Control system for tandem rolling mill

Abstract

This invention provides a control device for a tandem rolling mill that can prevent plate breakage from occurring during startup, even when the motor load between stands differs significantly to such an extent that it cannot be addressed solely by adjusting the Droop amount. [Solution] The control device for a tandem rolling mill according to the present disclosure comprises a plurality of stands and a plurality of drive devices that control the roller drive motors of each stand. The control device comprises a speed command output unit that outputs a speed command to each drive device based on the conveying speed of the rolled material, a speed feedback acquisition unit that acquires speed feedback from each drive device, a speed forcing amount calculation unit that calculates the speed forcing amount of each drive device so that the speed deviation between the speed command and the speed feedback is small, and a speed forcing amount addition unit that adds the speed forcing amount to the speed command.

Description

Technical Field

[0003]

[0001] The present disclosure relates to a control device for a tandem rolling mill. In particular, the present disclosure relates to a control device for a tandem rolling mill that controls the start-up of the tandem rolling mill from a state where a rolled material has entered a plurality of stands.

Background Art

[0002] A control device for this type of tandem rolling mill (hereinafter also referred to as a "rolling mill") is disclosed in, for example, Patent Document 1 below. In this device, a speed command is temporarily output to each stand before starting the rolling mill, and the Droop amount setting value of the stand on the more downstream side is made smaller. Thereby, even when the motor loads due to mechanical play between the stands are different, appropriate tension is applied to the rolled material between adjacent stands before starting, so as to prevent plate breakage when starting the rolling mill.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] Incidentally, in some cases, oil-film type Mogoyle bearings are still used as backup roll bearings for rolling mills, rather than the rolling bearings that have become mainstream in recent years. In this case, it has been found that simply controlling the set value of the Droop amount, as described in Patent Document 1 above, is insufficient to prevent plate breakage when the rolling mill starts up. The inventors have conducted extensive research and obtained the following findings. Specifically, if the thickness of the oil film of the Mogoyle bearings in each stand differs, the motor load will differ significantly between stands to such an extent that it cannot be addressed by simply setting the Droop amount. In this case, the responsiveness of the speed feedback to the speed standard will differ significantly between stands (see Figure 5), and the speed ratio between stands will be disrupted after startup, resulting in abnormal tension and, consequently, plate breakage.

[0005] Furthermore, when using rolling bearings, the rotational torque of the rolling bearings increases due to wear or deterioration of the rolling bearings or deterioration of the grease. Therefore, even when using rolling bearings, if the degree of wear or deterioration of the rolling bearings or the degree of grease deterioration differs from stand to stand, the motor load will differ so greatly between stands that it cannot be compensated for by simply adjusting the Droop amount.

[0006] This disclosure is based on the above findings and aims to provide a control device for a tandem rolling mill that can prevent plate breakage from occurring when the tandem rolling mill is started, even when the motor load between stands differs so greatly that it cannot be addressed by setting the amount of drop alone. [Means for solving the problem]

[0007] The first aspect of this disclosure relates to a control device for a tandem rolling mill comprising a plurality of stands and a plurality of drive devices that control the roller drive motors of each stand, respectively. The control device starts and controls the tandem rolling mill from a state in which the rolled material has entered the plurality of stands. The control device comprises a speed command output unit that outputs a speed command to each drive device based on the conveying speed of the rolled material, a speed feedback acquisition unit that acquires speed feedback from each drive device, a speed forcing amount calculation unit that calculates the speed forcing amount of each drive device so that the speed deviation between the speed command and the speed feedback is small, and a speed forcing amount addition unit that adds the speed forcing amount to the speed command.

[0008] The second aspect, in addition to the first aspect, further has the following features: This disclosure can be suitably applied when Mogoyle bearings are used as bearings for the backup rolls of each stand.

[0009] The third viewpoint has the following additional features in addition to those of the first or second viewpoint: The velocity forcing amount calculation unit is configured to calculate the velocity forcing amount by multiplying the deviation by a gain.

[0010] The fourth aspect, in addition to the third aspect, has the following further features: The velocity forcing amount calculation unit is configured to acquire at least one piece of information, such as ambient temperature, rolling reaction force at startup, and drive device stop time, and to set a gain based on the acquired at least one piece of information. [Effects of the Invention]

[0011] According to this disclosure, when starting a tandem rolling mill, the responsiveness of speed feedback to the speed command can be improved by using a speed command with an added speed forcing amount as the speed reference. Therefore, even when the motor load differs significantly between stands when starting the rolling mill, it is possible to prevent the occurrence of abnormal tension at startup, and as a result, plate breakage can be prevented. [Brief explanation of the drawing]

[0012] [Figure 1] This figure shows an example configuration of a tandem rolling mill to which the control device for a tandem rolling mill according to the embodiment is applied. [Figure 2] This is a block diagram showing an example of the configuration of a control device for a tandem rolling mill according to an embodiment. [Figure 3] This is a circuit diagram of the velocity forcing amount calculation unit. [Figure 4] This figure illustrates the responsiveness of speed feedback to speed commands in the embodiment. [Figure 5] This diagram illustrates the responsiveness of speed feedback to speed commands in conventional systems. [Modes for carrying out the invention]

[0013] The control device for a tandem rolling mill according to the embodiments of this disclosure will be described below with reference to the drawings. Common or corresponding elements in each figure are denoted by the same reference numerals, and their descriptions are simplified or omitted.

[0014] Figure 1 shows an example of the configuration of a tandem rolling mill to which the control device for a tandem rolling mill according to an embodiment is applied. The tandem rolling mill 1 comprises a plurality of stands (also called "rolling stands") 2 arranged in parallel along one direction in which the rolled material 10 is conveyed, and a control device 3. Each stand 2 has a pair of upper and lower work rolls 21 that sandwich and roll the rolled material 10, a plurality of backup rolls 22 arranged outside the work rolls 21, a motor 23, and a drive device 24 that controls the motor 23. The control device 3 is electrically connected to the plurality of drive devices 24. Mogoyle bearings, and Mogoyle bearings not shown, are used as bearings for the backup rolls 22 of each stand 2. Known types of Mogoyle bearings can be used, so further explanation is omitted.

[0015] Figure 2 is a block diagram showing an example configuration of the control device 3 of a tandem rolling mill 1 according to an embodiment. The control device 3 includes a speed command output unit 31, a speed feedback acquisition unit 32, a speed forcing amount calculation unit 33, and a speed forcing amount addition unit 34 for each drive device 24. That is, each of the units 31 to 34 is provided in the same number as the number of drive devices 24 (five in the example shown in Figure 1).

[0016] The speed command output unit 31 outputs a speed command for the motor 23 (also referred to as the "MRH standard") based on the transport speed of the rolled material 10. The speed feedback acquisition unit 32 acquires speed feedback, which is the actual speed of the drive device 24.

[0017] The speed forcing amount calculation unit 33 calculates the speed forcing amount for each drive device 24 so as to minimize the speed deviation between the speed command output from the speed command output unit 31 and the speed feedback acquired by the speed feedback acquisition unit 32.

[0018] Figure 3 is a circuit diagram of the speed forcing amount calculation unit 33. Figure 4 is a diagram illustrating the responsiveness of speed feedback to the speed reference in the embodiment. As shown in Figure 3, the speed forcing amount calculation unit 33 receives a speed forcing signal, a speed command (MRH reference), a successor, speed feedback, and a gain as inputs. The speed forcing signal is a switching signal (trigger signal) that turns ON for the time from the start time t1 to the start end time t2 shown in Figure 4. The time from time t1 to time t2 when the speed forcing signal is ON can be determined in advance by experimentation or simulation, and the determined time can be set in the timer. Successor is a known correction amount for suppressing torque fluctuations. Speed ​​feedback is a calculated or measured value obtained by the speed feedback acquisition unit 32. Gain is a set value that is set based on the load trend for each stand and is multiplied by the speed deviation as described later.

[0019] The speed forcing amount calculation unit 33 is configured to successively add the speed commands of each drive device 24 output by the speed command output unit 31, obtain a speed deviation by subtracting the speed feedback from the successively added speed commands, perform deadband processing with the speed deviation as an input, and multiply the gain by the speed deviation that is the output of the deadband processing. The deadband processing is a process of outputting zero to prevent hunting of speed control when the speed deviation is smaller than the threshold while outputting the speed deviation when the speed deviation is greater than or equal to a predetermined threshold. The speed forcing amount calculation unit 33 calculates, as the speed forcing amount, a value obtained by multiplying the gain by the speed deviation that is the output of the deadband processing while the speed forcing signal is ON, and calculates the speed forcing amount as zero when the speed forcing signal becomes OFF. That is, the speed forcing amount calculation unit 33 switches the value of the speed forcing amount according to the ON / OFF state of the speed forcing signal. As a result, since the speed forcing signal is ON during the time from the start-up start time t1 to the start-up end time t2, the speed forcing amount is calculated so that the speed deviation becomes smaller.

[0020] The speed forcing amount addition unit 34 adds the speed forcing amount calculated by multiplying the gain by the speed deviation during the time from the start-up start time t1 to the start-up end time t2 (that is, the time when the speed forcing signal is ON) to the speed command.

[0021] As described above, according to the present embodiment, as shown in FIG. 4, when starting up the tandem rolling mill 1, by using the speed command with the speed forcing amount added as the speed reference, the followability of the speed feedback with respect to the speed command can be improved. Therefore, when starting up the tandem rolling mill 1, even when there is a large difference in motor load between stands 2, the generation of abnormal tension is suppressed, and as a result, the occurrence of sheet breakage can be prevented.

[0022] While embodiments of the present disclosure have been described above, the present disclosure is not limited to the embodiments described above and can be implemented in various modified forms without departing from the spirit of the present disclosure. For example, in the above embodiments, a tandem rolling mill 1 with five stands 2 arranged in parallel was described as an example, but the number of stands 2 is not particularly limited and can be applied to a tandem rolling mill 1 with seven stands 2 arranged in parallel.

[0023] Incidentally, the state of the oil film in the Mogoyle bearing changes depending on the ambient temperature, the rolling reaction force at startup, and the stopping time of the drive device 24. The stopping time of the drive device 24 is the time from the stopping time of the drive device 24 (not shown) to the start-up time t1 (see Figure 4). Therefore, the velocity forcing amount calculation unit 33 may be configured to acquire (input) at least one piece of information, such as the ambient temperature, the rolling reaction force at startup, and the stopping time of the drive device 24, and to further perform the function of automatically setting the gain based on the acquired information, such as the ambient temperature, the rolling reaction force at startup, and the stopping time of the drive device 24. For example, the gain can be set based on the ambient temperature, which has the greatest impact on the state of the oil film. Also, when setting the gain based on two or more pieces of information acquired, the gain can be set using a correlation map or relational formula obtained in advance through experiments or simulations. By setting the gain using information such as the ambient temperature that affects the state of the oil film in this way, the gain of the velocity forcing amount can be set accurately, and as a result, the velocity forcing amount can be calculated accurately. This further improves the accuracy of the tracking performance of the velocity feedback.

[0024] Furthermore, although the above embodiment was described using the example of application to a tandem rolling mill 1 that uses Mogoyle bearings as bearings for the backup rolls 22, this disclosure can also be applied to a tandem rolling mill that uses rolling bearings as bearings for the backup rolls 22. When rolling bearings are used, the rotational torque of the rolling bearings increases due to wear or deterioration of the rolling bearings or deterioration of the grease. If the degree of wear or deterioration of the rolling bearings and the degree of grease deterioration differ for each stand, the motor load may differ so greatly between stands that it cannot be addressed by setting the Droop amount alone. In such cases, applying this disclosure can suppress the occurrence of abnormal tension, and as a result, the occurrence of plate breakage can be prevented.

[0025] Furthermore, when the number of elements, quantities, amounts, ranges, etc., are mentioned in the embodiments described above, the invention is not limited to the number mentioned unless it is specifically stated or clearly defined in principle. Also, the structures, etc., described in the embodiments described above are not necessarily essential to the invention unless they are specifically stated or clearly defined in principle. [Explanation of Symbols]

[0026] 1...Tandem rolling mill, 10...Rolled material, 2...Stand, 21...Work roll, 22...Backup roll, 23...Motor, 24...Drive device, 3...Control device, 31...Speed ​​command output unit, 32...Speed ​​feedback acquisition unit, 33...Speed ​​forcing amount calculation unit, 34...Speed ​​forcing amount addition unit

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