Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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This in~ention relates to an impro~ement on a
method of controlling flatness of strip by rolling
mill and an apparatus therefor.
In general, automatic flatness control for
rolling mill comprises as roll cooling means
including a plurality of coolant spray nozzles
disposed side by side in a longitudinal direction of
work rolls for controlling shapes or conditions of
the work roll surfaces during rolling and a flatness
meter for detecting broadwise flatness of rolled strip
to generate an output signal to operate the roll
cooling means. The coolant spray nozzles are
independently controlled in accordance with the
output signal from the flatness meter whereby thermal
crown of the work rolls is adjusted so that the
flatness of strip is properly controlled.
In one of the prior arts, in case a strip
portion or portions are judged by the output signal
form the flatness meter to have localized high
tension in a longitudinal direction of the work rolls
which corresponds to a broadwise direction of the
strip, roll coolant stops being sprayed corresponding
to the strip portion or portions while in case
another strip portion or other strip portions are
judged to have low tension due to their elongation,
roll coolant is sprayed onto the strip portion or
portions. This is accomplished by on-off control of
the coolant spray nozzles.
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In another prior art, a flow amount of roll
coolant is successively adjusted by coolant flow
adjusting valves provided corresponding to the
respective coolant spray nozzles so that the
thermal crown is controlled.
However, in the prior arts, since the roll
coolant is controlled in accordance with only the
output signal from the flatness meter, it is made
without any variation in control along the
longitudinal direction of the work rolls with the
result that any control cannot be made so as to
generate no localized buckle such as quarter buckle
due to thermal crown. Furthermore, since there has
no control logic to compensate for variation ratio of
flatness in a direction in which flatness varies,
there often occurs overshoot and, therefore, the
flatness of the strip cannot be controlled with
precision.
Accordingly, it is a principal obiect of the
invention to provide a method of controlling flatness
of strip by rolling mill in which the flatness of the
strip can be effectively controlled in accordance
with rolling conditions varying without any
complicated calculation.
It is another object of the invention to
provide automatic flatness control for rolling mill
adapted to control flatness of strip by rolling mill
in which the strip can be effectively controlled in
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accordance with rolling conditions varying without any
complicated calculation.
According to the present invention there is
provided a method of controlling flatness of strip by
rolling mill comprising an actuator for controlling shapes
or conditions of work roll surfaces during rolling and a
flatness meter for detecting broadwise flatness of rolled
strip to generate an output signal whereby the actuator is
operated so as to control the flatness of the strip in
lo accordance with a plurality of evaluation indexes which are
produced by analyzing the output signal, the method
comprising the steps of:
- converting the plurality of evaluation indexes
into a qualitative language information;
- determining from the qualitative language
information a degree necessary for controlling the actuator
by using a rule described in a language which is a
qualitative model; and
- converting the degree which is a language
information into a control quantity whereby the flatness of
the strip is controlled.
According to the present invention, there is also
provided a method of controlling flatness of strip by a
rolling mill comprising an actuator for controlling shapes
or conditions of work roll surfaces during rolling and a
flatness meter for detecting broadwise flatness of rolled
strip to generate an output signal whereby the actuator is
operated so as to control the flatness of the strip in
accordance with a plurality of evaluation indexes which are
produced by analyzing the output signal, the method
comprising the steps of:
- the evaluation indexes including at least
localized buckle evaluation index which is indicated by a
difference between elongation at first position and
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elongation at a second position adjacent to the first
position in a longitudinal direction of the work rolls;
- converting the plurality of evaluation indexes
into a qualitative language information;
- determining from the qualitative language
information a degree necessary for controlling the actuator
by using a rule described in a language which is a
qualitative model; and
- converting the degree which is a language
information into a control quantity whereby the flatness of
the strip is controlled.
According to the present invention, there is also
provided an apparatus for controlling flatness of strip by
a rolling mill comprising an actuator for controlling shapes
or conditions of work roll surfaces during rolling and a
flatness meter for detecting broadwise flatness of rolled
strip to generate an output signal whereby the actuator is
operated so as to control the flatness of the strip in
accordance with a plurality of evaluation indexes which are
produced by analyzing the output signal, the apparatus
further comprising:
- means to convert said plurality of evaluation
indexes into a qualitative language information;
- means to determine from the qualitative language
information a degree necessary for controlling the actuator
by using a rule described in a language which is a qualita-
tive model; and
- means to convert the degree which is a language
information into a control quantity whereby the flatness of
the strip is controlled.
According to the present invention, there is also
provided an apparatus for controlling flatness of strip by
a rolling mill comprising an actuator for controlling shapes
or conditions of work roll surfaces during rolling and a
~ .
.
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flatness meter for detecting broadwise flatness of rolled
strip to generate an output signal whereby the actuator is
operated so as to control the flatness of the strip in
accordance with a plurality of evaluation indexes which are
produced by analyzing the output signal, the apparatus
comprising:
- the evaluation indexes inclusing at least
localized buckle evaluation index which is indicated by a
difference between elongation at a first position and
elongation at a second position adjacent to the first
position in a longitudinal direction of the work rolls;
- means to convert the plurality of evaluation
indexes into a qualitative language information;
- means to determine from the qualitative language
information a degree necessary for controlling the actuator
by using a rule described in a language which is a
qualitative model; and
- means to convert the degree which is a language
information into a control quantity whereby the flatness of
the strip is controlled.
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The above and other objects and features of the
invention will be apparent from the description of-
the embodiments of the invention with reference to the
accompanying drawings in which;
Fig. 1 is a schematic diagram of an apparatus
used for a method of controlling flatness of strip in
accordance with one embodiment of the invention;
Fig. 2 is a schematic diagram of roll cooling
system used for t~le apparatus of Fig. l;
Fig. 3A illustrates curves indicating objective
flatness and actual flatness of the strip;
Fig. 3~ illustrates distribution of objective
values and actual values of relative difference in
elongation;
Figs. 4A through 4C illustrate membership
functions of fuzzy variables;
Fig. 5 is a flow chart in which -the method of
the invention is made in accordance with a computer;
Fig. 6 perspectively illustrates in a brief
manner work rolls having another actuator used for
another embodiment of the invention;
Fig. 7 illustrates in cross sec-tional view work
rolls having furttler actuator used for further
embodiment of the invention;
Fig. 8 illustrates in a front view roll means
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being controlled in accordance with another
embodiment of the invention;
Fig. 9 illustrates in a side elevational view
roll means being controlled in accordance with further
embodiment of the invention;
and Fig. 10 illsutrates in cross sectional view
a back up roll used for another embodiment of the
in~ention.
Referring now to Fig. 1, there is shown an
apparatus for controlling flatness of strip by
rolling mill in accordance with one embodiment of the
lnvention.
The rolling mill 10 comprises upper and lower
work rolls 14 and 14 for rolling strip 12,
intermediate rolls 16 and 16, and back up rolls 18
and 18. The strip 12 passes from a pay off reel 20
through the gap between the work rolls 14 and 14 and
is wound on a tension reel 22.
The rolling mill 10 also comprises outer roll
cooling means including a plurality of coolant spray
nozzles 24 disposed side by side in a longitudinal
direction of work rolls 14 for controlling shapes or
conditions of work roll surfaces and ser~ing as an
actuator for controlling the shapes or conditions of
the work roll surfaces during rolling and a flatness
meter 26 for detecting broadwise flatness of the
rolled strip 12 to generate an output signal. As
shown in Fig. 2, roll coolant is supplied to the
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respective coolant spray nozzles 24 from a coolant
tank 28 through a supply pump 30, a main conduit 32
and respective valve means 34. A control instruction
is fed to the respective valve means 34 from a valve
instruction means 36 which receives coolant output
signals calculated in accordance with the method of
the invention.
The flatness meter 26 supplies the output
signal corresponding to the detected flatness of the
strip 12 to a relative difference in elongation
calculation circuit 38 which serves to convert the
output signal (flatness signal) from the flatness
meter 26 into a relative difference in elongation
~ (i) . It should be noted that a symbol "(i)" of the
relative difference in elongation ~ (i) is an index
indicating the longitudinal position of the work
rolls corresponding to the respective coolant spray
nozzles 24.
A coolant output calculation circuit 40 serves
to analyze a deviation signal between the output
signal from the flatness meter 26 and an objective
flatness set value into a plurality of evalutaion
indexes so as to determine them as fuzzy quantities
whereby a spray amount of the respective coolant spray
nozzles 24 is set by fuzzy reasoning and fed to the
valve instrucion means 36 SQ as to properly control
the flatnss of the strip 12. In the illustrated
embodiment, the coolant output calculation circuit 40
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receives the relative difference in elongation (i)
which is the output from the relative difference in
elongation calculation circuit 3~ to determine a
coolant outputa (i) as described hereinjustbelow.
Fig. 3A indicates an objective flatness and
actual flatness of the rolled strip 12. In Fig. 3A, a
solid line indicates the objective flatness
(objective relative difference in elongation) r as
expressed by a quadratic function in case a center
of the strip 12 is supposed to be zero while a dotted
chain line of Fig. 3A indicates an example of the
flatness of the strip (actual relative difference in
elongation) in case a center of the strip 12 is
supposed to be zero. Fig. 3B indicates a distribution
of the objective relative differences in elongation
~ (i) and the actual relative differences in
elongation (i) in case the strip 12 is divided
into a plurality of zones corresponding to the
divided widths of the flatness meter 26. It should be
noted that the following three evaluation values can
be determined from the obiective relative differences
in elongation ~ (i) and the actual relative
differences in elongation (i).
(1) Control deviation A(i)
This is evaluated by a difference between the
objective relative differences in elongation ~ (i)
and the actual relative differences in elongation
(i) as expressed by the following;
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A(i) = (i) - ~ (i) ------------- (1)
(2)Flatness variation ratio B(i)
This is evaluated as variation ratio (variation
direction) of actual relative differences in
elongation (i) as expressed by the following;
B(i) = d (i) /dt -------------(2)
(3)Localized buckle evalutaion index C(i)
This is an evaluation of localized buckle
portions due to thermal crown as expressed by the
following;
C (i) = (i) - { ( (i-l) + (i+l) ) /2} -------(3)
wherein a symbol (i+l) indicates a position next to
one longitudinal position (i) of the work rolls while
a symbol (i-l) indicates a position reversely next to
the position (i).
The control output is determined by fuzzy
reasoning from the aforementioned evaluation
indexes. The reasoning rule are as follows;
(1) If the control deviation A(i) is slightly
minus, the flatness variation ratio B(i) slightly
increases in a plus direction and the localized
buckle evaluation index C(i) is zero, then the
coolant output a (i) is kept at the present value.
(2) If the control deviation A(i) is zero, the
flatness variation ratio B(i) largely decreases in a
minus direction and the localized buckle evaluation
index C(i) is slightly big, then the coolant output a
~i) slightly decreases.
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(3) If the control deviation A(i) is slightly
plus, the flatness variation ratio B(i) is zero and
the localized buckle evaluation index C(i) is much
large, then the coolant outputa(i) largely increases.
(4) The rest is omitted.
Although the three evalutaion indexes such as
A(i), B(i) and C(i) necessary for determining the
coolant output a (i) which is the control output by
fuzzy reasoning are defined by using the membership
functions, an example thereof is shown in Figs. 4A
through 4C.
Fig. 4A indicates a membership function of
fuzzy variable of the deviation A(i), Fig. 4B
indicates a membership function of fuzzy variable of
the variation ratio B(i) and Fig. 4C indicates a
membership function of fuzzy variable of the
localized buckle evaluation index C(i). In these
figures, ~PB~ is an abbreviation of ~Positive Big~
which means a mass of positive and big numbers, ~PS~
is an abbreviation of ~Positive Small~ which means a
mass of positive and small numbers, ~Z0~ is an
abbreviation of ~Zero~ , ~NS~ is an abbreviation of
~Negative Small~ which means a mass of negative and
small numbers, and ~NB~ is an abbreviation which
means a mass of negative and big numbers~. As the
aforementioned parameters are used, the reasoning rule
(1), for example, describes ~If A(i) is NS and B(i)
is PS and C(i) is Z0, then ~ a (i) is Z0~. In the
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illustrated embodiment, there are prepared 74 fuzzy control
rules in addition to the above rule (1) and the 75 rules are
totally prepared. It should be noted that various
parameters such as operating methods of experts are referred
to in preparation of the control rules and that unnecessary
rules can be properly omitted. For example, the following
tables I(A), I(B), and I(C) illustrate rule tables of
adjusting amount of control output when C(i) is zero, PS,
and PB, respectively.
TABLEI(A)
Variation
(Ci~Zero) ~now~t B(i)
PB PS ZO NS NB
PB PB PB PB PS PS
PS PB PS PS ZO ZO
De~iation ZO PB PS ZO NS NB
A(i)
NS ZO ZO NS NS NB
NB NS NS NB NB NB
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m ~ o ~ u~ m
o
z ~ ~ ~ z
o m ~ ~n o ~
,, N P~ ~ Z
o C~ -
O
m m m m ~ tn
m u~ o ~/? m
z ~
c
.
~, ,~ ,,
;~ ~
m m c~ ~ o o
z ~ ~ ~ ~ ~
~ m q ~ u~ o
z P~ ~ ~ ~ c~
o ~ ~ a~
o a:l
m m m m
m m Gq m
m ~ o u~ m
~ ~ ~ z z
~ cO
,~ ,,
,~ 11
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The values of ~ a (i) correspon~ing to the
aforementioned PB through N13 are expressed by the
following table II.
TA13LE I I
PB PS ZO NS NB
~ a (i) 20 10 0 -10 -20
In the table II. a a (i) h~
11a
,~ ~
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adjusting amount ~ a (i) of the coolant output a (i)
is caluculated by the fuzzy control rule table and is
added to the former coolant output a * (i) to
determine the present coolant output a (i) as
indicated by the following expression;
a (i) = a * (i) + ~ a (i) ~ -------(4)
The spray patern of the roll coolant is determined
from the coolant output a (i) which is fed to the
valve instruction means 36.
Fig. 5 shows an example of a program in case of
the coolant output calculation circuit 40 of Fig. 3
accomplished by a computer. This is actuated for a
predetermined period such as one second, for example.
Although, in the illustrated embodiment, the
spray pattern of roll coolant is determined by fuzzy
reasoning using the three fuzzy quantities of
deviation A(i) in relative difference in elongation,
variation ratio B(i) in relative difference in
elongation and localized buckle evaluation index
C(i), at least two of the three fuzzy quantities may
be combined. Furthermore, additional evaluation index
or indexes may be used as fuzzy quantity or
quantities in accordance with its object or objects.
Although, in the illustrated embodiment, fuzzy
control is made using one input (relative difference
in elongation) and one output (coolant output), it
may be made using multi-input (relative difference in
elongation and another or other sensor input or
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inputs) and multi-output (coolant output and another
or other acutator output or outputs).
Figs. 6 and 7 illustrate modifications of the
actuator used for the invention.
The actuator of Fig. 6 comprises outer heating
means 4Z including a plurality of outer heating
elements 44 such as induction heating coils or high
frequency heating elements disposed side by side in
a longitudinal direction of the work rolls 14 so
that they heat the corresponding zones of the work
rolls 14 through the outer surfaces thereof. The
conrtol output obtained by fuzzy reasoning is applied
to the outer heating means 42 so that the shapes or
conditions of the work roll surfaces can be
controlled whereby the flatness of the strip 12 is
properly controlled.
The actuator of Fig. 7 comprises inner heating
means 46 including a plurality of inner heating
elements 48 such as induction heating coils, high
frequency heating elements, electric heating elements
and steam flowing conduits, for example disposed
within the work rolls in a manner spaced to each
other in a longitudinal direction of the work rolls
14 so that a plurality of di~ided heating zones are5
formed along the work rolls 14. The conrtol output
obtained by fuzzy reasoning is applied to the inner
heating elements 48 so that the shapes or conditions
of the the work roll surfaces can be controlled
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whereby the flatness of the strip is properly
controlled. It will be noted that the inner heating
means 46 may be replaced by inner cooling means
including a plurality of cooling elements such as
coolant flowing conduits disposed within the work
rolls 14 in a manner spaced to each other in a
longitudinal direction of the work rolls 14. A
principle of operation of the inner cooling means is
identical to that of the inner heating means 46.
Figs. 8 through 10 illustrates three further
modifications of the invention different from each
other.
In the modification of Fig. 8, flatness control
is made by longitudinal shift of either or both of the
intermediate rolIs 16 and the work rolls 14. Thus, it
will be noted that the acutuator of the modification of
Fig. 8 will comprise shift means not shown to mo~e the
intermediate or work rolls 16 or 14. The conrtol
output obtained by fuzzy reasoning is applied to the
shift means so that the shapes or conditions of the
work roll surfaces can be controlled whereby the
flatness of the strip is properly controlled.
In the modification of Fig. 9, flatness control
is made by longitudinal bend of either or both of the5
intermediate rolls 16 and the work rolls 14. Thus, it
will be noted that the acutuator of the modification
of Fig. 9 will comprise bending means 50 to apply a
bending force BF to the intermediate or work rolls 16
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2006693
or 14. The control output obtained by fuzzy reasoning
is applied to the bending means so that the shapes or
conditions of the work roll surfaces can be
controlled whereby the flatness of the strip is
properly controlled. It should be noted that the
bending means 50 may have a plurality of bending
elements disposed in a divided manner along a
longitudinal direction of the rolls 14 or 16 so that
zone control of flatness can be made.
In the modification of Fig. 10, flatness
control is made by variation in crown of at least one
of the back up rolls 18, the intermediate rolls 16
and the work rolls 14. Thus, it will be noted that
the acutuator of the modification of Fig. 10 will
comprise crown variation means to vary crown of the
rolls 14, 16 or 18. The control output obtained by
fuzzy reasoning is applied to the crown variation
means so that the shapes or conditions of the work
roll surfaces can be controlled whereby the flatness
of the strip properly controlled. In the
modification of Fig. 10, the back up rolls 18 have
the crown variation means which may comprise oil
filling spaces 54 provided in the back up rolls 18.
In the illustrated embodiment, the back up roll 18
may be formed of a roll body 18A and a sleeve 18B
pro~ided on the roll body 18A and the oil filling
spaces 54 are provided in the sleeve 18B at its inner
face. An oil introduction p~ssage 56 may be provided
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in the roll body 18A so that it communicates with the
oil filling spaces 54. The crown can vary in
accordance with an amount of oil filled in the spaces
54.
Thus, it will be noted that the actuator for
controlling the shapes or conditions of the work
roll surfaces may be in various forms so long as the
flatness of the strip can be controlled along the
width thereof.
Although, in the illustrated embodiments, only
one actuator for controlling the shapes or
conditions of the work roll surfaces is used, it will
be noted by those skilled in the art that two or more
than two actuators to be operated by fuzzy control may
be used for controlling the shapes and/or conditions
of the work woll surfaces. Roll cooling means and
bending means, for example, may be combined and
operated by fuzzy control.
While some preferred embodiments of the
invention have been illustrated and described with
reference to the accompanying drawings, it will be
understood by those skilled in the art that they are
by way of exmaples, and that various changes and
modifications may be made without departing from the
spirit and scope of the invention, which is intended
to be defined only by the appended claims.
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