JPH07178430A - Speed control method of tandem mill - Google Patents

Abstract

PURPOSE:To effectively utilize the control function of a rolling stand with high responsiveness and to execute stable rolling in a tandem mill in which rolling stands having high responsiveness and low responsiveness coexist. CONSTITUTION:Speed control systems by which motors for driving the rolling stands are controlled are provided every stand and a 1st to a 4th rolling stands ST1-ST4 in which high responsiveness is realizable and a 5th and 6th rolling stands ST5, ST6 with low responsiveness coexist in the tandem mill. A speed command value D4 by which the AC motor ACM of the 4th rolling stand ST4 in which high responsiveness is realizable is calculated as the product of the actual speed Dc of the adjacent 5th rolling stand ST5 which is detected with a speed detector 20 and the speed ratio R4(v4/v5) corresponding to the ratio (h5/h4) of respective thickness on the inlet and outlet sides of the 5th rolling stand ST5 and the speed control of the 4th rolling stand ST4 is executed by outputting the speed command value D4 to a speed adjuster 14.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is applied to a tandem rolling mill in which two types of rolling stands having different responsiveness of speed control coexist when controlling the rolling stand driving electric motor to control the rolling speed. The present invention relates to a suitable speed control method for a tandem rolling mill.

[0002]

2. Description of the Related Art Generally, in a tandem rolling mill, a speed control system for a driving electric motor is provided for each rolling stand constituting the rolling mill, and the rotational speed of the electric motor shaft is detected for each stand to detect the speed. The motor is feedback-controlled by the speed regulator so that there is no deviation between the value and the speed command value.

There are various types of speed control methods for the electric motor for driving each rolling stand, depending on the type of electric motor and the type of power source. In the past, since a DC motor was mainly used as an electric motor, a word Leonard system, a thyristor system or the like was adopted as its speed control system.

However, since the rolling stand for controlling the DC motor by the word Leonard system has low speed response,
In recent years, when renewing the equipment of a tandem rolling mill, a control system having a high speed response in which an AC motor and a cycloconverter are combined has been adopted.

As a result, in the same rolling line consisting of a plurality of stands, a case where a conventional word-leonard type rolling stand having a low speed response and an AC motor type rolling stand having a high speed response coexist. I've been

Here, an example of the speed control system of the word Leonard system and the AC motor system will be briefly described respectively.

A word leonard type speed control system has a speed regulator 50, as shown in FIG.
A current regulator 52, a voltage regulator 54, a field current regulator 56 including a thyristor and a coil, and an induction motor M.
It is known that the motor generator 58 includes a DC generator G and a speed detector 60 that detects the rotation speed of the DC motor DCM that drives the rolling mill. Note that some word Leonard systems do not have the current regulator 52.

The speed regulator 50 outputs a current command value to the current regulator 52 according to the deviation between the speed command value D and the speed feedback signal from the speed detector 60. When the current regulator 52 outputs a voltage command value according to the deviation between the input current command value and the current feedback signal to the voltage regulator 54, the voltage regulator 54 controls the adjusted voltage command value. Output to the magnetic current regulator 56. The field current regulator (converter) 56 generates a field current according to the adjusted voltage command value input from the voltage regulator 54 to cause the motor generator 58 to generate a voltage according to the command,
It is designed to control the speed of the DC motor DCM.

As shown in FIG. 7, the main parts of the AC motor type speed control system are a speed regulator 50, a current regulator 52, a voltage regulator 54, a power converter 62, and a rolling mill. And a speed detector 60 that detects the rotation speed of the AC motor ACM that drives the motor. Here, the signal processing up to the voltage regulator 54 is performed in the same manner as in the case of the word Leonard system, and the adjusted voltage command value input from the voltage regulator 54 is applied to the motor drive power (for example, voltage) by the power converter 62. Or frequency) to control the speed of the AC motor ACM.

If two types of rolling stands having different speed responsiveness are mixed in the same rolling line, such as the above-mentioned word Leonard system and AC motor system, the line starts or stops during acceleration or deceleration. When the speed changes greatly as in the case of time, the two types of stands have different speed responsiveness, which may cause troubles such as breaking of the rolled material. Therefore, in order to prevent the occurrence of such troubles, it is conceivable to reduce the speed response of the high responsive rolling stand to the level of the low responsive rolling stand.

[0011]

However, it may be difficult to accurately match the speed responsiveness of the AC motor system and the ward Leonard system because the control systems are different. For example, in the case of the word-leonard type speed control system without the current regulator 52 shown in FIG. 6, even if the speed response in the idling state is combined with that of the AC motor system, the magnitude of the speed fluctuation with respect to the load torque fluctuation is large. However, the tension fluctuations between the stands increase during acceleration / deceleration of the tandem rolling mill, which causes product defects or plate breaks in extreme cases.

Further, in order to simply adjust the speed responsiveness of all rolling stands, there is no method other than adjusting the high speed responsiveness of the AC motor system to the low speed responsiveness of the word Leonard system. The high speed response inherent in the motor system is sacrificed. In addition, setting the speed responsiveness of all stands to a low level in this way means that for rolling with a tandem rolling mill, control with higher speed responsiveness such as tension control and plate thickness control is more effective. Therefore, it is not an effective control method considering the entire control of the rolling mill.

The present invention has been made to solve the above-mentioned conventional problems. A rolling stand provided with a speed control system in each stand and capable of achieving high response and a rolling stand having low response are provided. Even in mixed tandem rolling mills, fluctuations in tension between stands can be reliably prevented without sacrificing the control function originally possessed by a rolling stand that can achieve high responsiveness, and product defects and strip breakage can be reliably prevented. The problem is to prevent such troubles.

[0014]

According to the present invention, a speed control system for controlling an electric motor for driving a rolling stand is provided for each rolling stand, and a rolling stand capable of realizing high responsiveness and a low responsiveness are provided. In a speed control method for a tandem rolling mill in which rolling stands coexist, a speed command value for driving an electric motor of a rolling stand capable of achieving high responsiveness is set to an actual speed of an adjacent low responsive rolling stand and the rolling stand. The above-mentioned problem is solved by calculating based on the respective plate thicknesses of the entrance side and the exit side.

[0015]

In the present invention, a rolling stand equipped with an electric motor capable of realizing high responsiveness, that is, having a high speed response (hereinafter, referred to as
The high speed response stand) is set to the maximum speed response state, and the actual speed of an adjacent rolling stand having low speed response (hereinafter also referred to as low response stand) is detected,
The speed of the high response stand is made to follow the speed value calculated in consideration of the plate thickness ratio between the entrance side and the exit side of the same stand.

For example, a case where the i-th stand (i is a natural number) has a high response and the i + 1-th stand adjacent to the downstream side has a low response will be described. In the meantime, the ratio of the actual velocity v _i of the i- _th stand to the actual velocity v _{i + 1} of the i _{+ 1-} th stand (v _i / v _{i + 1} ) is calculated from the law of constant mass flow. I + the plate thickness of (+1 stand entry side)
There is a relation that it is equal to the plate thickness ratio (h _{i + 1} / h _i ) on the stand-out side.

Therefore, the speed control system of the i-th stand is maintained in a high response state, and the speed v _i of the _i- th stand is
The actual speed v _{i + 1} of the _{i +} 1th stand measured is added to the i + th stand.
By controlling the value calculated by the following equation (1) in consideration of the plate thicknesses of the entrance side and the exit side of one stand, the i +
Even if the speed v _{i + 1} of one stand fluctuates due to load fluctuation, the speed of the i-th stand can be made to follow the speed fluctuation of the (i + 1) th stand with certainty.
It is possible to roll under tension, and it is possible to effectively prevent product failure as well as plate breakage.

V _i = v _{i + 1} × (h _{i + 1} / h _i ) ... (1)

To explain this more specifically, for example,
In the case of a high response stand in which the speed response of the motors of the first to third stands is fast and a low response stand in which the speed response of the motor of the fourth stand is slow, the speed command value for the motor of the third stand is Follow-up control is performed so that v ₃ given by equation (2) is obtained.

V ₃ = v ₄ × (h ₄ / h ₃ ) ... (2) where v _{4 is the} degree of actual measurement of the fourth stand h ₄ : The plate thickness on the delivery side of the fourth stand h ₃ : The third stand Thickness of the exit side (entry side of the 4th stand)

For example, when the high response stand is an AC motor system and the low response stand is a MG (Motor Generator) system of the word Leonard system for driving a DC motor, the speed response of both is different by 10 times or more. Even when the speed of the motor of the fourth stand fluctuates due to load fluctuation, the speed fluctuation is gentle, so that the speed of the AC motor for driving the first to third stands, which is highly responsive, is the fourth stand. It is possible to easily follow the speed fluctuation of.

[0022]

Embodiments of the present invention will now be described in detail with reference to the drawings.

FIG. 1 is an explanatory view showing a schematic configuration of the entire tandem rolling mill applied to this embodiment.

The tandem rolling mill is provided with six rolling stands ST1 to ST6 from the first to the sixth along the flow direction of the material P to be rolled. Each of the first to fourth rolling stands ST1 to ST4 includes an AC motor ACM as a driving electric motor, and a cycloconverter type speed control system 10 as a speed control system.

Each of the fifth and sixth stands ST5 and ST6 is provided with a direct current motor DCM as a driving electric motor, and as a speed control system is provided with a word-leonard type speed control system 30 having low responsiveness.

In the tandem rolling mill applied to this embodiment, the speed control system 10 of each of the first to fourth rolling stands ST1 to ST4 and the speed control of each of the fifth and sixth rolling stands ST5 and ST6. The system 30 and an acceleration / deceleration command device 40 that outputs an acceleration / deceleration command signal to the speed control system 30 constitute a speed control device for the entire rolling mill.

The speed control system 10 of each of the first to fourth rolling stands ST1 to ST4 includes a speed ratio setting device 12 for individually setting a speed ratio for each rolling stand, and an AC motor speed adjusting device 14. And AC motor torque regulator 1
6, an AC motor power converter 18, and a speed detector 20 for detecting the rotation speed of the AC motor ACM.

The AC motor speed regulator 14 is set so as to exhibit a high level of responsiveness that can be realized by combining the AC motor ACM and the cycloconverter.
Each AC motor speed adjuster 14 has a speed command value corresponding to a product of a speed ratio set by the speed ratio setter 12 and a speed command value for an adjacent downstream rolling stand, and a feedback signal from the speed detector 20. A torque command value corresponding to the deviation is calculated and output to the AC motor torque adjuster 16.

The AC motor torque adjuster 16 calculates a power command value corresponding to the input torque command value and outputs the power command value to the AC motor power converter 18. The power converter 18 adjusts the frequency or the pulse width according to the input power command value,
Controls the speed of the AC motor ACM.

In this embodiment, the first to fourth stands ST1 to ST1
The speed ratio setter 12 of each speed control system 10 included in ST4 includes a speed ratio (v _i / v _i) of the rolling speed of the i-th stand to the rolling speed of the i + 1-th stand on the downstream side adjacent to the i-th stand. ₊₁ ) is set, and the speed ratio is multiplied by the speed command value Di + 1 corresponding to the rolling speed of the rolling stand on the downstream side to obtain the speed command value Di of the i-th stand.
(I = 1 to 4) is determined.

Originally, the speed v _i of the i-th stand is set and controlled based on the equation (1), but as described above,
Since the relationship of h _{i + 1} / h _i = v _i / v _{i + 1} always holds, the speed ratio can be used instead of the plate thickness ratio. Further, since it is easier to set the speed ratio, the present embodiment uses the equation (3) in which the speed ratio is adopted instead of the plate thickness ratio.

V _i = v _{i + 1} × (v _i ′ / v _{i + 1} ′) (3) Where, v _i ′: Set speed of the i-th stand v _{i + 1} ′: i-th of the i + 1 stand Set speed

On the other hand, the fifth and sixth rolling stands ST5, S
Each speed control system 30 of T6 includes a speed setter 32 for individually setting the speed, a generator side speed adjuster 34, a generator side torque adjuster 36, a field current adjuster 38, and a direct current A motor drive generator 40 and a speed detector 20 for detecting the rotation speed of the DC motor DCM are provided.

The generator-side speed adjuster 34 has a speed command value given as a product of the acceleration / deceleration command value from the acceleration / deceleration command device 40 and the set speed from the speed setter 32, and the speed detector 2
A torque command value corresponding to the deviation from the feedback signal from 0 is output to the generator-side torque adjuster 36. The generator-side torque adjuster 36 calculates an electric power command value corresponding to the torque command value, and the calculated electric power command value is used as the field current adjuster 38.
Output to. When the field current regulator 38 adjusts the field current of the DC motor driving generator 40 according to the input power command value, the DC current driving generator 40 uses the field current to adjust the voltage according to the command. DC motor DC
It controls the speed of M.

Further, in this embodiment, the speed command values D1 to ST4 of the first to fourth stands ST1 to ST4 having high speed control responsiveness.
D4 is calculated from the actual speed of the fifth stand ST5 having a low speed response, and is output to each speed adjuster 14. Therefore, a compensation circuit 42 for compensating the roll speed detection value of the fifth stand ST5 is provided between the speed control system of the fourth stand ST4 and the speed control system of the fifth stand ST5. 5 speed command value D5 set in ST5 and speed detector 2
From the actual speed measured at 0, the compensation circuit 42 corrects the time delay and the like to calculate a compensation speed value that is infinitely close to the actual speed, and the speed command value Dc corresponding to the compensation speed value is the fourth speed value.
It is adapted to be input to the multiplier included in the speed control system of the stand ST4.

In the present embodiment, the speed control systems 10 of the first to fourth stands ST1 to ST4 are set in a high speed control response. And the fourth stand S
The speed command value D4 input to the speed adjuster 14 of T4 is calculated by correcting the speed command value D5 in the fifth stand ST5 and the actual speed of the DC motor DCM detected by the speed detector 20 in the compensation circuit 42. the compensation speed command value Dc, setting a value obtained by multiplying the speed ratio is set _{R4 (= v 4 / v 5} ) at a speed ratio setter 12 of the fourth stand. As described above, when the speed command value D4 of the fourth stand ST4 is determined, the speed command values D3 to D1 are sequentially set to the speed command values of the adjacent downstream stands with respect to the third to first stands on the basis of the speed command value D4. It is calculated by multiplying the value by the speed ratio.

That is, the speed controller 1 of the third stand ST3
Speed command value D3 for 4, speed and the speed command value D4 of the fourth stand ST4 calculated above, is set at a speed ratio setter 12 of the third stand ST3 ratio R3 (= v ₃ /
Set with a value multiplied by v ₄ ). Also for the second stand ST2 and the first stand ST1, the speed command values D2 and D1 for the respective speed adjusters 14 are calculated in the same manner as the third stand ST3.

According to the present embodiment, as described above, the speed command value D4 of the high responsive fourth stand ST4 is set to the actual speed of the adjacent low responsive fifth stand ST5 and the set speed of the stand ST5. Since it is set to a value obtained by multiplying the ratio of the setting speed of the fourth stand to
Even if speed fluctuations occur at T5, ST4 ST4
The speed of can be reliably followed. As a result, the fourth stand ST4 (same for the first to third stands)
The original high responsivity possessed by can be effectively functioned, and troubles such as product defects and plate breaks can be prevented, and stable rolling work can be performed.

FIG. 2 is a diagram showing the control results when rolling is actually carried out according to the speed control method of this embodiment, where the horizontal axis represents time and the vertical axis represents relative fluctuation.

This FIG. 2 shows the speed v ₅ of the fifth stand ST5 (B) when the load fluctuation as shown in (A) occurs in the fifth stand ST5 during acceleration and deceleration of the rolling mill.
, The speed v ₄ of the 4th stand is (C), and the speed ratio (v ₄ / v ₅ ) corresponding to the plate thickness of the 5th stand is (D).
The tension between the fourth and fifth stands is shown in (E).

Further, FIG. 3 shows the speed responsiveness of the first to fourth rolling stands ST1 to ST4 having high responsiveness in accordance with the speed responsiveness of the fifth and sixth stands ST5 and ST6 having low responsiveness. FIG. 2 shows the control results obtained by the conventional method of rolling similarly.
It is a diagram corresponding to.

According to the conventional method shown in FIG. 3, the fifth method is used.
The load fluctuation of the stand ST5 causes the speed fluctuation of the stand ST5, and the load fluctuation of the fourth stand also causes the speed fluctuation of the fourth stand ST4. As described above, the load response cannot be accurately matched between the AC motor system and the word Leonard system. Even if they are combined, the magnitude of the load variation varies from stand to stand, so that the speeds of the third to first stands vary differently. As a result, as shown in FIG.
The speed ratio (v ₄ / v ₅ ) fluctuates, and the plate thickness fluctuates on the exit side of the fifth stand ST5. As shown in FIG.
This will induce tension variations between the fifth stands.

On the other hand, according to this embodiment, as shown in FIG.
As is clear from others, the 5th stand ST with slow speed response
No. 5 causes moderate speed fluctuations even with load fluctuations
Therefore, the 4th stand ST4 (1st to 3rd stage) with fast speed response
The same applies to tands ST1 to ST3) is the fifth stand ST5.
To the actual speed of the plate considering the plate thickness ratio (actually the speed ratio)
As it can be easily tracked, it is shown in Fig. 2 (D).
Sea urchin, speed ratio (v_Four/ V _Five) Can be constant
It Therefore, it is possible to reliably prevent variations in plate thickness and tension.
It becomes possible to do.

FIG. 4 shows the response of the speed control in the fourth stand when the control signal of the short cycle shown in (A) is input to the control system for the thickness control, the tension control, etc. in this embodiment ( FIG. 5 is a diagram shown in FIG. 5B, and FIG. 5 is a diagram corresponding to FIG. 4 showing a control result when the same control is performed by the conventional method.

As shown in FIG. 5B, the conventional method reduces the speed response of the AC motor system, so that the control signal of FIG.
It can be seen that the tracking can be performed extremely accurately as shown in FIG.

Although the present invention has been specifically described above, the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the scope of the invention.

For example, in the embodiment, the first to fourth stands S
T1 to ST4 are highly responsive and the 5th and 6th stand ST
5 and ST6 show the case of low responsiveness, but the present invention is not limited to this, and the number of each stand can be changed.

The order of arrangement of the high responsive stand and the low responsive stand may be reversed from that in the above embodiment. For example,
The speed response of the first to fourth stands ST1 to ST4 is slow,
The fifth and sixth stands ST5 and ST6 may be arranged so that the speed response is fast. Also in the case of this arrangement, as in the case of the above-described embodiment, the actual speed of the fourth stand ST4,
Similarly effective speed control can be performed by calculating the speed command values of the fifth stand and the sixth stand in consideration of the outlet plate thicknesses of the fifth and sixth stands ST4, ST5, ST6.

[0049]

As described above, according to the present invention, each stand is provided with a speed control system and a rolling stand capable of achieving high responsiveness and a rolling stand having low responsiveness coexist. In a tandem rolling mill, fluctuations in tension between stands can be reliably prevented without sacrificing the control function inherent in the rolling stand that can realize high responsiveness, and problems such as product defects and plate breakage occur. Can be prevented.

Further, according to the present invention, since the rolling stand having high speed response can be set to the maximum speed response of its capability, control such as plate thickness control and tension control becomes more effective as the speed response becomes faster. The present invention can be used very effectively also for the above.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing a schematic configuration of a tandem rolling mill applied to an embodiment according to the present invention.

FIG. 2 is a diagram showing the effect of the embodiment.

FIG. 3 is a diagram showing a control result by a conventional method.

FIG. 4 is another diagram showing the effect of the embodiment.

FIG. 5 is another diagram showing the control result by the conventional method.

FIG. 6 is an explanatory diagram showing a main part of a control system based on a word Leonard system.

FIG. 7 is an explanatory diagram showing a main part of a control system using an AC motor system.

[Explanation of symbols]

 10 ... Cycloconverter type speed control system 12 ... Speed ratio setter 14 ... Speed adjuster 16 ... AC motor torque adjuster 18 ... AC motor power converter 20 ... Speed detector 30 ... Word Leonard type speed control system 32 ... Speed setter 34 ... Generator-side speed regulator 36 ... Generator-side torque regulator 38 ... Field current regulator 40 ... DC motor driving generator 42 ... Compensation circuit

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical indication location H02P 5/50 A B21B 37/00 BBP (72) Inventor Kenjiro Yasuda Kawasaki-cho, Chuo-ku, Chiba-shi, Chiba Prefecture No. 1 Kawasaki Steel Co., Ltd. in Chiba Steel Works (72) Inventor Hiroaki Masuda No. 1 Kawasaki-cho, Chuo-ku, Chiba City, Chiba Prefecture In Kawasaki Steel Co., Ltd. Chiba Works (72) Inventor Hiroshi Saito 5, Omika-cho, Hitachi City, Ibaraki Prefecture 2-1 Hitachi Ltd. Omika factory

Claims (1)

[Claims] 1. A speed control system for controlling an electric motor for driving a rolling stand is provided for each rolling stand, and
In a speed control method for a tandem rolling mill in which a rolling stand capable of achieving high responsiveness and a rolling stand capable of achieving low responsiveness coexist, speed command values for driving the motors of rolling stands capable of achieving high responsiveness are adjacent to each other. A speed control method for a tandem rolling mill, which is calculated based on an actual speed of a low-responsiveness rolling stand and respective plate thicknesses on an inlet side and an outlet side of the rolling stand.