Environmental Engineering Reference
In-Depth Information
by the damper and VVVF. Tuning was made with reference to the parameters of the
test furnace.
5.3.3 D
ISTURBANCE
S
UPPRESSION
C
ONTROL
OF
D
OOR
O
PEN
AND
C
LOSE
A change in the furnace pressure upon charging steel material into a heating furnace
is a typical example of a disturbance. However, the characteristics of such distur-
bances are not fully known. The operation of opening or closing the charging door
of a furnace constitutes a typical pattern that is determined by such factors as the
volume and heat capacity of the steel to be newly fed into the furnace. Because steel
data can be partially obtained before charging, it can be considered a disturbance
factor
D
(
k
). With a certain amount of compensation added to the input, the variation
in the quantity of state due to disturbance can be prevented in advance. For the
purpose mentioned above, a Kalman filter is used as a parameter identification unit
to control the variation in the quantity of state previously forecast on the basis of
incomplete disturbance information. The filter can also be installed in the feedback
control loop, as shown in
Figure 5.57
.
Figure 5.58
shows a block diagram of the
simulator using a Kalman filter.
Simulation was conducted by using a simulator for furnace pressure control
equipped with feedforward control including an identification unit using this Kalman
filter. The disturbance resulting from opening/closing the door can be expressed by
a first-order lag model of step input, as in the case of the response by the control
terminal. However, the time constant and the gain are different. In the current study,
the empirical parameters were not available. Simulation was conducted by assuming
several patterns for the parameters. As a result, it was learned that the Kalman filter
can estimate the gain no matter what value it may take. Further, the simulation
showed that a time constant with only a minimum degree of deviation with respect
to the time constant in the basic response was sufficiently effective. The closer the
time constant of disturbance is to the basic response, the more easily the disturbance
can be controlled.
Yo kogawa Electric Works Ltd and other manufacturers are promoting a change
in the style of furnace operation from the so-called stockpile charging method in
which slabs of conventional dimensions are controlled within the plant yard on a
lot basis, to “schedule-free heating” method in which slabs of the desired dimensions
-
r
+
+
u
x
Adjusting
section
Object to be
controlled
+
u
Optimum
compensation
calculation
Kalman
filter for
parameter
identification
Disturbance
FIGURE 5.57
Compensation using Kalman filter to control disturbance.
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