1. A rolling mill control apparatus for controlling a tandem mill which rolls a roll material (8) by a plurality of pairs of rolls, comprising: a rolling speed control unit (631, 632, 633) for controlling rotational speeds of the roll corresponding to a measuring position and the rolls arranged on its upstream side or downstream side on the basis of a deviation of state amounts which are measured; an oscillation detecting unit (660) for detecting an oscillation of the measured state amounts; and an oscillation control unit (660) for changing control responses in the control of the rotational speeds of the roll corresponding to the measuring position where the oscillation has been detected and the same roll as that of the control of the rotational speeds based on the deviation of said state amounts in the rolls arranged on its upstream side or downstream side.

2. The rolling mill control apparatus according to claim 1, wherein said oscillation detecting unit (660) detects the oscillation of said state amounts on the basis of a result of a frequency analysis of results of the state amounts which are measured.

3. The rolling mill control apparatus according to claim 1, wherein: said oscillation detecting unit (660) repeatedly detects the oscillation of said state amounts at every predetermined interval, and said oscillation control unit (660) gradually and continuously changes said control response while said oscillation is detected and, when said oscillation is not detected, stops the change in said control response.

4. A plant control apparatus for controlling a plant in which the same kind of process is repeated in a plurality of control subjects, comprising: a state control unit (831,832,833) for changing control states of the control subject corresponding to a measuring position and the control subjects arranged on its upstream side or downstream side on the basis of a deviation of state amounts which are measured; an oscillation detecting unit (660) for detecting an oscillation of the measured state amounts; and an oscillation control unit (660) for changing control responses in the change in the control states of the control subject whose oscillation has been detected and the same control subject as that of the change in the control state based on the deviation of said state amounts in f the control subjects arranged on its upstream side or downstream side. |

5. A rolling control method of controlling a tandem mill which rolls a roll material I (8) by a plurality of pairs of rolls, comprising the steps of: 1 W6833 -20- controlling rotational speeds of the roll corresponding to a measuring position and the rolls arranged on its upstream side or downstream side on the basis of a deviation of state amounts which are measured; detecting an oscillation of the measured state amounts; and changing control responses in the control of the rotational speeds of the roll corresponding to the measuring position where the oscillation has been detected and the same roll as that of the control of the rotational speed based on the deviation of said state amounts in the rolls arranged on its upstream side or downstream side.

6. A rolling mill control apparatus, substantially as herein described with reference to accompanying drawings and examples.

7. A plant control apparatus, substantially as herein described with reference to accompanying drawings and examples.

8. A rolling control method, substantially as herein described with reference to accompanying drawings and examples.

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BACKGROUND OF THE INVENTION
5 The invention relates to a rolling mill control apparatus, a plant control apparatus,
and a rolling control method and, more particularly, to suppression of an oscillation in the case
where a control gain is large.
In a hot tandem mill, a tension and a roll force which are applied to a roll material
(that is, a material to be rolled) and a plate thickness on an exit side of the rolling mill are
10 controlled by using a roll gap serving as an interval between upper and lower work rolls and
rolling speeds of facilities before and after the rolling mill, thereby executing a rolling operation.
Between mill stands, a looper for supporting the roll material between the stands is disposed.
Since a tension which is applied to the roll material changes by changing a supporting state of
the roll material by the looper, the tension of the roll material can be detected by measuring a
15 pressure applied to the looper. Control to make a height of looper constant by a pressure by a
hydraulic cylinder is made by using proportional integral control.
In plate thickness control, a plate thickness on each mill stand exit side is
controlled in such a manner that a plate thickness on the rolling mill exit side is equal to a
predetermined setting value by using a detection result by a plate thickness meter or a roll force,
20 a plate thickness prediction value from the roll gap, or the like. Automatic tension control is
necessary to prevent looseness of the roll material between the mill stands or a decrease in plate
width due to an overtension. For this purpose, the automatic tension control is performed by
using a tension result from tension detecting means between the stands.
In the general hot tandem mill, the plate thickness control is performed by the roll
25 gap adjustment of each stand and the tension control is performed by the adjustment of a rolling
speed on the front stage side of the adjacent stand roll. As tension detecting means, the tension
which is received by the looper from the roll material is detected from the pressure applied to the
hydraulic cylinder of a load cell or looper.
In a tandem mill in which a plurality of mill stands are arranged in a line, in the
30 case of adjusting the rolling speed of the ith stand, an influence is exerted on both of the tension
between the ith stand and the (i-l)th stand and the tension between the ith stand and the (i+l)th
stand. Since such an influence has a possibility that an oscillation occurs by an interference of
the tension control between the stands, it results in deterioration in plate thickness precision. To
solve such a problem, a method whereby an interval between the rolls is corrected in accordance
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with a tension result on the upstream side and response speeds of tension control means arranged
between the adjacent mill stands are set to different characteristics has already been known (for
example, refer to JP-A-5-15913).
SUMMARY OF THE INVENTION
5 In the hot tandem mill, in order to roll the roll materials of various kinds of
: product specifications, it is necessary to set the control gain according to the product
specification. On the other hand, there is such a problem that since a model of a rolling
phenomenon and parameters of the model of the rolling phenomenon such as deformation
resistance, friction coefficient, and plate temperature which are used at the time of calculation of
10 the model are inaccurate, an error of the control gain setting is large.
In the tandem mill, the rolling speed of each mill is controlled by a speed control
apparatus. In the case of using the rolling speed as an actuator of the automatic tension control,
the tension control system is designed in consideration of a response of a speed control system
including the speed control apparatus and the rolling mill. However, in the case where the
15 control gain is set to a slightly large value because of the error of the control gain setting as
mentioned above or the case where the high control gain is dare set in order to improve the
control response, a case where the control oscillates due to a response of the speed control
system occurs. This is because although the speed control system is simply approximated as a
second-order lag system, it has a resonant frequency.
20 In this case, there is such a problem that in the case where the tension control
system has performed the control in a step response manner due to a large tension disturbance, a
vibration at the resonant frequency remains continuously (oscillation) or the vibration or
amplitude increases gradually (divergence; it is included in the oscillation hereinbelow). Such a
situation that when there is a tension disturbance (for example, a hardness fluctuation of the roll
25 material or a mechanical vibration of the mill) of frequency components around the resonant
frequency, the tension fluctuation increases also occurs.
There is, consequently, such a problem that in the case where a hot tandem mill is
newly started up, a production of new products is started, or the like, it takes a long time for
adjustment of the tension control, and a stop of the rolling operation or defective products due to
30 defective control that is caused by the excessive or insufficient control gain is caused.
The technique disclosed in the JP-A-5-15913 is a method for previously
suppressing the oscillation and is not suitable as a method of suppressing the oscillation when it
has occurred. The problem mentioned above is not limited to the tandem mill but can similarly
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become a problem so long as it is control of such a plant that the same kind of control is repeated
like a tandem mill and in such a case where a change in control amount at a certain control point
exerts an influence on control of a control point at the front stage.
The invention copes with the above problems and it is an object of the invention
5 to suppress an oscillation of control in which a rolling mill speed of the tension control or the
j like is used as an operation factor even when a control gain is large.
According to an aspect of the invention, there is provided a rolling mill control
apparatus for controlling a tandem mill which rolls a roll material by a plurality of pairs of rolls,
comprising: a rolling speed control unit for controlling rotational speeds of the roll
10 corresponding to a measuring position and the rolls arranged on its upstream side or downstream
side on the basis of a deviation of state amounts which are measured; an oscillation detecting
unit for detecting an oscillation of the measured state amounts; and an oscillation control unit for
changing control responses in the control of the rotational speeds of the roll corresponding to the
measuring position where the oscillation has been detected and the same roll as that of the
15 control of the rotational speeds based on the deviation of the state amounts in the rolls arranged
on its upstream side or downstream side.
According to another aspect of the invention, there is provided a plant control
apparatus for controlling a plant in which the same kind of process is repeated in a plurality of
control subjects, comprising: a state control unit for changing control states of the control subject
20 corresponding to a measuring position and the control subjects arranged on its upstream side or
downstream side on the basis of a deviation of state amounts which are measured; an oscillation
detecting unit for detecting an oscillation of the measured state amounts; and an oscillation
control unit for changing control responses in the change in the control states of the control
subject whose oscillation has been detected and the same control subject as that of the change in
25 the control state based on the deviation of the state amounts in the control subjects arranged on
its upstream side or downstream side.
According to further another aspect of the invention, there is provided a rolling
control method of controlling a tandem mill which rolls a roll material by a plurality of pairs of
rolls, comprising the steps of: controlling rotational speeds of the roll corresponding to a
30 measuring position and the rolls arranged on its upstream side or downstream side on the basis of
a deviation of state amounts which are measured; detecting an oscillation of the measured state
amounts; and changing control responses in the control of the rotational speeds of the roll
corresponding to the measuring position where the oscillation has been detected and the same
roll as that of the control of the rotational speed based on the deviation of the state amounts in
I
!
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the rolls arranged on its upstream side or downstream side.
By using the invention, even when the control gain is large, the oscillation of the
control in which the rolling mill speed of the tension control or the like is used as an actuator can
be suppressed.
5 Other objects, features and advantages of the invention will become apparent
from the following description of the embodiments of the invention taken in conjunction with the
accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
Fig. 1 is a diagram showing a whole construction of a rolling apparatus according to an
10 embodiment of the invention.
Figs. 2Aand 2B are diagrams showing the operation of a looper in the rolling apparatus
according to the embodiment of the invention.
Fig. 3 is a diagram showing a construction of feedback control in a general rolling apparatus.
Fig. 4 is a diagram showing a frequency response of a control gain in the general rolling
15 apparatus.
Figs. 5 A, 5B and 5C are diagrams showing a construction of a convergence, an oscillation, and a
divergence of a state amount due to a difference of the control gains.
Fig. 6 A and 6B are diagrams showing a construction of a speed control system according to the
related art and the embodiment of the invention.
20 Figs. 7 A 7B, 7C and 7D are diagrams showing an example of a step response of the speed
control system.
Figs. 8 A, 8B, 8C and 8D are diagrams showing an example of a closed loop response of the
speed control system.
Fig. 9 is a diagram showing an example of a phase shift and an amplitude change.
25 Figs. 10A, 10B, IOC and 10D are diagrams showing a board diagram of a control example of
interstand tension control.
Fig. 11 is a diagram showing an example of a suppression form of an oscillating state of the
interstand tension control.
Fig. 12 is a diagram showing an example of a case where there is a disturbance of a resonant
30 frequency.
Fig. 13 is a diagram showing a control construction of a tandem mill in the related art.
Fig. 14 is a diagram showing a construction of a stand speed deciding apparatus in the related art.
Fig. 15 are diagrams showing a construction of interstand tension control in the related art.
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Fig. 16 is a diagram showing a construction of the speed control system according to the
embodiment of the invention.
Fig. 17 is a diagram showing a control construction of the tandem mill according to the
embodiment of the invention.
5 Fig. 18 is diagrams showing a construction of interstand tension control according to the
embodiment of the invention.
Fig. 19 is a flowchart showing the operation of a speed response adjustment according to the
embodiment of the invention.
Figs. 20 A and 20B are diagrams showing an adjustment form of a speed response according to
10 the embodiment of the invention.
Figs. 21A and 2 IB are diagrams showing the adjustment form of the speed response according to
the embodiment of the invention.
Fig. 22 is a diagram showing a hardware construction of the interstand tension control according
to the embodiment of the invention.
15 DESCRIPTION OF THE EMBODIMENTS
Embodiment 1
An embodiment of the invention will be described hereinbelow with respect to
tension control between mill stands in a hot mill as an example. Fig. 1 is a diagram showing a
tension control system according to the embodiment. As shown in Fig. 1, in an interstand
20 tension control unit 10, a tension which is applied to a roll material 8 existing between an i-1
stand rolling mill 1 and an i stand rolling mill 2 of a hot tandem mill is detected by a tension
meter 9 disposed in a looper 7 and a speed instruction to an i-1 stand speed control apparatus 11
is changed, thereby controlling a rolling speed of the i-1 stand rolling mill 1.
The looper 7 is constructed by: a looper arm 15 which can be rotated around a
25 looper fulcrum 14 existing at a position which is mechanically fixed; a hydraulic cylinder 13 for
changing a position of a looper roll 16 by rotating the looper arm 15 around the looper fulcrum
14; and a cylinder position detector 17 for detecting a cylinder position. By pushing the roll
material 8 upward, the looper roll 16 receives the tension which is applied to the roll material 8.
By measuring the force which is applied to the looper roll 16 by the tension meter 9, the
30 interstand tension control unit 10 obtains the tension which is applied to the roll material 8.
The operation of the looper 7 is shown in Figs. 2 A and 2B. When a front edge
portion 30 of the roll material exists between the i-1 stand rolling mill 1 and the i stand rolling
mill 2, if the looper roll 16 collides with the roll material front edge portion 30, a machine is
i
1
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broken. Therefore, the looper roll 16 is on standby at a position lower than a passing position
of the roll material 8 as shown in Figs. 2 A. When the roll material front edge portion 30
reaches the i stand rolling mill 2, the looper roll 16 is moved to such a position that the roll
material 8 is lifted up as shown in Figs. 2B, so that the tension which is applied to the roll
5 material 8 can be measured by the tension meter 9.
Since the tension of the roll material 8 is propagated from the looper roll 16 to the
hydraulic cylinder 13 through the looper arm 15, when the tension of the roll material 8
fluctuates, a difference occurs between this tension and a pressure of the hydraulic cylinder 13
and the cylinder position changes. Thus, the position of the looper roll 16 changes. Since the
10 position fluctuation of the looper roll 16 becomes a tension fluctuation and also exerts an
influence on the stability of the rolling operation, looper position control adapted to make the
position constant is made. A looper position control apparatus 20 operates and controls the
pressure of the hydraulic cylinder 13 by using the cylinder position measured by the cylinder
position detector 17 so that the position of the looper roll 16 becomes constant.
15 Fig. 3 is a block diagram showing a construction of interstand tension control in
the hot tandem mill in the related art. The interstand tension control unit 10 outputs a control
instruction to the i-1 stand speed control apparatus 11 by using the proportional integral control
so as to eliminate a deviation between a tension instruction and a tension result, and changes an
i-1 stand rolling speed. When the i-1 stand rolling speed changes, the tension result changes by
20 a speed - tension response 31. This fluctuation is detected by the tension meter 9 and used as a
tension result.
The fluctuation of the tension result becomes a pressure fluctuation of the
hydraulic cylinder 13 by a plate tension - cylinder pressure 32 serving as a mechanical system.
However, when the pressure of the hydraulic cylinder 13 fluctuates, the cylinder position
25 changes, the looper position fluctuates by a looper mechanical system 35, and an interstand plate
road length fluctuates eventually by a looper position - interstand plate road length 34.
The interstand plate road length fluctuation becomes a tension fluctuation by a
plate road length change - tension response 33 and the tension result fluctuates. The speed -
tension response 31 is shown by the following equation (1). The plate road length change -
30 tension response 33 is shown by the following equation (2).
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Al KffV
= ~— (1 )
AT KtfLP-S
= - — ^ (2)
AV 1+Tt f -S
The speed - tension response 31 and the plate road length change - tension
response 33 are caused by a rolling phenomenon and change in dependence on a material, a plate
thickness, a rolling speed, and the like (hereinbelow, called a rolling schedule) of the roll
material 8. On the contrary, if their values are known, a response of the i-1 stand speed control
5 apparatus 11 can be approximated in a second-order lag system by the following equation (3).
—, 2 (3)
Sz + 2?:wnS+ and changes a rolling mill speed in accordance with a moment J of inertia of the
mill roll.
Fig. 6B is the block diagram of the speed control system in the case where an FFASR
(Feed Forward ASR) 903 is provided. The FF-ASR 903 includes an FF-ASR instruction
compensation 904 and an FF-ASR current compensation 905. In the FF-ASR instruction
25 compensation 904, by inserting the first-order lag of a time constant TFF into the speed
instruction, a first-order lag response according to the time constant TFF is set. In the FF-ASR
instruction compensation 904, in response to the speed instruction in which the first-order lag of
the time constant TFF has been inserted, an acceleration/deceleration current instruction
corresponding thereto is formed by a differentiation and a conversion gain TM- If the operation
30 of the FF-ASR current compensation 905 is proper, since the speed instruction to the FB-ASR
900 serving as an output of the FF-ASR 903 and the speed result coincide, the FB-ASR 900
hardly operates (a slight operation occurs due to a vain time or the like of the current control
system).
Figs. 7 A to 7D are diagrams showing step responses of the speed control system.
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Fig. 7A shows the response in the case of using the normal speed control system. In this
instance, the control response of the FB-ASR 900 sets a gain cross frequency ©c of an open-loop
transfer function into ©c = 20 [rad/s]. A broken line indicates the speed instruction which was
given in a step-like manner, a solid line indicates the speed result of the speed control system,
5 and an alternate long and short dash line indicates the speed instruction in the case where the
first-order lag system set to ©FF = 20 [rad/s] has been inserted into the speed instruction. It is
the same as an output of the FF-ASR instruction compensation 904 in the speed control system
with the FF-ASR.
Fig. 7B shows the response in the case where the FF-ASR 903 is provided and
10 shows a result in the case where the FF-ASR current compensation 905 was executed by 100%.
In this case, the speed result can be made to coincide with the output of the FF-ASR instruction
compensation 904. Fig. 7C shows the response in the case where the FF-ASR current
compensation 905 is not executed (0% compensation amount). The response deteriorates by an
amount in which the step-like speed instruction has become the first-order lag system by the FF-
15 ASR instruction compensation 904. Fig. 7D shows the step response in the case where the
response of the FF-ASR is set to ©FF = 40 [rad/s]. Since the FF-ASR current compensation 905
has been executed by 100%, the control response coincides with the first-order lag of 40 [rad/s].
Figs. 8 A to 8D show board diagrams of closed loop responses of the speed control
system corresponding to Figs. 7 A to 7D. By changing the response ©FF of the FF-ASR 903 or
20 the gain of the FF-ASR current compensation 905, the response of the speed control system can
be changed.
With respect to the control output of the interstand tension control unit 10 in Fig.
3, the phase lag and magnitude are converted by the frequency by the i-1 stand speed control
apparatus 11, becomes a tension fluctuation amount by the control in the speed - tension
25 response 31, and corrects the tension result. To the tension result, as for the tension fluctuation
amount by the control, a different phase shift occurs by the frequency. However, a resonant
point is determined by a balance between the phase shift and an attenuation amount of the actual
speed fluctuation to the speed instruction.
A sine wave is given as Ax, a phase difference is added to Ax, a resultant Ax is
30 multiplied with a gain, and a resultant value is subtracted from Ax, so that Ay is obtained. Fig.
9 shows how Ay changes from Ax. In Fig. 9, a solid line indicates a case where the gain is
equal to 1.0, a broken line indicates a case where the gain is equal to 0.5, and a dotted line
indicates a case where the gain is equal to 0.3, respectively. As the phase shift increases, the
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more an amplitude of Ay increases. For example, when a phase difference is equal to 180° and
the gain is equal to 1 time, Ay is increased to 2 times. Even if the operator intends to eliminate
the control deviation Ax by the relation between the gain and the phase, a case where Ay
increases occurs eventually. Even when the phase difference increases, if the gain decreases,
5 Ay decreases.
Aboard diagram of the tension control in the case where speed control
apparatuses shown in Figs. 7 A to 7D and Figs. 8 A to 8D are used as an i-1 stand speed control
apparatus 11 in the tension control of the hot tandem mill shown in Fig. 3 is shown in Fig. 10.
The control gain of the interstand tension control unit 10 is set to be constant. By changing the
10 response of the FB-ASR 900, frequency characteristics of the interstand tension control can be
changed. In accordance with it, the resonant point also fluctuates.
As mentioned above, even if the response of the FB-ASR 900 is constant, by
changing the response of the FF-ASR 903 serving as a response to the control output of the
interstand tension control unit 10, a frequency at the resonant point can be changed. By using
15 it, the control in which the interstand tension control has been oscillated at the resonant point can
be suppressed.
An example in the case where the interstand tension control unit 10 of the hot
tandem mill shown in Fig. 3 is set to the gate at which the tension deviation oscillates and is
oscillated by the step response, thereafter, in order to change the response of the FF-ASR 903,
20 the gain of the FF-ASR current compensation 905 is changed from 0 to 0.1 is shown in Fig. 11.
It will be understood that by changing the gain of the FF-ASR current correction, the resonant
frequency is shifted, so that the oscillating state is eliminated.
Fig. 12 shows an example of a case where an interstand tension disturbance of a
resonant frequency component has occurred. In Fig. 12, the tension disturbance is increased by
25 the interstand tension control unit 10. In this case, when the FF-ASR current correction is
changed from 0% to 100%, since the resonant frequency is shifted, a control effect is obtained.
In this case, the control effect is obtained because the resonant frequency is shifted in such a
direction that it rises. However, even by shifting the resonant frequency in such a direction that
it decreases, control can be made so as not to increase the tension disturbance (the control effect
30 attenuates). In the case where a problem occurs (the resonant frequency approaches a resonant
frequency of the mechanical system) if the resonant frequency is shifted to a high direction, it is
desirable to shift the resonant frequency to such a direction that it decreases.
As an example of the hot tandem mill, an interstand tension control system about
a 4-stand tandem mill is shown in Fig. 13. As shown in Fig. 13, interstand tension control 831
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to 833 are executed to a rolling mill constructed by #1 to #4 stand rolling mills 801 to 804, #1 to
#4 stand speed control apparatuses 811 to 814, a #1 - #2 interstand tension meter 841, a #2 - #3
interstand tension meter 842, and a #3 - #4 interstand tension meter 843.
The i-1 stand speed control apparatus 11 described in Fig. 6A corresponds to the
5 #1 to #4 stand speed control apparatuses 811 to 814 in Fig. 13. In a speed reference generating
apparatus 850, a speed VR4 of the #4 stand rolling mill 804 is decided. As a deciding method, a
manual operation by the operator or an automatic acceleration/deceleration according to the
rolling state is considered.
In the mill, since exit side plate thicknesses in the mill stands differ, the rolling
10 speeds in the mill stands differ. Since the exit side plate thickness of each mill stand and the
interstand tension setting are decided in dependence on the product specification of the roll
material, a forward slip of each mill stand is decided in accordance with the rolling model. By
using the forward slips, calculations as shown in Fig. 14 are performed in stand speed deciding
apparatuses 821 to 823, thereby deciding a speed setting value VRI0 to each mill stand. Where,
15 hi shown in Fig. 14 denotes an exit side plate pressure of the #i stand and f; indicates a forward
slip of the #i stand.
As shown in Fig. 15, the interstand tension control 831 to 833 obtain deviations
between tension results Ti2fb, T23&, and T34fb from the interstand tension meters 841 to 843 and
set tension targets T^ref, T23ref, and T34ref and obtain ATR (tension control) speed instructions by
20 the proportional integral control, respectively. The foregoing tension targets are set by a
predetermined method such as table lookup, model calculation, or the like in accordance with the
product specification of the roll material.
In the tandem mill, since it is important to construct in such a manner that even
VR4 changed by the acceleration/deceleration, a speed ratio VRi/Viu+i of the mill stands does not
25 fluctuate, as for tension control instructions, values as show by the following equation(6) are
output as tension control instructions on the basis of the speed ratio. The tension control
instructions which were output as mentioned above is multiplied with each mill stand speed
reference VRi0 and speed instructions VRiref, VR2ref, VR3ref, and VR4ref to the mill stands are finally
determined, respectively.
AVroATR AVRZATR , AVr e A 1R
1 + > 1 + f 1 + (6)
VR10 VR20 VR3O
30 For example, if the # 2 - 3 interstand tension control changed the #2 mill stand
speed, in order to prevent that a speed ratio RRI/VR2 of the #1 mill stand and the #2 mill stand
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fluctuates in accordance with it, the #1 mill stand speed is also changed at the same ratio.
Consequently, a relation of the following equation (7) is satisfied.
, AVr e A TR
V„u,-(H— )
Mao _ VRIO
V R 2 0 - ( 1 + — )
VR20
Thus, since the ratio between the #1 mill stand speed and the #2 mill stand speed
does not change, no influence is exerted on the tension between the #1 mill stand and the #2 mill
5 stand and on the #2 mill stand exit side plate thickness. This is called "successive". In the 4-
stand tandem mill, there are successive 835 (Fig. 13) of a control output of the #3-4 interstand
tension control 833 and successive 836 (Fig. 13) of a control output of the #2-3 interstand
tension control 832. As for successive, there is also a case where it is not executed.
When the above points are summarized, speed instructions to the speed control
10 apparatuses 811 to 814 of the mill stands are expressed by the following equations (8) to (11).
AVmATR AVr e f l l R AVRSATR V
VR1Pef=Vmo- 1 + — 1+ v • 1+ v . (8)
VRIO J I VR2Q J I vreo J
V R ^ ^ V R J B - H ' 1 + - — (9)
L VR2° J I VRM J
VR3ref=VR3B- 1+ (10)
L Vrao J
V»lw=VW0 (11)
Each of the speed instructions to the mill stand speed control apparatuses 811 to
814 is obtained by multiplying the three kinds of speed reference, interstand tension control
signal, and successive.. As mentioned before, in order to shift the resonant frequency of the
speed control system, it is necessary that the response of the FF-ASR 903 is changed only with
15 respect to each interstand tension control instruction, the speed reference is set to a response
which is common in each mill stand, and the successive is set to the same response as that for the
interstand tension control output serving as a source.
For example, although the successive of the #3-4 interstand tension control
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output is executed to the #1 stand and the #2 stand, it is executed in accordance with the response
of the speed control system of the #3-4 interstand tension control output, and although the
successive of the #2-3 interstand tension control output is executed to the #1 stand, it is
executed in accordance with the response of the speed control system of the #2-3 interstand
5 tension control output.
A construction of a speed control system in the invention to realize it is shown in
Fig. 16. When considering the 4-stand tandem mill, in the #1 stand, it is necessary to input
three control instructions AVi, AV2, and AV3 of an amount of the successive of the #3-4
interstand tension control, an amount of the successive of the #2-3 interstand tension control,
10 and the #1-2 interstand tension control output and a #1 stand speed reference Vo. Therefore, in
Fig. 16, besides the speed reference Vo, as control instructions, AVi, AV2, and AV3, a response
time constant TFFO of the speed reference, and response time constants TFFI, TFF2, and TFF3 of the
control instructions are inputted. In the case of using the construction as shown in Fig. 16, the
instruction of the FF-ASR is expressed by the following equation (12) and the first-order lag
15 response can be changed by each control instruction.
1 f AV, 1 + TFFD-s1
VFFrtf=V0 1+
1 + TFHJ-S V„ 1 + T m -S
( 1 2 )
T AV2 H-TFFP-s"l f AV3 l + Tpre-sl
V0 1 + TFf2-S " + V0 1+TW-S
V J V J
By performing the FF-ASR current compensation 905 by using VFFref, a speed
result Vfb can be used as an FF-ASR instruction VFFref- In this case, if a gain of the FF-ASR
current compensation 905 is changed, responses to the speed reference and all control
instructions change. Therefore, in order to change the control responses every control
20 instructions AVi, AV2, and AV3, the first-order lag time constants TFFI, TFF2, and TFF3 to the
control instructions are changed.
Fig. 17 is a diagram showing an interstand tension control system with respect to
the 4-stand tandem mill according to the embodiment. As shown in Fig. 17, in the interstand
tension control system according to the embodiment, #1 to #4 stand speed control apparatuses
25 611 to 614 are used in place of the #1 to #4 stand speed control apparatuses 811 to 814.
Interstand tension control 631 to 633 are used in place of the interstand tension control 831 to
833. The #1 to #4 stand speed control apparatuses 611 to 614 correspond to the speed control
system described in Fig. 16.
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Fig. 18 is a diagram showing details of the interstand tension control 631 to 633.
As shown in Fig. 18, as inputs described in Fig. 16, the interstand tension control 631 to 633
according to the embodiment set control outputs into speed change amounts AVR^ATR, AVR23ATR,
and AVR34ATR and output response settings T^ATRFF, T23ATRFF, and T34ATRFF for the speed control
5 apparatuses 611 to 614, respectively. That is, each of the interstand tension control 631 to 633
functions as a rolling speed control unit and an oscillation control unit.
As shown in Fig. 17, the speed change amounts AVRI2ATR, AVR23ATR, and
AVR34ATR and the response settings THATRFF, T23ATRFF, and T34ATRFF are input not only to the
speed control apparatuses of the roll arranged just before the detecting position of the tension
10 results, that is, the roll according to the measuring position of each tension result but also to the
speed control apparatuses of the rolls arranged on their upstream side. For example, the tension
result between the #3 stand rolling mill 803 and the #4 stand rolling mill 804 is used not only for
the control of the #3 stand rolling mill which should directly reflect the tension result to the
rolling speed but also for the control of the #2 stand rolling mill 802 and the #1 stand rolling mill
15 801 arranged on its upstream side. Therefore, by adjusting the speed control of the roll of justbefore,
the oscillation of the tension result can be suppressed. Further, by adjusting the speed
control of the rolls on the upstream side, an influence occurring between other rolls based on the
adjustment of the speed control of the roll of just-before can be cancelled.
Fig. 19 is a flowchart showing the operation of a speed response adjusting
20 apparatus 660 shown in Fig. 18. As shown in Fig. 19, the speed response adjusting apparatus
660 performs an FFT (frequency analysis) of the tension result at a predetermined periodic
interval (for example, at an interval of 1 second) (SI901) and sums frequency component
intensities in a resonant frequency region (for example, ±5% around the resonant frequency as a
center) which is preliminarily calculated by the control setting values of the speed control system
25 and the interstand tension control system (SI902). When it exceeds a predetermined threshold
value (for example, 10% of the tension setting value) (S1903/YES), it is regarded that the
resonance of the speed control system has occurred, and the apparatus 660 changes the control
response by +AT (S1904). That is, in S1902 and S1903, the speed response adjusting apparatus
660 functions as an oscillation detecting unit. In SI904, the speed response adjusting apparatus
30 660 functions as an oscillation control unit.
This AT corresponds to AT^ATRFF, AT23ATRFF, and AT34ATRFF shown in Fig. 17 and
is applied not only to the speed control of the stands on the upstream side between the stands in
which the oscillation of the tension has been detected but also to the speed control of the stands
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on the further upstream side. Thus, even if the speed control between the stands was adjusted
by the tension oscillation between the stands of any one pair, an influence occurring on the
tension between the stands of another pair can be previously cancelled.
A value of 1 [rad/s] or the like is preliminarily set into AT which is changed. In
5 the case where the interstand tension control resonated and the tension result fluctuated, the
vibration is suppressed by the change in control response. However, in the case where the
tension disturbance of the resonant frequency component occurred, the vibration is suppressed
only to a certain extent. Therefore, the vibration is not equal to a value less than the threshold
value and there is a possibility that the control response is changed without limitation.
10 Therefore, upper and lower limit values are set into the control response and a change exceeding
the upper and lower limit values is not performed. The upper and lower limit values are set to,
for example, a lower limit of 0.5 time and an upper limit of 2.0 times or the like of the standard
setting value which is determined from the facility specifications.
Such an operation is repeated until the rolling of one roll material is completed
15 (S1905/NO). When the rolling of one roll material is completed (S1905/YES), the control
response is initialized to the predetermined standard value (S1906).
As for a discrimination about whether the control response is set to +AT or -AT at
the time of changing the control response, +AT is desirable from such a viewpoint that the
control response is not lowered. However, since there are upper and lower limit values of the
20 control response, a method whereby if it was once fully raised up to the upper limit side, it is
subsequently lowered to the lower limit side as a - side, and it is raised to the upper limit side
again as a + side is also considered.
An outline of the operation of a speed response adjusting apparatus is shown in
Figs. 20A and 20B and Figs. 21A and 2IB. Fig. 20A is the diagram showing a change in rolling
25 speed of the rolling operation. Fig. 20B is the diagram showing an example of the tension
result in a range shown by an ellipse of a broken line in Fig. 20 A. In Fig. 20B, a case where a |
tension oscillation as shown in the diagram has occurred is considered. In this case, Fig. 21A is 1
the diagram showing a result obtained by executing the FFT by using the tension result for 2
seconds at a point of time of timing ti in Fig. 20B. As mentioned above, by using the FFT, the |
30 oscillation can be easily detected. I
Assuming that an FFT result exceeds the threshold value in the resonant |
frequency region as shown in Fig. 21 A, the control response is changed. A case of changing f.
the control response by -AT (0.05) is considered as an example here. Fig. 2IB is the diagram j
I
showing an FFT result at a point of time of timing t2 in Fig. 20B. The sampling is performed [
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every second, the control response is continuously lowered, and assuming that the FFT result at
the point of time of timing t2 becomes lower than the threshold value in the resonant frequency
region as shown in Fig. 2IB, a process for changing the control response is stopped at this point
of time. By such a process, the oscillation can be preferably suppressed. After completion of
5 the rolling, the control response is initialized to the preset standard value, thereby preparing for
the rolling of the next roll material.
By executing such processes as mentioned above, in the case of executing the
interstand tension control using the front stage stand speed as an actuator, the interstand tension
result is monitored, the oscillation around the resonant frequency of the speed control system is
10 detected, and the response of the speed control system is changed, so that the oscillation can be
suppressed. By detecting an appearing phenomenon of the control system early, the oscillation
can be prevented without a deterioration of a work efficiency such as a decrease in rolling speed
or the like and without substantially sacrificing the response of the interstand tension control.
Therefore, the improvement of the work efficiency and the improvement of the product quality
15 can be accomplished.
The control construction of the interstand tension control as shown in Fig. 18 is
t
realized by a combination of software and hardware. The hardware to realize the functions of |
the interstand tension control according to the embodiment as shown in Fig. 18 will now be |
described with reference to Fig. 22. Fig. 22 is a block diagram showing the hardware I
20 construction of the interstand tension control according to the embodiment. As shown in Fig. 2, 1
t
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an information processing apparatus according to the embodiment has a construction similar to |
that of an information processing terminal such as general server, PC (Personal Computer), or
the like. I
That is, in the information processing apparatus according to the embodiment, a 1
25 CPU (Central Processing Unit) 101, a RAM (Random Access Memory) 102, a ROM (Read Only
Memory) 103, an FfDD (Hard Disk Drive) 104, and an I/F 105 are connected through a bus 108. I
An LCD (Liquid Crystal Display) 106 and an operating unit 107 are connected to the I/F 105. I
The CPU 101 is arithmetic operating means and controls the operation of the 1
whole information processing apparatus. The RAM 102 is a volatile storage medium from/into 1
30 which information can be read out and written at a high speed. The RAM 102 is used as a work I
area when the CPU 101 processes the information. The ROM 103 is a read only non-volatile I
storage medium. A program such as firmware or the like has been stored in the ROM 103. I
The HDD 104 is a non-volatile storage medium into/from which information can 1
be written and read out. An OS (Operating System), various kinds of control programs, an |
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application, a program, and the like have been stored in the HDD 104. The I/F 105 connects
the bus 108 and various kinds of hardware, network, and the like and controls them. The I/F
105 is also used as an interface for allowing apparatuses/devices to transmit and receive
information or inputting information to the rolling mill.
5 The LCD 106 is a visual user interface for allowing the operator to confirm the
state of the information processing apparatus. The operating unit 107 is a user interface such as
keyboard, mouse, or the like for allowing the operator to input information to the information
processing apparatus. In such a hardware construction, the program stored in the ROM 103, the
HDD 104, or a recording medium such as an optical disk (not shown) or the like is read out into
10 the RAM 102 and the CPU 101 executes arithmetic operations in accordance with the program,
so that a software control unit is constructed. The functions of the control construction of the
interstand tension control according to the embodiment are realized by a combination of the
software control unit constructed as mentioned above and the hardware.
Other Embodiments
15 Although the oscillation of the interstand tension control has been detected by the
FFT (frequency analysis) in the foregoing embodiments, the oscillation may be detected by
another means, for example, from the correlation with the sine wave of the resonant frequency or
from the phase relation between the speed instruction and the speed result and the control
response of the speed control system can be also changed.
20 In the foregoing embodiments, the oscillation of the interstand tension control has
been suppressed by detecting the oscillation of the interstand tension control from the tension
result and changing the control response. However, even by periodically changing the response
of the speed control system regularly within a predetermined range or at random, if the interstand
I
tension control has been oscillated, the oscillation can be suppressed. 25 Although the foregoing embodiments have been described with respect to the
interstand tension control of the 4-stand hot tandem mill, a similar method can be applied to a
hot tandem mill with an arbitrary number of mill stands or a cold tandem mill with an arbitrary
[
number of mill stands. Although the foregoing embodiments have been described with respect
to the interstand tension control using the speed as an actuator, a similar method can be also
30 applied to arbitrary control using the speed as an actuator, for example, plate thickness control or
the like. [
For example, in the case of the plate thickness control, the exit side plate j
j
thickness of each stand is used as a state amount of the measurement subject so as to control the I
rolling speed of the #3 stand rolling mill 803 on the basis of the exit side plate thickness of the j
ii.
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#3 stand rolling mill 803, and the rolling speed of the stand is controlled on the basis of the I
measured exit side plate thickness. That is, the exit side of each stand is a measuring position 1
and the roll whose exit side plate thickness has been measured is a roll corresponding to the 1
measuring position. The state amount control based on the exit side plate thickness of the #3 I
5 stand rolling mill 803 is used not only for the #3 stand rolling mill 803 but also for the #2 stand I
rolling mill 802 and the #1 stand rolling mill 801 arranged on its upstream side. I
Although the foregoing embodiments have been described with respect to the hot I
tandem mill using the speed as an actuator, a similar method can be also applied to a control
system using the speed of an arbitrary plant as an actuator. That is, a similar effect can be
10 obtained by applying the control according to the foregoing embodiments so long as it is control
of such a plant that the same kind of control is repeated like a tandem mill as mentioned above
and in such a case where a change in control amount at a certain control point exerts an influence
on control of a control point at the front stage. Although the foregoing embodiments have been
described with respect to the case where the speed control is adjusted by the speed control
15 apparatus, a similar method can be also applied to the adjustment of the speed control by
executing such an adjustment by a computer side for performing the tension control or plate
thickness control.
It should be further understood by those skilled in the art that although the
foregoing description has been made on embodiments of the invention, the invention is not
20 limited thereto and various changes and modifications may be made without departing from the
spirit of the invention and the scope of the appended claims. I.
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, • W6833
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CLAIMS:
1. A rolling mill control apparatus for controlling a tandem mill which rolls a roll
material (8) by a plurality of pairs of rolls, comprising:
a rolling speed control unit (631, 632, 633) for controlling rotational speeds of the
roll corresponding to a measuring position and the rolls arranged on its upstream side or
downstream side on the basis of a deviation of state amounts which are measured;
an oscillation detecting unit (660) for detecting an oscillation of the measured
state amounts; and
an oscillation control unit (660) for changing control responses in the control of
the rotational speeds of the roll corresponding to the measuring position where the oscillation has
been detected and the same roll as that of the control of the rotational speeds based on the
deviation of said state amounts in the rolls arranged on its upstream side or downstream side.
2. The rolling mill control apparatus according to claim 1, wherein said oscillation
detecting unit (660) detects the oscillation of said state amounts on the basis of a result of a
frequency analysis of results of the state amounts which are measured.
3. The rolling mill control apparatus according to claim 1, wherein:
said oscillation detecting unit (660) repeatedly detects the oscillation of said state
amounts at every predetermined interval, and
said oscillation control unit (660) gradually and continuously changes said control
response while said oscillation is detected and, when said oscillation is not detected, stops the
change in said control response.
4. A plant control apparatus for controlling a plant in which the same kind of process
is repeated in a plurality of control subjects, comprising:
a state control unit (831,832,833) for changing control states of the control subject
corresponding to a measuring position and the control subjects arranged on its upstream side or
downstream side on the basis of a deviation of state amounts which are measured;
an oscillation detecting unit (660) for detecting an oscillation of the measured
state amounts; and
an oscillation control unit (660) for changing control responses in the change in
the control states of the control subject whose oscillation has been detected and the same control
subject as that of the change in the control state based on the deviation of said state amounts in f
the control subjects arranged on its upstream side or downstream side. |
5. A rolling control method of controlling a tandem mill which rolls a roll material I
(8) by a plurality of pairs of rolls, comprising the steps of: 1
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controlling rotational speeds of the roll corresponding to a measuring position and
the rolls arranged on its upstream side or downstream side on the basis of a deviation of state
amounts which are measured;
detecting an oscillation of the measured state amounts; and
changing control responses in the control of the rotational speeds of the roll
corresponding to the measuring position where the oscillation has been detected and the same
roll as that of the control of the rotational speed based on the deviation of said state amounts in
the rolls arranged on its upstream side or downstream side.
6. A rolling mill control apparatus, substantially as herein described with reference
to accompanying drawings and examples.
7. A plant control apparatus, substantially as herein described with reference to
accompanying drawings and examples.
8. A rolling control method, substantially as herein described with reference to
accompanying drawings and examples.