ............ ·> .... · ..... ·-· Noconool
~ -150 ...
] -200 . . .. . '": .... ~::-.. ~.~~. ~: ........ .
Q.. -250
-300
-3501~ to-2
Frequency
F1aURE 5-9 Bode plot for no backflow thre~tank process, integral-only
control with i = 0.004.
figure show that when the phase is -180° the gain is less than
unity (or 0 dB). Likewise, when the gain is unity the phase is
greater than -180°. The time domain performance for this gain is
shown in Fig. 5-10.

1.5
1
>-
..
:
:
.
. ... s
.
"E 0.5 : ... · ..... · .. ~· · ..... · ..
V)
0 ~- ... : .... : .. -Y .. . : .... · ....
-0.50
50 100 150 200 250 300 350 400 450 500
0.2
0.15
:::s 0.1

•
•
0
0.05 ...........................
0
50 100 150 200 250 300 350 400 450 500
Tune
F1aURE 5-10 Integral-only control of thre~tank process without backflow.