1. A rolling control apparatus for controlling a rolling mill (2, 3) which rolls material between at least a pair of rolls (301), the rolling control apparatus comprising: a rolling condition change recognition unit (103 or 104) for recognizing that rolling conditions which influence the quality of rolled material change non-linearly; a time-sequential change pattern storage unit (102) for storing previously generated time-sequential change patterns in order to change parameters related to the rolling operations of the rolling mill (2, 3) in accordance with the non-linear changes of the rolling conditions; a time-sequential change pattern acquisition unit (103) for acquiring time-sequential change patterns corresponding to the non-linear changes in the recognized rolling conditions when it is recognized that the rolling conditions change non-linearly; and a time-sequential change pattern output unit (101) for outputting the acquired time-sequential change patterns in order to control roll gap and roll speed of the rolling mill.

2. A rolling control apparatus as claimed in Claim 1, wherein the rolling conditions include at least any one of the strip thickness or strip width of the rolled material, target values in rolling and the height of a looper (200) for supporting the rolled material; and the parameters related to the rolling operation include at least any one of the roll gap or rolling speed of the pair of rolls (301), the height of the looper (200), and the positions of an adjusting unit (301, 302, 304) arranged in accordance with the strip width of the rolled material.

3. A rolling control apparatus as claimed in Claim 1, wherein the time-sequential change pattern storage unit (102) stores plural kinds of time-sequential change patterns in accordance with the non-linear changes in the plural kinds of rolling conditions; and the time-sequential change pattern acquisition unit (103) determines which one of the plural kinds of time-sequential change patterns is to be acquired.

4. A rolling control apparatus as claimed in Claim 3, wherein the time-sequential change pattern acquisition unit (103) determines which one of the plural kinds of time-sequential change patterns is to be acquired on the basis of the rolling conditions and data on the position relative to the rolling mills (2, 3) of the point on the rolled material at which the rolling conditions are to be changed.

5. A rolling control apparatus as claimed in Claim 3, wherein the time-sequential change pattern acquisition unit (103) determines a time-sequential change pattern to be acquired on the basis of the thickness of the material fed to the pair of rolls (301).

6. A rolling control apparatus as claimed in Claim 3, wherein time-sequential change pattern storage unit (102) stores the plural kinds of time-sequential change patterns in accordance with the non-linear changes in the rolling conditions of different kinds whose modes of change in the rolling target values are different.

7. A rolling control apparatus as claimed in Claim 1, wherein the time-sequential change pattern storage unit (102) stores plural kinds of time-sequential change patterns which are different from one another in terms of a condition of the deviation from a preset value for the material fed to the pair of rolls (301); and the time-sequential change pattern acquisition unit (103) determines a time-sequential change pattern to be acquired on the basis of the thickness of the material fed to the pair of rolls (301).

8. A rolling control apparatus as claimed in Claim 1, wherein the rolling condition change recognition unit (104) recognizes that the rolling conditions changes non-linearly in accordance with the change in the rolling target values.

9. A rolling control apparatus as claimed in Claim 1, wherein the rolling condition change recognition unit (104) recognizes that the rolling conditions changes non-linearly on the basis of data on the position relative to the rolling mills (2, 3) of the point on the rolled material at which the rolling conditions are to be changed.

10. A rolling control apparatus as claimed in Claim 1, wherein the rolling condition change recognition unit (104) recognizes that the rolling conditions changes non-linearly on the basis of the thickness of the material fed to the pair of rolls (301).

11. A rolling control apparatus as claimed in Claim 1, wherein the time-sequential change patterns stored in time-sequential change pattern storage unit (102) are generated through simulation by a rolling simulator.

12. A rolling control apparatus as claimed in Claim 1, wherein the time-sequential change patterns stored in time-sequential change pattern storage unit (102) are those for the respective control periods of the rolling control apparatus.

13. A rolling control apparatus as claimed in Claim 1, wherein the time-sequential change pattern is that which is used to change at least one of the tension exerted on the material fed to the pairs of rolls (301) and the tension exerted on the material rolled by and delivered from the pair of rolls (301).

14. A rolling control apparatus as claimed in Claim 1, including a pair of rolling stands (2, 3) so that rolled material delivered from a first rolling stand is fed to a second rolling stand, wherein the time-sequential change pattern is that which is used to change the tension exerted on the rolled material delivered from the first rolling stand and fed to the second rolling stand. is. A rolling control method for controlling a rolling mill (2, 3) which rolls material between at least a pair of rolls (301), the rolling control method comprising: a step of recognizing that rolling conditions which influence the quality of rolled material change non-linearly; a step of acquiring, when it is recognized that the rolling conditions change non-linearly, those time-sequential change patterns which correspond to the non-linear changes in the recognized rolling conditions, from a storage unit (102) that stores previously generated time-sequential change patterns in order to change parameters related to the rolling operation of the rolling mill (2, 3) in accordance with the non-linear change in the rolling conditions; and a step of outputting the acquired time-sequential change patterns in order to control the parameters.

16. A rolling control program for controlling a rolling mill (2, 3) which rolls material between at least a pair of rolls (301), the rolling control program causing an information processing apparatus to execute: a step of recognizing that rolling conditions which influence the quality of rolled material change non-linearly; a step of acquiring, when it is recognized that the rolling conditions change non-linearly, those time-sequential change patterns which correspond to the non-linear changes in the recognized rolling conditions, from a storage unit (102) that stores previously generated time-sequential change patterns in order to change parameters related to the rolling operation of the rolling mill (2, 3) in accordance with the non-linear changes in the rolling conditions; and a step of outputting the acquired time-sequential change patterns in order to control the parameters.

17. A rolling control apparatus for controlling a rolling mill, substantially as herein described with reference to accompanying drawings and example.

18. A rolling control method for controlling a rolling mill, substantially as herein described with reference to accompanying drawings and example.

19. A rolling control program for controlling a rolling mill, substantially as herein described with reference to accompanying drawings and example.

BACKGROUND OF THE INVENTION
This invention relates to a rolling control apparatus, a rolling control method and a rolling control program, and more particularly to the control of a rolling control apparatus in which rolling conditions are varied.
The operation of rolling material by a rolling mill is controlled by controlling the tension exerted on the material to be rolled and the rolling force through the control of the roll gap between the upper and lower work roll, and the roll speeds at the installations on entry and delivery side of the rolling mill. In the rolling operation, feedback control is employed wherein the roll gap and the roll speed, which are the manipulated variables of the rolling mill, are manipulated in accordance with predetermined change patterns, whereas the thickness and tension of the material to be rolled, and the rolling force, which are the control state variables of the rolling mill, are maintained at preset values.
The method in which the roll gap and the roll speed are changed in response to the changes in the thickness of the material to be rolled, the target thickness and the conditions of rolling operation, is realized by providing, in a feed-forward manner, time-sequential change patterns in which the command values for the roll gap and the roll speed are changed with the lapse of time. In this case, the time-sequentially changing patterns supplied to the control actuators were those patterns which were able to be easily generated by an integrator installed in the control unit used generally in a rolling mill.
As such a technique using feed forward control is known a method in which, with a rolling mill resorting to a former process and a later process, the values for control in the later process are determined on the basis of the result of measurement on the rolled material in the former process, (e.g., see JP-A-7-75811 or JP-A-9-122723) Also, a method is disclosed in, for example, JP-A-6-234010, in which the delay in response is obtained by calculating the difference in phase between the feed forward command value and the position under actual pressure in order to make the time instant at which the control value obtained from the feed forward is supplied to the rolling mill, coincident with the rolling position that the control value indicates.
The techniques disclosed in JP-A-7-75811 and JP-A-9-122723 resort to the former and later processes, and aim at taking disturbance in the former process into consideration, whereas the technique disclosed in JP-A-6-234010 makes it objective to suitably
perform a feed forward control on the basis of the result of detecting the thickness of strip on the entry side of the rolling mill. On the other hand, the object of this invention is to properly control the rolling operation in which rolling conditions are changed. Hence, those techniques disclosed in the prior art documents are different in purpose from that disclosed in this invention.
SUMMARY OF THE INVENTION
In order to change the thickness and tension of rolled material, which are the control state variables of the rolled material, by changing the operating conditions of a rolling mill, the roll speed and the roll gap at the control actuators of the rolling mill are usually manipulated. In general, the changes in thickness and tension occurring in control at the control actuators are non-linear since rolling phenomenon is complicated. In spite of this fact, the time-sequential change patterns, which can be generated by using an integrator according to a conventional technique, are merely a simple ramp-shaped change pattern or an S-curved change pattern that smoothes the start and end of change.
With these time-sequential change patterns, however, it is difficult to operate a rolling mill so that the changes in delivery strip thickness, delivery strip speed and entry strip speed, that are the control state variables of the rolling mill, can be prevented from following the non-linear phenomenon. Further, since the change in strip speed causes the changes in tension, which in turn causes the changes in strip thickness, delivery strip speed and entry strip speed, then it is difficult to change the operating conditions in rolling mill while the differences of the actual strip thickness and the actual tension from the corresponding preset values are being kept minimized. As a result, adverse effects such as deterioration in the quality of rolled material and unexpected halt of rolling mill operation may be incurred.
In view of the above adverse effects, the changes in operating conditions to be taken into consideration may include all the changes that influence rolling phenomenon, that is, not only the changes in the strip speed or tension as mentioned above but also the changes in the strip width of rolled material and the positions of loopers which are located between rolling mills arranged in tandem layout, to support the rolled material.
The object of this invention is to reduce the difference of the actual values of such control state variables for rolling mills as strip thickness and tension from the corresponding preset values in the case where the opening conditions of a rolling mill is changed.
According to one aspect of this invention, there is provided a rolling control apparatus for controlling a rolling mill which rolls material between at least a pair of rolls, the rolling control apparatus comprising:
a rolling condition change recognition unit for recognizing that rolling conditions which influence the quality of rolled material change non-linearly;
a time-sequential change pattern storage unit for storing previously generated time-sequential change patterns in order to change parameters related to the rolling operations of a rolling mill in accordance with the non-linear changes of the rolling conditions;
a time-sequential change pattern acquisition unit for acquiring time-sequential change patterns corresponding to the non-linear changes in the recognized rolling conditions when it is recognized that the rolling conditions change non-linearly; and
a time-sequential change pattern output unit for outputting the acquired time-sequential change patterns in order to control the roll gap and roll speed of the rolling mill.
According to another aspect of this invention, there is provided a rolling control method for controlling a rolling mill which rolls material between at least a pair of rolls, the rolling control method comprising:
a step of recognizing that rolling conditions which influence the quality of rolled material change non-linearly;
a step of acquiring, when it is recognized that the rolling conditions change non-linearly, those time-sequential change patterns which correspond to the non-linear changes in the recognized rolling conditions, from a storage unit that stores previously generated time-sequential change patterns in order to change parameters related to the rolling operation of the rolling mill in accordance with the non-linear changes in the rolling conditions; and
a step of outputting the acquired time-sequential change patterns in order to control roll gap and roll speed.
According to still another aspect of this invention, there is provided a rolling control program for controlling a rolling mill which rolls material between at least a pair of rolls, the rolling control program causing an information processing apparatus to execute:
a step of recognizing that rolling conditions which influence the quality of rolled material change non-linearly;
a step of acquiring, when it is recognized that the rolling conditions change non-linearly, those time-sequential change patterns which correspond to the non-linear changes in the recognized rolling conditions, from a storage unit that stores previously generated time-sequential change patterns in order to change parameters related to the rolling operation of the rolling mill in accordance with the non-linear changes in the rolling conditions; and
a step of outputting the acquired time-sequential change patterns in order to control the parameters.
By putting this invention into practice, it is possible to reduce the degree of deviation of the actual values of the rolling state variables such as strip thickness and tension from the corresponding preset values.
BRIEF DESCRIPTION OF DRAWINGS
Fig. 1 schematically shows the entire structure of a rolling mill as an embodiment of this invention;
Fig. 2 schematically shows a control mechanism for rolling control according to an embodiment of this invention;
Fig. 3 schematically shows a control mechanism used in a 2-stand tandem rolling mill as an embodiment of this invention;
Fig. 4 shows examples of time-sequential change patterns generated by using an integrator;
Fig. 5 graphically shows how control is executed in the flying gauge change process according to an embodiment of this invention;
Fig.6 graphically shows how control is executed in the flying gauge change procedure according to another embodiment of this invention;
Fig. 7 gives mathematical formulas used in the calculations of setting values while the flying gauge change procedure is being carried out;
Fig. 8 graphically shows examples of time-sequential change patterns for delivery strip thickness, roll gap, forward slip ratio and roll speed;
Fig. 9 schematically shows an example of the configuration of a rolling mill simulator as another embodiment of this invention;
Fig. 10 graphically shows how optimal time-sequential change pattern are determined according to another embodiment of this invention;
Fig. 11 graphically shows how optimal time-sequential change patterns are decided according to another embodiment of this invention;
Fig. 12 shows how control output variable in the control period of control computer is determined according to another embodiment of this invention;
Fig. 13 graphically shows examples of optimal control actuator time-sequential change patterns according to another embodiment of this invention;
Fig. 14 shows a flow of operation for generating optimal control actuator time-sequential change patterns through simulation according to another embodiment of this invention;
Fig. 15 graphically shows how optimal time-sequential change patterns are selected depending on actual state variables according to another embodiment of this invention;
Fig. 16 illustrates how optimal time-sequential change pattern is selected on the basis of plural time-sequential change patterns according to another embodiment of this invention;
Fig. 17 schematically shows the entire structure of a rolling mill as another embodiment of this invention;
Fig. 18 illustrates how material to be rolled is inserted between the work rolls of a rolling mill according to another embodiment of this invention;
Fig. 19 graphically shows a relationship between looper roll position and inter-stand tension;
Fig. 20 graphically shows examples of time-sequential change patterns according to another embodiment of this invention;
Fig. 21 shows a flow of operation for generating optimal control actuator time-sequential change patterns through simulation according to another embodiment of this invention;
Fig. 22 schematically shows the entire structure of a rolling mill as another embodiment of this invention; and
Fig. 23 illustrates how the shift amounts of intermediate rolls are changed in a rolling mill according to another embodiment of this invention.
DETAILED DESCRIPTION OF THE EMBODIMENTS [Embodiment 1]
This embodiment 1 is an application of this invention to the flying gauge change procedure for a 2-stand tandem rolling mill. When the 2-stand tandem rolling mill as shown in Fig. 1 is operated, the flying gauge change procedure is performed in which the setting of the thickness of rolled material is changed without shutting down the rolling mill.
The flying gauge change procedure is a process of changing the roll gap and the roll speed, which are controlled variables in rolling control, to values suitable for product specifications without shutting down a rolling mill in the manufacture of rolled materials having different specifications. This process may involve the change of the thickness of the original material to be fed to the rolling mill and to be rolled as well as the change in the target thickness of rolled material.
The flying gauge change procedure is a process to solve a problem regarding the
quality of product produced by a rolling mill and a problem regarding the lowering of production efficiency. The problem regarding the quality of product is that if a rolling mill is shut down while a material strip is still running between the work rolls of the rolling mill, there is formed a portion in the material strip called "stop mark", which is too degraded in thickness to satisfy the product specification. On the other hand, the problem regarding the lowering of the production efficiency is that if the rolling mill is once shut down, it takes an appreciable amount of time to resume the operation of the rolling mill.
In the case where the thickness of the original material to be fed to a rolling mill is also changed, different materials having different specifications are joined by welding on the entry side of the rolling mill, and the roll gap and the roll speed, that are the manipulated variables of the rolling mill, are changed in synchronism with the passing of the welded portion between the work rolls of the rolling mill. On the other hand, in the case where the target thickness of the rolled material alone is changed, the roll gap and the roll speed are changed in order to change only the thickness of the continuous rolled material on the delivery side of the rolling mill. In the description that follows, the latter case will be enlarged upon, but it is needless to say that the former case will also be similar in process.
In the operation of a rolling control apparatus of this embodiment shown in Fig. 1, a command value generating unit 104 outputs command values suitable for the product specification of rolled material during the flying gauge change procedure. When the command value outputted by the command value generating unit 104 is changed, a control actuator change pattern generating units 101 transforms the change in the command value into a time-sequential change pattern to manipulate the roll gaps and the roll speeds, that are the manipulated variables at the control actuators.
As shown in Fig. 1, the rolling mill according to this embodiment further includes roll speed control units 11, 21, 31, 41 for controlling the speeds of rolls; and hydraulic roll gap controllers 22, 32 for controlling the positions of roll gaps by changing the oil pressure in the hydraulic cylinders. The control actuator change pattern generating units 101 controls the roll gaps and the roll speeds by inputting change patterns to these controllers and control units.
The change in the rolling condition during the flying gauge change procedure used with the rolling mill in general is according to the preset production schedule. That is, the change in the rolling condition during the flying gauge change procedure is what is previously determined, and therefore the preferable time-sequential change pattern associated therewith can also be obtained previously. In other words, the time-sequential change pattern is meant to be the information including control parameters time-sequentially defined for the rolling operation
of a rolling mill. The gist of this embodiment is that a control actuator change pattern storage unit 102 stores information on control actuator change patterns, that are the time-sequential change patterns corresponding to the changes in the rolling conditions, and that an optimal control actuator time-sequential change pattern setting unit 103 inputs the control actuator change pattern read out of the control actuator change pattern storage unit 102, to the control actuator change pattern generating units 101.
Fig. 2 shows in block diagram a simplified structure of a rolling mill control system. In the rolling mill control system, the command values supplied to the control actuators are changed through the controls by the command value generating unit 104 for calculating the preset values of control state variables and the manipulated variables at the control actuators so as to realize them in accordance with the product specification, and the control actuator change pattern generating units 101 for outputting, as commands for the control actuator, the manipulated variables for the control actuators in accordance with the time-sequential change patterns. Consequently, the rolling condition is changed in (rolling mill + rolling phenomenon) 901 to change the actual control state variable. A feedback control unit 902 outputs a control command to the control actuator so that the difference between the actual value of the control state variable and the target value of the control state variable can be reduced to zero.
Since metal rolling is of a non-linear phenomenon, it is necessary to change the operating point in control if the thickness and tension of material to be rolled, that are the control state variables, are changed. The command value generating unit 104 and the control actuator change pattern generating unit 101 serve to change the operating point. When the rolling condition becomes different from the preset condition and when command values supplied to the control actuators still causes fluctuation of the rolling condition with respect to the preset condition, the feedback control unit 902 compensates for the fluctuation. In an ideal case, it will be unnecessary for the feedback control unit 902 to operate if such a value of the control state variable as to realize a desired product specification can be obtained by the application to the control actuators of the time-sequential change patterns generated by the command value generating unit 104 and the control actuator change pattern generating unit 101.
In reality, however, since control state variable in rolling fluctuates differently from the preset value due to the fluctuations of strip thickness and tension on the entry side of the rolling mill and tension on the delivery side of the rolling mill, that are disturbances in control, then the feedback control unit 902 for compensating the disturbances is required. The flying gauge change procedure according to a prior art technique, for example, can be performed
by causing the command value generating unit 104 to set the values of control state variables before and after a pattern change and by causing the control actuator change pattern generating unit 101 to manipulate the roll gaps and the roll speeds, that are the actual manipulated variables, in accordance with the time-sequential change patterns. In fact, the parameters in rolling operation that are changed in accordance with the time-sequential change patterns in this embodiment are the roll gaps and the roll speeds.
Now, rolling phenomenon associated with a 2-stand tandem rolling mill will be described with reference to Fig. 3. As shown in Fig. 1, the 2-stand tandem rolling mill comprises No. 1 stand rolling mill 2, No. 2 stand rolling mill 3, an entry bridle roll 1 installed on the entry side of the No.l stand rolling mill 2, and a delivery bridle roll 4 installed on the delivery side of the No. 2 stand rolling mill 3. Material to be rolled, that is wound in the form of a coil, is fed out of entry equipment through the entry bridle roll 1 to the rolling mill. The material to be rolled is fed into the No. 1 stand rolling mill 2 and the No. 2 stand rolling mill 3 so that the material is rolled to have a desired thickness. The rolled material is then fed via a delivery bridle roll 4, taken up by delivery equipment and wound in the form of a coil.
The stands of the rolling mill determine delivery strip thickness, delivery strip speed and entry strip speed, that are the control state variables of the rolling mill, depending on the rolling mill and the rolling phenomenon in accordance with the entry strip thickness, entry tension and delivery tension, that are control disturbances, and also in accordance with the roll speeds and roll gaps of the rolling mill stands, the entry bridle roll speed and the delivery bridle roll speed, that are the manipulated variables. Between the entry bridle roll 1 and the No. 1 sand rolling mill 2 is generated the entry tension at the No. 1 stand rolling mill 2 (referred to briefly as entry tension) on the basis of the time-integral of the difference between the No. 1 stand rolling mill entry strip speed and the entry bridle roll seed. And the No. 2 sand rolling mill entry tension (= No. 1 stand rolling mill delivery tension referred hereafter as inter-stand tension) is generated on the basis of the time-integral of the difference between the entry strip speed of the No. 2 stand rolling mill 3 and the delivery strip speed of the No. 1 stand rolling mill 2.
The delivery tension at the No. 2 stand rolling mill 3 (referred to briefly as delivery tension) is generated on the basis of the time-integral of the difference between the speed of the delivery bridle roll 4 and the delivery strip speed at the No. 2 stand rolling mill 3. And the delivery strip thickness at the No. 1 stand rolling mill 2 becomes the entry strip thickness at the No. 2 stand rolling mill 3 since the rolled material moves from the delivery side of the No. 1 stand rolling mill 2 to the entry side of the No. 2 stand rolling mill 3. Since the delivery strip
thickness, entry strip speed and delivery strip speed at the rolling mill changes depending on the entry tension, delivery tension and entry strip thickness at the rolling mill, the time-sequential changes in the entry tension, delivery tension and entry strip thickness appear as the time-sequential changes in the delivery strip thickness, entry tension and delivery tension of each rolling mill. Therefore, the control using the command value generating unit 104, the control actuator change pattern generating unit 101 and the feedback control unit 902 can only achieve a limited precision in the delivery strip thickness in the flying gauge change procedure. On the other hand, if it is intended to achieve a target thickness by using the feedback control alone, the time required for the actual value to converge to the target value is prolonged and therefore the ensuing product yield is lowered.
Fig. 4 graphically shows time-sequential change patterns that can be generated by using the above mentioned integral calculations. As shown in Fig. 4, when a signal having a constant amplitude is inputted for a certain period of time, the corresponding output assumes a simple ramp-shaped change pattern. On the other hand, when a signal is inputted, which first gradually increases in amplitude, then levels off, and finally gradually decreases in amplitude, the corresponding output assumes an S-curve change pattern which has smooth start and end portions as compared with the ramp-shaped change pattern.
It is difficult to avoid the changes in the delivery strip thickness, delivery strip speed and entry strip speed, that are the control state variables of the rolling mill, even if these time-sequential change patterns are used in an attempt to cope with the non-linear rolling phenomenon occurring in the flying gauge change procedure. Since the change in the strip speed causes the change in the tension, and since the change in the tension causes in turn the changes in the strip thickness, delivery strip speed and entry strip speed, then it is difficult to change the operating state of rolling mill while the deviations of the actual values of thickness and tension from their corresponding preset values are being kept minimized.
In the flying gauge change procedure according to this embodiment, a case is considered where thickness and tension are changed as graphically shown in Figs. 5(a) and 5(b). In the figures, the horizontal axis represents the position coordinate on rolled material, and the setting of the thickness and tension are changed in the region of the flying gauge change procedure. The values set for the delivery strip thickness and the inter-stand tension are changed following a ramp function that changes linearly from one fixed value to another. In the figures, subscripts I and II indicate the values set for the control state variables before and after the flying gauge change procedure, respectively. The entry strip thickness is the same before and after the flying gauge change procedure, but the delivery strip thicknesses at the No. 1 and
No. 2 stand rolling mills change before and after the flying gauge change procedure. In like manner, the entry tension is the same before and after the flying gauge change procedure, but the inter-stand tension and the delivery tension change before and after the flying gauge change procedure.
Fig. 6 graphically shows how roll gaps and roll speeds, that are the control state variables of rolling mills, are changed to perform the flying gauge change procedure as shown in Figs. 5(a) and 5(b). In Fig. 6, the horizontal axis represents lapse of time, and roll gaps and roll speeds at the control actuators are changed in synchronism with the timing at which thicknesses are changed from Schedule I to Schedule II at the No. 1 and No. 2 stand rolling mills simultaneously.
To be concrete, in the flying gauge change procedure, the point on the material to be rolled where the thickness is to be changed (hereafter referred to also as thickness changing point) is determined beforehand, and when the thickness changing point passes the No. 1 and No. 2 sand rolling mills, the corresponding roll gaps and roll speeds are changed. In other words, in the case where the rolling condition is changed, as shown in the graph relating to strip thickness setting in Fig. 6, from Schedule I represented by a dashed curve to Schedule II represented by a solid curve, the roll gaps and the roll speeds are changed as shown in the graphs relating to roll gap and roll speed in Fig. 6 while the material at the thickness changing point is being rolled by the No. 1 and No. 2 stand rolling mills, respectively.
The roll gaps and the roll speeds for the Schedules I and II can be obtained in accordance with the rolling model formula. The command value generating unit 104 calculates the roll gaps and the roll speeds by using such expressions as shown in Fig. 7. The roll gaps and the roll speeds required in the Schedules I and II are set through calculation in the command value generating unit 104, and then changed to the roll gaps and the roll speeds set by the pattern change generating unit 101. In this case, the change from Schedule I to Schedule 2 cannot be made stepwise in view of the stabilization of rolling operation. In the conventional technique, this change was such as shown in Fig. 6, using a ramp function.
Rolling phenomenon is a non-linear one and even if roll gap is changed along a ramp-shaped curve, delivery strip thickness does not assume a ramp shape, but changes in a complicated manner, as shown in Fig. 8(a). In other words, even if roll gap and roll speed are changed following a ramp-shaped curve, the resulting thickness and tension will not change in like manner.
In order that the delivery strip thickness can be changed along a ramp curve, the roll gap must be changed in accordance with the time-sequential change pattern as shown in Fig.
8(b). In the assumption that forward slip ratio changes along a ramp curve in accordance with the ramp change of the roll gap, the forward slip ratio does not follow a ramp change if the roll gap is changed in accordance with the time-sequential change pattern shown in Fig. 8(b) in an attempt to cause the delivery strip thickness to follow a ramp change.
The delivery tension at a rolling stand is given by the time-integral of the difference between (the entry strip speed at the following rolling stand) and [(the roll speed at this following rolling stand) × (1+forward slip ratio)]. If the entry strip speed at the posterior rolling stand is kept constant, the resulting delivery tension becomes constant provided that the roll speed is manipulated in such a manner that the roll speed is given by 1 / (1+forward slip ratio). Alternatively, if this roll speed is changed with a constant difference from the entry strip speed at the posterior rolling stand, the roll speed can be given by the time-integral of a constant so that the tension can be changed along a ramp curve.
Accordingly, it becomes possible to change the thickness and tension, that are the control state variables, ramp-wise by optimizing the patterns of change in the roll gap and the roll speed, that are the manipulated variables in rolling control. For example, if the roll speed is changed following the time-sequential change pattern as shown in Fig. 8(b), the thickness can be changed ramp-wise, following the expression [(roll speed) x (1 + forward slip ratio)].
According to this embodiment, the thus optimized change patterns for roll gap and roll speed are stored in the control actuator change pattern storage unit 102. In the regions of flying gauge change procedure at the No. 1 and No. 2 stand rolling mills as shown in Fig. 6, the optimal control actuator time-sequential change pattern setting unit 103 reads a desired change pattern stored in the control actuator change pattern storage unit 102 and inputs the read change pattern to the control actuator change pattern generating unit 101. Accordingly, the delivery strip thickness makes a ramp-shaped change from the state before the pattern change to the state after the pattern change, as shown in Fig. 8(b). In other words, the control actuator change pattern storage unit 102 serves as a time-sequential pattern change storage unit and also the optimal control actuator time-sequential change pattern setting unit 103 functions as a time-sequential change pattern output unit.
It is to be noted here that the optimal control actuator time-sequential change pattern setting unit 103 detects beforehand at least the coming of the region of flying gauge change procedure at the No. 1 stand rolling mill. In other words, the optimal control actuator time-sequential change pattern setting unit 103 works as both a rolling condition change detecting unit and a time-sequential pattern change acquiring unit. This detection can be effectuated by detecting the change in a command value delivered from the command value
generating unit 104.
As described above, rolling operation using a rolling mill is run in accordance with a production plan scheduled beforehand. According to such a production plan with a rolling mill, the position on the material to be rolled at which the thickness is to be changed, is previously determined. The rolling control apparatus knows how far the position is from the rolling mill, through the measurement of roll rotation amount. For example, a punched hole is made at the position on the material to be rolled at which the thickness is to be changed; light is cast on the material to be rolled, while it is being fed; and the punched hole is detected by detecting the light passed through the punched hole. If a detector 50 for detecting the punched hole is installed on the entry side of the rolling mill as shown in Fig. 1, it becomes possible to detect the arrival of the position at the rolling mill. Further by detecting the rotational number of the entry bridle roll, it becomes possible to detect the arrival of the position at the regions of flying gauge change procedure for the No. 1 and No. 2 stand rolling mills. At the time of such arrivals the command value generating unit 104 performs the change in the command value.
It is to be noted that in the example shown in Fig. 6, the roll gap of the No. 1 stand rolling mill is also changed in the region of the flying gauge change procedure for the No. 2 stand rolling mill. This is because a large change at a time in roll gap may cause heavy load on the rolling mill to lead to a poor operational efficiency, or because there is a limit to a tolerable amount of change at a time. In other words, this is for the purpose of eliminating such a problem described above by gradually approaching the final state to be reached after the region of flying gauge change procedure for the No. 2 stand rolling mill.
In this embodiment, since the optimized change pattern is stored in the control actuator change pattern storage unit 102 as described above, change patterns are generated through rolling simulation. Fig. 9 schematically shows the structure of a rolling simulation apparatus (hereafter referred briefly as a rolling simulator) according to this embodiment, used for generating change patterns stored in the control actuator change pattern storage unit 102. The rolling simulator consists of a rolling mill simulator for simulating the operating states of the entry bridle roll 1, the No. 1 stand rolling mill 2, the No. 2 stand rolling mill 3, and the delivery bridle roll 4 and a model as a rolling phenomenon simulator including entry tension and delivery tension.
The rolling mill simulator inputs the command values of roll gap and roll speed and outputs the corresponding roll gap and roll speed to the rolling phenomenon simulator. Further, the rolling phenomenon simulator inputs the entry strip thickness, deformation resistance and friction coefficient of material to be rolled; calculates the delivery strip
thicknesses, entry tensions and delivery tensions at the respective stand rolling mills, and the inter-stand tension, from the roll gaps and roll speeds of the respective stand rolling mills; and outputs those calculated quantities as rolling state variables.
It is to be noted here that the deformation resistance and the friction coefficient of material to be rolled are determined depending on the machine specification of rolling mill facility, the product specification of material to be rolled, and the specification of lubricant. Since each of the entry tension, the inter-stand tension and the delivery tension, that are the control state variables of rolling mills, is given as the integral of speed difference, then they are so designed as to be set by externally charging the integration term representing the simulation of the tension in the rolling mill simulator. This is because it is necessary to perform such a simulation in the state where the operating condition of rolling mill is preferably the same as the operating condition assumed before flying gauge change procedure since, rolling phenomenon being a non-linear phenomenon, a change in the initial value of tension, rolling force or thickness may cause a time-sequential change in thickness or tension. Such a design can also make it possible to perform rolling simulations of previously set, various types of rolling.
Each of the control units at the respective control actuators, such as the roll speed control units 11 through 41, and the hydraulic control units 22, 32, performs calculation control for a period shorter than the period for which a computer for controlling rolling mills shown in Fig. 1 or 2 performs calculation control. Accordingly, the rolling mill simulator performs simulation in consideration of the time response from the instant that the control actuator change pattern generating unit 101 outputs change patterns for roll speed and roll gap, to the instant that the roll speed control units 11 through 41, and the hydraulic control units 22, 32 change the associated roll speeds and roll gaps.
According to the rolling simulator of this embodiment, the rolling mill simulator simulates roll gaps and roll speeds in accordance with the output of the control actuator change pattern generating unit 101. Since the roll gaps and the roll speeds change with the rolling state variables, they will be finally calculated at a calculating period for rolling phenomenon. This calculating period will become the calculating period for the rolling simulator.
It is possible in the actual operation that the actual values of the rolling mill state variables such as the thickness and tension at the instant that the flying gauge change procedure is initiated may differ from their corresponding preset values. As described above, since rolling phenomenon is a non-linear one, the changes in the entry strip thickness and tension, that are the control state variables, cause different responses. In order to cope with such a situation, it is preferable that several types of differences between the actual value of control state variable in
rolling and the corresponding preset value should be assumed, that simulations should be performed on the assumed differences, and that the change patterns obtained as a result of the respective simulations should be stored in the control actuator change pattern storage unit 102.
For example, assumption is made of three cases relating to entry strip thickness where the actual entry strip thickness HI at the No. 1 stand rolling mill is greater or smaller than and equal to its preset value, and of three other cases relating to tension where the inter-stand tension Tfl is higher or lower than and equal to its preset value. Simulation is performed for the combinations of those cases, that is, nine cases.
The delivery strip thicknesses hi and h2 respectively at the No. 1 and No. 2 stand rolling mills can be determined depending on the roll gaps and roll speeds that are the control state variables and the control manipulated variables of the rolling mills. The entry tension is kept at its preset value by using entry bridle roll speed or through entry tension control using current as manipulated variable whereas the delivery tension is kept at its preset value by using delivery bridle roll speed or through delivery tension control using current as manipulated variable. Accordingly, it is assumed here that these actual values of the control state variables are equal to their preset values. Regarding the entry and delivery bridle rolls, there is no factor of change caused by, for example, forward slip ratio that is the rolling state variable since no rolling operation is performed.
In simulations, it is important to judge whether the result is good or poor. In this embodiment, regarding the roll gap change pattern and the roll speed change pattern for the No. 1 stand rolling mill, assessment is regarded better when the mean square error, along the time axis within the region of flying gauge change procedure, of the deviation of the actual delivery strip thickness at the No. 1 stand rolling mill and the inter-stand tension from their corresponding preset values, is smaller. And regarding the roll gap change pattern and the roll speed change pattern for the No. 2 stand rolling mill, assessment is regarded better when the mean square error, along the time axis within the region of flying gauge change procedure, of the deviation of the actual delivery strip thickness at the No. 2 stand rolling mill and the inter-stand tension from their corresponding preset values, is smaller.
Fig. 10(a) graphically shows the control period of a computer used for controlling rolling mills, the process period of a computer used for controlling the manipulated variables of rolling mills at the control actuators, and the calculation period in the rolling simulation of rolling mills and rolling phenomena that are physical phenomena of controlled systems. The control computer (i.e. computer for controlling rolling mills) used to control the control actuator change pattern generating unit 102 and the command value generating unit 104 repeats its
control operation at a period of, for example, 20 ms. Therefore, a time-sequential change pattern having a resolution smaller than the control period cannot be delivered to the control actuators.
The control of the control actuator is simulated at the control period of the control actuator control computer whose control period is shorter than the control period of the rolling mill control computer, and the operation of the rolling mill control actuator and the simulation of rolling phenomenon are performed in a still shorter period. In other words, the roll gap and the roll speed, that are the control manipulated variables, at the control actuator are outputted as command values at the control period of the rolling mill control computer; the control actuator control computer changes the actual value at the control actuator so as to equate it to the command value; and the rolling mill and rolling phenomenon are simulated in accordance with the ensuing result, so that the delivery strip thickness, tension and rolling force and the like, that are the control state variables of the interested rolling mill, can be calculated within the next control period of the rolling control computer.
The command value at the control actuator is changed so that the control state variable thus calculated for the next control period of the rolling mill control computer can become nearest to the preset value. Hence, the optimal time-sequential change pattern can be obtained by repeatedly performing similar calculations at the control period of the rolling mill control computer from the initial to final points of the region of flying gauge change procedure.
Fig. 10(b) and Fig. 11(a) graphically show how optimal time-sequential change patterns for roll gap and roll speed in the flying gauge change procedure are set. The simulation of time-sequential change patterns at control actuator is performed which patterns can give the entry and delivery strip thicknesses and the entry and delivery tensions at the No. 1 and No. 2 stand rolling mills, and the inter-stand tension as shown in Fig. 5 while roll gaps and roll speeds are being determined for each control period of the rolling mill control computer.
In Fig. 10(b), let the k-th control period of the rolling mill control computer and the 1-th control period of the rolling mill control actuator control computer be considered respectively. In the i-th control period of the rolling mill control computer during flying gauge change procedure, roll gap is so determined as to be the target value for entry strip thickness in the next (i+l)-th control period. The change in the roll gap accompanies the changes in forward slip ratio and tension. In order to prevent these changes, it is necessary to change roll speed as well.
Here, let it be assumed that a command is outputted to cause changes in roll gap by ΔS1 and roll speed by ΔV1. According to this command, rolling simulation is performed.
Accordingly, the control actuator control computer receives the command for changing the roll gap, and changes the roll gap in accordance with the command so that the roll gap is adjusted to the actual value as shown in Fig. 10(b). Finally, the actual roll speed is changed as shown in Fig. 11(a).
Let it be assumed as a result that the fact that the actual delivery strip thickness changes as shown in Fig. 10(a) and the fact that the inter-stand tension changes as shown in Fig. 11(b), are obtained as a result of rolling simulation. The fact that the delivery strip thickness is smaller than its target value by Ah while the inter-stand tension is larger than its target value by AT, can be resulted in. It is then necessary to determine the manipulated variable at the control actuator which may minimize the deviation of the control state variable in the control period of the rolling control computer from its target value. For this purpose, the so-called "mountain-climbing method" is utilized.
As shown in Fig. 12, according to the mountain-climbing method, the point is determined at which the assessment function constructed on the basis of the degrees of deviations of the delivery strip thickness and the inter-stand tension from their preset values takes the minimum value. The point is determined through a rolling simulation in which manipulation is done according to a round-robin algorithm within the manipulable range of control actuator. The mountain-climbing method is a search method using the round-robin algorithm and various procedures for enhancing the searching efficiency have been proposed to date. It therefore is possible to improve the searching efficiency by resorting to a suitable one of them.
The optimal time-sequential change patterns for the respective control actuators can be obtained by obtaining the optimal command values for the manipulated variables supplied to the control actuators for each control period of the rolling mill control computer, over the entire region of flying gauge change procedure.
Fig. 14 shows in block diagram the operation flow of the optimal control actuator time-sequential change pattern setting unit 103, that is the summing-up of the foregoing description. The initial condition for the control state variable of a rolling simulator 110 is determined by causing an initial condition setting unit 111 to virtually set various kinds of deviations, each being an error between the actual value of the control state variable such as thickness and tension before the flying gauge change procedure and the preset value of the control state variable. After the initial condition has been set, a control period managing unit 114 set determines the target value of each state variable for each control period of the rolling control computer.
A control actuator manipulated variable setting unit 112 outputs a control manipulated variable for the control actuator so that the preset target value of the control state variable may be obtained. The outputted manipulated variable is then inputted to a rolling simulator 110. The rolling simulator 110 calculates rolling phenomenon through simulation until the next control period of the rolling control computer, and outputs the actual control variable for the next control period.
An optimal decision unit 113 obtains an assessment function J as the square of the deviation of the actually obtained value of control state variable from the preset target value of control variable. Through the repeated use of the assessment function while the control manipulated variable for control actuator is being properly changed as in the above mentioned "mountain-climbing method", the optimal control manipulated variable is obtained. If this process is performed for all the initially set conditions for control state variable, optimal time-sequential change patterns for respective initially set conditions can be obtained.
As described above, the optimal time-sequential change patterns for respective initially set conditions can be calculated and stored in the control actuator change pattern storage unit 102. Accordingly, when the region of flying gauge change procedure starts in an actual rolling operation, the optimal control actuator time-sequential change pattern setting unit 103 selects an optimal time-sequential change pattern calculated on the basis of a initially set condition hat best approximates the actual value of rolling state variable, and performs a flying gauge change procedure by using the optimal time-sequential change pattern.
As described above, assumption is made of three cases relating to entry strip thickness where the actual entry strip thickness H1 at the No. 1 stand rolling mill is greater or smaller than and equal to its preset value, and of three other cases relating to tension where the inter-stand tension Tfl is higher or lower than and equal to its preset value. And simulation is performed on all the combinations of them, that is, nine cases. Thereafter, optimal time-sequential change patterns corresponding to the respective combinations are determined for the control actuators.
For example, as shown in Fig. 15(b), initially set conditions 1 through 9 are allocated to the combinations of three entry strip thicknesses and three inter-stand tensions, the entry strip thicknesses being "large", "equal to preset value" and "small"; and the inter-stand tensions being "high", "equal to preset value" and "low". And these initially set conditions 1 through 9 are made corresponding to the respective time-sequential change patterns for the control actuator.
Further, regarding entry strip thickness, ranges represented by the terms "equal to
set value", "large" and "small" are predetermined in accordance with the initially set conditions. Then, the optimal control actuator time-sequential change pattern setting unit 103 decides on whether the thickness belongs to range "equal to set value", "large" or "small", on the basis of the input actual value, and selects the optimal time-sequential change pattern. In like manner, regarding inter-stand tension, ranges "high" , "equal to set value" and "low" are predetermined so that the optimal control actuator time-sequential change pattern setting unit 103 selects the optimal time-sequential change pattern on the basis of the input actual value.
At the time of initiation of the flying gauge change procedure, one of the nine initially set conditions is determined by the optimal control actuator time-sequential change pattern setting unit 103 on the basis of actual entry strip thickness and actual inter-stand tension. In the example shown in Fig. 15, it is decided that the entry strip thickness is "large" and the inter-stand tension is "equal to set value", and the result of this decision leads to the selection of the initially set condition No. 2.
Accordingly, in the region of the flying gauge change procedure, the time-sequential change pattern for control actuator corresponding to the initially set condition having the thus selected number is read out of the control actuator change pattern storage unit 102 by the optimal control actuator time-sequential change pattern setting unit 103; the read-out initially set condition is then delivered to the control actuator change pattern generating nit 101; and as a result the control actuator change pattern generating nit 101 delivers the command value corresponding to the read-out initially set condition to the roll gap and roll speed control units that are actually the control actuators.
As described above, in the flying gauge change procedure, such flying gauge change as can be minimize the deviation of the actual value of control state variable from the corresponding preset value can be effected. Consequently, since such time-sequential change pattern for control actuator as can minimize the deviation of the actual value of control state variable, like the thickness or tension of rolled or to-be-rolled material that are important for rolling mill control, from the corresponding preset value of control state variable can be determined and set, it becomes possible to improve product quality and operation efficiency.
In the above described embodiment, demonstrated is a case where the result of simulation by the rolling simulator as shown in Fig. 9 is stored in the control actuator change pattern storage unit 102. However, it is also possible to store any of change patterns generated on the basis of various combinations of experimental or measurement values. Even in this case, the same effect can be obtained.
Further, in the above described embodiment where there are two rolling
conditions such as Schedules I and II, there are two kinds of flying gauge change procedures: one involving flying gauge change transition from Schedule I to Schedule II and the other from Schedule II to Schedule I. Accordingly, the control actuator change pattern storage unit 102 must store at least two time-sequential change patterns, and the optimal control actuator time-sequential change pattern setting unit 103 must decide which of the two time-sequential change patterns to read when it reads time-sequential change patterns from the control actuator change pattern storage unit 102. Since rolling operation is performed in accordance with production plan as described above, this decision can be effectuated by monitoring the point on the material to be rolled where the thickness is to be changed. [Embodiment 2]
In Embodiment 1 described in the foregoing, demonstrated is a method in which roll gap and roll speed are obtained by successively calculating their optimal values in consecutive control periods of a rolling mill control computer by using a rolling simulator. However, the following procedure can also be alternative: plural time-sequential change patterns are generated beforehand, a flying gauge change procedure using the generated time-sequential change patterns is executed, and a time-sequential change pattern that renders the dependent value of assessment function minimum can be adopted.
In this case, operation flow is as follows. As shown in Fig. 16, such time-sequential change patterns as previously generated are successively selected by a time-sequential change pattern selecting unit 121, the successively selected time-sequential change patterns are delivered to a time-sequential manipulated variable changing unit 120, actual manipulated variables are delivered as time-sequential change patterns to a rolling simulator 110, and an optimum decision unit 122 calculates a mean-square sum along time axis of the deviations of the actual values of control state variable from the target value of control state variable on the basis of the resultant values of control state variable (i.e. values of time-sequential variable within the region of flying gauge change procedure). This process is executed with respect to different time-sequential change patterns to select an optimal time-sequential change pattern. [Embodiment 3]
The method according to this embodiment can be applied to not only a rolling mill but also a controlled system in which its control actuators must be controlled with certain time-sequential change patterns in a feed-forward manner so as to change the control state variable of the control actuators of the controlled system in accordance with certain time-sequential change patterns. [Embodiment 4]
As shown in Fig. 17, a looper 200 is installed between the rolling mill stands 2 and 3 of a hot rolling mill. The looper 200 includes a looper arm 202 rotatable around the pivot 203, a looper roll 201 attached to the tip of the looper arm 202 to lift rolled material in contact thereof, and a hydraulic cylinder 204 for adjusting the vertical position (i.e. height) of the looper roll 201 and the force which the looper roll 201 exerts on the rolled material. In fact, the looper 200 is a supporting member for supporting the rolled material.
The force which the rolled material exerts on the looper roll 201 and therefore the tension of the rolled material can be obtained by measuring the reaction force that the looper arm 204 exerts on the hydraulic cylinder 204. The change in the position of the looper roll 201 causes the change in the length of the rolled material extending between the rolling mill stands so that the tension of the rolled material also changes. That is, the looper 200 is a means for not only detecting but also adjusting the tension of the rolled material between the rolling mill stands.
Since the looper roll 201 must be lifting the rolled material in order to measure the tension of the rolled material, the upper edge of the looper roll 201 must be set higher than a line (referred to also path line) connecting the upper edges of the lower work rolls of the anterior and posterior stands. Even in that case, if the contact angle at which the rolled material is in contact with the surface of the looper roll 201 is too small, the precision of tension measurement becomes poor. Therefore, at least a certain contact angle must be maintained.
When material to be rolled is passed through a rolling mill, it is required to insert the front edge of the material between the work rolls of the rolling mill. In such an occasion, as shown in Fig. 18, the front end of the material travels from the No. 1 stand rolling mill 2 to the No. 2 stand rolling mill 3. Therefore, the looper roll 201 must be kept lower than the above mentioned path line so that the looper roll 201 may not disturb the forward movement of the material. After the front end of the material has been inserted between the work rolls of the No. 2 stand rolling mill 3, the looper roll 201 is lifted up to the position shown in Fig. 17 so that the inter-stand tension can be measured and also that the looper roll 201 can be used as a terminal for controlling the inter-stand tension.
Fig. 19 graphically shows the change in the position of the looper roll 201 and the change in the inter-stand tension in synchronism with each other. As shown in the upper graph of Fig. 19, when the looper roll 201 is lifter up, the geometrical length of the material under rolling operation is prolonged. Accordingly, as shown in the lower graph of Fig. 19, the inter-stand tension rises. With the distance between the two rolling mill stands and the roll speeds with respect to the two rolling mill stands kept constant, it is only during the period for which the
inter-stand tension of the rolled material is increasing due to the lifting of the looper roll 201 that the inter-stand tension rises. When the position of the looper roll 201 has been fixed and therefore the length of the material between the rolling mill stands has become constant, the inter-stand tension is restored to its original value.
When the inter-stand tension increases, the thickness and the strip width of the rolled material decrease. Although the thickness can be readjusted by the No. 2 stand rolling mill 3 at the posterior stage, the reduced strip width cannot be readjusted so that a problem occurs concerning product quality. It is therefore necessary to correct the roll speed and the roll gap of the No. lstand rolling mill 2 while the looper roll 201 is being lifted, so that the change in tension due to the lifting of the looper roll 201 can be prevented.
In the embodiment 1 described above, the thickness of the rolled material and the target value of the rolled material were described as rolling conditions for detecting non-linear changes. In the embodiment 3, however, the change in the position of the looper roll 201 is regarded as the change in the rolling condition, and time-sequential patterns for the roll speed and the roll gap of the No. 1 stand rolling mill 2 are given to the respective control actuators. Consequently, the gist of this embodiment 3 is that the change in the inter-stand tension as shown in Fig. 19 can be prevented and therefore that the quality of the resulted rolled material can be improved.
Fig. 20 shows in example the time-sequential change patterns for the control actuators accompanying the the changes in the position of the looper roll 201 as described above, and the resulting time-sequential change in the inter-stand tension. As described above, the elevation of the position of the looper roll 201 causes the length of the rolled material between the rolling mill stands and therefore the inter-stand tension increases. In order to prevent the increase in the inter-stand tension, it is necessary to change the roll speed of the No. 1 stand rolling mill 2 in synchronism with the change in the length due to the change in the position of the looper roll 201 so that the length of the material may coincide with the geometrical length. To be concrete, the roll speed of the No. 1 stand rolling mill 2 is accelerated so that the rolled material can be delivered from the No. 1 stand rolling mill 2 in accordance with the increase in the length of the material between the two rolling stands.
Further, the change in the roll speed of the No. 1 stand rolling mill 2 accompanies the change in the rolling force and therefore the change in the delivery strip thickness. In order to prevent these related changes, the roll gap of the No. 1 stand rolling mill 2 must be adjusted. To be concrete, since the increase in roll speed accompanies the decrease in rolling force, the roll gap of the No. 1 stand rolling mill 2 is decreased in accordance with the decrement of the rolling
force. If the roll speed and the roll gap of the No. 1 stand rolling mill 2 are changed in accordance with the change in the position of the looper roll 201, the change in the inter-stand tension can be confined within a constant region as shown in Fig. 20. That is, even in this embodiment 4, roll gap and roll speed can be parameters for the rolling operation that are changed in accordance with time-sequential change patterns.
However, the change in the geometrical length of the material between the rolling stands, accompanying the change in the position of the looper roll 201 becomes non-linear if the wrapping of the rolled material around the rolls is taken into consideration. Accordingly, even if the position of the looper roll 201 follows a ramp-shaped change, the inter-stand geometrical length of the rolled material does not follow a ramp-shaped change. This is a geometrical problem, and it is possible to output such a command to change the position of the looper roll 201 that the geometrical length of the material between the rolling stands may follow a ramp-shaped change. Even by doing so, the change in the roll speed of the No. 1 stand rolling mill 2 causes changes in rolling conditions, thereby leading to changes in forward slip ratio and roiling force.
Although the change in the rolling force can be suppressed by adjusting the roll gap of the No. 1 stand rolling mill 2, the adjustment of the roll gap may also cause a change in the forward slip ratio. As a result, the inter-stand tension changes to further change the forward slip ratio. Thus, unless the time-sequential change patterns for the respective control actuators are proper, a result is incurred where tension change cannot be suppressed.
According to this embodiment, such time-sequential change patterns as shown in Fig. 20 are obtained by such a simulator as shown in Fig. 21, and the obtained time-sequential change patterns are stored in the control actuator change pattern storage unit 102. In the rolling simulator shown in Fig. 21, a rolling mill simulator obtains the inter-stand geometrical length of the rolled material (referred to also as geometrical strip length) on the basis of the value of command for changing the position of the looper roll 201. Then, a rolling phenomenon simulator calculates the thickness and the tension of the material on the delivery side of the No. 1 stand rolling mill 2 on the basis of the geometrical length mentioned above, roll gap and roll speed.
The inter-stand tension cannot be measured unless the position of the looper roll 201 is elevated. Accordingly, a plurality of initially set conditions are prepared on the basis of the actual entry strip thickness measured on the entry side of the No. 1 stand rolling mill 2 and the rolling force of the No. 1 stand rolling mill 2; time-sequential control patterns corresponding to the prepared initially set conditions are obtained as shown in Fig. 15(b); and the obtained
time-sequential control patterns are stored in the control actuator change pattern storage unit 102.
The instant at which the position of the looper roll 201 is to be changed, that is, the instant at which the command value generating unit 104 delivers a command for changing the position of the looper roll 201, is sometime later than the instant at which the front end of the rolled material reaches the work rolls of the No. 2 stand rolling mill 3. To be concrete, the instant is later by a predetermined time length than the instant at which the front end of the rolled material reaches the work rolls of the No. 2 stand rolling mill 3.
The command value generating unit 104 calculates the position of the front of the rolled material on the basis of the rotational speed of the No. 1 stand rolling mill 2 and decides the above mentioned instant on the basis of the result of calculation. There is a sudden increase in the rolling force of the No. 2stand rolling mill 3 when the front end of the rolled material has been inserted between the work rolls of the No. 2 stand rolling mill 3. Since the rolling forces at the respective stand rolling mills are always monitored to effectuate feedback control, the command value generating unit 104 may alternatively decide the instant at which the front end of the rolled material has just been inserted between the work rolls of the No. 2 stand rolling mill 3 on the basis of the monitoring of the rolling force of the No. 2 stand rolling mill 3.
Then, as in the embodiment 1 described above, the optimal control actuator time-sequential change pattern setting unit 103 detects the change in the operating condition on the basis of the change in the command value inputted from the command value generating unit 104, reads the optimal time-sequential change pattern set as shown in Fig. 20 out of the control actuator change pattern storage unit 102, and delivers the read pattern to the desired control actuator. Accordingly, the change in tension due to the elevation of the looper roll 201 can be suppressed to a minimal level.
This embodiment was described as an example in which the command value generating unit 104 delivers such a command to change the position of the looper roll 201 as shown in the top graph of Fig. 20; the optimal control actuator time-sequential change pattern setting unit 103 obtains from the control actuator change pattern storage unit 102 the time-sequential change patterns such as "No. 1 stand roll speed" and "No. 1 stand roll gap" as shown in Fig. 29 on the basis of the command values delivered by the command value generating unit 104; and the obtained time-sequential change patterns are inputted to the control actuator change pattern generating unit 101.
In this example, the control actuator change pattern generating unit 101 must synchronize the command value to change the position of the looper roll 201, inputted from the command value generating unit 104 with the time-sequential change patterns inputted from the
ptimal control actuator time-sequential change pattern setting unit 103.
Alternatively, the optimal control actuator time-sequential change pattern setting unit 103 may detect changes in rolling conditions by detecting the position of the front end of the rolled material obtained as a result of calculation on the basis of the roller speed of the No. 1 stand rolling mill 2 and the sudden increase in the rolling force of the No. 2 stand rolling mill 3, as described above; obtain from the control actuator change pattern storage unit 102 such time-sequential change patterns as includes the time-sequential change pattern associated with the command to change the position of the looper roll 201 shown in the top graph of Fig. 20; and send the thus obtained time-sequential change patterns to the control actuator change pattern generating unit 101.
In this case, parameters for rolling operation changeable in accordance with time-sequential change patterns are the position of the looper roll 201, roll gap and roll speed. Accordingly, the control actuator change pattern generating unit 101 obtains time-sequential change patterns including "looper roll position", "No. 1 stand roll speed" and "No. 1 stand roll gap" shown in Fig. 20, and therefore does not need time-synchronization with the command value inputted from the command value generating unit 104. As a result, simplification of process can be effectuated. [Embodiment 5]
Fig. 22 shows a rolling mill stand as shown in Fig 1, as viewed in the direction in which the rolled material is fed. As shown in Fig. 22, the rolling mill stand according to this embodiment includes work rolls 301 that are actually in contact with material P to be rolled and perform rolling operation, backup rolls 303 located over and under the work rolls 301so as to aid the application of rolling force to the material P by the work rolls 301, and intermediate rolls 302 each located between the work roll 301 and the associated backup roll 303 to correct the warp of the surface of the rolled material P cause by the bend of the work rolls 301. This rolling mill stand is called a six high mill since it has six vertically arranged rolls in total.
Fig. 23 shows a rolling mill stand as shown in Fig. 22, with the positions of the intermediate rolls 302 changed. As shown in Fig. 24, the intermediate rolls 302 of a six high rolling mill can be moved in the direction parallel to the surface of rolled material P and perpendicular to the direction of the movement in feed of the rolled material P (hereafter this direction is referred to as strip width direction). This movement helps adjust the distribution of rolling force applied to the material to be rolled along the strip width direction so that the warp of the surface of the rolled material P due to the bend of the work rolls 301 can be prevented and the good profile and shape of the rolled material P can be assured. The range of the lateral shift
of the intermediate rolls 302 are so set that they can move by a predetermined distance beyond the lateral edges of the rolled material P.
In the six high rolling mill, a bender 304 is provided as a mechanism for adjusting the pressures between the adjacent rolls. In the adjustment of the shift amount of the intermediate rolls 302, the influence on the rolling force and the tension exerted on the rolled material P is corrected by adjusting the pressure by the bender 304.
In a tandem type rolling mill, rolling operation is performed by joining materials having different thicknesses or widths together by welding. Therefore, it is necessary to change the shift amounts of the intermediate rolls 302 (i.e. performs intermediate roll shift) in accordance with the instant at which the strip width of material P changes, that is, at which the point of welding passes through the rolling mill stand. During the period for which the intermediate rolls are being shifted, the rolling force applied to the rolled material P varies along the width direction of the material P so that the shape of the rolled material P is deformed to a great extent. Therefore, it is necessary to prevent the shape deterioration of the rolled material P due to the intermediate roll shift by adjusting the bender 304.
The relationship among the degree of intermediate roll shift, the bender pressure and the deformation of the rolled material can only be described by a complex non-linear phenomenon including such phenomena as rolling phenomenon in the strip width direction, the bending of rolls, etc. Accordingly, if it is required to change the amount of intermediate roll shift in a ramp-shaped change pattern, the change of the bender pressure must be in accordance with the time-sequential change pattern that can suppress the shape deformation of the rolled material, but not a ramp-shaped change pattern. In this embodiment, the change in the strip width of the rolled material P is regarded as the change in rolling condition, and the shift amounts of the intermediate rolls 301, that are the control actuators, and the time-sequential change patterns of the pressure of the bender 304 are given to the respective control actuators just as in the embodiment 1 described above. Hence, the gist of this embodiment is to suppress the deformation of the shape of the rolled material P as described above and to improve production quality. In fact, in this embodiment, parameters of rolling operation what are changed in accordance with time-sequential change pattern are the pressures of the bender 304.
Consequently, just as in the examples shown in Figs. 9 and 21, a rolling phenomenon model is used to obtain the shape of the surface of the material P after rolling on the basis of the shift amounts of the intermediate rolls 302, the pressures of the bender 304 and the rolling force in the rolling simulator, and the shift amounts of the intermediate rolls 304 and the time-sequential adjustment pattern for the bender 304, which provide a minimal shape
deformation, are obtained and stored in the control actuator change pattern storage unit 102.
The instant that the shift amounts of the intermediate rolls 302 are to be changed, that is, the instant that the command value generating unit 104 outputs the command to change the shift amounts of the intermediate rolls 302, is determined in accordance with the position where the strip width of the material P is changed, that is, the instant that the point of joint of materials to be rolled having different strip widths reach the rolling stand. The command value generating unit 104 calculates the position in feed of the rolled material P on the basis of the roll speed of the rolling stand. Accordingly, the instant that the front end of the rolled material P reaches the rolling stand, can be obtained by calculating the point of welding.
As in the above embodiment 1, the optimal control actuator time-sequential change pattern setting unit 103 detects the change in operating condition on the basis of the change in command value inputted from the command value generating unit 104, reads the optimal time-sequential set pattern determined as described above out of the control actuator change pattern storage unit 102, and sends the read optimal time-sequential set pattern to the control actuator. Accordingly, it becomes possible to minimize the deformation of the material strip due to the change in the shift amounts of the intermediate rolls 302 adjusted in accordance with the change in the strip width of the rolled material P.
In the example described above, the time-sequential change pattern read in accordance with the change in the shift amounts of the intermediate rolls 302 was the time-sequential change pattern related to the pressures of the bender 304. However, this invention is by no means limited to that example, but roll gap and roll speed may be regarded as quantities to be controlled as in the embodiments 1 and 4 described above.
Further, according to this embodiment, an example was described where the command value generating unit 104 delivers a command to change the shift amounts of the intermediate rolls 302, and the optimal control actuator time-sequential change pattern setting unit 103 obtains from the control actuator change pattern storage unit 102 the time-sequential change pattern related to the change in the pressures of the bender 302 on the basis of the command value outputted from the command value generating unit 104; and the obtained time-sequential change pattern is inputted to the control actuator change pattern generating unit 101.
In this example, the control actuator change pattern generating unit 101 must synchronize the shift amounts of the intermediate rolls 302 inputted from the command value generating unit 104 with the time-sequential change patterns inputted from the optimal control actuator change pattern setting unit 103.
Alternatively, the optimal control actuator change pattern setting unit 103 may
detect the instant that the point where the strip width of the rolled material P changes, reaches rolling stand as described above, obtain time-sequential change patterns including time-sequential patterns related to the changes in the shift amounts of the intermediate rolls 302 from the control actuator change pattern storage unit 102, and input the obtained time-sequential change patterns to the control actuator change pattern generating unit 101.
In such a case, the parameters changed in accordance with time-sequential change patterns are the shift amounts of the intermediate rolls 302 and the pressures of the bender 304. As a result, the control actuator change pattern generating unit 101 obtains time-sequential change patterns related to the shift amounts of the intermediate rolls 302 and the pressures of the bender 304, and therefore need not provide synchronization with the command value inputted from the command value generating unit 104. Hence, required control process can be simplified.

CLAIMS:
1. A rolling control apparatus for controlling a rolling mill (2, 3) which rolls material
between at least a pair of rolls (301), the rolling control apparatus comprising:
a rolling condition change recognition unit (103 or 104) for recognizing that rolling conditions which influence the quality of rolled material change non-linearly;
a time-sequential change pattern storage unit (102) for storing previously generated time-sequential change patterns in order to change parameters related to the rolling operations of the rolling mill (2, 3) in accordance with the non-linear changes of the rolling conditions;
a time-sequential change pattern acquisition unit (103) for acquiring time-sequential change patterns corresponding to the non-linear changes in the recognized rolling conditions when it is recognized that the rolling conditions change non-linearly; and
a time-sequential change pattern output unit (101) for outputting the acquired time-sequential change patterns in order to control roll gap and roll speed of the rolling mill.
2. A rolling control apparatus as claimed in Claim 1, wherein the rolling conditions include at least any one of the strip thickness or strip width of the rolled material, target values in rolling and the height of a looper (200) for supporting the rolled material; and the parameters related to the rolling operation include at least any one of the roll gap or rolling speed of the pair of rolls (301), the height of the looper (200), and the positions of an adjusting unit (301, 302, 304) arranged in accordance with the strip width of the rolled material.
3. A rolling control apparatus as claimed in Claim 1, wherein the time-sequential change pattern storage unit (102) stores plural kinds of time-sequential change patterns in accordance with the non-linear changes in the plural kinds of rolling conditions; and the time-sequential change pattern acquisition unit (103) determines which one of the plural kinds of time-sequential change patterns is to be acquired.
4. A rolling control apparatus as claimed in Claim 3, wherein the time-sequential change pattern acquisition unit (103) determines which one of the plural kinds of time-sequential change patterns is to be acquired on the basis of the rolling conditions and data on the position relative to the rolling mills (2, 3) of the point on the rolled material at which the rolling conditions are to be changed.
5. A rolling control apparatus as claimed in Claim 3, wherein the time-sequential change pattern acquisition unit (103) determines a time-sequential change pattern to be acquired on the basis of the thickness of the material fed to the pair of rolls (301).
6. A rolling control apparatus as claimed in Claim 3, wherein time-sequential change
pattern storage unit (102) stores the plural kinds of time-sequential change patterns in accordance with the non-linear changes in the rolling conditions of different kinds whose modes of change in the rolling target values are different.
7. A rolling control apparatus as claimed in Claim 1, wherein the time-sequential change pattern storage unit (102) stores plural kinds of time-sequential change patterns which are different from one another in terms of a condition of the deviation from a preset value for the material fed to the pair of rolls (301); and the time-sequential change pattern acquisition unit (103) determines a time-sequential change pattern to be acquired on the basis of the thickness of the material fed to the pair of rolls (301).
8. A rolling control apparatus as claimed in Claim 1, wherein the rolling condition change recognition unit (104) recognizes that the rolling conditions changes non-linearly in accordance with the change in the rolling target values.
9. A rolling control apparatus as claimed in Claim 1, wherein the rolling condition change recognition unit (104) recognizes that the rolling conditions changes non-linearly on the basis of data on the position relative to the rolling mills (2, 3) of the point on the rolled material at which the rolling conditions are to be changed.
10. A rolling control apparatus as claimed in Claim 1, wherein the rolling condition change recognition unit (104) recognizes that the rolling conditions changes non-linearly on the basis of the thickness of the material fed to the pair of rolls (301).
11. A rolling control apparatus as claimed in Claim 1, wherein the time-sequential change patterns stored in time-sequential change pattern storage unit (102) are generated through simulation by a rolling simulator.
12. A rolling control apparatus as claimed in Claim 1, wherein the time-sequential change patterns stored in time-sequential change pattern storage unit (102) are those for the respective control periods of the rolling control apparatus.
13. A rolling control apparatus as claimed in Claim 1, wherein the time-sequential change pattern is that which is used to change at least one of the tension exerted on the material fed to the pairs of rolls (301) and the tension exerted on the material rolled by and delivered from the pair of rolls (301).
14. A rolling control apparatus as claimed in Claim 1, including a pair of rolling stands (2, 3) so that rolled material delivered from a first rolling stand is fed to a second rolling stand, wherein the time-sequential change pattern is that which is used to change the tension exerted on the rolled material delivered from the first rolling stand and fed to the second rolling stand.
is. A rolling control method for controlling a rolling mill (2, 3) which rolls material
between at least a pair of rolls (301), the rolling control method comprising:
a step of recognizing that rolling conditions which influence the quality of rolled material change non-linearly;
a step of acquiring, when it is recognized that the rolling conditions change non-linearly, those time-sequential change patterns which correspond to the non-linear changes in the recognized rolling conditions, from a storage unit (102) that stores previously generated time-sequential change patterns in order to change parameters related to the rolling operation of the rolling mill (2, 3) in accordance with the non-linear change in the rolling conditions; and
a step of outputting the acquired time-sequential change patterns in order to control the parameters.
16. A rolling control program for controlling a rolling mill (2, 3) which rolls material
between at least a pair of rolls (301), the rolling control program causing an information processing apparatus to execute:
a step of recognizing that rolling conditions which influence the quality of rolled material change non-linearly;
a step of acquiring, when it is recognized that the rolling conditions change non-linearly, those time-sequential change patterns which correspond to the non-linear changes in the recognized rolling conditions, from a storage unit (102) that stores previously generated time-sequential change patterns in order to change parameters related to the rolling operation of the rolling mill (2, 3) in accordance with the non-linear changes in the rolling conditions; and
a step of outputting the acquired time-sequential change patterns in order to control the parameters.
17. A rolling control apparatus for controlling a rolling mill, substantially as herein described with reference to accompanying drawings and example.
18. A rolling control method for controlling a rolling mill, substantially as herein described with reference to accompanying drawings and example.
19. A rolling control program for controlling a rolling mill, substantially as herein described with reference to accompanying drawings and example.