CONTROL DEVICE FOR ROLLING MILL AND CONTROL METHOD THEREOF
BACKGROUND OF THE INVENTION Field of the Invention
The present invention relates to a rolling mill, and more specifically, a rolling-mill control device for controlling a tension reel used for feeding/winding of a rolling-target material, and a control method thereof. Description of the Related Art
FIG. 7 is a conceptual diagram showing a control configuration of a single stand rolling mill SI 00 which is an example of conventional rolling mills.
The single stand rolling mill SI00 includes an entry tension reel 2 (hereinafter, entry-side TR 2) which feeds a rolling-target material u and is provided at an entry side of a mill 1 relative to a rolling direction (indicated by an arrow in FIG. 7) of the mill 1, and an exit tension reel 3 (hereinafter, delivery-side TR 3) which winds up the rolling-target material u having undergone rolling by the mill 1 and is provided at a delivery side.
The entry-side TR 2 and the delivery-side TR 3 are driven by respective electric motors, and an entry-side-TR control device 5 and a delivery-side-TR control device 6 which control respective electric motors are also provided.
According to such a structure, rolling by the single stand rolling mill SI00 is carried out as the rolling-target material u unwound from the entry-side TR 2 is rolled by the mill 1 and wound up by the delivery-side TR 3.
The mill 1 is provided with a roll gap control device 7 which controls a slab thickness (a product thickness) of the rolling-target material u having undergone rolling by changing a roll gap that is a distance between an upper work roll Rsl and a lower work roll Rs2, and a mill speed control device 4 which controls the speed (circumferential speeds of the upper and lower work rolls Rsl, Rs2) of the mill 1.
At the time of rolling, a rolling-mill-speed setting device 10 outputs a speed instruction to the mill speed control device 4, and the mill speed control device 4 executes controlling in such a way that the speed of the mill 1 (circumferential speeds of the upper and lower work rolls Rsl, Rs2) becomes constant.
Tension is applied to the rolling-target material u at the entry side of the mill 1 (left of the mill 1 in FIG. 7) and at the delivery side thereof (right of the mill 1 in FIG. 7), making the rolling stable and efficient.
An entry-side tension setting device 11 and a delivery-side tension setting device 12 are devices that calculate such necessary tension, respectively.
Based on entry-side and delivery-side tension set values calculated by respective entry-side and delivery-side tension setting devices 11, 12, an entry-side tension/current converter 15 and a delivery-side tension/current converter 16 calculate current values for respective electric motors of the entry-side TR 2 and the delivery-side TR 3 for acquiring respective electric-motor torques necessary to apply set tensions to the rolling-target material u at the entry side and the delivery side, and the calculated current values are output to the entry-side-TR control device 5 and the delivery-side-TR control device 6, respectively.
The entry-side-TR control device 5 and the delivery-side-TR control device 6 control currents of respective electric motors so as to acquire the calculated currents, and predetermined tension is applied to the rolling-target material u based on electric-motor torques given to the entry-side TR 2 and the delivery-side TR 3, respectively.
The entry-side and delivery-side tension/current converters 15, 16 calculate a current setting value (electric-motor-torque setting value) so as to acquire a tension setting value on the basis of a model of a TR (tension reel) mechanical system and that of the TR (tension reel) control device, but because such a control model includes an error, an entry-side tension control device 13 and a delivery-side tension control device 14 correct respective tension setting values based on actual tension measured by an entry-side tension gauge 8 provided at
the delivery side of the mill 1 and actual tension measured by a delivery-side tension gauge 9 provided at the delivery side. The corrected values are output to respective entry-side and delivery-side tension/current converters 15, 16, and the entry-side and delivery-side tension/current converters 15, 16 change respective current values to be set for the entry-side-TR control device 5 and the delivery-side-TR control device 6.
Because the slab thickness of the rolling-target material u is important from the standpoint of a product quality, a slab thickness is controlled.
The slab thickness at the delivery side of the mill 1 (right of the mill 1 in FIG. 7) is controlled as a delivery-side thickness control device 18 causes the roll gap control device 7 to control a roll gap of the mill 1 by operating the upper and lower work rolls Rsl, Rs2 based on an actual slab thickness detected by a delivery-side thickness gauge 17.
As explained above, according to the single stand rolling mill, the delivery-side TR 3 and the entry-side TR 2 for winding and unwinding are subjected to a torque constant control for causing torques generated by respective electric motors to be constant, and tension applied to the rolling-target material u is controlled so as to become constant by correcting an electric-motor-current instruction based on actual tensions measured by respective entry-side and delivery-side tension gauges 8, 9.
Electric-motor torques of the motors of respective entry-side and delivery-side TRs 2, 3 are acquired based on an electric-motor current, so that the torque constant control may be regarded as a current constant control (see JPH10-277618A and JP2000-84615A).
When the TR (tension reel) is controlled through the torque constant control, as is disclosed in Japan Patent No. 4107760, the torque constant control interferes with a slab thickness control which is applied to the mill, resulting in a poor precision of delivery-side slab thickness. The effect to the delivery-side slab thickness becomes large with entry-side tension in comparison with delivery-side tension, and problems of the mill 1 and that of the entry-side TR 2 relating to such effect will be explained below.
FIG. 8 is a conceptual diagram showing a rolling phenomenon between the entry-side TR 2 and the mill 1 in the single stand rolling mill SI00.
As shown in FIG. 8, at the entry-side TR 2, an entry-side TR (tension reel) speed 20 is set by integrating a total of electric-motor torque 22 which is an output of the entry-side-TR control device 5 and tension torque 25 set based on entry-side tension 24 (Tb) and a mechanical condition (reel diameter D and reel gear ratio Gr), that is, by integrating the total of the electric-motor torque 22 and the tension torque 25. Note that J is a moment of inertia (kg-m2) of the entry-side TR 2.
In the rolling mill 1, a delivery-side slab thickness 26 is set based on a value acquired by multiplication of a roll gap change amount 23 (= AS) by an illustrated predetermined coefficient M/(M+Q), and a value acquired by multiplication of entry-side tension 24 of the mill 1 by a predetermined coefficient 5P/5Tb/(M+Q). A mill entry-side speed 21 is set from the set delivery-side slab thickness 26 through the mass-flow conservation rule. The entry-side tension 24 is acquired by integrating a difference between the mill entry-side speed 21 and the entry-side TR speed 20.
In FIG. 8, M is a mill constant M (kN/m), Q is a plasticity constant (kN/m), and dP/5Tb/(M+Q) is an effect coefficient (kb) to the delivery-side slab thickness due to variation in a rolling load P (kN) originating from variation in entry-side tension Tb.
The mass-flow conservation rule is a basic theory of the mill 1. When the rolling-target material u is continuous from the entry side of the mill 1 (left of the mill 1 in FIG. 7) to the delivery side of the mill 1 (right of the mill 1 in FIG. 7), this theory can be expressed by formula (1).
H-Ve = h-V0 (1)
where:
H is a slab thickness at the entry side of the mill 1;
h is a slab thickness at the delivery side of the mill 1;
Ve is a slab speed at the entry side of the mill 1; and
V0 is a slab speed at the delivery side of the mill 1.
As is clear from the formula (1) of the mass-flow conservation rule, if the entry-side slab thickness is constant, when the entry-side slab speed changes, the delivery-side slab thickness also changes.
In the case of the single stand rolling mill (the single mill 1 shown in FIG. 7), the entry-side slab speed is the entry-side TR speed. The entry-side TR 2 changes the entry-side TR speed 20 in such a way that the tension torque 25 matches the electric-motor torque 22, but this change is brought by the inertia of the entry-side TR 2, the mill 1, and a rolling phenomenon, so that there is no means for suppressing any change in the entry-side TR speed
Accordingly, in the mill 1, as AS of the roll gap change amount 23 is changed through a slab thickness control in order to make the delivery-side slab thickness (the thickness of the rolling-target material u at the delivery side of the mill 1) constant, in response to such a change, the mill entry-side speed 21 (the speed of the rolling-target material u at the entry side of the mill 1) also changes, resulting in generation of a deviation (ATb) in the entry-side tension (24).
The entry-side TR speed 20 is changed in order to suppress any generation of such a deviation, but such a change generates a variation in the delivery-side slab thickness. An entry-side tension suppressing system 27 executed by the entry-side TR 2 may have a large time constant in some cases depending on a rolling condition as disclosed in Japan Patent No. 4107760. This may cause a variation in the delivery-side slab thickness with a large waviness.
The entry-side tension 24 is also suppressed by a rolling phenomenon. As the entry-side tension 24 changes, the rolling load P of the mill 1 also changes, resulting in a change in the mill entry-side speed 21. This entry-side tension and rolling phenomenon
system 28 (see FIG. 8) also changes the entry-side tension 24. Because the response of the entry-side tension and rolling phenomenon system 28 is extremely faster than that of the entry-side tension suppressing system 27, the entry-side rolling phenomenon in FIG. 8 can be converted as shown in FIG. 9.
FIG. 9 is a block diagram which simplifies a rolling-phenomenon part in FIG. 8.
As shown in FIG. 9; the roll gap change amount 23 (= AS) of the mill 1 appears as the deviation ATb of the entry-side tension 24 at the same phase, and the entry-side TR speed 20 changes with such a deviation being integrated at the entry-side TR 2. Therefore, relationships between the roll gap change amount 23 (= AS) and the deviation ATb in the entry-side tension 24, the change in the entry-side TR speed 20, and the change in the delivery-side slab thickness become as shown in FIG. 10.
FIG. 10 is a diagram showing a relationship among the roll gap change amount 23, the entry-side tension 24 (Tb), the entry-side TR speed 20, and the delivery-side slab thickness.
As shown in FIG. 10, as the roll gap change amount 23 changes, the entry-side speed of the mill 1 changes, and the entry-side tension 24 thus changes. Together with the change in the entry-side tension 24, the entry-side TR speed 20 changes through an operation by the inertia of the entry-side TR 2 because the entry-side TR 2 is performing a torque constant control.
As the entry-side TR speed 20 changes, a variation in the delivery-side slab thickness is generated through the mass-flow conservation rule (formula (1)).
As the variation in the delivery-side slab thickness occurs, the delivery-side thickness control device 18 (see FIG. 7) controls the roll gap change amount 23 in order to make the delivery-side slab thickness constant. When such successive operations continue, as shown in FIG. 10, the delivery-side slab thickness starts vibrating.
In practice, because the delivery-side thickness gauge 17 (see FIG. 7) is located at a position apart from the mil device 1, there is a time lag until the delivery-side thickness
control device 18 (see FIG. 7) detects a delivery-side slab thickness, but such a time lag can be ignorable if it is sufficiently shorter than a vibration period of the delivery-side slab thickness.
SUMMARY OF THE INVENTION
As explained above, in the conventional mill 1, a torque constant control (a current constant control) performed on the entry-side TR 2 and the delivery-side TR 3 is a factor which causes a variation in the entry-side and delivery-side speeds of the mill 1, and such a variation also causes a variation in the delivery-side slab thickness.
This is because when a torque constant control is performed, a tension reel speed changes due to the inertia of the entry-side TR 2 and that of the delivery-side TR 3 because the torques of the entry-side and delivery-side TRs 2, 3 are set to be constant. As a result, from the mass-flow conservation rule (see formula (1)), the delivery-side slab thickness becomes varying.
The most important thing for the rolling-target material u produced by the mill 1 is the precision of a delivery-side slab thickness (product thickness precision). Tension at the entry side and at the delivery-side is important for stabilization of the operation, but it is no problem if such tension varies slightly for the purpose of maintaining the product thickness.
The present invention has been made in view of the foregoing circumstances, and it is an object of the present invention to provide a rolling-mill control device and a control method thereof which suppress any variation in a delivery-side slab thickness of the rolling mill which is caused due to a variation in a speed of an entry-side TR and that of a delivery-side TR.
In order to achieve the object, the present invention according to a first aspect provides a control device for a rolling mill including tension reels for feeding and winding a rolling-target material arranged at an entry side of a mill and at a delivery side of the mill, respectively. The control device includes a tension/speed control means which controls a tension between the tension reel and the mill so as to maintain the tension at a desired value,
takes precedence to make a speed of the tension reel constant with respect to a deviation from a tension set value within a preset range, and refrains from correcting the tension deviation, thereby suppressing any variation in the speed of the tension reel.
The present invention according to a second aspect provides a method of controlling a rolling mill having tension reels for feeding and winding a rolling-target material arranged at an entry side of a mill and at a delivery side of the mill, respectively. The method includes a step of causing a control device to control tension between the tension reel and the mill so as to maintain the tension at a desired value, a step of taking precedence to make a speed of the tension reel constant with respect to a deviation from a tension set value within a preset range, and a step of refraining from correcting the tension deviation, thereby performing a control of suppressing any variation in the speed of the tension reel.
According to the present invention, there are provided a rolling-mill control device and a control method thereof that suppress any variation in a slab thickness at the delivery side of a mill which is caused due to a variation in the speed of an entry tension reel and that of an exit tension reel.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a conceptual diagram showing a control configuration of a single stand rolling mill S according to a first embodiment of the present invention;
FIG. 2 is a diagram showing a control configuration when an entry-side TR is controlled by an entry-side TR speed according to the first embodiment;
FIG. 3A is a diagram showing a detailed configuration of an entry-side tension/speed control device of the first embodiment;
FIG. 3B is a diagram showing a dead-band setting curve;
FIG. 4A is a diagram showing a configuration of an entry-side-TR-speed control device of the first embodiment;
FIG. 4B is a diagram showing an I-control integrated value relative to an elapsed time in an I-control of the entry-side-TR-speed control device shown in FIG. 4A;
FIG. 4C is a diagram showing a torque-constant-control current instruction input into the I-control of the entry-side-TR-speed control device shown in FIG. 4A from an entry-side TR control mode determination device relative to an elapsed time;
FIG. 4D is a diagram showing a signal of a torque-constant-control mode input into the I-control of the entry-side-TR-speed control device shown in FIG. 4A from the entry-side TR control mode determination device relative to an elapsed time;
FIG. 5 is a diagram showing a general configuration of the entry-side TR control mode determination device of the first embodiment;
FIG. 6 is a diagram showing a control configuration when an entry-side TR is controlled by an entry-side TR speed in a single stand rolling mill having no tension gauge at an entry side and at a delivery side of a mill according to a second embodiment;
FIG. 7 is a conceptual diagram showing a control configuration of a single stand rolling mill as an example of conventional rolling mills;
FIG. 8 is a conceptual diagram showing a rolling phenomenon between an entry-side TR and a rolling mechanism of the single stand rolling mill;
FIG. 9 is a block diagram of a simplified rolling phenomenon shown in FIG. 8; and
FIG. 10 is a diagram showing a relationship among a conventional roll gap change amount, entry-side tension, an entry-side TR speed, and a delivery-side slab thickness.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Embodiments of the present invention will be explained with reference to the
accompanying drawings.
FIG. 1 is a conceptual diagram showing a control configuration of a single stand rolling
mill S according to a first embodiment of the present invention.
«First Embodiment»

The single stand rolling mill S of the first embodiment controls an entry tension reel 2 (hereinafter, an entry-side TR 2) through a speed constant control, and controls tension of a rolling-target material u at the entry side and at the delivery side of a mill 1 through a tension control with a tension reel speed being as a control end. As a dead-band is established in a tension deviation which is to be controlled through the tension control, a variation in a speed of the entry-side TR 2 is suppressed, thereby minimizing a deviation of a delivery-side slab thickness of the rolling-target material u.
That is, the entry-side TR 2 is subjected to a speed constant control to prevent the speed of the entry-side TR 2 from varying in accordance with a variation in tension.
Moreover, when a variation in the delivery-side slab thickness of the rolling-target material u (variation in a product thickness) is large, a speed constant control for the entry-side TR 2 is selected, and when a variation in the delivery-side slab thickness of the rolling-target material u is small, a torque constant control is selected so as to perform a control which can maintain the quality of the product. Configuration of Single Stand Rolling Mill S>
The single stand rolling mill S shown in FIG. 1 has the same configuration as that of the single stand rolling mill S100 (see FIG. 7) except an entry-side-TR-speed control device 41, i an entry-side tension/speed control device 42, and an entry-side TR control mode determination device 43 (i.e., a section H indicated by double dashed lines in FIG. 1), so that the same structural element as that of the single stand rolling mill SI00 will be denoted by the same reference numeral, and a detailed explanation thereof will be omitted.
The entry-side-TR-speed control device 41, the entry-side tension/speed control device i 42, and the entry-side TR control mode determination device 43 are described as a control program written in, for example, a C language stored in a PLC (Programmable Logic
Controller) and realized by executing the program.
Note that the entry-side-TR-speed control device 41, the entry-side tension/speed control device 42, and the entry-side TR control mode determination device 43 may be realized using a circuit, and how to realize those devices is not limited to any particular technique.
According to the single stand rolling mill S which is a cold rolling mill, a variation in entry-side tension of the mill 1 (tension of the rolling-target material u at the left of the mill 1 shown in FIG. 1) and a variation in an entry-side slab speed (the speed of the rolling-target material u at the left of the mill 1 shown in FIG. 1) largely affect the delivery-side slab thickness of the rolling-target material u having undergone rolling (a slab thickness of the rolling-target material u at the right of the mill 1 in FIG. 1).
An explanation will be given of a case in which the entry-side TR 2 of the mill 1 is controlled through a speed constant control (ASR).
FIG. 2 is a diagram showing a control configuration when the entry-side TR 2 is controlled by an entry-side TR speed 20.
As shown in FIG. 2, in the entry-side tension/speed control device 42, an actual value Tb of entry-side tension 24 measured by an entry-side tension gauge 8 (see FIG. 1) is subjected to feedback and the speed of the entry-side TR 2 is set in such a manner as to acquire tension which is equal to entry-side tension set by an entry-side tension setting device 11. The entry-side-TR-speed control device 41 into which an entry-side-TR-speed instruction of the entry-side tension/speed control device 42 is input detects an entry-side TR speed 20, and controls the entry-side TR speed 20 so as to match the entry-side-TR-speed instruction which is an output by the entry-side tension/speed control device 42.
According to such a configuration, it becomes possible to control the entry-side TR speed 20 based on a request from another control system (e.g., a delivery-side thickness control device 18 (see FIG. 1)).
In the case of a conventional torque constant control, as shown in FIG. 8 and FIG. 9, the entry-side tension suppressing system 27 sets the entry-side TR speed 20 which enables acquisition of entry-side tension torque matching the electric-motor torque 22 given to the entry-side TR 2. According to the configuration of the first embodiment, however, the entry-side tension/speed control device 42 (see FIG. 2) controls the entry-side TR speed 20 in such a way that an actual value of the entry-side tension 24 becomes a set value by the entry-side tension setting device 11 (see FIG. 2).
In general, an electric-motor torque constant control is applied to the entry tension reel 2 of the conventional single stand rolling mill SI00. According to a torque constant control, the mechanical system of the entry-side TR 2 and the entry-side tension suppressing system 27 which is a rolling phenomenon at the mill 1 operates so as to acquire a torque matching the electric-motor torque 22.
Therefore, a response is extremely fast in comparison with a case in which a speed constant control is applied.
Hence, when a phenomenon which is a problem to be solved by the present invention occurs is a case in which a response of the entry-side tension suppressing system 27 which is set based on an entry-side slab speed Ve, a delivery-side slab thickness h of the rolling-target material u, an effect coefficient kb (= 3P/5Tb/(M+Q)), and the like decreases, i.e., a case in which a time constant becomes large, and it is preferable that a torque constant control which is a simpler control system is applied in a normal case.
For example, as shown in FIG. 2, when the entry-side slab speed Ve is large, the delivery-side slab thickness h is small, and the effect coefficient kb is large all of which set the gain of the entry-side tension suppressing system 27, the time constant becomes large, so that a variation in the product thickness of the rolling-target material u becomes large.
Therefore, according to the first embodiment, the entry-side TR control mode determination device 43 (see FIG. 1 and FIG. 2) which determines whether a speed constant
control is proper or a torque constant control is proper is provided. A control is changed over in such a way that when a speed constant control is executed, a current instruction which is an output from the entry-side-TR-speed control device 41 is input into an entry-side TR control device 5 in accordance with actual data, such as the entry-side slab speed Ve of a rolling speed, the delivery-side slab thickness h of the rolling-target material u, and the effect coefficient kb and when a torque constant control is executed, a current instruction acquired by an entry-side tension/current converter 15 from tension set by the entry-side tension setting device 11 is input into the entry-side TR control device 5.
FIG. 3A is a diagram showing a detailed configuration of the entry-side tension/speed control device 42, and FIG. 3B is a diagram showing a dead-band setting curve.
The entry-side tension/speed control device 42 shown in FIG. 3A performs a PI (Proportional Integral)-control 421 based on a deviation between actual data of entry-side tension detected by the entry-side tension gauge 8 (see FIG. 1) and a tension setting by the entry-side tension setting device 11.
In order to maintain the entry-side tension 24 of the mill 1 to be a set value, it is necessary to control the speed of the entry-side TR 2, so that a dead-band in the amount of variation in the entry-side tension is established, and a control is not performed up to a certain value of a tension deviation to be set based on the rolling condition. This is because if a control is performed without establishing a dead-band in the amount of variation in the entry-side tension, a variation in the speed of the entry-side TR 2 in accordance with the amount of variation in the entry-side tension becomes large, and as a result, the delivery-side slab thickness of the rolling-target material u (product thickness) becomes varying (see formula (1) of mass-flow conservation rule).
Therefore, as shown in FIG. 3A, a dead-band setting device 424 receives actual data of the delivery-side slab thickness from the delivery-side thickness gauge 17 which detects the
slab thickness of the rolling-target material u at the delivery side of the mill 1 (see FIG. 1), and the dead-band setting device 24 sets how much a variation in the tension can be allowed in accordance with actual data of the delivery-side slab thickness. More specifically, as shown in FIG. 3B, an entry-side-tension dead-band amount relative to a predetermined slab i thickness is acquired beforehand by a calculation or the like, set as a dead-band setting curve 425, and stored in a memory.
As shown in FIG. 1, when the rolling-target material u is being rolled, the dead-band setting device 424 receives actual data of the slab thickness from the delivery-side thickness gauge 17, sets an entry-side-tension dead-band amount from the actual data of the slab thickness in accordance with the dead-band curve 425, and sets such amount in the dead-band device 422.
The dead-band device 422 which sets the entry-side tension dead-band amount executes a dead-band process on the entry-side tension deviation, and outputs such a deviation having undergone the process to a Pi-control 421. The Pi-control 421 performs a Pi-control using the value of the tension deviation, and outputs an entry-side-TR-speed change amount based on the tension deviation.
The entry-side-TR-speed change amount is a deviation from the entry-side-TR-speed set value.
Accordingly, an entry-side speed calculating device 423 acquires an entry-side-TR-speed set value from the speed setting for the mill 1 set by a rolling-mill-speed setting device 10, and an entry-side-TR-speed instruction acquired by adding the entry-side-TR-speed change amount to the entry-side-TR-speed set value is output. A deviation between the entry-side-TR-speed instruction and the actual data of the entry-side TR speed 20 (indicated by a negative symbol in FIG. 3A, see FIG. 2) is acquired and given to the entry-side-TR-speed control device 41 (see FIG. 1 and FIG. 3).
FIG. 4A is a diagram showing a configuration of the entry-side-TR-speed control device 41, and FIG. 4B to FIG. 4D are diagrams showing operations of the entry-side-TR-speed control device 41, where FIG. 4B is a diagram showing an I-control integrated value relative to an elapsed time t in an I-control 412 shown in FIG. 4A, FIG. 4C is a diagram showing a torque-constant-control current instruction input into the I-control 412 in FIG. 4A from the entry-side TR control mode determination device 43 relative to an elapsed time t, and FIG. 4D is a diagram showing a signal of a torque-constant-control mode input into the I-control 412 shown in FIG. 4A from the entry-side TR control mode determination device 43 relative to an elapsed time t.
As shown in FIG. 4A, the entry-side-TR-speed control device 41 calculates a current instruction through the Pi-control from a deviation between the speed instruction from the entry-side tension/speed control device 42 and the actual data of the entry-side TR speed.
According to the single stand rolling mill S of the present invention, because a switching between a torque constant control and a speed constant control is caused, the Pi-control at the entry-side-TR-speed control device 41 is divided into a P (Proportional)-control 411 and an I (Integral)-control 412, and for the I-control 412, a correction using the output by the entry-side TR control mode determination device 43 is performed.
In a torque constant control mode, as shown in FIG. 1 and FIG. 2, a current instruction converted by the entry-side tension/current converter 15 from a tension instruction by the entry-side tension setting device 11 is output to the entry-side TR control device 5 through the entry-side TR control mode determination device 43. However, because the entry-side-TR-speed control device 41 is not in operation, the output by the I-control 412 shown in FIG. 4A is 0. In this condition, as a control mode is switched from the torque constant control to the speed constant control, a current instruction becomes 0, so that it becomes difficult to maintain tension.
Accordingly, when the entry-side TR control mode determination device 43 (see FIG. 1
and FIG. 4A) is selecting a torque constant mode (torque constant control) (see al in FIG. 4D), a process of replacing an integral term with a current instruction of the torque constant control is always executed on the I-control 412 of the entry-side-TR-speed control device 41 (see FIG. 4A). When a control mode is switched from the torque constant control (see al in FIG. 4D) to the speed constant control (see a2 in FIG. 4D), a process of replacing the integral term is terminated, and the entry-side-TR-speed control device 41 starts controlling with a current instruction at the time of the torque constant control.
FIG. 5 is a diagram showing a general configuration of the entry-side TR control mode determination device 43.
In the entry-side TR control mode determination device 43, an output switching device 431 selects either the torque constant control or the speed constant control based on the actual data of rolling, for example, a large entry-side slab speed Ve, a small delivery-side slab thickness h, and an effect coefficient kt,.
When the output switching device 431 selects the torque constant control in accordance with a selection result, an output 435 acquired by adding a current value stored in a hold memory 433 to correct the output by the entry-side tension/current converter 15 is given to a current instruction 436.
Conversely, when the output switching device 431 selects the speed constant control, an output 434 of the entry-side-TR-speed control device 41 shown in FIG. 5 is given to the current instruction 436.
When the output switching device 431 switches a control mode from the speed constant control to the torque constant control (current constant control), there may be a case in which the output by the entry-side tension/current converter 15 does not match the output by the entry-side-TR-speed control device 41 (see FIG. 1 and FIG. 5). In this case, the current instruction changes in a stepping manner (see (31 in FIG. 4C), so that the entry-side TR speed
20 becomes varying, and thus tension of the rolling-target material u at the entry side of the mill 1 and the slab thickness of the rolling-target material u at the delivery side become varying.
Accordingly, at a speed-constant-control OFF timing (see (32 in FIG. 4D), as shown in FIG. 5, a difference between the output by the entry-side-TR-speed control device 41 and the output by the entry-side tension/current converter 15 is stored in the hold memory 433, the stored value is added to the output by the entry-side tension/current converter 15, thereby preventing the current instruction from changing in a stepping manner (see P3 in FIG. 4B).
In a rule base 432 of the entry-side TR control mode determination device 43 shown in FIG. 5, whether the torque constant control (the current constant control) or the speed constant control should be applied in accordance with rolling setting information and rolling actual data information is set as a control rule.
For example, as shown in FIG. 2, when the effect coefficient kb (= 9P/5Tb/(M+Q)) is large, the delivery-side slab thickness h is small, and the entry-side slab speed Ve is large, all setting the gain of the entry-side tension suppressing system 27, the time constant becomes large, and a variation at the delivery side (product thickness) becomes large, so that the speed constant control is selected. In other cases, the torque constant control is selected. Note that J (moment of inertia of the entry-side TR 2) and Gr (a gear ratio of entry-side TR 2 to electric motor driving the entry-side TR 2) are determined by the mechanical systems thereof, it is assumed that those are fixed values.
That is, the source code of a control program in the PLC becomes as follow. A conclusion part becomes (select speed constant control) or (select torque constant control).
IF (kb>kl)AND(hVl)
THEN (select speed constant control)
ELSE (select torque constant control)
where kl, hi, and VI are constant, and respective values thereof can be selected
appropriately according to various conditions.
According to the foregoing configuration, it is possible not only to operate the entry-side TR 2 through the torque constant control but also to operate it through the speed constant control, and both control modes can be switched and applied appropriately in accordance with rolling actual data. Therefore, it becomes possible to minimize a variation in the delivery-side slab thickness (a variation in the product thickness) of the mill 1 originating from a variation in the entry-side TR speed 20.
In the entry-side tension/speed control device 42 (see FIG .3) of the first embodiment, the dead-band (dead-band device 422, the dead-band setting device 424) is established in the entry-side tension deviation, but instead of such a configuration, it is possible to suppress any variation in the delivery-side slab thickness by establishing a limiter in the speed instruction and by controlling the entry-side TR speed so as not to exceed a limited value. In this case, a control is executed in accordance with a priority order of the entry-side tension 24 and that of the delivery-side slab thickness variation.
In the first embodiment, the explanation has been given of an example in which the speed constant control for the entry-side TR 2 and the torque constant control thereof are switched over in accordance with a rolling condition of the rolling-target material u. However, the speed constant control and the torque constant control may be switched over in accordance with a product specification of the rolling-target material u, or may be set before rolling. Furthermore, those control modes may be switched over in accordance with a rolling condition of the rolling-target material u currently in rolling, or a past (last, last but one, etc.,) rolling condition of the rolling-target material u. «Second Embodiment»
Next, an explanation will be given of a single stand rolling mill of the second embodiment with reference to FIG. 6.
FIG. 6 is a diagram showing a control configuration when the entry-side TR 2 is
controlled by the entry-side TR speed 20 in the single stand rolling mill having no tension gauge at an entry side of the mill and at a delivery side thereof according to a second embodiment.
The single stand rolling mill of the second embodiment has no entry-side and delivery-side tension gauges 8, 9 (see FIG. 1) which measure actual data of tension at the entry side of the mill 1 and at the delivery side thereof.
In a case in which no tension gauge which measures actual data of tension is provided at the entry side of the mill and at the delivery side thereof in the single stand rolling mill, as shown in FIG. 6, a change in the entry-side TR speed 20 becomes zero when the i electric-motor torque 22 matches the entry-side tension torque 25. Accordingly, the entry-side tension/speed control device 42 is configured in such a way that a current value i 1 converted by the entry-side tension/current converter 15 from the set tension by the entry-side tension setting device 11 matches a current instruction i2 which is a result acquired as the entry-side-TR-speed control device 41 performs control so as to match the speed instruction from the entry-side tension/speed control device 42.
According to such a configuration, it is possible to apply a structure that controls the entry-side TR 2 by the entry-side TR speed 20 through the scheme of the present invention to the rolling mill having no tension gauge.
In the first and second embodiments, the explanation has been given of how to control the entry-side TR 2, but the similar configuration can be applied to a controlling of the delivery-side TR 3.
In the foregoing embodiments, the rolling mill is a single stand rolling mill, but the present invention is not limited to the single stand rolling mill, and can be applied to a tandem rolling mill having a plurality of, including multiple rolling stands if it has a tension reel at an entry side or at a delivery side. «Conclusion»
A variation in the speed of a tension reel is suppressed as a control method of the tension reels (2, 3) is changed from a current constant control (torque constant control) to a speed constant control, a tension control (torque constant control) is performed with a speed instruction, and the speed of the tension reel is not changed if a variation in tension is within an acceptable range, thereby eliminating a variation in the delivery-side slab thickness of the rolling-target material u (product thickness variation).
From the standpoint of a control responsiveness, the torque constant control is preferable, so that the torque constant control and the speed constant control is switched over in accordance with a rolling condition.
In a rolling mill having no tension gauge (8, 9), a tension-reel-speed control is carried out as a control which controls a tension-reel-speed instruction in such a way that the actual data of a current matches a current instruction for the tension reel (2, 3) is performed to maintain tension at the entry and delivery sides of the rolling mill to be a set value. «Working and Effect»
According to the present invention, in comparison with a conventional case in which a tension reel is controlled through a torque constant control (a current constant control), it is possible to suppress any variation in a slab thickness at the delivery side of a rolling mill, and to improve the precision of the slab thickness (product thickness precision).
The present invention can be applied to a controlling of a cold rolling mill, and has no practical problem.

What is claimed is:
1. A control device for a rolling mill including tension reels for feeding and winding a
rolling-target material arranged at an entry side of a mill and at a delivery side of the mill,
respectively, the control device comprising:
tension/speed control means which controls a tension between the tension reel and the mill so as to maintain the tension at a desired value, takes precedence to make a speed of the tension reel constant with respect to a deviation from a tension set value within a preset range, and refrains from correcting the tension deviation, thereby suppressing any variation in the speed of the tension reel.
2. The rolling-mill control device according to claim 1, further comprising:
speed/torque control switching means which switches a control mode between a control of making the tension constant by the tension/speed control means
through the speed of the tension reel; and
a control of making the tension constant by tension-reel-torque constant control
means which makes a drive torque of the tension reel constant, in accordance with a rolling condition.
3. The rolling-mill control device according to claim 2,
wherein the speed/torque control switching means switches a control mode between the control of making the tension constant by the tension/speed control means and the control of making the tension constant by the tension-reel-torque constant control means in accordance with a rolling condition of the rolling-target material and a product specification of the rolling-target material.
4. The rolling-mill control device according to claim 2,
wherein the speed/torque control switching means sets a control mode in advance in either the control of making the tension constant by the tension/speed control means or the control of making the tension constant by the tension-reel-torque constant control means 5 before rolling in accordance with a product specification of the rolling-target material.
The rolling-mill control device according to claim 2, wherein the speed/torque control switching means sets a control mode in either the control of making the tension constant by the tension/speed control means or the control of making the tension constant by the tension-reel-torque constant control means during rolling of the rolling-target material in accordance with a rolling condition of the rolling-target material.
6. The rolling-mill control device according to claim 1,
wherein the control of the tension between the tension reel and the mill by the tension/speed control means is performed based on an actual value of tension applied to the rolling-target material measured by tension detecting means arranged at, at least either one of the entry side of the mill and the delivery side of the mill.
7. The rolling-mill control device according to claim 1,
wherein the control of the tension between the tension reel and the mill is so performed as to cause actual data of a drive torque instruction of the tension reel to match a drive torque instruction of the tension reel calculated from a set value of the tension.
8. The rolling-mill control device according to any one of claims 2 to 5 and 7,
wherein the drive torque instruction to the tension reel is given as a drive current
instruction to the tension reel.
9. A method of controlling a rolling mill having tension reels for feeding and winding a
rolling-target material arranged at an entry side of a mill and at a delivery side of the mill,
respectively, the method comprising:
causing a control device to control tension between the tension reel and the mill so as to maintain the tension at a desired value;
taking precedence to make a speed of the tension reel constant with respect to a deviation from a tension set value within a preset range; and
refraining from correcting the tension deviation, thereby performing a control of suppressing any variation in the speed of the tension reel.
10. The rolling-mill control method according to claim 9, further comprising:
performing a control of making the tension constant through the speed of the tension reel;
performing a control of making the tension constant by making a drive torque of the tension reel constant; and
switching over the control of making the tension constant through the speed of the tension reel and the control of making the tension constant by making a drive torque of the tension reel constant.
11. The rolling-mill control method according to claim 10, further comprising:
switching a control mode in accordance with a rolling condition of the rolling-target material and a product specification of the rolling-target material between the control of making the tension constant through the speed of the tension reel and the control of making the tension constant by making the drive torque of the tension reel constant.
12. The rolling-mill control method according to claim 10, further comprising:
setting the control mode in advance in either the control of making the tension constant through the speed of the tension reel or the control of making the tension constant by making the drive torque of the tension reel constant before rolling in accordance with a product specification of the rolling-target material.
13. The rolling-mill control method according to claim 10, further comprising:
setting the control mode in either the control of making the tension constant through the speed of the tension reel or the control of making the tension constant by making the drive torque of the tension reel constant during rolling of the rolling-target material in accordance with a rolling condition of the rolling-target material.
14. The rolling-mill control method according to claim 9, further comprising:
performing the control of the tension between the tension reel and the mill based on an actual value of tension measured by tension detecting means arranged at, at least either one of the entry side of the mill and the delivery side of the mill.
15. The rolling-mill control method according to claim 9, further comprising:
performing the control of the tension between the tension reel and the mill so as to cause actual data of a drive torque instruction of the tension reel to match a drive torque instruction of the tension reel calculated from a set value of the tension.
16. The rolling-mill control method according to any one of claims 10 to 13 and 15, further
comprising:
giving a drive torque instruction to the tension reel as a drive current instruction to the
tension reel.
17. A control device for a rolling mill including tension reels for feeding and winding a rolling-target material arranged at an entry side of mill and at a delivery side of the mill, substantially as herein described with reference to accompanying drawings and example.
18. A method of controlling a rolling mill having tension reels for feeding and winding a rolling-target material arranged at an entry side of mill and at a delivery side of the mill, substantially as herein described with reference to accompanying drawings and example.