1. A plant control device for performing a feedforward control at a processing treatment of a controlled object, the feedforward control being performed based on a variation of a prior-to-control state quantity occurred in the controlled object caused by a variation factor included in the controlled object, the plant control device comprising: a phase difference obtainer configured to obtain a phase difference between a variation in the prior-tocontrol state quantity and a variation in a postcontrol state quantity, the post-control state quantity being a quantity of state of the controlled object after the processing treatment is performed; and a feedforward adjusting unit configured to decide an amount of phase shift until a measurement result of the prior-to-control state quantity is reflected to the feedforward control based on the phase difference.

2. The plant control device as claimed in claim 1, wherein the feedforward adjusting unit is configured to decide the amount of phase shift based on a relationship between a value predetermined with respect 47 to the phase difference and the phase difference.

3. The plant control device as claimed in claim 1, wherein the feedforward adjusting unit is configured to decide a control gain in the feedforward control based on the phase difference.

4. The plant control device as claimed in claim 1, wherein the feedforward adjusting unit is configured to decide the amount of phase shift based on a variation width of the post-control state quantity and the phase difference.

5. The plant control device as claimed in claim 4, further comprising a controlled variable phase obtainer configured to obtain a controlled variable phase, the controlled variable phase being a phase of a variation in a controlled variable occurred according to the variation factor at the processing treatment, wherein when the variation width of the post-control state quantity is within a predetermined range, the feedforward adjusting unit is configured to decide the 48 amount of phase shift based on a phase difference between a phase of the variation in the prior-tocontrol state quantity and the controlled variable phase.

6. The plant control device as claimed in claim 5, further comprising a condition information storage unit configured to associate the amount of phase shift in a state where the variation width of the post-control state quantity is within the predetermined range with a condition affecting a control of the processing treatment and store the amount of phase shift in a storage medium, wherein the feedforward adjusting unit is configured to decide an amount of phase shift until a measurement result of the prior-to-control state quantity is reflected to the feedforward control based on the amount of phase shift, the amount of phase shift being stored on the storage medium corresponding to the condition affecting the control of the processing treatment.

7. A rolling control device for performing a feedforward control at a rolling process of a rolled 49 material based on a variation in a sheet thickness before rolling, the variation in the sheet thickness occurring in the rolled material based on a high degree of variation according to a position included in the rolled material, the rolling control device comprising: a phase difference obtainer configured to obtain a phase difference between the variation in the sheet thickness before the rolling and a variation in a sheet thickness after the rolling, the sheet thickness after the rolling being a sheet thickness of the rolled material after the rolling process is performed; and a feedforward adjusting unit configured to decide an amount of phase shift until a measurement result of the variation in the sheet thickness before the rolling is reflected to the feedforward control based on the phase difference.

8. A plant control method for performing a feedforward control at a processing treatment of a controlled object, the feedforward control being performed based on a variation of a prior-to-control state quantity occurred in the controlled object caused by a variation factor included in the controlled object, the plant control method comprising: obtaining a phase difference between a variation 50 in the prior-to-control state quantity and a variation in a post-control state quantity, the post-control state quantity being a quantity of state of the controlled object after the processing treatment is performed; and deciding an amount of phase shift until a measurement result of the prior-to-control state quantity is reflected to the feedforward control based on the phase difference.

9. A plant control program for performing a feedforward control at a processing treatment of a controlled object, the feedforward control being performed based on a variation of a prior-to-control state quantity occurred in the controlled object caused by a variation factor included in the controlled object, the plant control program causing an information processing device to execute: a step of obtaining a phase difference between a variation in the prior-to-control state quantity and a variation in a post-control state quantity, the postcontrol state quantity being a quantity of state of the controlled object after the processing treatment is performed; and a step of deciding an amount of phase shift until 51 a measurement result of the prior-to-control state quantity is reflected to the feedforward control based on the phase difference.

Title of Invention
PLANT CONTROL DEVICE, ROLLING CONTROL DEVICE, PLANT
CONTROL METHOD, AND PLANT CONTROL PROGRAM
Technical Field
The present invention relates to a plant control
device, a rolling control device, a plant control
method, and a plant control program.
Background Art
A rolling mill, which is a plant rolling metal
plates to efficiently produce thin metallic materials,
possibly causes a failure in plate thickness due to
unevenness in hardness of a metal plate, which is a
rolled material. The unevenness in hardness means a
state where hardness of the rolled material is not
entirely uniform in the rolled material. The hardness
of the rolled material works as a deformation
resistance during rolling. Therefore, when the
unevenness in hardness occurs in a rolling direction,
which is a conveying direction of conveying the rolled
material during rolling, the rolled material is
differently squashed depending on positions, resulting
in variations in the sheet thickness after being rolled.
Generally, the rolling is performed by causing
the rolled material to pass through the rolling mill
several times so as to decrease from an original sheet
2
thickness, which is a sheet thickness of an original
metal sheet, to a product thickness. A presence of
unevenness in hardness differentiates the hardness of
the rolled material depending on the positions;
therefore, a variation in sheet thickness occurs.
Through several rollings, a sheet thickness deviation
additionally occurs each time. To improve accuracy of
sheet thickness of products, the rolling mill performs
a sheet thickness control. However, it was difficult
to remove the variation in sheet thickness, which
occurs due to the unevenness in hardness whenever the
rolling is performed, by the sheet thickness control.
For example, the variation in sheet thickness due
to the unevenness in hardness occurred at a rolling of
a certain time is detected by the entry-side sheet
thickness gauge at the next rolling, and the sheet
thickness control is feedforwardly performed to
restrain the variation in sheet thickness. However,
since the unevenness in hardness additionally generates
the variation in sheet thickness, a gain larger than a
usual control gain is required. The frequency analysis
determines the presence/absence of the unevenness in
hardness, and the control gain in the feedforward sheet
thickness control is changed (JP-A-2000-33409).
With the technique disclosed in JP-A-2000-33409,
3
to remove a variation in deformation resistance in the
conveying direction of the rolled material due to
unevenness in hardness, the feedforward control removes
a variation in sheet thickness occurred during the
previous rolling at the next rolling as an entry-side
variation in sheet thickness. Then, according to the
presence/absence of unevenness in hardness, the control
gain of the feedforward control is changed.
The feedforward control is a proportional control,
and this outputs with phase and amplitude corresponding
to a target control deviation ensures the maximized
control effect. As the control deviation, a sine wave
is assumed, and a control output, which is found by
multiplying the sine wave by the control gain, is
provided. Then, how the resultant phase and amplitude
change is examined. For example, as a control output
with respect to sine wave sin (ωt), a sine wave found
by multiplying a control gain G and a phase shift Δ is
created and the obtained result is defined as y.
In this case, y is expressed by the following
Expression (1).
Here, an amplitude of y in Expression (1) is
expressed by the following Expression (2), and a phase
4
of y is expressed by the following Expression (3).
Fig. 19 is a drawing of graphs showing X, which
is the amplitude of y, and a phase discrepancy δ in the
case where the control gain G and the phase shift Δ are
changed. It is found that, as illustrated in Fig. 19,
an increase in the phase shift Δ also increases the
amplitude. Therefore, depending on the control gain G,
an excess of 60 degrees fails to obtain a control
effect, on the contrary, this brings an adverse effect.
In the case where the phase shift Δ occurs by
performing the control, the phase of y of the control
result, which is obtained as the result, is shifted
from the original sine wave sin (ωt).
That is, if phases are shifted between a
controlled object and a control output, that is, the
phase shift Δ is present, even if a control gain for a
feedforward control, which is the proportional control,
is increased, this causes a possibility of small
control effect or on the contrary, worsening the phase
shift.
Here, assume the case where a variation in sheet
5
thickness caused by unevenness in hardness occurs.
Since the rolling performs the sheet thickness control
and a tension control, a phase relationship between the
variation in sheet thickness and the unevenness in
hardness is shifted. This phase relationship indicates
that how much angle a peak position in each waveform is
shifted with respect to one cycle, 360 degrees.
Accordingly, even if the feedforward control is
performed with an entry-side sheet thickness deviation
of the rolled material, since the phase relationship is
shifted from the original unevenness in hardness, the
control effect cannot be obtained.
Such problem is not limited to the unevenness in
hardness in the rolled material caused by rolling a
metallic material. In a plant control, when a
controlled object before the control has a variation
factor, which has generated based on a reference
variation factor, is controlled to obtain a control
result, a problem possibly occurs similarly in the case
where the phases are shifted between the reference
variation factor and the variation factor before the
control.
The problem to be solved with the present
invention is to preferably adjust an amount of phase
shift of a control output to enhance a control effect
6
in the case where a controlled object has a plurality
of variation factors of different phases when a
feedforward control is performed in a plant such as a
rolling mill.
Summary
The present invention, for example, employs
configurations described in the claims. Although this
application includes a plurality of components to solve
the problems, one example is as follows. The present
invention is a plant control device for performing a
feedforward control at a processing treatment of a
controlled object. The feedforward control is
performed based on a variation of a prior-to-control
state quantity occurred in the controlled object caused
by a variation factor included in the controlled object.
The plant control device includes a phase difference
obtainer and a feedforward adjusting unit. The phase
difference obtainer is configured to obtain a phase
difference between a variation in the prior-to-control
state quantity and a variation in a post-control state
quantity. The post-control state quantity is a
quantity of state of the controlled object after the
processing treatment is performed. The feedforward
adjusting unit is configured to decide an amount of
7
phase shift until a measurement result of the prior-tocontrol
state quantity is reflected to the feedforward
control based on the phase difference.
According to the present invention, an amount of
phase shift of a control output is preferably adjusted
to ensure enhancing a control effect in the case where
a controlled object has a plurality of variation
factors of different phases when a feedforward control
is performed in a plant such as a rolling mill. The
problem, configuration, and effect other than those
described above are clarified by the description of the
following embodiments.
Brief Description of Drawings
Fig. 1 is a drawing illustrating an overall
configuration of rolling mills and rolling control
devices according to an embodiment of the present
invention;
Fig. 2 is a drawing illustrating a rolling
phenomenon of the rolling mill and respective
parameters related to the rolling phenomenon;
Fig. 3 is a drawing illustrating basic
expressions of a rolling control;
Fig. 4 is a drawing illustrating a process
content of a sheet thickness control by a sheet
8
thickness control unit;
Fig. 5 is a drawing illustrating a process
content of a tension control by a tension control unit;
Fig. 6 is a drawing illustrating simulation
results of the rolling phenomenon;
Fig. 7 is a drawing illustrating simulation
results of the rolling phenomenon;
Fig. 8 is a drawing illustrating simulation
results of the rolling phenomenon;
Fig. 9 is a drawing illustrating process contents
by the sheet thickness control unit and a feedforward
control adjusting device according to the embodiment of
the present invention;
Fig. 10 is a drawing illustrating a function
composition of a control gain/timing shift amount
setting device according to the embodiment of the
present invention;
Fig. 11 is a flowchart showing a calculation
operation of a phase difference according to the
embodiment of the present invention;
Figs. 12A to 12C are drawings illustrating the
calculation operation of the phase difference according
to the embodiment of the present invention;
Fig. 13 is a drawing illustrating simulation
results of the rolling phenomenon;
9
Fig. 14 is a drawing illustrating simulation
results of the rolling phenomenon;
Fig. 15 is a drawing illustrating simulation
results of the rolling phenomenon;
Fig. 16 is a drawing illustrating simulation
results of the rolling phenomenon;
Fig. 17 is a drawing illustrating simulation
results of the rolling phenomenon;
Fig. 18 is a drawing illustrating a hardware
configuration of the rolling control device according
to the embodiment of the present invention; and
Fig. 19 is a drawing illustrating a relationship
between an amount of phase shift and an amount of phase
discrepancy in a phase control and an amplitude.
Description of Embodiments
As an embodiment of a plant control device
according to the present invention, the following gives
a description using a control device for a rolling mill
that performs rolling as a processing treatment to a
rolled material made of a metallic material as an
example. One feature of this embodiment is a control
method where four-stand tandem rolling mills minimalize
a variation in sheet thickness occurred due to
unevenness in hardness in the case where the unevenness
10
in hardness occurs, which is a deformation resistance
variation of the rolled material. Fig. 1 is a block
diagram illustrating four-stand rolling mills and a
control composition of the four-stand rolling mills
according to the embodiment.
As illustrated in Fig. 1, the tandem rolling
mills are formed by continuously disposing #1 stand
rolling mill 11 to #4 stand rolling mill 14, which are
constituted of a plurality of rolls, by four. The
rolling mills each perform rolling as illustrated in
Fig. 2. In this embodiment, one rolling mill is
constituted of six rolls. Sandwiching a rolled
material, the rolls are referred to as work rolls,
intermediate rolls, and backup rolls from the inside.
As illustrated in Fig. 2, the rolling is
performed by squashing the rolled material between
upper and lower work rolls. At this time, a rolled
material 0 is pulled by an entry-side tension Tb and an
exit-side tension Tf. By being squashed by a rolling
load P, an entry-side sheet thickness H becomes an
exit-side sheet thickness h. A rolling phenomenon
generates the rolling load P, a forward slip f, and a
backward slip b. At a roll speed VR, respective entryside
speed Ve and exit-side speed Vo become as shown in
Fig. 2.
11
Fig. 3 illustrates a modelled rolling phenomenon
of Fig. 2. The entry-side speeds Ve and the exit-side
speeds Vo of an own stand rolling mill and stand
rolling mills before and after the own stand rolling
mill change the entry-side tension Tb and the exit-side
tension Tf. The change in tension also changes the
rolling load P, the exit-side sheet thickness h, the
entry-side speed Ve, and the exit-side speed Vo. As
described above, the rolling phenomenon is a
complicated phenomenon that has inputs of the entryside
sheet thickness H, the roll speed VR, and a roll
gap S, and has outputs of the entry-side tension Tb,
the exit-side tension Tf, and the exit-side sheet
thickness h. The rolling phenomenon is also related to
a rolling phenomenon in the rolling mill stands before
and after the own rolling mill via the tension.
As illustrated in Fig. 1, the respective fourstand
rolling mills include electric motors, which
operate the work roll speed, electric motor speed
control devices 21 to 24, and roll gap control devices
31 to 34, which operate roll gaps, which are intervals
between the work rolls. In the rolling, sheet
thicknesses of rolled materials processed as products
are important in terms of quality. Sheet thickness
gauges 41 to 44, which measure sheet thicknesses of the
12
rolled materials, are installed on exit-sides of the
respective rolling mill stands. A tension applied to
the rolled materials is important for stability of a
rolling operation and are involved in sheet thickness
accuracy. Accordingly, tension gauges 51 to 54 are
installed on respective stand exit-sides. On the exitside
of the #4 stand rolling mill 14, to control the
exit-side tension of the #4 stand rolling mill 14, an
exit-side bridle roll 15, an electric motor, and a
speed control device 25 are installed.
The #1 stand rolling mill 11 includes a sheet
thickness control unit 61, which operates the roll gap
of the #1 stand rolling mill 11. A #2 stand rolling
mill 12 to the #4 stand rolling mill 14 include sheet
thickness control units 62 to 64, which operate a
front-stage stand speed. For example, in the case of
the #2 stand rolling mill 12, a speed control is
performed on the #1 stand rolling mill 11.
The sheet thickness control units 62 to 64, which
are disposed at or after the #2 stand rolling mill 12,
perform a feedforward control using a detection result
by an entry-side sheet thickness gauge and a feedback
control using a detection result by an exit-side sheet
thickness gauge. For example, the sheet thickness
control unit 62 at the #2 stand performs the
13
feedforward control using the detection result by the
sheet thickness gauge 41 on the exit-side of the #1
stand and the feedback control using the detection
result by a sheet thickness gauge 42 on the exit-side
of the #2 stand.
Regarding the tension, tension control units 71
to 73 control exit-side tensions of the respective
rolling mill stands using roll gaps of the subsequent
stand rolling mills. For example, the tension control
unit 71 controls the exit-side tension at the #1 stand
rolling mill 11 by operating the roll gap of the #2
stand rolling mill 12 by a roll gap control device 32.
A tension control unit 74 controls the exit-side
tension at the #4 stand rolling mill 14 by operating a
speed of the exit-side bridle roll 15 by the speed
control device 25.
Fig. 4 is a drawing illustrating an outline of
the sheet thickness control unit 64. As illustrated in
Fig. 4, the sheet thickness control unit 64 performs a
transfer process such that an entry-side sheet
thickness deviation ΔH measured at the exit-side of a
#3 stand rolling mill 13 by a sheet thickness gauge 43
is delayed until a measuring position of the rolled
material reaches immediately below the #4 stand rolling
mill 14. The measurement result of this entry-side
14
sheet thickness deviation ΔH is a prior-to-control
state quantity, which is a quantity of state before
rolling, and a phase before rolling is a prior-tocontrol
phase.
The sheet thickness control unit 64 outputs a
control output found by adding a feedforward control
output multiplied by a control gain GFF, to a feedback
control output, which is the exit-side sheet thickness
deviation Δh measured by the sheet thickness gauge 44
on the exit-side of the #4 stand rolling mill 14 and is
multiplied by a control gain GFB, and performing an
integral treatment on the found value. The measurement
result of this exit-side sheet thickness deviation Δh
is a post-control state quantity, which is a sheet
thickness after rolling, and a phase after rolling is a
post-control phase.
The other sheet thickness control units 61 to 63
also have similar configurations. The sheet thickness
control units 61 to 63 perform the feedforward control
with the entry-side sheet thickness deviation and the
feedback control with the exit-side sheet thickness
deviation with respect to each rolling mill stand. The
variation in sheet thickness cannot be detected
immediately below the #4 stand rolling mill 14 where
the variation in sheet thickness occurs but is detected
15
by the sheet thickness gauge 44, which is installed at
a position away from the #4 stand rolling mill 14.
Therefore, dead time from occurrence of the variation
in sheet thickness until the detection of the variation
occurs. Accordingly, the feedback control is
configured to be an integral control.
Fig. 5 is a drawing illustrating an outline of
the tension control unit 73. This configuration
performs a proportional-integral control using a
deviation ΔT34 between tension performance T34FB, which
is measured by the 34 stands tension gauge 53
installed between the #3 stand rolling mill 13 and the
#4 stand rolling mill 14, and a tension command T34REF.
In the integral control, the phase of the control
output shifts by 90 degrees with respect to a control
state quantity. Accordingly, in the resultant exitside
sheet thickness of the #4 stand rolling mill 14,
the phase of the sheet thickness deviation shifts with
respect to an original position at which unevenness in
hardness occurs.
Fig. 6 to Fig. 8 are drawings illustrating
simulation results of the rolling phenomenon by the
four-stand tandem rolling mills as illustrated in Fig.
1. Fig. 6 illustrates the simulation results showing
how the entry-side sheet thickness at the #4 stand, the
16
exit-side sheet thickness at the #4 stand, the tension
between the #3 stand and the #4 stand, and the exitside
tension at the #4 stand vary due to the
deformation resistance variation, which is the
unevenness in hardness, as the time elapses in the case
where neither the sheet thickness control nor the
tension control is performed.
In the "variation in sheet thickness" of Fig. 6
to Fig. 8, a variation of the entry-side sheet
thickness is indicated by solid line while a variation
of the exit-side sheet thickness is indicated by dashed
line. In the "variation in tension" of Fig. 6 to Fig.
8, a variation of the entry-side tension is indicated
by solid line while a variation of the exit-side
tension is indicated by dashed line. In the "variation
in rolling load" of Fig. 6 to Fig. 8, a variation of
the rolling load is indicated by solid line while the
deformation resistance variation is indicated by dashed
line.
In this case, the unevenness in hardness directly
appears as the variation in sheet thickness.
Accordingly, it is found that peak positions of
waveforms of the deformation resistance variation, the
#4 stand entry-side sheet thickness deviation, and the
#4 stand exit-side sheet thickness deviation match;
17
therefore, there is no discrepancy in a phase
relationship.
Fig. 7 is the case where the tension control unit
73 between the #3 stand and the #4 stand, which is
disposed on the entry-side of the #4 stand, and the
tension control unit 74, which is disposed on the exitside
of the #4 stand, perform the proportional-integral
control. Additionally, only the sheet thickness
control unit 64 on the #4 stand exit-side performs the
feedback control. In this case, a phase lead where the
phase of the #4 stand exit-side sheet thickness
deviation becomes earlier than the #4 stand entry-side
sheet thickness deviation occurs.
This is because of the following reason. Since
the sheet thickness control unit 64 at the #4 stand
performs the integral control, the control output
becomes a phase lag by 90 degrees. From the
relationships shown in Expressions (1) to (3) and Fig.
19, Δ is a negative; therefore, the #4 stand exit-side
sheet thickness deviation δ, which is the control
result, becomes a positive side.
As described above, by performing the control on
the variation factor such as the unevenness in hardness
that the controlled object originally has, another
variation factor of different phases occurs, resulting
18
in a variation in the phase relationship between the
quantities of state of the controlled objects. When
the sheet thickness control unit 63 at the #3 stand,
which is the stand at the previous stage of the #4
stand, also performs the feedback control, as
illustrated in Fig. 8, the #4 stand entry-side sheet
thickness deviation produces a leading phase with
respect to the deformation resistance.
Usually, the tandem rolling mills perform the
sheet thickness control in the respective rolling mill
stands starting from the #1 stand. Therefore, it is
found that phases of the deformation resistance
variation and the resultant variation in sheet
thickness are shifted. Accordingly, in the case where
the feedforward control is performed using the entryside
sheet thickness deviation of the rolling mill
stand, due to an influence of the phase shift between
the deformation resistance variation and the variation
in the entry-side sheet thickness deviation, the
control effect cannot be obtained.
Conventionally, as a method for adjusting the
feedforward control, considering dead time and a
response from the control output to an end of a control
operation, a control output timing shift amount ΔTFF
for feedforward control in Fig. 4 was set, and a
19
control gain was changed with the exit-side sheet
thickness deviation, which is the control result.
However, the use of this method generates a phase
difference between the entry-side sheet thickness
deviation, which is the state quantity of the
controlled object, and the deformation resistance
variation, which is the unevenness in hardness;
therefore, a control effect fails to be obtained.
As shown in Expressions (1) to (3) and Fig. 19,
the feedforward control is required to appropriately
set the control gain G and the control output timing
shift amount ΔTFF. This setting needs to be determined
considering a rolling speed and an execution situation
of another control, being a complicated adjustment. In
the case of the rolling speed, since a frequency of a
variation in sheet thickness deviation changes, the
response from the control output to the operation of
the end of control operation changes. With the tandem
rolling mills, the setting differs depending on which
rolling mill stand performs and what sort of sheet
thickness control and tension control are performed.
In the feedforward control, it is important to
appropriately set the control output timing shift
amount ΔTFF and the control gain G. Both are linked
with the relationship described in Expressions (1) to
20
(3). For example, changing the control gain G also
varies an amount of phase discrepancy between state
quantities δ. Inversely, changing the control output
timing shift amount ΔTFF also varies the amplitude X of
the control state quantity. Accordingly, it is
difficult to adjust both so as to be appropriately set.
In Expression (3), the amount of phase
discrepancy between state quantities δ is an arctangent
function; therefore, −90 degrees to +90 degrees is set
as a domain with respect to −∞ to +∞. However, from
Expression (1), if the amount apparently exceeds
+infinity and turns out to be −, this value is larger
than 90 degrees. Accordingly, for convenience, as
shown in Fig. 19, the amount is assumed to exceed 90
degrees. From Expression (3), when the control gain G
is not larger than 1, the amount of phase discrepancy
between state quantities δ does not exceed 90 degrees.
Accordingly, when the amount of phase discrepancy
between state quantities δ exceeds 90 degrees, it can
be predicted that the control gain G is excessively
large.
Since an amount of control timing shift Δ and the
amount of phase discrepancy between state quantities δ
are in opposite directions, as long as the amount of
phase discrepancy between state quantities δ is found,
21
it is possible to predict how the amount of control
timing shift Δ changes. For example, when the amount
of phase discrepancy between state quantities δ is in
the + direction, it is only necessary to change the
amount of control timing shift Δ to an increasing
direction, namely, a direction from the negative side
to the positive side. Meanwhile, a direction heading
from the positive side to the negative side is a
decreasing direction.
In the case of a feedforward control in the sheet
thickness control by the rolling mill, it can be
considered that the phase relationship between the
entry-side sheet thickness deviation detected by the
entry-side sheet thickness gauge and the exit-side
sheet thickness deviation detected by the exit-side
sheet thickness gauge as the amount of phase
discrepancy between state quantities δ and the control
output timing shift amount ΔTFF from the entry-side
sheet thickness deviation to the control output as the
amount of control timing shift Δ. Accordingly, it is
only necessary to adjust the control output timing
shift amount ΔTFF and the control gain GFF in the
feedforward control using these quantities of state.
As illustrated in Fig. 9, a feedforward control
adjusting device 101 according to the embodiment
22
performs a sheet transfer process to the entry-side
sheet thickness deviation ΔH detected by the sheet
thickness gauge 43 on the entry-side of the #4 stand.
Thus, the feedforward control adjusting device 101
takes out the entry-side sheet thickness deviation ΔH
at a timing of passing immediately below the sheet
thickness gauge 44 on the exit-side of the #4 stand and
defines the value as an entry-side sheet thickness
deviation ΔHTRK. The feedforward control adjusting
device 101 inputs the exit-side sheet thickness
deviation Δh detected by the sheet thickness gauge 44
on the exit-side of the #4 stand.
The transfer process is performed on the rolling
load P obtained by a rolling load gauge 46, which
measures a rolling load of the #4 stand rolling mill 14,
from immediately below the #4 stand rolling mill 14 to
immediately below the sheet thickness gauge 44 on the
exit-side of the #4 stand and is defined as a rolling
load PTRK. These exit-side sheet thickness deviation Δh,
entry-side sheet thickness deviation ΔHTRK, and rolling
load PTRK at the #4 stand are input to a control
gain/timing shift amount setting device 102 at the #4
stand. The variation of this rolling load P is a
variation of a controlled variable occurred according
to unevenness in hardness of the rolled material, and
23
the phase is a controlled variable phase.
The control gain/timing shift amount setting
device 102 adjusts the feedforward control gain GFF and
the control output timing shift amount ΔTFF according
to a phase relationship of ΔHTRK, Δh, and P and a
magnitude of Δh. That is, the control gain/timing
shift amount setting device 102 functions as a
feedforward adjusting unit.
Fig. 10 is a drawing illustrating a function
composition of the control gain/timing shift amount
setting device 102. As the quantity of state of the
controlled-object rolling mill as the controlled object,
the above-described entry-side sheet thickness
deviation ΔHTRK of the rolled material, the exit-side
sheet thickness deviation Δh by the exit-side sheet
thickness gauge, and the rolling load PTRK are input.
Adjusting the amount of phase shift of the control
output based on the phase relationship between ΔHTRK and
Δh is one feature according to the embodiment.
A purpose of the feedforward control is to avoid
the entry-side sheet thickness deviation to be the
exit-side sheet thickness deviation. Therefore, if the
feedforward control preferably works and the exit-side
sheet thickness deviation decreases, the abovedescribed
determination on the phase relationship
24
between the entry-side sheet thickness deviation and
the exit-side sheet thickness deviation is difficult.
In view of this, it is also one feature according to
the embodiment that adjusts the phases also using the
control output and the phase relationship between the
rolling load, which is affected by the unevenness in
hardness causing the variation in sheet thickness, and
the entry-side sheet thickness deviation.
A PP value operating device 103 obtains a maximum
value and a minimum value in a range in one cycle of
the entry-side sheet thickness deviation ΔHTRK with the
exit-side sheet thickness deviation Δh and the entryside
sheet thickness deviation ΔHTRK and subtracts the
minimum value from the maximum value to obtain an exitside
sheet thickness deviation PP value ΔhPP. Here, the
range in one cycle is decided similar to the
determination by phase difference arithmetic devices
104a and 104b. ΔhPP is a value indicative of an extent
of variation of the exit-side sheet thickness, namely,
a variation width of the exit-side sheet thickness.
The phase difference arithmetic devices 104a and
104b obtain the phase discrepancy of the comparison
signal with respect to a reference signal by the method
illustrated in Fig. 11. First, a signal of a variation
of the reference signal in one cycle is taken out
25
(S1101). That is, at S1101, the phase difference
arithmetic devices 104a and 104b function as a priorto-
control phase obtainer. In the one cycle, an
oscillation frequency may be obtained using a Fast
Fourier Transform (FFT) with the reference signal to
obtain a period for one cycle, for example, the one
cycle may be obtained from time intervals of the
maximum value of the reference signal. The period is
not strictly necessary to be one cycle and may be equal
to or more than one cycle.
Similarly, the phase difference arithmetic
devices 104a and 104b take out signals of the
comparison signals from a point at which the extraction
of the reference signal has been started until a point
at which the extraction has been terminated (S1101).
That is, at S1101, the phase difference arithmetic
devices 104a and 104b also function as a post-control
phase obtainer and a controlled variable phase obtainer.
Specifically, as illustrated in Fig. 12A, tables
storing data at each sampling cycle (a fixed cycle) of
a calculator are prepared for the reference signal and
the comparison signal such that data during the current
sampling is recorded last. When the period for one
cycle is found, as illustrated in Fig. 12B, tables are
taken out by the number traced back from the current
26
sampling point by the period and is copied to the table
by one cycle.
Next, the maximum value and the minimum value by
one cycle in the table are obtained and are defined as
an upper limit value and a lower limit value,
respectively. The data in the table by one cycle is
normalized such that the upper limit value and the
lower limit value become +1 and −1, respectively
(S1102). Then, using the reference signal as a
reference, the phase of the comparison signal is
shifted (S1103). The process of shifting the phase of
the comparison signal is performed by disposing a
comparison signal change table as illustrated in Fig.
12C, shifting a table position from a comparison signal
one-cycle table, and copying the table. Fig. 12C
illustrates the case where the table position is
shifted by two samplings.
The phase difference arithmetic devices 104a and
104b obtain a sum of squared differences between the
respective table data of the comparison signal change
table and the reference signal one-cycle table on all
the one-cycle tables (S1104). This value (hereinafter
referred to as a "one-cycle square error") becomes an
index value for determination on how extent the
reference signal is similar to the comparison signal
27
whose phase has been shifted.
The phase difference arithmetic devices 104a and
104b repeat processes from S1103 while changing an
amount of shifting the phase (hereinafter referred to
as an "amount of phase shift") (S1105/NO). When the
process is completed by a given predetermined number of
amounts of phase shift (S1105/YES), a shift amount at
which the one-cycle square error becomes the minimum is
selected (S1106), and the process is terminated. A
selection result at S1106 is a calculation result of
the phase discrepancy.
Here, in the amount of phase shift, a direction
that the phase of the comparison signal advances with
respect to the reference signal is defined as a + side
and a delaying direction as a − side. As an amount of
table shift, the case where the phase is shifted as
illustrated in Fig. 12C becomes the − side. The phase
difference arithmetic device 104a obtains the entryside
sheet thickness deviation ΔHTRK as the reference
signal and the exit-side sheet thickness deviation Δh
as the comparison signal to obtain a phase difference
between entry-side sheet thicknessexit-side sheet
thickness ΔTED. The phase difference arithmetic device
104b obtains the entry-side sheet thickness deviation
ΔHTRK as the reference signal and the rolling load PTRK
28
as the comparison signal to obtain a phase difference
between entry-side sheet thicknessrolling load ΔTEP.
A purpose of the feedforward control is to
decrease the exit-side sheet thickness deviation using
the entry-side sheet thickness deviation. That is, the
state quantity of the controlled object is the exitside
sheet thickness deviation. Since an influence
from the deformation resistance variation, which is the
unevenness in hardness, has already appeared at the #4
stand entry-side as the entry-side sheet thickness
deviation, the sheet thickness control unit 64 at the
#4 stand performs the feedforward control using the
entry-side sheet thickness deviation. The feedforward
control adjusting device 101 adjusts the feedforward
control from the phase relationship between the entryside
sheet thickness deviation and the exit-side sheet
thickness deviation.
In contrast to this, when an effect from the
feedforward control preferably appears, the exit-side
sheet thickness deviation Δh decreases and ideally
becomes 0. In this case, it is difficult to obtain the
phase relationship between the entry-side sheet
thickness deviation and the exit-side sheet thickness
deviation. In contrast to this, since the rolling load
largely varies as a result of removing the exit-side
29
sheet thickness deviation due to the unevenness in
hardness, this can substitute for the exit-side sheet
thickness deviation. That is, the feedforward control
adjusting device 101 has a function to adjust the
control output timing shift amount ΔTFF for feedforward
control from the phase relationship between the entryside
sheet thickness deviation and the rolling load.
The control gain/timing shift amount setting
device 102 needs to perform the above-described
determination; therefore, fuzzy reasoning is conducted.
A membership function 105 uses the exit-side sheet
thickness deviation PP value ΔhPP as an input and the
membership function as shown in Fig. 10 to obtain SHS
and SHB. SHS is a value indicative of the case where
the exit-side sheet thickness deviation is small.
Meanwhile, SHB is a value indicative of the case where
the exit-side sheet thickness deviation is large.
A membership function 106 uses the phase
difference between entry-side sheet thicknessexit-side
sheet thickness ΔTED as the input and the membership
function as shown in Fig. 10 to obtain TEDB, TEDM, TEDZ,
TEDP, and TEDT. TEDB is a value that indicates how
large the phase difference between entry-side sheet
thicknessexit-side sheet thickness at the − side.
TEDM is a value that indicates a degree of the phase
30
difference between entry-side sheet thicknessexit-side
sheet thickness being at the − side. TEDZ is a value
that indicates a degree of the phase difference between
entry-side sheet thicknessexit-side sheet thickness
being none. TEDP is a value that indicates a degree of
the phase difference between entry-side sheet
thicknessexit-side sheet thickness at the + side.
TEDT is a value that indicates how large the phase
difference between entry-side sheet thicknessexit-side
sheet thickness is at the + side.
A membership function 107 uses the phase
difference between entry-side sheet thicknessrolling
load ΔTEP as an input and the membership function as
shown in Fig. 10 to obtain TEPM, TEPZ, and TEPP. TEPM
is value that indicates a degree of the phase
difference between entry-side sheet thicknessrolling
load on the − side. TEPZ is a value that indicates a
degree of the phase difference between entry-side sheet
thicknessrolling load being none. TEPP is a value
that indicates a degree of the phase difference between
entry-side sheet thicknessrolling load at the + side.
Predetermined values are used for values of the
horizontal axis for each membership function. SB in
the membership function 105 is a threshold used for
judgement on availability of the adjustment of the
31
feedforward control using the exit-side sheet thickness
deviation. For example, with the variation in sheet
thickness on the exit-side being 1 μm or less, when the
exit-side sheet thickness deviation is not used to
adjust the feedforward control, SB = 1 μm. Thus, when
the variation width of the exit-side sheet thickness
deviation is within a predetermined range, the control
gain/timing shift amount setting device 102 according
to the embodiment refers to a phase of the variation in
the rolling load, not the exit-side sheet thickness
deviation.
DB and DT in the membership function 106 are
thresholds used for judgement on whether the control
gain is excessively high or not. For example, when the
phase difference between entry-side sheet
thicknessexit-side sheet thickness exceeds 90 degrees,
the control gain is determined as high. In this case,
the control gain needs to be decreased. Accordingly,
DB = −90 degrees and DT = 90 degrees.
DM and DP in the membership function 106 and PM
and PP in the membership function 107 are thresholds
used for judgement on whether an adjustment of an
amount of output timing shift is unnecessary or not.
For example, with the phase difference between entryside
sheet thicknessexit-side sheet thickness of
32
within ±20 degrees, the adjustment of the amount of
output timing shift is unnecessary. Therefore, DM =
−20 degrees and DP = 20 degrees. Similarly, PM = −20
degrees and PP = 20 degrees. These values are one
example and are changed appropriately according to a
rolling condition and a property of facility.
DP and PZ set the phase difference between entryside
sheet thicknessexit-side sheet thickness and the
phase difference between entry-side sheet
thicknessrolling load at which the exit-side sheet
thickness deviation becomes the minimum and the effect
of the feedforward control becomes the maximum. The
settings of these phase differences may be decided and
performed from performance data or similar data during
a rolling simulation and a manual adjustment in actual
rolling. Thus, the control gain/timing shift amount
setting device 102 decides an amount of timing shift
based on a relationship between the value predetermined
with respect to the phase difference and the phase
difference.
A fuzzy reasoning device 108 obtains a degree of
changing the control output timing shift amount ΔTFF
for feedforward control to the increasing side TFFP, a
degree of the change to the decreasing side TFFM, a
degree of changing the feedforward control gain GFF to
33
the increasing side GFFP, and a degree of the change to
the decreasing side GFFM from the above-described
respective degrees, which are obtained using the
membership functions, using the fuzzy reasoning and the
following reasoning rules.
Although methods for processing the reasoning
rule are variously available, the fuzzy reasoning
device 108 according to the embodiment performs a
process meeting the following Expressions (4) and (5).
When "IF (A and B) then C" is met, C = min (A, B) (4)
When "IF (A or B) then C" is met, C = max (A, B) (5)
As the used reasoning rule, in the case where the
exit-side sheet thickness deviation is large and the
phase difference between entry-side sheet
thicknessexit-side sheet thickness is zero, the
feedforward control gain is considered as small;
therefore, a process such as the following Expression
(6) is performed.
IF (SHB and TEDZ) then GFFP (6)
In the case where the exit-side sheet thickness
deviation is large and the phase difference between
entry-side sheet thicknessexit-side sheet thickness is
present, it can be determined that the control output
timing shift amount ΔTFF is shifted. Therefore, it can
be expected that eliminating the shift decreases the
34
exit-side sheet thickness deviation. Accordingly,
processes such as the following Expressions (7) and (8)
are performed.
IF (SHB and TEDP) then TFFP (7)
IF (SHB and TEDM) then TFFM (8)
In the case where the exit-side sheet thickness
deviation is large and the phase difference between
entry-side sheet thicknessexit-side sheet thickness
largely exceeds 90 degrees, it can be determined that
the feedforward control gain is excessively large. In
this case, it is considered that decreasing the gain
first and then adjusting the control output timing
shift amount ΔTFF after the appropriate control gain is
obtained is preferable; therefore, processes such as
the following Expressions (9) and (10) are performed.
IF (SHB and TEDT) then GFFM (9)
IF (SHB and TEDB) then GFFM (10)
In the case where the exit-side sheet thickness
deviation is small and the phase difference between
entry-side sheet thicknessrolling load is large, since
adjusting the control output timing shift amount ΔTFF
can be expected to further decrease the exit-side sheet
thickness deviation, processes such as the following
Expressions (11) and (12) are performed.
IF (SHS and TEPP) then TFFM (11)
35
IF (SHS and TEPM) then TFFP (12)
When the rolling phenomenon is simulated,
changing the amount of control output timing shift ΔTFF
to the increasing side when the phase difference
between entry-side sheet thicknessrolling load is at
the − side and changing the amount of control output
timing shift ΔTFF to the decreasing side when the phase
difference between entry-side sheet thicknessrolling
load is at the + side decreases the phase difference
between entry-side sheet thicknessrolling load.
Accordingly, the above-described control rules are
employed. The relationship in Fig. 19 illustrates how
the state quantity of the controlled object changes
before and after the control, like the entry-side sheet
thickness deviation and the exit-side sheet thickness
deviation. The rolling load is generated by the
rolling phenomenon caused by the variation in sheet
thickness on the entry-side, the variation in sheet
thickness on the exit-side, and the tensions on the
entry-side and the exit-side. Accordingly, the
relationship between the phase difference between
entry-side sheet thicknessrolling load and the amount
of control timing shift differ from the relationship in
Fig. 19. However, as long as a trend of change in
phase difference when the amount of control timing
36
shift is changed is found, like this embodiment, the
trend is usable for adjustment of control timing.
By using the above-described reasoning rules,
TFFP, which indicates the degree of changing the
control output timing shift amount ΔTFF for feedforward
control to the increasing side, TFFM, which indicates
the degree of the change to the decreasing side, GFFP,
which indicates the degree of changing the feedforward
control gain GFF to the increasing side, and GFFM,
which indicates the degree of the change to the
decreasing side, are obtained.
The above-described reasoning rules are one
example. As long as there is a possibility of ensuring
decreasing the exit-side sheet thickness deviation by
changing the state quantity in the feedforward control,
the feedforward control gain GFF, and the control
output timing shift amount ΔTFF for feedforward control,
the rule can be set and used as the control rule.
Deciding the control rule by the result of manual
adjustment in the actual rolling, not only through
simulations of the rolling phenomenon, can employ an
adjustment method further matching the actual rolling
phenomenon.
A parameter change device 109 changes the
feedforward control gain GFF and the control output
37
timing shift amount ΔTFF for feedforward control by the
following Expressions (13) and (14) with the degrees of
change: TFFP, TFFM, GFFP, and GFFM obtained above.
Here, CTFFP, CTFFM, CGFFP, and CGFFM are parameters
for adjustment. CTFFP is a value indicative of an
amount of change of the control output timing shift
amount on the increasing side in one time. CTFFM is a
value indicative of an amount of change of the control
output timing shift amount on the decreasing side in
one time. CGFFP is a value indicative of an amount of
change of the control gain on the increasing side in
one time. CGFFM is a value indicative of an amount of
change of the control gain on the decreasing side.
With the above-described method, the feedforward
control adjusting device 101 can always optimizely
adjust the feedforward control gain GFF and the control
output timing shift amount ΔTFF for feedforward control
in the feedforward control by the sheet thickness
control unit 64 at the #4 stand, substantially
improving the control effect brought by the feedforward
control.
Fig. 13 to Fig. 17 illustrate results of
verifying the effects of the feedforward control
38
adjusting device 101 by a rolling simulator. Fig. 13
is the case where the feedforward control is added to
the sheet thickness control unit 64 at the #4 stand to
the state illustrated in Fig. 8. Fig. 13 illustrates a
phase of the entry-side sheet thickness by solid
vertical line, a phase of the exit-side sheet thickness
by dashed vertical line, and a phase of the rolling
load by one dot chain vertical line.
That is, it is found that the phase difference
between entry-side sheet thicknessexit-side sheet
thickness ΔTED is indicated by intervals between the
solid vertical line and the dashed vertical line and is
the leading phase. The phase difference between entryside
sheet thicknessrolling load ΔTEP is indicated by
the intervals between the solid vertical line and the
one dot chain vertical line and is the lagging phase.
As illustrated in Fig. 13, the exit-side sheet
thickness deviation is large. Therefore, here, first,
the control output timing shift amount ΔTFF for
feedforward control is changed to the leading phase
side, namely, the increasing direction. The results
are as illustrated in Fig. 14.
As illustrated in Fig. 14, both the phase
difference between entry-side sheet thicknessexit-side
sheet thickness ΔTED, which is indicated between the
39
solid line and the dashed line, and the phase
difference between entry-side sheet thicknessrolling
load ΔTEP, which is indicated between the solid line
and the one dot chain line, decrease, and the amplitude
of the exit-side sheet thickness slightly decreases.
With this state, it is determined that although the
control output timing shift amount ΔTFF for feedforward
control is matched, the feedforward control gain GFF is
insufficient, and the feedforward control gain GFF is
increased. The results are as illustrated in Fig. 15.
As illustrated in Fig. 15, the exit-side sheet
thickness deviation becomes considerably small. With
this state as well, when the phase difference between
entry-side sheet thicknessexit-side sheet thickness
ΔTED is determined as the lagging phase, the control
output timing shift amount ΔTFF for feedforward control
is changed to a phase lag direction. Consequently, the
exit-side sheet thickness deviation can be mostly
removed as shown in the results in Fig. 16.
At this time, as illustrated in Fig. 16, the
phase difference between entry-side sheet
thicknessrolling load ΔTEP becomes a lagging phase.
Setting this value as PZ in the membership function 107
ensures adjusting the control output timing shift
amount ΔTFF for feedforward control similarly with the
40
phase difference between entry-side sheet
thicknessrolling load ΔTEP.
Fig. 17 is a drawing illustrating the case where
the control output timing shift amount ΔTFF for
feedforward control is shifted to the side opposite
from Fig. 13. The phase difference between entry-side
sheet thicknessrolling load ΔTEP appears as the
leading phase. It is found from this simulation that,
with the phase difference between entry-side sheet
thicknessrolling load on the + side, by adjusting the
control output timing shift amount ΔTFF to the
decreasing side, further decreasing the exit-side sheet
thickness deviation can be expected.
As described above, correcting the amount of
timing shift ΔTFF and the control gain GFF in the
feedforward control while retrieving rolling
performance data during the rolling operation ensures
improving the effects brought by the feedforward
control. Besides, according to the rolling status such
as the rolling speed, a steel grade, and the sheet
thickness, the control output timing shift amount ΔTFF
for feedforward control and the feedforward control
gain GFF are associated to one another and stored, thus,
a database is created. When similar rolling conditions
are established, the control output timing shift amount
41
ΔTFF for feedforward control and the feedforward
control gain GFF stored in the database are taken out
for use and corrected by the rolling performance. Thus,
the control effects brought by the feedforward control
can be maximized. This database functions as a
condition information storage unit.
This embodiment describes the case where the
feedforward control adjusting device 101 is applied to
the sheet thickness control unit 64 at the #4 stand in
the four-stand rolling mills. However, this should not
be constructed in a limiting sense. Similarly, the
feedforward control adjusting device 101 is also
applicable to the sheet thickness control by any given
stands that perform the feedforward control such as the
sheet thickness control unit 62 at the #2 stand and the
sheet thickness control unit 63 at the #3 stand.
This method is also applicable to tandem rolling
mills with any given number of stands other than the
four-stand tandem rolling mills. This system is also
applicable to a feedforward control by a single-stand
rolling mill with an entry-side sheet thickness
deviation detected by an entry-side sheet thickness
gauge.
This description employs the adjustment method
for feedforward control using the entry-side sheet
42
thickness deviation, which is detected by the detection
result by the entry-side sheet thickness gauge.
However, the adjustment method is also similarly
applicable to a proportional control in a mass flow
sheet thickness control using an entry-side sheet
thickness deviation and sheet speeds on an entry-side
and an exit-side.
This embodiment describes the four-stand tandem
rolling mills as the controlled object. However, in
addition to the rolling mill, this embodiment is
applicable to any given plant where the proportional
control or the feedforward control is performed on a
controlled object.
The rolling control device that mainly uses the
above-described sheet thickness control unit 64 at the
#4 stand and feedforward control adjusting device 101
can be achieved by a combination of software and
hardware. Here, the following describes hardware to
achieve the respective functions of the rolling control
device according to the embodiment with reference to
Fig. 18. Fig. 18 is a block diagram illustrating a
hardware configuration of an information processing
device constituting the rolling control device
according to the embodiment. As illustrated in Fig. 18,
the rolling control device according to the embodiment
43
has a configuration similar to an information
processing terminal such as a general server and a
Personal Computer (PC).
That is, the rolling control device according to
the embodiment includes a Central Processing Unit (CPU)
201, a Random Access Memory (RAM) 202, a Read Only
Memory (ROM) 203, a Hard Disk Drive (HDD) 204, and an
I/F 205, which are coupled via a bus 208. To the I/F
205, a Liquid Crystal Display (LCD) 206 and an
operating unit 207 are coupled together.
The CPU 201 is arithmetic means to control the
entire operations of the rolling control device. The
RAM 202 is a volatile storage medium where high-speed
information reading and writing are possible. The CPU
201 uses the RAM 202 as a working area when the CPU 201
processes information. The ROM 203 is read-only nonvolatile
storage medium and stores programs such as
firmware.
The HDD 204 is a non-volatile storage medium
where high-speed information reading and writing are
possible. The HDD 204 stores an Operating System (OS),
various control programs, application programs, and
similar programs. The I/F 205 couples the bus 208,
various pieces of hardware, network, and similar
members together for control. The I/F 205 is also used
44
as an interface to exchange information between the
respective devices or to input information to the
rolling mill.
The LCD 206 is a visual user interface that
displays various pieces of information such that an
operator checks the state of the rolling control device.
The operating unit 207 is a user interface such as a
keyboard and a computer mouse for the operator to input
information to the rolling control device. With such
hardware configuration, the program stored on a
recording medium such as the ROM 203, the HDD 204, or
an optical disk (not illustrated) is read to the RAM
202, and the CPU 201 performs an operation in
accordance with the program. Thus, a software control
unit is configured. The combination of the software
controls unit thus configured and the hardware achieve
the functions of the rolling control device according
to the embodiment.
The embodiment describes an example where the
rolling control device includes all the respective
functions. Thus, the one information processing device
may achieve all the functions or the respective
functions may be decentrally achieved by a plurality of
information processing devices.
The present invention is not limited to the
45
above-described embodiments, and includes various
modifications. For example, the above-described
embodiments are described in detail for simply
describing the present invention, and the present
invention is not necessarily limited to one that
includes all the described configurations. A part of
the configurations of one embodiment can be replaced by
the configuration of another embodiment. A part of the
configurations of one embodiment can be used with the
addition of the configuration of another embodiment.
Regarding a part of the configurations in the
respective embodiments, another configuration can be
added, deleted, or replaced.

We claim:
1. A plant control device for performing a
feedforward control at a processing treatment of a
controlled object, the feedforward control being
performed based on a variation of a prior-to-control
state quantity occurred in the controlled object caused
by a variation factor included in the controlled object,
the plant control device comprising:
a phase difference obtainer configured to obtain
a phase difference between a variation in the prior-tocontrol
state quantity and a variation in a postcontrol
state quantity, the post-control state quantity
being a quantity of state of the controlled object
after the processing treatment is performed; and
a feedforward adjusting unit configured to decide
an amount of phase shift until a measurement result of
the prior-to-control state quantity is reflected to the
feedforward control based on the phase difference.
2. The plant control device as claimed in claim 1,
wherein
the feedforward adjusting unit is configured to
decide the amount of phase shift based on a
relationship between a value predetermined with respect
47
to the phase difference and the phase difference.
3. The plant control device as claimed in claim 1,
wherein
the feedforward adjusting unit is configured to
decide a control gain in the feedforward control based
on the phase difference.
4. The plant control device as claimed in claim 1,
wherein
the feedforward adjusting unit is configured to
decide the amount of phase shift based on a variation
width of the post-control state quantity and the phase
difference.
5. The plant control device as claimed in claim 4,
further comprising
a controlled variable phase obtainer configured
to obtain a controlled variable phase, the controlled
variable phase being a phase of a variation in a
controlled variable occurred according to the variation
factor at the processing treatment, wherein
when the variation width of the post-control
state quantity is within a predetermined range, the
feedforward adjusting unit is configured to decide the
48
amount of phase shift based on a phase difference
between a phase of the variation in the prior-tocontrol
state quantity and the controlled variable
phase.
6. The plant control device as claimed in claim 5,
further comprising
a condition information storage unit configured
to associate the amount of phase shift in a state where
the variation width of the post-control state quantity
is within the predetermined range with a condition
affecting a control of the processing treatment and
store the amount of phase shift in a storage medium,
wherein
the feedforward adjusting unit is configured to
decide an amount of phase shift until a measurement
result of the prior-to-control state quantity is
reflected to the feedforward control based on the
amount of phase shift, the amount of phase shift being
stored on the storage medium corresponding to the
condition affecting the control of the processing
treatment.
7. A rolling control device for performing a
feedforward control at a rolling process of a rolled
49
material based on a variation in a sheet thickness
before rolling, the variation in the sheet thickness
occurring in the rolled material based on a high degree
of variation according to a position included in the
rolled material, the rolling control device comprising:
a phase difference obtainer configured to obtain
a phase difference between the variation in the sheet
thickness before the rolling and a variation in a sheet
thickness after the rolling, the sheet thickness after
the rolling being a sheet thickness of the rolled
material after the rolling process is performed; and
a feedforward adjusting unit configured to decide
an amount of phase shift until a measurement result of
the variation in the sheet thickness before the rolling
is reflected to the feedforward control based on the
phase difference.
8. A plant control method for performing a
feedforward control at a processing treatment of a
controlled object, the feedforward control being
performed based on a variation of a prior-to-control
state quantity occurred in the controlled object caused
by a variation factor included in the controlled object,
the plant control method comprising:
obtaining a phase difference between a variation
50
in the prior-to-control state quantity and a variation
in a post-control state quantity, the post-control
state quantity being a quantity of state of the
controlled object after the processing treatment is
performed; and
deciding an amount of phase shift until a
measurement result of the prior-to-control state
quantity is reflected to the feedforward control based
on the phase difference.
9. A plant control program for performing a
feedforward control at a processing treatment of a
controlled object, the feedforward control being
performed based on a variation of a prior-to-control
state quantity occurred in the controlled object caused
by a variation factor included in the controlled object,
the plant control program causing an information
processing device to execute:
a step of obtaining a phase difference between a
variation in the prior-to-control state quantity and a
variation in a post-control state quantity, the postcontrol
state quantity being a quantity of state of the
controlled object after the processing treatment is
performed; and
a step of deciding an amount of phase shift until
51
a measurement result of the prior-to-control state
quantity is reflected to the feedforward control based
on the phase difference.