DESCRIPTION
Title of Invention: COATING WEIGHT CONTROL APPARATUS AND
COATING WEIGHT CONTROL METHOD
Technical Field
[0001]
The present invention relates to a technique of a coating
weight control apparatus and a coating weight control method
which control nozzles in a steel coating plant.
Background Art
[0002]
In a continuous coating line for coating steel, a weight
of a coating attached to a strip is determined by a strip speed
(strip speed), which is the speed of the strip referred to as
a line speed, a nozzle gap (nozzle-strip distance) which is
a distance between a nozzle and the strip, a nozzle pressure
(gas pressure) which is a pressure of gas discharged from the
nozzle, and the like. In many plants automatically
controlling coating weights, with respect to the strip speed
and the nozzle gap determined by an operator's manual operation,
a nozzle pressure realizing a target coating weight that is
transferred from a host computer is controlled by calculating
the nozzle pressure using a coating weight prediction model.
As a method in the related art for increasing the accuracy of
3
the control of the coating weight, for example, a technique
described in PTL 1 is disclosed.
[0003]
PTL 1 discloses a preset control method of a control
system and a control apparatus using a control model in which
"a first preset unit that calculates a control reference
corresponding to a set value using a control model and sets
the control reference as a preset value and a second preset
unit that calculates a value of a control reference that needs
to be changed in accordance with the amount of change of a
control specification, and adds or subtracts the value to or
from a current control reference, thereby obtaining a preset
value are provided, a preset unit, which is capable of
performing an appropriate control using manufacturing
information or control information obtained from a plant by
focusing on a control error and a model error is selected, and
the control reference is changed." (refer to the abstract).
Citation List
Patent Literature
[0004]
PTL 1: JP-A-2004-013393
Summary of Invention
Technical Problem
[0005]
In low-grade strips, there are many cases in which a strip
4
shape in a vicinity of a welding point (head end and tail end
of strip) is not favorable.
Accordingly, there is a concern that a nozzle may come
into contact with the strip in the vicinity of the welding point.
In order to avoid such a situation, a so-called nozzle opening
and closing control in which, before the welding point passes
through the nozzle position, the nozzle is opened (nozzle gap
is increased), and, after the welding point passes through the
nozzle position, the nozzle is closed again to an appropriate
position is performed. Therefore, near a welding point where
the preset calculation in PTL 1 is performed, the nozzle is
positioned not in a normal operating position, but in a position
greatly distant from the strip.
[0006]
In many cases, the coating weight prediction model is
used for preset calculation. The coating weight prediction
model is constructed using data at the time of a stable
condition. Here, the time of a stable condition means a time
when a coating is performed in a condition in which the nozzle
gap or the nozzle pressure does not change. In other words,
a stable condition is a condition in which the coating weight
acquired from the steel coating plant is a coating weight based
on each of a current strip speed, a current nozzle pressure,
and a current nozzle gap (each determined individually)
imported from the steel coating plant. However, at the time
5
of controlling the nozzle opening and closing, the coating
weight has already been predicted when a nozzle gap which has
become an abnormally large value is input. In the technique
described in PTL 1, since there is no consideration with respect
to this point, a prediction accuracy of the coating weight in
the preset calculation at the time of controlling the nozzle
opening and closing is degraded. As a result, in the technique
described in PTL 1, there is a problem in that the accuracy
of calculating the nozzle pressure is degraded.
[0007]
In addition, at the time of opening the nozzle, generally,
the nozzle pressure becomes a high pressure for keeping the
coating weight, and thus it becomes a saturated pressure. In
the technique described in PTL 1, at the time of a second preset
control which calculates a relative value, a second preset unit,
which performs the second preset control, performs adding and
subtracting a control reference (nozzle pressure)
corresponding to the change of amount of a control
specification (target value of the coating weight) to or from
a current control reference (nozzle pressure control
reference). That is, based on the current control reference
(nozzle pressure control reference), the control reference
(nozzle pressure) at a next timing is calculated. In a case
in which the nozzle pressure reaches a saturated condition,
based on the saturated pressure, the nozzle pressure in the
6
next time is calculated. As a result, in the next time, there
is a problem in that a greatly reduced nozzle pressure is
calculated. That is, when the saturated pressure puts a limit,
based on the current nozzle pressure which is greatly
deteriorated further than an original nozzle pressure, the
nozzle pressure in the next time is calculated, and thus there
is a problem in that the nozzle pressure in the next time is
greatly reduced to lower than that of a nozzle pressure needed
to be calculated originally.
[0008]
The invention has been made in view of such a background,
and the invention has an object of allowing nozzle control to
be performed with high accuracy.
Solution to Problem
[0009]
In order to solve the problems described above, the
invention provides a coating weight control apparatus which
receives result information from a steel coating plant, which
attaches a coating having a desired coating weight to a strip
by immersing a continuously sent strip into a bath of a molten
coating and spraying high pressure gas from a nozzle so as to
peel an unnecessary coating off immediately after the strip
is lifted, generates control information for controlling a
coating weight which is a coating weight of a coating based
on the received result information, and transfers the generated
7
control information to the steel coating plant, the apparatus
including a preset control unit that calculates at least the
gas pressure as a set value for a control reference of the nozzle
for attaching a coating having a desired coating weight, by
calculation based on a coating weight prediction model
indicating at least a relationship between a strip speed which
is a moving speed of the strip, a gas pressure which is a pressure
of the gas being sprayed from the nozzle, a nozzle-strip
distance which is a distance between the nozzle and the strip,
and the coating weight being attached to the strip, a tracking
unit that specifies positional information in the strip based
on a movement distance of the strip obtained by importing the
strip speed from the steel coating plant and integrating the
imported strip speed, a stable condition determination unit
that determines whether or not the coating weight imported from
the steel coating plant is a stably-detected coating weight
by determining whether or not a current coating weight imported
from the steel coating plant is a coating weight in accordance
with each of a current strip speed, a current gas pressure,
and a current nozzle-strip distance imported from the steel
coating plant, based on the positional information of the strip
specified by the tracking unit, and a stable value storage
processing unit that stores a combination of a second coating
weight, a second strip speed, a second gas pressure, and a
second nozzle-strip distance, which are imported, when the
8
coating weight imported from the steel coating plant is
determined to be the stably-detected coating weight, by the
stable condition determination unit, in a stable value storage
unit, in which the preset control unit imports a first strip
speed which is the current strip speed, a first nozzle-strip
distance which is the current nozzle-strip distance, and a
first target coating weight which is a target value of the
current coating weight from the steel coating plant, calculates
a first gas pressure of a set value which is the gas pressure
for realizing the first target coating weight based on the
coating weight prediction model, imports the second strip speed,
the second nozzle-strip distance, and the second coating weight
from the stable value storage unit, calculates a third gas
pressure of a set value which is the gas pressure for realizing
the coating weight corresponding to the second strip speed and
the second nozzle-strip distance using the coating weight
prediction model, adds the first gas pressure to the second
gas pressure imported from the stable value storage unit, and
calculates a fourth gas pressure which is a set value for a
control reference of the nozzle by subtracting the third gas
pressure.
The other solving means will be described in embodiments.
Advantageous Effects of Invention
[0010]
According to the invention, control of nozzles with high
9
accuracy can be performed.
Brief Description of Drawings
[0011]
[Fig. 1] Fig. 1 is a diagram illustrating a configuration
example of a coating weight control system according to a first
embodiment.
[Fig. 2] Fig. 2 is a diagram illustrating a hardware
configuration of a control apparatus according to the first
embodiment.
[Fig. 3] Fig. 3 is a flow chart illustrating a sequence
of a process in a preset control unit according to the first
embodiment.
[Fig. 4] Fig. 4 is a flow chart illustrating a sequence
of a process in a tracking unit according to the first
embodiment.
[Fig. 5] Fig. 5 is a diagram schematically illustrating
a stable condition established timing inside one strip.
[Fig. 6] Fig. 6 is a flow chart illustrating a process
sequence of a stable coating weight determination unit
according to the first embodiment.
[Fig. 7] Fig. 7 is a diagram illustrating an example of
nozzle controlling according to the first embodiment.
[Fig. 8] Fig. 8 is a diagram illustrating a configuration
example of a coating weight control system according to a second
embodiment.
10
[Fig. 9] Fig. 9 is a diagram illustrating a hardware
configuration of a control apparatus according to the second
embodiment.
[Fig. 10] Fig. 10 is a flow chart illustrating a sequence
of a process in an absolute value calculating unit according
to the second embodiment.
[Fig. 11] Fig. 11 is a flow chart illustrating a process
sequence in a welding point vicinity determination unit
according to the second embodiment.
[Fig. 12] Fig. 12 is a flow chart illustrating a sequence
of a process in a control method selecting unit according to
the second embodiment.
[Fig. 13] Fig. 13 is a diagram illustrating an example
of nozzle controlling according to the second embodiment.
Description of Embodiments
[0012]
Next, embodiments for realizing the invention (refer to
as embodiment) will be described in detail with reference to
appropriate drawings.
[0013]
[First Embodiment]
Fig. 1 is a diagram illustrating a configuration example
of a coating weight control system according to a first
embodiment.
The coating weight control system includes a control
11
apparatus (coating weight control apparatus) 1, a steel coating
plant 2, and a host computer (external device) 3.
The control apparatus 1 controls the steel coating plant
2 which is a target to be controlled, and a coating having a
desired coating weight is attached to a strip 401.
The steel coating plant 2 is the target to be controlled
of the control apparatus 1 as described above, and attaches
a coating to the strip 401 based on a control reference of the
control apparatus 1.
The host computer 3 inputs information of a target
coating weight, and the like to the control apparatus 1.
[0014]
First, a configuration of the steel coating plant 2 will
be described. The steel coating plant 2 immerses the strips
401, which are continuously sent, into a molten coating 202
accumulated in a pot 201. Accordingly, the strip 401 is plated.
Also, the steel coating plant 2 peels an unnecessary coating
off by spraying high pressure gas from a nozzle 211 immediately
after the strip 401 is lifted from the molten coating 202.
Accordingly, the steel coating plant 2 controls a coating
weight of the coating attached to the strip 401 to be a desired
value. The strips 401 (coil) are connected with each other
in a welding manner, and have a configuration in which a
continuous coating process is performed.
[0015]
12
A welding point 411 is coincide with, in general, a change
point of a target coating weight. However, there is a case
in which a plurality of coils are produced from one strip 401.
That is, there is a case in which another coating is performed
on one strip 401. In this case, in addition to the welding
point 411, a target value change point of the coating weight
is present, and one strip 401 is controlled with another target
coating weight. The coating weight W attached to the strip
401 is detected by a coating weight gauge 212. The coating
weight gauge 212 is provided on a position apart away from a
nozzle 211. In addition, as a detection method, it is general
that the coating weight gauge 212 is traversed in a width
direction of the strip 401, and an average value of the coating
weight with respect to the width direction is output.
Therefore, although a nozzle pressure (gas pressure) which is
pressure of gas sprayed from the nozzle or a nozzle gap
(nozzle-strip distance) which is a distance between the nozzle
211 and the strip 401 is operated, the coating weight can be
detected as a result thereof after one or two minutes elapse.
Accordingly, a preset control which predicts the coating weight
and determines the nozzle pressure is a high importance target
to be controlled.
[0016]
A roll 203 and a top roll 204 support the strip 401. The
coating weight W is changed when receiving influence of various
13
factors, but is mainly determined by a strip speed (strip speed)
V of the strip 401 which is a moving speed of the strip 401,
a nozzle pressure P, and a nozzle gap D. Also, the strip speed
V of the strip 401 is calculated on the basis of a rotation
speed, or the like of the roll 203 or the top roll 204.
This relationship is expressed by, for example,
Expression (1) as follows.
[0017]
ln (W) = a0+a1∙ln (P)+a2∙ln (V)+a3∙ln (D) … (1)
[0018]
Here, a0 to a3 are constants.
As illustrated in Fig. 1, in general, there are many cases
in which the nozzles 211 are respectively provided in a front
side and a back side of the strip 401. When the nozzle pressures
P in the front side and the back side of the strip 401 are
different from each other, an average value of both of them
may be set to the nozzle pressure P. In the same manner, when
the nozzle gaps D in the front side and the back side of the
strip 401 are different from each other, or a right side and
a left side are different from each other, an average value
of them may be set to the nozzle gap D. In addition, in actual,
it is considered that the coating weight W is also changed due
to a temperature of the molten coating or the strip 401, a height
of the nozzle 211, an angle with respect to the strip 401 of
the nozzle 211, and the like. However, in a regression model
14
like Expression (1), the temperature of the molten coating or
the strip 401, the height of the nozzle 211, the angle with
respect to the strip 401 of the nozzle 211, and the like are
not served as significance, and often omitted. In the
embodiment, hereinafter, the coating weight prediction model
will be described as Expression (1).
[0019]
Also, the strip 401, in which the coating weight is
detected by the coating weight gauge 212, is cut by a cutting
machine which is not illustrated finally, and is wound as a
coil.
[0020]
Next, a configuration of the control apparatus 1 will
be described.
The control apparatus 1 receives manufacturing
information of the types of a steel, a thickness of a strip,
a width of a strip, and the like of the strip 401 from the host
computer 3 by adding the target coating weight W* corresponding
to the strip 401 which will be processed next. There is a case
in which an upper and lower limit value of the coating weight
W or standard information of the strip 401 is included in the
manufacturing information.
[0021]
The control apparatus 1 includes a preset control unit
101, a tracking unit (stable condition determination unit) 102,
15
a stable coating weight determination unit (stable value
storage processing unit) 103, a stable value storage unit
(storage unit) 104, a feed back (FB) control unit 105, and an
addition output unit 106.
The preset control unit 101 uses a current target coating
weight W*c acquired from the host computer 3, a current nozzle
pressure Pc acquired from the steel coating plant 2, a current
strip speed Vc, a current nozzle gap Dc, stable data of the
stable value storage unit 104, and the like, and calculates
a control reference (preset value Pref) of the nozzle pressure
P. The stable data will be described later. In addition, the
preset control unit 101 starts a process at the timing of
receiving one of a change of the target coating weight W* from
the host computer 3, a change of the nozzle gap D and a change
of the strip speed V from the steel coating plant 2, and
terminates the process when receiving a stable condition
trigger from the stable coating weight determination unit 103.
[0022]
The tracking unit 102 traces a movement distance of the
strip 401 by integrating the strip speed V acquired from the
steel coating plant 2. In addition, the tracking unit 102
issues the stable condition trigger in a case of the stable
condition.
Here, the stable condition refers to a condition in which
a coating is attached by being corresponded to the nozzle
16
pressure P, the nozzle gap D, and the strip speed V, and then
the nozzle pressure P, the nozzle gap D, and the strip speed
V are detected as the coating weight W by the coating weight
gauge 212 while being not changed as they are. On the contrary,
when any one of the nozzle pressure P, the nozzle gap D, and
the strip speed V is changed before the coating weight of that
part is detected by the coating weight gauge 212, the stable
condition is not recognized. In other words, the stable
condition refers to a condition in which a result value of the
current coating weight W acquired from the steel coating plant
2 is the coating weight W based on (each determined
individually) the current strip speed V, the current nozzle
pressure P, and the current nozzle gap D which are imported
from the steel coating plant 2.
[0023]
The stable coating weight determination unit 103
acquires the current coating weight Wc, the nozzle pressure
Pc, the nozzle gap Dc, and the strip speed Vc from the steel
coating plant 2. In addition, when receiving the stable
condition trigger from the tracking unit 102, the stable
coating weight determination unit 103 stores the acquired
current coating weight Wc, the nozzle pressure Pc, the nozzle
gap Dc, and the strip speed Vc in the stable value storage unit
104 as the coating weight Ws, the nozzle pressure Ps, the nozzle
gap Ds, and the strip speed Vs in the stable condition.
17
Hereinafter, the coating weight Ws, the nozzle pressure Ps,
the nozzle gap Ds, and the strip speed Vs are respectively
referred to as a stable coating weight Ws, a stable nozzle
pressure Ps, a stable nozzle gap Ds, and a stable strip speed
Vs. All of the stable coating weight Ws, the stable nozzle
pressure Ps, the stable nozzle gap Ds, and the stable strip
speed Vs are the result value. The stable coating weight Ws,
the stable nozzle pressure Ps, the stable nozzle gap Ds, the
stable strip speed Vs, and the like stored by the stable coating
weight determination unit 103 are stored in the stable value
storage unit 104.
[0024]
When receiving the stable condition trigger from a stable
condition coating weight determination unit 103, based on a
deviation between the stable coating weight Ws acquired from
the steel coating plant 2 and the current target coating weight
W*c acquired from a host computer 3, a FB control unit 105
changes the nozzle pressure P in a direction in which the
deviation is decreased.
The addition output unit 106 outputs an output of the
preset control unit 101 and an output of the FB control unit
105 by adding to each other.
[0025]
Hereinafter, in the embodiment, simply, a case in which
a target to be controlled of the steel coating plant 2 is the
18
nozzle pressure P will be described as an example. In the
control apparatus 1, the preset control unit 101 performs a
preset-control at the timing when the strip speed V and the
nozzle gap D acquired from the target coating weight W* or the
steel coating plant 2 are changed and switches the current
nozzle pressure Pc to a nozzle pressure P realizing a desired
coating weight.
Also, in the embodiment, although a case in which the
target to be controlled is the nozzle pressure P has been
described; however, the target to be controlled is not limited
to the nozzle pressure P, and the nozzle gap D, and the like
may be the target to be controlled.
[0026]
(Hardware Configuration)
Fig. 2 is a diagram illustrating a hardware configuration
of the control apparatus according to the first embodiment.
The control apparatus 1 may be a personal computer (PC),
and may be a programmable logic controller (PLC).
The control apparatus 1 includes a memory 501 such as
a random access memory (RAM), and a storage device 503 such
as a central processing unit (CPU) 502, or a hard disc (HD).
Here, the storage device 503 corresponds to the stable value
storage unit 104 of Fig. 1.
In the memory 501, the preset control unit 101, the
tracking unit 102, the stable coating weight determination unit
19
103, the FB control unit 105, and the addition output unit 106
are implemented, when a program stored in the storage device
503 is load and the loaded program is executed by the CPU 502.
[0027]
(Preset Control Process)
Fig. 3 is a flow chart illustrating a sequence of a process
in the preset control unit according to the first embodiment.
Fig. 1 is appropriately referred to.
Also, this process is a process which is performed when
a nozzle opening and closing process is performed.
Specifically, the process is a process which starts at the
timing when the control apparatus 1 receives a change of the
nozzle gap D, before and after the welding point 411 passes
through the nozzle 211.
[0028]
In addition, a process illustrated in Fig. 3 is
terminated when the change of the nozzle gap D is terminated.
Also, a process by the FB control unit 105 is stopped during
performing the process by the preset control unit 101.
[0029]
First, the preset control unit 101 acquires the current
strip speed (first strip speed) Vc, the current nozzle gap
(first nozzle-strip distance) Dc, and the current nozzle
pressure Pc (S101) from the steel coating plant 2.
Incidentally, the current nozzle pressure Pc is a setting value
20
of the current nozzle pressure P. Also, in Step S101, the
preset control unit 101 may not acquire the current nozzle
pressure Pc.
Next, the preset control unit 101 acquires the current
target coating weight W*c from the host computer 3 (S102).
[0030]
Next, the preset control unit 101 acquires the stable
data from the stable value storage unit 104 (S103). The stable
data is a combination of the stable strip speed (second strip
speed) Vs, stable nozzle gap (second nozzle-strip distance)
Ds, and the stable coating weight (information of coating
weight) Ws.
[0031]
A determination method of the stable condition or a
storage of the stable data to the stable value storage unit
104 will be described later.
Also, the preset control unit 101 calculates the preset
value Pref which is a control reference of the nozzle pressure
based on the acquired stable data (S104).
[0032]
Here, a calculating method of the preset value Pref in
Step S104 will be described in detail.
In a case in which Expression (1) is assumed as the coating
weight prediction model, Expression (1) can be rewritten in
Expression (2) as follows.
21
[0033]
W = f (P, V, D) = exp (a0+a1∙ln (P)+a2∙ln (V)+a3∙ln (D))
… (2)
[0034]
When the strip speed is set to V, and the nozzle gap is
set to D by Expression (2), the nozzle pressure P realizing
a coating weight W can be expressed by Expression (3) as
follows.
[0035]
P = exp{(ln (W) -a0-a2∙ln (V)-a3∙ln (D))/a1} … (3)
[0036]
Accordingly, the preset value Pref calculated by the
preset control unit 101 is calculated by adding and subtracting
deviations between the current target coating weight W*c, the
current strip speed Vc, the current nozzle gap Dc, and the
stable coating weight Ws, the stable strip speed Vs, and the
stable nozzle gap Ds stored in the stable value storage unit
104 to and from the stable nozzle pressure (second gas pressure)
Ps stored in the stable value storage unit 104 by Expression
(4) as follows.
[0037]
Pref = Ps+f-1 (W*c, Vc, Dc)-f-1 (Ws, Vs, Ds) … (4)
[0038]
A second term (f-1 (W*c, Vc, Dc)) in a right side of
Expression (4) indicates a nozzle pressure (first gas pressure)
22
corresponding to the current target coating weight (first
coating weight) W*c, the current strip speed Vc, and the current
nozzle gap Dc. In addition, a third term (f-1 (Ws, Vs, Ds))
on the right side in Expression (4) indicates a nozzle pressure
(third gas pressure) corresponding to the stable coating weight
(result value of coating weight) Ws, the stable strip speed
Vs, the stable nozzle gap Ds stored in the stable value storage
unit 104. The preset value Pref (fourth gas pressure) is
determined by Expression (5) as follows by proceeding with the
second term and the third term of Expression (4).
[0039]
Pref = Ps+exp{(ln (W*c)-a0-a2∙ln (Vc) -a3∙ln
(Dc))/a1}-exp{(ln (Ws)-a0-a2∙ln (Vs) -a3∙ln (Ds))/a1} … (5)
[0040]
An image of control in the preset control unit 101 will
be described later. Also, information relating to the coating
weight prediction model of Expression (5), and the like is
stored in the stable value storage unit 104, and the like.
[0041]
(Tracking Process)
Fig. 4 is a flow chart illustrating a sequence of a process
in the tracking unit according to the first embodiment. Fig.
1 is appropriately referred to.
The tracking unit 102 determines whether or not the
coating weight of the strip 401 detected by the coating weight
23
gauge 212 is the stable coating weight. In order to determine
the stable coating weight, the tracking unit 102 defines a
tracking distance L which is a movement distance of the strip
401. The tracking distance L is added in accordance with a
movement of the strip 401, and is reset at the timing when the
welding point 411 passes through the nozzle 211 and at the
timing of changing any one of the nozzle pressure P, the nozzle
gap D, and the strip speed V.
Also, a process of Fig. 4 is executed during operating
the steel coating plant 2.
[0042]
First, the tracking unit 102 resets the tracking distance
L as an initializing process (S201).
Next, the tracking unit 102 determines whether or not
the welding point 411 passes through a position of the nozzle
211 (nozzle position) based on the tracking distance L (S211).
In the steel coating plant 2, including a part which is not
illustrated in Fig. 1, the movement of the strip 401 is
consistently managed from beginning to the end. Accordingly,
in Step S211, the tracking unit 102 is capable of easily
determining whether or not the welding point 411 passes through
the position of the nozzle 211 (nozzle position).
In Step S211, in a case in which it is determined that
whether or not the welding point 411 does not pass through the
nozzle position (S211N), the tracking unit 102 proceeds a
24
process to Step S213.
[0043]
In Step S211, in a case in which it is determined that
the welding point 411 passes through the nozzle position
(S211Y), the tracking unit 102 determines that new process
of the strip 401 is started, resets the tracking distance L
(S212), and proceeds the process to Step S213.
In Step S213, the tracking unit 102 acquires the current
strip speed Vc from the steel coating plant 2.
[0044]
Also, the tracking unit 102 calculates the tracking
distance L of the strip 401 by integrating the acquired strip
speed Vc (S214). That is, the tracking unit 102 calculates
the tracking distance L by Expression (6) as follows.
[0045]
L = Vc∙t … (6)
[0046]
Also, t in Expression (6) is an acquisition period of
the strip speed Vc.
Next, the tracking unit 102 compares the current strip
speed Vc with a reference speed Vo, and determines whether or
not the strip speed Vc is less than the reference speed Vo (S221).
The reference speed Vo is a determination index of whether or
not the steel coating plant 2 is operated. That is, when the
strip speed Vc is smaller than the reference speed Vo, the
25
tracking unit 102 determines that a line is stopped.
As a result of Step S221, in a case in which the strip
speed Vc is less than the reference speed Vo (S221Y), the
tracking unit 102 determines that operating of the steel
coating plant 2 is terminated, and terminates the process.
[0047]
As the result of Step S221, in a case in which the strip
speed Vc is equal to or more than the reference speed Vo
(S221N), the tracking unit 102 determines whether or not the
tracking distance L is greater than a reference distance Ls
(S222). The reference distance Ls is a distance corresponding
to a distance where the stable condition is established, and
is defined as a value obtained by adding a distance
corresponding to detection delay of the coating weight gauge
212 to a distance between the nozzle 211 and the coating weight
gauge 212. That is, the reference distance Ls is a distance
for determining whether or not the welding point 411 reaches
the coating weight gauge 212.
As a result of Step S222, in a case in which the tracking
distance L is equal to or less than the reference distance Ls
(S222N), the tracking unit 102 proceeds the process to Step
S224.
[0048]
As the result of Step S222, in a case in which the tracking
distance L is greater than the reference distance Ls (S222Y),
26
the tracking unit 102 determines that the stable condition is
established, and issues the stable condition trigger to the
stable coating weight determination unit 103 (S223). An
establishment condition of the stable condition is same as
described above. The tracking distance L is greater than the
reference distance Ls because a part of the strip 401 right
under the nozzle 211 shows that any one of the nozzle pressure,
the nozzle gap, and the strip speed is not changed until the
coating weight gauge 212 detects the coating weight. That is,
when the tracking distance L is greater than the reference
distance Ls, it means that the welding point 411 passes through
the coating weight gauge 212. Also, during this time, since
the part of the strip 401 right under the nozzle 211 shows that
any one of the nozzle pressure, the nozzle gap, and the strip
speed is not changed until the coating weight gauge 212 detects
the coating weight, the tracking unit 102 determines them to
be the coating weight in accordance with each of a current strip
speed, a current gas pressure, and a current nozzle-strip
distance which are imported from the steel coating plant.
In this way, the tracking unit 102 determines whether
or not the coating weight acquired from the steel coating plant
2 is the coating weight which is stably detected (whether or
not the coating weight is in the stable condition) using a
positional information of the strip 401 based on the tracking
distance of the strip 401.
27
[0049]
Also, in Step S224, the tracking unit 102 determines
whether or not at least one of the nozzle pressure P, the nozzle
gap D, and the strip speed V is changed.
As a result of Step S224, in a case in which at least
one of the nozzle pressure P, the nozzle gap D, and the strip
speed V is changed (S224Y), the tracking unit 102 returns
the process to Step S212 after waiting for a predetermined time
(t), and resets the tracking distance L. At this time, the
tracking unit 102 performs a notification to the effect that
the condition is not the stable condition to the preset control
unit 101, and the preset control unit 101 which receives the
notification may start the process illustrated in Fig. 3.
In a case in which any one of the nozzle pressure P, the
nozzle gap D, and the strip speed V is not changed (S224N),
the tracking unit 102 returns the process to Step S211 after
waiting for the predetermined time (t), and repeats a process
after Step S211.
In this way, determination whether or not the condition
is the stable condition is performed in a period of the
predetermined time (t).
[0050]
Fig. 5 is a diagram schematically illustrating a stable
condition established timing inside one strip.
Here, a previous strip 401a and a next strip 401b are
28
connected to the welding point 411 by welding. In an example
of Fig. 5, in the previous strip 401a, after the welding point
411 passes through the position of the nozzle 211, an example
in which four times stable conditions are established indicated
by numerals 602a to 602d is illustrated. Here, a distance
between the welding point 411 and the numeral 602a is great,
because between the welding point and the numeral, for example,
the nozzle gap is changed and the tracking distance L is reset.
In the same manner, a distance between the numeral 602b and
the numeral 602c is great, because between the numeral and the
numeral, for example, the strip speed is changed at a timing
of the numeral 601 and the tracking distance L is reset.
[0051]
(Stable Coating Weight Determination Process)
Fig. 6 is a flow chart illustrating a process sequence
in the stable coating weight determination unit according to
the first embodiment. Fig. 1 is appropriately referred to.
At the timing when a detection value of the coating weight
is obtained from the coating weight gauge 212 of the steel
coating plant 2, the stable coating weight determination unit
103 determines whether or not the obtained coating weight is
a value of the stable condition according to an output of the
tracking unit 102. Also, when the coating weight is the value
of the stable condition, the stable coating weight
determination unit 103 updates the stable data stored in the
29
stable value storage unit 104 to be the value. Here, the stable
coating weight Ws indicates the coating weight W when the nozzle
pressure P, the nozzle gap D, and the strip speed V are not
changed while a detection part of the coating weight is moved
from the nozzle 211 to the coating weight gauge 212. In other
words, the stable coating weight Ws indicates the coating
weight W at the time of a condition in which the result value
W of the current coating weight acquired from the steel coating
plant 2 becomes the coating weight W based on each of the current
strip speed V, the current nozzle pressure P, and the current
nozzle gap D acquired from the steel coating plant 2. The
coating weight (stable coating weight Ws), the nozzle pressure
(stable nozzle pressure Ps), the strip speed (table strip speed
Vs), and the nozzle gap (stable nozzle gap Ds) at this time
are stored in the stable value storage unit 104 as a set of
data items (stable data).
[0052]
First, the stable coating weight determination unit 103
acquires the current coating weight Wc, the nozzle pressure
Pc, the nozzle gap Dc, and the strip speed Vc from the steel
coating plant 2 (S301).
Next, the stable coating weight determination unit 103
determines whether or not the tracking unit 102 issues the
stable condition trigger (S302).
As a result of Step S302, in a case in which the tracking
30
unit 102 does not issue the stable condition trigger (S302N),
the stable coating weight determination unit 103 terminates
the process.
[0053]
As the result of Step S302, in a case in which the tracking
unit 102 issues the stable condition trigger (S302Y), the
stable coating weight determination unit 103 updates the stable
data in which the coating weight Wc, the nozzle pressure Pc,
the nozzle gap Dc, and the strip speed Vc acquired in Step S301
are respectively stored in the stable value storage unit 104
as the stable coating weight Ws, the stable nozzle pressure
Ps, the stable nozzle gap Ds, the stable strip speed Vs (S303).
Also, the stable coating weight determination unit 103
performs feedback-controlling on the FB control unit 105 (S304).
The FB control unit 105 calculates a correction amount P of
the nozzle pressure for closing the stable coating weight Ws
to the target coating weight W*c, for example, by Expression
(7) when comparing the stable coating weight Ws obtained in
the stable condition with the current target coating weight
W*c.
[0054]
P = (P/W)(W*c -Ws) … (7)
[0055]
Here,  is a constant corresponding to a control gain,
and (P/W) is a constant corresponding to an influence
31
coefficient.
The addition output unit 106 outputs a value obtained
by adding the preset value Pref output by the preset control
unit 101 and the correction amount P of the nozzle pressure
output by the FB control unit 105 with respect to the nozzle
211 as the control reference (preset value) of the nozzle
pressure.
[0056]
(Modification Example of First Embodiment)
Also, in the embodiment, as the coating weight stored
in the stable value storage unit 104, an example in which the
result value of the coating weight detected by the coating
weight gauge 212 is described, but the target coating weight
acquired from the host computer 3 may be stored instead. The
result value of the coating weight is controlled to be close
to the target coating weight. Accordingly, at the timing of
obtaining the stable coating weight, the coating weight and
the target coating weight become a similar value. Accordingly,
the target coating weight can be used instead of the result
value of the coating weight.
[0057]
Also, at the timing of acquiring the stable nozzle
pressure Ps, the stable strip speed Vs, and the stable nozzle
gap Ds, in a case in which the target coating weight (second
coating weight) W*s at the time of the stable condition is
32
acquired instead of the result value of the coating weight at
the time of the stable condition from the host computer 3,
Expression (4) and Expression (5) are replaced by Expression
(4a) and Expression (5a) as follows.
[0058]
Pref = Ps+f-1 (W*c, Vc, Dc)-f-1 (W*s, Vs, Ds) … (4a)
Pref = Ps+exp{(ln (W*c)-a0-a2∙ln (Vc)-a3∙ln (Dc)
/a1}-exp{(ln (W*c)-a0-a2∙ln (Vs)-a3∙ln (Ds) /a1} … (5a)
[0059]
Also, even when Expression (4a) and Expression (5a) are
used, a same effect as that of a control using Expression (4)
and Expression (5) can be obtained.
In addition, there are many cases in which a detector
measuring distance between the nozzle 211 and the strip 401
is not provided in a general coating weight control apparatus.
However, even in this case, since distance of a previous nozzle
and a rear nozzle of the strip 401 can be checked from nozzle
position information, the embodiment can be applied as it is
by considering of 1/2 of the distance as the nozzle gap
(nozzle-strip distance).
[0060]
(Nozzle Control)
Fig. 7 is a diagram illustrating an example of a nozzle
control according to the first embodiment.
In Fig. 7, when the nozzle is opened and closed in a
33
vicinity of the welding point 411, a change of the nozzle gap
and the nozzle pressure by the preset control unit 101 is
schematically illustrated.
In Fig. 7, the previous strip 401a and the next strip
401b are connected to the welding point 411. An opening and
closing operation of the nozzle gap (change of nozzle gap) is
illustrated by a line 701 of an upper side of Fig. 7, and a
change of the nozzle pressure output by the preset control unit
101 is illustrated by a line 702 of a lower side thereof.
[0061]
When the welding point 411 comes close, and the nozzle
gap begins to open, the nozzle pressure is increased by a nozzle
pressure calculation of the preset control unit 101, and an
influence of opening of the nozzle gap on the coating weight
is offset.
[0062]
The numeral 611 indicates a timing where the stable
condition is established in the previous strip 401a at the end,
before the nozzle gap is changed.
The preset control unit 101 acquires the current nozzle
gap Dc, the strip speed Vc, and the like from the steel coating
plant 2 at the timing of calculating the nozzle pressure P after
the numeral 611 (refer to Step S101 of Fig. 3).
In addition, the preset control unit 101 acquires a
target value W*c of the current coating weight from the host
34
computer 3 at the timing of calculating the nozzle pressure
P after the numeral 611 (refer to Step S102 of Fig. 3).
Also, the preset control unit 101 acquires the stable
nozzle gap Ds, the stable strip speed Vs, a stable coating
weight Ws acquired at the timing of the numeral 611 (refer to
Step S103 of Fig. 3), at the timing of calculating the nozzle
pressure P after the numeral 611.
Also, the preset control unit 101 calculates the preset
value Pref by Expression (5) at the timing of calculating the
nozzle pressure P after the numeral 611 (refer to Step S104
of Fig. 3).
[0063]
In general, since the nozzle gap D has a significant
influence on the coating weight W, in order to eliminate this
influence, as illustrated in Fig. 7, the nozzle pressure P
increases in a process of the nozzle gap D opening and is
saturated at the upper limit value before the nozzle gap is
fully opened.
Also, the welding point 411 passes through the nozzle
position, and the nozzle pressure P is also decreased according
to closing of the nozzle gap D. The nozzle pressure after the
nozzle closing is terminated is also preset-calculated, in the
same manner, until next stable condition is established, based
on the stable nozzle pressure Ps, the stable nozzle gap Ds,
the stable strip speed Vs, and the stable coating weight Ws
35
stored in the stable value storage unit 104.
[0064]
That is, the preset control unit 101 calculates a
subsequent nozzle pressure, based on the nozzle pressure 711
at a timing 611 where the stable condition is established in
the end in the previous strip 401a as a referent point, as
described in the numeral 712.
This condition is terminated when an opening and closing
operation of the nozzle gap D is terminated.
Also, in the next strip 401b, after the stable condition
is detected, feedback-controlling by the FB control unit 105
(refer to Fig. 2) is performed.
[0065]
In the embodiment, as illustrated in Fig. 7, based on
the stable nozzle pressure 711 at the timing 611 where the
stable condition is established in the end in the previous strip
401a as a reference, a subsequent nozzle pressure is calculated.
As seen from the above, the preset value of the calculated
nozzle pressure does not affect a calculating result at an
operating point where the nozzle gap is greatly opened. That
is, even at the time where saturation outputting is terminated,
since the nozzle pressure which becomes a reference point is
the nozzle pressure 711 at the timing 611 as it is, the nozzle
pressure can be stably controlled.
In addition, in the embodiment, based on the stable
36
nozzle pressure 711 at the timing 611 where the stable condition
is established in the end in the previous strip 401a as a
reference, errors can be prevented from being accumulated by
calculating a subsequent nozzle pressure, and therefore,
making it possible to controlling the nozzle pressure with high
accuracy.
[0066]
Also, as illustrated in Fig. 7, based on the stable nozzle
pressure 711 at the timing 611 where the stable condition is
established in the end in the previous strip 401a as a reference,
the control apparatus 1 illustrated in the embodiment
calculates a subsequent nozzle pressure, but it is not limited
thereto. According to the nozzle pressure when the stable
condition is established, it may not be the stable nozzle
pressure 711 at the timing 611 where the stable condition is
established in the end.
At this time, the stable coating weight Ws, the target
coating weight W*s at the time of the stable condition, the
stable strip speed Vs, the stable nozzle gap Ds which are used
in Expression (4), Expression (5), Expression (4a), and
Expression (5a), are acquired at the timing where the stable
nozzle pressure Ps used in each Expression is acquired.
[0067]
In the embodiment, an example in which a control
reference of control is the nozzle pressure P has been
37
described; however, in actual plant, a control reference may
be the nozzle gap D, and may be both of the nozzle pressure
P and the nozzle gap D. In any case, the method of the
embodiment can be applied to.
Also, in the embodiment, the nozzle pressure is limited
to be the saturated pressure, but if there is no need to limit,
the nozzle pressure may not be limited to the saturated
pressure.
[0068]
[Second Embodiment]
(System)
Fig. 8 is a diagram illustrating a configuration of a
coating weight control system according to a second embodiment.
Also, in Fig. 8, same numerals as those of Fig. 1 are
given to configuration components which are the same as those
of Fig. 1, and description thereof will be omitted.
First, a preset control unit 101a in a control apparatus
1a in Fig. 8 includes an absolute value calculating unit (first
preset control unit) 111, a relative value calculating unit
(second preset control unit) 112, a control method selecting
unit (selecting unit) 113, and a switching unit 114.
The absolute value calculating unit 111 presets the
nozzle pressure by calculating an absolute value of the nozzle
pressure using the coating weight prediction model. Here, the
absolute value of the nozzle pressure is a nozzle pressure which
38
is calculated on the basis of only information at the current
timing without referring to a nozzle pressure at a previous
timing.
The relative value calculating unit 112 calculates the
nozzle pressure which is need to be changed with respect to
the amount of change of the target coating weight, and performs
a preset by performing adding and subtracting with respect to
the current nozzle pressure. That is, a preset process which
is performed by the relative value calculating unit 112 is the
same process as that of the preset control unit 101 in the first
embodiment.
Hereinafter, a preset control executed by the absolute
value calculating unit 111 is referred to as an absolute value
preset, and a preset control executed by the relative value
calculating unit 112 is referred to as a relative value preset.
In addition, the preset value of the nozzle pressure calculated
by the absolute value calculating unit 111 is appropriately
referred to as an absolute preset value, and the preset value
of the nozzle pressure calculated by the relative value
calculating unit 112 is appropriately referred to as a relative
preset value.
[0069]
In addition, based on information, and the like
transferred from a welding point vicinity determination unit
121, the control method selecting unit 113 selects which one
39
of the absolute preset value calculated by the absolute value
calculating unit 111 and a relative preset value calculated
by the relative value calculating unit 112 is actually used.
The switching unit 114 switches an output of the preset
control unit 101a to an output from the absolute value
calculating unit 111 and an output from the relative value
calculating unit 112 in accordance with the output of the
control method selecting unit 113.
[0070]
In addition, the control apparatus 1a illustrated in Fig.
8 includes the welding point vicinity determination unit 121.
The welding point vicinity determination unit 121
determines whether or not the welding point 411 comes close
to the nozzle position from the current strip speed Vc acquired
from the steel coating plant 2, the timing when the welding
point 411 passes through the nozzle position, and the like,
and notifies a condition to the preset control unit 101a at
the time of being close.
Also, the preset control unit 101a is started as long
as at a timing when the welding point 411 is determined to be
near the nozzle position by the welding point vicinity
determination unit 121. That is, when the preset control unit
101a receives a vicinity trigger issued by the welding point
vicinity determination unit 121 in Steps S503 and S533 of Fig.
11 to be described later, the preset control unit 101a starts
40
the process. In addition, when the preset control unit 101a
receives a vicinity release trigger issued by the welding point
vicinity determination unit 121 in Step S523 of Fig. 11 to be
described later, the preset control unit 101a terminates the
process.
[0071]
(Hardware Configuration)
Fig. 9 is a diagram illustrating a hardware configuration
of a control apparatus according to the second embodiment.
Also, in Fig. 9, same numerals are given to the same
components as those of Fig. 2 and description thereof will be
omitted.
In the control apparatus 1a, when a program stored in
the storage device 503 is loaded by the memory 501, and executed
by CPU 502, in addition to each unit 102, 103, 105, and 106
illustrated in Fig. 2, the welding point vicinity determination
unit 121 or, the absolute value calculating unit 111, the
relative value calculating unit 112, the control method
selecting unit 113, the switching unit 114, and the like
executed by the preset control unit 101a are implemented.
[0072]
Hereinafter, processes of the absolute value calculating
unit 111, the welding point vicinity determination unit 121,
and the control method selecting unit 113 will be described.
Processes of the tracking unit 102, the stable coating weight
41
determination unit 103, the FB control unit 105, and the
addition output unit 106 are the same as those of the first
embodiment, and thus descriptions of those will be omitted
here.
In addition, as described above, the process executed
by the relative value calculating unit 112 is the same as the
process executed by the preset control unit 101 of the first
embodiment using Expression (4) and Expression (5), and thus
descriptions of those will be omitted here.
[0073]
(Absolute Value Calculation Process)
Fig. 10 is a flow chart illustrating a sequence of a
process in the absolute value calculating unit according to
the second embodiment.
First, the absolute value calculating unit 111 acquires
the current strip speed Vc and the current nozzle gap Dc from
the steel coating plant 2, and acquires the current target
coating weight W*c from the host computer 3 (S401). Also, the
absolute value calculating unit 111 acquires, for example, the
current strip speed Vc, the current nozzle gap Dc, and the
target coating weight W*c for every constant time, and as
illustrated in the first embodiment, it does not matter whether
or not it is the stable condition.
Also, the absolute value calculating unit 111 calculates
the preset value Pref (fifth gas pressure) of the nozzle
42
pressure by Expression (8) as follows (S402).
[0074]
Pref = f-1 (W*c, Vc, Dc) … (8)
[0075]
Also, the target coating weight W*c is expressed by
Expression (9) as follows.
[0076]
W*c = f (Pref, Vc, Dc) = exp (a0+a1∙ln (Pref)+a2∙ln
(Vc)+a3∙ln (Dc)) … (9)
[0077]
Accordingly, Expression (8) can be rewritten in
Expression (10) as follows by Expression (9).
[0078]
Pref = exp{(ln (W*c)-a0-a2∙ln (Vc) -a3∙ln (Dc)) /a1} …
(10)
[0079]
(welding point vicinity determination process)
Fig. 11 is a flow chart illustrating a process sequence
in the welding point vicinity determination unit according to
the second embodiment.
Here, an example in which a region including a range where
the nozzle opening and closing is performed is determined using
the tracking distance with respect to the welding point 411
of the strip 401 is shown.
First, the welding point vicinity determination unit 121
43
determines whether or not the current strip speed Vc is greater
than the reference speed Vo (S501). The reference speed Vo
is a determination index for determining whether or not the
steel coating plant 2 is operated as described above, and when
the strip speed Vc is greater than the reference speed Vo, it
indicates that the steel coating plant 2 is performing the
process of the strip 401.
As a result of Step S501, in a case in which the current
strip speed Vc is equal to or less than the reference speed
Vo (S501N), the welding point vicinity determination unit
121 returns the process to Step S501.
[0080]
As a result of Step S501, in a case in which the current
strip speed Vc is greater than the reference speed Vo (S501Y),
the welding point vicinity determination unit 121 determines
whether or not the welding point 411 passes through the nozzle
position (S502). Determination whether or not the welding
point 411 passes through the nozzle position is performed on
the basis of the tracking distance L calculated by the tracking
unit 102.
[0081]
As a result of Step S502, in a case in which the welding
point 411 does not passes through the nozzle position (S502N),
the welding point vicinity determination unit 121 returns the
process to Step S501.
44
As a result of Step S502, in a case in which the welding
point 411 passes through the position of the nozzle 211
(S502Y), that is, according to a start of a process of new
strip 401 (coil), the welding point vicinity determination unit
121 determines whether or not the nozzle position is near the
welding point 411, issues the vicinity trigger (S503), and
starts a process as follows.
[0082]
Next, the welding point vicinity determination unit 121
determines whether or not the welding point 411 passes through
the position of the nozzle 211 (S511).
As a result of Step S511, in a case in which the welding
point 411 does not pass through the position of the nozzle 211
(S511N), the welding point vicinity determination unit 121
proceeds the process to Step S513.
As the result of Step S511, in a case in which the welding
point 411 passes through the position of the nozzle 211
(S511Y), the welding point vicinity determination unit 121
resets the tracking distance L (S512), and proceeds the process
to Step S513.
In Step S513, the welding point vicinity determination
unit 121 acquires the strip speed Vc from the steel coating
plant 2, and calculates the tracking distance L of the strip
401 by Expression (6) whenever the speed is acquired (S514).
[0083]
45
Also, the welding point vicinity determination unit 121
determines whether or not the acquired strip speed Vc is greater
than the reference speed Vo (S521).
As a result of Step S521, in a case in which the strip
speed Vc is equal to or less than the reference speed Vo
(S521N), the welding point vicinity determination unit 121
determines that operating of the steel coating plant 2 is
terminated, and terminates the process.
As the result of Step S521, in a case in which the strip
speed Vc is greater than the reference speed Vo (S521Y), the
welding point vicinity determination unit 121 determines
whether or not the tracking distance L is greater than a first
reference distance Ld (S522). The first reference distance
Ld is set in advance to a value which is sufficiently longer
than a length between a timing when the nozzle opening and
closing in the next strip 401 is terminated after the welding
point 411 passes through, and the welding point 411. An example
of the first reference distance Ld is illustrated in Fig. 13.
That is, in Step S522, the welding point vicinity
determination unit 121 determines whether or not a part of the
strip 401, which is a range of the first reference distance
Ld in Fig. 13, when passing through the nozzle 211, already
passed through the coating weight gauge 212.
[0084]
As a result of Step S522, in a case in which the tracking
46
distance L is equal to or less than the first reference distance
Ld (S522N), after waiting for a predetermined time (t), the
welding point vicinity determination unit 121 returns the
process to Step S513.
As the result of Step S522, in a case in which the tracking
distance L is greater than the first reference distance Ld
(S522Y), the welding point vicinity determination unit 121
determines whether or not it is not near the welding point 411,
issues a vicinity release trigger (S523), and releases a
welding point vicinity determination.
[0085]
Also, the welding point vicinity determination unit 121
acquires the strip speed Vc from the steel coating plant 2
(S524), and calculates the tracking distance L of the strip
401 by Expression (6) whenever the speed is acquired (S525).
Next, the welding point vicinity determination unit 121
determines whether or not the acquired strip speed Vc is greater
than the reference speed Vo (S531).
As a result of Step S531, in a case in which the strip
speed Vc is equal to or less than the reference speed Vo
(S531N), the welding point vicinity determination unit 121
determines that operating of the steel coating plant 2 is
terminated, and terminates the process.
[0086]
As the result of Step S531, in a case in which the strip
47
speed Vc is greater than the reference speed Vo (S531Y), the
welding point vicinity determination unit 121 determines
whether or not a value (Lc-L) which is obtained by subtracting
the tracking distance L from a coil length Lc is less than a
second reference distance Le (S532). Here, the second
reference distance Le is set in advance to be a value which
is sufficiently longer than a length between the timing when
the nozzle opening and closing is started in the current strip
401 before passing through the welding point 411, and the
welding point 411. The second reference distance Le is
illustrated in Fig. 13. In addition, here, the coil length
Lc is a length from the welding point 411 to the welding point
411.
That is, in Step S532, the welding point vicinity
determination unit 121 determines whether or not a part of the
strip 401, which is a range of the second reference distance
Le in Fig. 13 at the time of passing through the nozzle 211,
currently passes through the coating weight gauge 212.
[0087]
As a result of Step S532, in a case in which a value (Lc-L)
which is obtained by subtracting the tracking distance L from
the coil length Lc is equal to or more than Le (S532N), the
welding point vicinity determination unit 121 returns the
process to Step S524 after waiting for the predetermined time
(t).
48
In a case in which a value (Lc-L) obtained by subtracting
the tracking distance L from the coil length Lc is less than
Le (S532Y), the welding point vicinity determination unit
121 determines that it is near the welding point 411, issues
the vicinity trigger (S533), and returns the process to Step
S511.
[0088]
(Control Method Selecting Process)
Fig. 12 is a flow chart illustrating a sequence of a
process in the control method selecting unit according to the
second embodiment. The process is started at the same time
when the process of the preset control unit 101a is started.
That is, when the preset control unit 101a receives the vicinity
trigger issued by the welding point vicinity determination unit
121 in Step S503 and S533 of Fig. 11, a process of Fig. 12 is
started. In addition, when the preset control unit 101a
receives a vicinity release trigger issued by the welding point
vicinity determination unit 121 in Step S523 of Fig. 11, the
process of Fig. 12 is terminated.
[0089]
The control method selecting unit 113 selects which one
of the absolute preset value and the relative preset value is
used according to whether or not the welding point 411 passes
through the position of the nozzle 211 in addition to a degree
of similarity of a control specification of a control value,
49
and the like in a coating control. In the embodiment, an
example is described of which the degree of similarity of the
control specification after the welding point 411 passes is
reprehensive of the target value of the coating weight.
[0090]
First, the control method selecting unit 113 acquires
the current target coating weight W*c from the host computer
3, and further acquires the result value W of the coating weight
obtained in the last controlling from the coating weight gauge
212 in the steel coating plant 2 (S601). Also, since the result
value W of the coating weight obtained in the last controlling
is actually considered to be a result value of the current
coating weight, it is set to be the coating weight Wc here.
Next, the control method selecting unit 113 determines
whether or not the welding point 411 passes through the position
of the nozzle 211 (S602). The control method selecting unit
113 determines whether or not, the welding point vicinity
determination unit 121 acquires a signal of resetting the
tracking distance L, and the welding point 411 passes through
the position of the nozzle 211 based on the signal in a process
in Step S511 of Fig. 11.
[0091]
As a result of Step S602, in a case in which the welding
point 411 does not pass through the position of the nozzle 211
(S602N), the control method selecting unit 113 instructs the
50
switching unit 114 to select the relative value calculating
unit 112 (S605).
As the result of Step S602, in a case in which the welding
point 411 passes through the position of the nozzle 211
(S602Y), the control method selecting unit 113 determines
whether or not an absolute value (deviation) of a difference
between the target coating weight W*c and the coating weight
Wc is greater than a certain value Z (S603).
[0092]
As a result of Step S603, in a case in which an absolute
value of a difference between the target coating weight W*c
and the result coating weight Wc is equal to or less than the
certain value Z (S603N), the control method selecting unit
113 instructs the switching unit 114 to select the relative
value calculating unit 112 (S605).
As a result of Step S604, in a case in which the absolute
value of the difference between the target coating weight W*c
and the result coating weight Wc is greater than the certain
value Z (S603Y), the control method selecting unit 113
instructs the switching unit 114 to select the absolute value
calculating unit 111 (S604).
[0093]
The switching unit 114 switches the output of the
relative value calculating unit 112 and the output of the
absolute value calculating unit 111, and outputs them according
51
to the instruction of the control method selecting unit 113.
[0094]
In the second embodiment, attention has been paid to the
target coating weight as the index for the control method
selecting unit 113 to select the output, but it is also possible
to consider that the degree of similarity is calculated by
adding the mutual difference or the like of the lower limit
values of the coating weight in the previous strip 401a (Fig.
13) and a next strip 402b (Fig. 13).
[0095]
(Nozzle Controlling)
Fig. 13 is a diagram illustrating an example of the nozzle
controlling according to the second embodiment.
In Fig. 13, when opening and closing is performed near
the welding point 411 with respect to the nozzle 211, the nozzle
pressure output by the preset control unit 101a is
schematically illustrated.
In Fig. 13, the previous strip 401a and the next strip
401b are connected to the welding point 411.
A vicinity range of the welding point 411 is defined to
sufficiently include a range where the nozzle gap is opened
and closed over the welding point 411. The opening and closing
operation of the nozzle gap is illustrated by a line 801 of
an upper side of Fig. 13, and nozzle pressure operation output
by the preset control unit 101a is illustrated by a line 802
52
of a lower side of Fig. 13.
[0096]
When the nozzle gap to which the welding point 411 comes
close starts opening, the nozzle pressure becomes greater by
calculating the nozzle pressure of the preset control unit 101a,
and an influence of opening of the nozzle gap on the coating
weight is offset. In addition, the welding point 411 passes
through the nozzle position, and the nozzle pressure is also
decreased as the nozzle gap is closed.
[0097]
Here, the numeral 611 indicates a timing when the stable
condition is established in the end in the previous strip 401a.
As illustrated in Fig. 13, before the welding point 411 passes
through the position of the nozzle 211, the relative value
calculating unit 112 is selected in the preset control unit
101a. That is, in a time region 811 before the welding point
411 passes through the position of the nozzle 211, a process
same as that of the first embodiment is performed.
[0098]
After that, after the next strip 401b becomes a process
target (time region 812), focusing on a difference between the
current target coating weight W*c and the result coating weight
Wc acquired from the coating weight gauge 212, the preset
control unit 101a calculates the nozzle pressure by an absolute
preset using the absolute value calculating unit 111 when the
53
difference is great, and by a relative value calculation using
the stable data stored in the stable value storage unit 104
when the difference is small.
Also, the time regions 811 and 812 are respectively near
the welding point 411, and include time when the nozzle opening
and closing are controlled.
[0099]
That is, in the second embodiment, when the welding point
411 passes through the nozzle position and the next strip 401b
is processed, a similarity is compared. In the second
embodiment, a difference between the current target coating
weight W*c and the result coating weight Wc is applied as the
similarity. Also, when a previous section number 401a and a
process in the next strip 401b are similar to each other, the
same process as that of the first embodiment is performed. In
addition, when the previous strip 401a and the process in the
next strip 401b are not similar to each other, since reliability
is deteriorated if the stable data acquired at the time of the
stable condition in the end in the previous strip 401a is used
for the next strip 401b, the nozzle pressure control by the
absolute preset value is performed.
In this way, reliability of the nozzle pressure control
can be improved.
[0100]
Incidentally, the tracking unit 102 and the welding point
54
vicinity determination unit 121 in Fig. 8 may be combined into
one.
[0101]
The invention is not limited to the embodiment described
above, and various modification examples are included therein.
For example, the embodiment described above is described in
detail in order to easily understand the invention, and the
invention is not necessarily limited to apparatuses and methods
including all of the described configurations. In addition,
a part of a configuration of a certain embodiment can be
replaced with a configuration of another embodiment, and the
configuration of another embodiment can be also added to the
configuration of a certain embodiment. In addition, addition,
deleting, and substitutions of another configuration can be
made to a part of a configuration of each embodiment.
[0102]
In addition, in each configuration, function, units 101
to 103, 105, 106, 101a, 111 to 114, and 121, the stable value
storage unit 104, and the like, some or all thereof may be
implemented by, for example, hardware when being designed as
an integrated circuit. In addition, as illustrated in Fig.
2 and Fig. 9, each configuration, function, and the like
described above, may be implemented by software when a
processor such as the CPU 502 interprets and executes a program
realizing each function. Information of a program, table,
55
file, and the like realizing each function can be stored in
a recording device, such as a memory or a solid state drive
(SSD), or a recording medium such as an integrated circuit (IC)
card, a secure digital (SD) card, or a digital versatile disc
(DVD), in addition to storing in a hard disk (HD).
In addition, in each embodiment, only a control line or
a information line that are considered to be necessary for
description are indicated and products may not indicate all
of the control lines or information lines. Actually, almost
all of the configurations may be considered to be connected
to each other.
Reference Signs List
[0103]
1 control apparatus (coating weight control apparatus)
2 steel coating plant
3 host computer (external device)
101 preset control unit
102 tracking unit (stable condition determination unit)
103 stable coating weight determination unit (stable
value storage processing unit)
104 stable value storage unit (storage unit)
105 FB control unit
106 addition output unit
111 absolute value calculating unit (first preset
control unit)
56
112 relative value calculating unit (second preset
control unit)
113 control method selecting unit (selecting unit)
114 switching unit
121 welding point vicinity determination unit
201 pot
202 molten coating
203 roll
204 top roll
211 nozzle
212 coating weight gauge
401 strip
401a previous strip
401b next strip
411 welding point

WE CLAIM:
[Claim 1]
A coating weight control apparatus which receives result
information from a steel coating plant, which attaches a
coating having a desired coating weight to a strip by immersing
a continuously sent strip into a bath of a molten coating and
spraying high pressure gas from a nozzle so as to peel an
unnecessary coating off immediately after the strip is lifted,
generates control information for controlling a coating weight
which is a coating weight of the coating based on the received
result information, and transfers the generated control
information to the steel coating plant, the apparatus
comprising:
a preset control unit that calculates at least the gas
pressure as a control reference for a control reference of the
nozzle for attaching the coating having a desired coating
weight, by calculation based on a coating weight prediction
model indicating at least a relationship between a strip speed
which is a moving speed of the strip, a gas pressure which is
a pressure of the gas being sprayed from the nozzle, a
nozzle-strip distance which is a distance between the nozzle
and the strip, and the coating weight being attached to the
strip;
a tracking unit that specifies positional information
in the strip based on a movement distance of the strip obtained
58
by importing the strip speed from the steel coating plant and
integrating the imported strip speed;
a stable condition determination unit that determines
whether or not the coating weight imported from the steel
coating plant is a stably-detected coating weight by
determining whether or not a current coating weight imported
from the steel coating plant is a coating weight in accordance
with each of a current strip speed, a current gas pressure,
and a current nozzle-strip distance imported from the steel
coating plant, based on the positional information of the strip
specified by the tracking unit; and
a stable value storage processing unit that stores a
combination of a second coating weight, a second strip speed,
a second gas pressure, and a second nozzle-strip distance,
which are imported, when the coating weight imported from the
steel coating plant is determined to be the stably-detected
coating weight, by the stable condition determination unit,
in a stable value storage unit,
wherein the preset control unit imports a first strip
speed which is the current strip speed, a first nozzle-strip
distance which is the current nozzle-strip distance, and a
first target coating weight which is a target value of the
current coating weight from the steel coating plant, calculates
a first gas pressure of a control reference which is the gas
pressure for realizing the first target coating weight based
59
on the coating weight prediction model, imports the second
strip speed, the second nozzle-strip distance, and the second
coating weight from the stable value storage unit, calculates
a third gas pressure of a control reference which is the gas
pressure for realizing the coating weight corresponding to the
second strip speed and the second nozzle- strip distance using
the coating weight prediction model, adds the first gas
pressure to the second gas pressure imported from the stable
value storage unit, and calculates a fourth gas pressure which
is a control reference of the nozzle by subtracting the third
gas pressure.
[Claim 2]
The coating weight control apparatus according to Claim
1,
wherein the second coating weight is a result value of
the coating weight imported from the steel coating plant at
a timing when the coating weight imported from the steel coating
plant is determined to be the stably-detected coating weight
by the stable condition determination unit.
[Claim 3]
The coating weight control apparatus according to Claim
1,
wherein the second coating weight is a target coating
weight, which is a target value of the coating weight imported
from an external device, at a determination timing when the
60
coating weight imported from the steel coating plant is
determined to be the stably-detected coating weight, by the
stable condition determination unit.
[Claim 4]
The coating weight control apparatus according to Claim
1,
wherein the preset control unit is a second preset
control unit, and
wherein the preset control unit further includes
a first preset control unit that calculates a fifth gas
pressure for realizing a desired coating weight corresponding
to at least the strip speed and the nozzle-strip distance
imported from the steel coating plant, using the coating weight
prediction model,
a selecting unit that calculates a deviation between the
target value and the result value of the coating weight imported
from the steel coating plant, selects the first preset control
unit when the deviation is greater than a predetermined value,
and selects the second preset control unit when the deviation
is less than a predetermined value, and
a switching unit that performs switching between the
first preset control unit and the second preset control unit
according to a determination result of the selecting unit.
[Claim 5]
A coating weight control method in a coating weight
61
control apparatus which receives result information from a
steel coating plant, which attaches a coating having a desired
coating weight to a strip by immersing a continuously sent strip
into a bath of a molten coating and spraying high pressure gas
from a nozzle so as to peel an unnecessary coating off
immediately after the strip is lifted, generates control
information for controlling a coating weight which is a coating
weight of the coating based on the received result information,
and transfers the generated control information to the steel
coating plant, the method comprising:
in the coating weight control apparatus,
storing a coating weight prediction model indicating a
relationship between at least a strip speed which is a moving
speed of the strip, a gas pressure which is a pressure of the
gas sprayed from the nozzle, a nozzle-strip distance which is
a distance between the nozzle and the strip, and the coating
weight attached to the strip, in a storage unit;
importing the strip speed from the steel coating plant,
and specifying positional information in the strip, based on
a movement distance of the strip obtained by integrating the
imported strip speed;
based on the specified positional information of the
strip, determining whether or not the coating weight imported
from the steel coating plant is the stably-detected coating
weight by determining whether or not the current coating weight
62
imported from the steel coating plant is the coating weight
respectively based on a current strip speed, a current gas
pressure, and a current nozzle-strip distance which are
imported from the steel coating plant;
storing a combination of a second coating weight, a
second strip speed, a second gas pressure, and a second
nozzle-strip distance which are imported when the coating
weight imported from the steel coating plant is determined to
be the stably-detected coating weight, in a stable value
storage unit; and
importing a first strip speed which is the current strip
speed, a first nozzle-strip distance which is the current
nozzle-strip distance, and a first target coating weight which
is a target value of the current coating weight from the steel
coating plant, calculating the first gas pressure of a control
reference which is the gas pressure for realizing the first
target coating weight, importing a second strip speed, a second
nozzle-strip distance, and a second coating weight from the
stable value storage unit based on the coating weight
prediction model, calculating a third gas pressure of the
control reference which is the gas pressure for realizing the
coating weight corresponding to the second strip speed and the
second nozzle-strip distance using the coating weight
prediction model, adding the first gas pressure to the second
gas pressure imported from the stable value storage unit, and
63
calculating a fourth gas pressure which is a control reference
of the nozzle by subtracting the third gas pressure.
[Claim 6]
The coating weight control method according to Claim 5,
wherein the second coating weight is the result value
of the coating weight imported from the steel coating plant
at the timing when the coating weight imported from the steel
coating plant is determined to be the stably-detected coating
weight.
[Claim 7]
The coating weight control method according to Claim 5,
wherein the second coating weight is a target coating
weight which is a target value of the coating weight imported
from an external device at the timing when the coating weight
imported from the steel coating plant is determined to be the
stably-detected coating weight.
[Claim 8]
The coating weight control method according to Claim 5,
the method further comprising:
in the coating weight control apparatus,
calculating a deviation between a desired coating weight
and the result value of the coating weight imported from the
steel coating plant;
selecting a fifth gas pressure for realizing the desired
coating weight corresponding to at least the strip speed and
64
the nozzle-strip distance imported from the steel coating plant
when the deviation is greater than a predetermined value, as
the control reference of the nozzle; and
selecting the fourth gas pressure as the set value of
the control reference of the nozzle when the deviation is less
than the predetermined value.