Page 157 - Practical Control Engineering a Guide for Engineers, Managers, and Practitioners
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132 Cha11ter Fiwe
25
20
10
. .
5 '\ .............. .
20 25 30
Tune
F1aURI 5-8 Step response of third-order process-three-tank system with
backftow.
given in Fig. 5-7. Note that, unlike the case with no backflow, the three
amplitude curves do not converge to a common asymptote as the fre-
quency decreases because, as we mentioned in question 5-2, the steady-
state levels are not the same.
50.-~~~--~~~r-~~~~~~~~~~~~
~~
~ -100
o~~~~~~~~~~~~~~~~~~~
-50
en -100
M -1so
..c:
Q.. -200
-250
Frequency
F1aURE 5-7 Bode plot for three tanks with backftow.
