JPH01170510A - Device for controlling tension between stands of continuous rolling mill - Google Patents

Abstract

PURPOSE:To accurately detect rolling torque and to perform high accurate rolling by inputting an armature current signal and a speed signal of a motor and using a minimal dimension observer of a basic equation simulating a system consisting of a rolling mill and a motor. CONSTITUTION:A rolling torque arithmetic unit 30 operates a rolling torque G1 of a rolling stand 1 based on an armature current signal Ia of a motor 3 detected by a current detector 15 and a rotating speed signal NF1 of the motor 3 detected by a speed detector 5. A speed correction amount arithmetic unit 40 operates and outputs a speed correction amount DELTAN1 based on a rolling load signal P1 detected by a load detector 14, the rotating speed signal NF1 of the motor 3 detected by the speed detector 5, and the rolling torque G1 found by operation. Thus, tension control for tension between stands without detection delay is performable.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to an inter-stand tension control device for a continuous rolling mill.

(Prior Art) One of the disturbances that deteriorate the dimensional accuracy of products rolled by a rolling mill is fluctuations in tension between stands.

In order to eliminate this variation in tension between stands, control using louvers has conventionally been performed.

However, it is difficult to use the looper when the material is thick, such as during rough rolling in a hot rolling mill, or when the shape of the material is complex.

Therefore, from the fluctuation of the generated torque of the rolling mill driving electric motor,
A technology for detecting fluctuations in the tension between stands and controlling the tension between the stands based on the fluctuation was disclosed in Japanese Patent Application Laid-Open No. 54-1327.
This method is disclosed in Japanese Patent Application Laid-Open No. 117816/1983, and the like.

Figure 4 is shown in Japanese Unexamined Patent Publication No. 132712/1982
FIG. 2 is a block diagram showing an inter-stand tension control device applied to a stand tandem rolling mill. In the same figure, rolling mill 1
．． 2 are each driven by an electric motor 3.4, which is each controlled to a target speed by a speed control device 7.8. The speed reference for both stands is given by a speed ratio setter 11.12 that determines the speed ratio between the stands and a main speed ratio setter 13 that sets the line speed. In the stand 1, an adder 9 adds the speed reference NR1 and the speed signal NPI of the speed detector 5 that detects the rotational speed of the electric motor 3, and the speed control device 7 controls the electric motor so that the difference becomes zero. Control the speed of 3. Similarly, in the stand 2, an adder 10 adds the speed reference NR2 and the speed signal NF2 from the speed detector 6, and the speed control device 8 controls the electric motor 4 so that the difference becomes zero. In addition to these control systems for each stand, an inter-stand tension control device 17 is provided. This inter-stand tension control device 17 controls the stand 1 tension detected by the rolling load detector 14.
, the armature current 11 of the motor 3 detected by the current detector 15, the terminal voltage V1 of the motor 3 detected by the voltage detector 16, and the speed NFL of the motor 3 detected by the speed detector 5. The tension between the stands 1 and 2 is controlled by determining a speed correction amount ΔN1 and adding this speed correction amount ΔN1 as the third input of the adder 9 to manipulate the speed of the electric motor 3. The principle of this inter-stand tension control device will be explained below.

Generally, in rolling a steel plate or the like, there is a relationship between rolling load P and rolling torque G as shown in the following equation.

-m, 1...(1) Here, a is called a torque arm, and is assumed to be constant regardless of changes in the deformation resistance of the material. Furthermore, in so-called hot rolling, in which a material is heated and rolled, it is known that changes in rolling load with respect to changes in tension applied to the material are much smaller than changes in rolling torque. Inter-stand tension control is performed using these relationships.

In FIG. 4, the rolling load of the stand 1 in a tension-free state until the material 18 is bitten by the stand 1 and reaches the stand 2 is Pol, and the rolling torque is G. Set to 1. Further, if the rolling load and rolling torque after the material is bitten by the stand 2 are Pl and G1, respectively, the torque Gt due to the tension generated between the stands 1 and 2 is expressed by the following equation.

Here, the rolling load P1 is detected by the rolling load detector 14, and the rolling torque G1 can be calculated by the following formula R1, where the effective load current is 1 and the back electromotive force coefficient is Φ1.

G1-Φ111?1...(3) The effective load current IR in this equation (3) is based on Japanese Patent Application Laid-Open No. 132712-1982.
As explained in detail in the publication, the armature current Ia
Calculated from t.

The speed of the stand 1 is corrected so that the tension torque Gt□ determined by the above equation (2) becomes a certain target tension torque. This speed correction amount can be determined using the following equation.

ΔN1-g1 (G t l-G t Ot )-(
4) Here, gl is the gain of tension control between stands, G
t ol is the target tension torque between stand 1 and stand 2.

On the other hand, in order to obtain the effective current in equation (3),
No. 4-132712 uses a motor simulation circuit 22 shown in FIG. Here, Φ shown in block 19 is the back electromotive force coefficient, J in block 20 is the moment of inertia converted to the motor axis, S is the Laplace operator, and block 21 is the transfer function of the armature circuit, and the internal R is the armature resistance, T is the time constant of the armature circuit, and S is the Laplace operator. Also, ■ is the motor terminal voltage, ■ is the electric a
This is the a-state current.

Here, as described above, the armature current I includes the effective load current 1acc corresponding to the rolling torque G and the acceleration/deceleration current 1acc associated with changes in the speed NF.

This motor simulation circuit 22 simulates the no-load state of the actual motor section, and a signal V 1 equal to the actual armature voltage is applied to it. Therefore, only the acceleration/deceleration current corresponding to the actual acceleration/deceleration of the motor flows as the armature current in the motor simulation circuit 22. If this acceleration/deceleration current 1 ace is subtracted from the actual armature current l 2 using the adder 23, the output becomes the effective load current JR.

(Problems to be Solved by the Invention) The conventional effective load current detection device shown in FIG. 5 simulates the effective load current IR by observing only the motor terminal voltage V. Directly detects acceleration/deceleration current Iacc caused by changes in speed NF.
There was a detection delay until the armature voltage V was changed to keep the speed Np constant, and as a result, there was a problem that the effective load current could not be accurately determined when the rolling torque G suddenly changed. .

In addition, in the conventional effective load current detection device shown in FIG. 5, if the field current of the DC motor is large to a certain extent, it is sufficient to use blocks 19A and 19B with predetermined transfer functions. In this case, the back electromotive force coefficient Φ is calculated by the following formula in blocks 19A and 19B.

Here, L is the armature glue actance, R is the electric a
The a-like resistance, ■ is the armature current, but since the armature current I actually includes ripples, the back electromotive force coefficient cannot be estimated accurately, and for this reason, the effective load current There was also the problem that it could not be determined accurately.

This invention was made in order to solve the above-mentioned problems. Even if the rolling condition changes, the rolling torque can be accurately detected, thereby controlling the tension between the stands of a rolling mill that enables high-precision rolling. The purpose is to obtain equipment.

[Structure of the invention]

(Means for Solving the Problems) The first invention of this application is an inter-stand tension control device for a continuous rolling mill that corrects the speed standard of an electric motor that drives the rolling mill so that the inter-stand tension is constant. a first arithmetic circuit that inputs an armature current signal and a speed signal of the electric motor and calculates the rolling torque using a minimum dimension observer of a basic equation that simulates a system consisting of the rolling mill and the electric motor; and a second arithmetic circuit that calculates a speed correction amount for correcting the speed reference based on a rolling load signal of a rolling mill, a speed signal of the electric motor, and a rolling torque obtained by the first arithmetic circuit. It is characterized by this.

Further, a second invention of this application is an inter-stand tension control device for a continuous rolling mill that corrects the speed standard of an electric motor that drives the rolling mill so that the inter-stand tension is constant.
a first calculation circuit that receives an armature current signal, an armature voltage signal, and a speed signal of the motor and calculates a back electromotive force coefficient of the motor using a minimum-dimensional observer of a basic equation that simulates the motor; , a second arithmetic circuit that inputs an armature current signal and a speed signal of the electric motor and calculates the rolling torque using a minimum dimension observer of a relational expression that simulates a system consisting of the rolling mill and the electric motor; A third step of determining a speed correction amount for correcting the speed reference based on the rolling load signal of the machine, the speed signal of the electric motor, and the rolling torque determined by the second calculation circuit.
The present invention is characterized by comprising an arithmetic circuit.

(Function) Generally, the basic equation of motion of an electric machine-mechanical system consisting of an electric motor and a rolling mill is expressed by the following equation.

Here, Φ is a back electromotive force coefficient, J is a moment of inertia in terms of a motor shaft, D is a braking coefficient in terms of a motor shaft, and G is a rolling torque. Since digitalization is progressing in recent control devices, in order to cope with this, equation (6) is discretized by the sampling time Δt, and the discretized state equation at the i step becomes as follows.

From this equation, the speed N, (t) and rolling torque G (i) are considered as state quantities, and the theory of the minimum-dimensional finite-settling observer (
If this equation is transformed according to the theory of the minimum dimension observer (including the present invention), it becomes the following equation.

ω (1+1)−0≦αL1αωc (1) + (1
-α)...(8A)...(8B) Here, α is the time constant of the observer, and its thickness is set in the range of 0≦α to 1 depending on the size of ripples, etc.
For example, when α-0, it becomes a finitely stable observer. this(
The rolling torque G can be estimated by repeatedly calculating equations 8A) and (8B).

The principle of this minimum dimension observer and its configuration are described in "Digital Control Theory" (written by Tsutomu Mita, published by Shokodo,
1986), so please refer to the above (8A).
), the process of deriving equation (8B) is omitted.

In the first invention of this application, since the rolling torque is calculated by the calculation unit having the function of this minimum dimension observer, it is possible to reliably capture sudden changes in the rolling torque due to changes in the acceleration/deceleration current I ace of the electric motor. This allows for highly accurate tension control between the stands.

On the other hand, the induced voltage of the DC motor is expressed by the following equation (5) above. When this equation (5) is discretized using the sampling time Δt, the discretized state equation of the i-th step becomes as shown in the following equation.

I (1+1)-e' ”I (i)
a a a From this equation, if 1 a(1) and Φ・NF(i) are regarded as state quantities and transformed based on the theory of the minimum dimension observer, the following equation is obtained.

ω (i+ 1)−βωΦ(4) +(1−β)■Φ
a
...(IOA) ...(IOB) Here, β is the time constant of the observer, and its size is adjusted in the range of 0≦β to 1 depending on the size of ripples, etc.
For example, when β-0, it becomes a finitely stable observer. this(
The back electromotive force coefficient Φ can be estimated by repeatedly calculating the equations IOA) and (IOB).

In the second invention of this application, since the back electromotive force coefficient is calculated by the arithmetic unit configured according to the theory of the minimum dimension observer, the DC motor is controlled by field weakening, so that the electric Even if the child current includes ripples, the rolling torque can be calculated accurately, and thereby the inter-stand tension can be controlled with high precision.

(Embodiment) FIG. 1 is a block diagram showing the configuration of an embodiment corresponding to the first invention. In the figure, the same reference numerals as in FIG. 4 indicate the same elements. A rolling torque calculation section 30 and a speed correction amount calculation section 40 are provided in place of the inter-stand tension control device 17 in the figure.

Of these, the rolling torque calculation unit 30 receives the armature current signal (hereinafter simply referred to as armature current) of the motor 3 detected by the current detector 15 and the rotational speed signal of the motor 3 detected by the speed detector 5. (hereinafter simply referred to as rotational speed) NFl
The rolling torque G1 of the rolling stand 1 is calculated using the above equations (8A) and (8B). In addition, the speed correction amount calculation unit 40 calculates the rolling load signal (
From Pl (hereinafter simply referred to as rolling load), the rotational speed N,1 of the electric motor 3 detected by the speed detector 5, and the rolling torque G1 obtained by calculation, the rolling The speed correction amount ΔN1 of the stand 1 is calculated and output.

FIG. 2 is a block diagram showing the detailed configuration of the rolling torque calculation section 30 that embodies the above formulas (8A) and (8B).
is a coefficient unit related to the moment of inertia, block 33 is a coefficient unit related to the braking coefficient, blocks 34 and 35 are coefficient units related to the observer time constant, and block 37 is a storage device that stores the value of the previous step for one sampling time Δt. It is.

FIG. 3 is a block diagram showing the configuration of an embodiment according to the second invention, and in the figure, the same reference numerals as in FIGS. 2 and 4 indicate the same elements. this is,
A back electromotive force coefficient calculator 50 is added to the configuration of FIG. 2, and a back electromotive force coefficient calculator 31 of the rolling torque calculator 30 is added.
Instead, a multiplier 37 is provided to multiply the armature current I by the back electromotive force coefficient Φ.

On the other hand, the back electromotive force coefficient calculating section 50 is as described above (IOA).

In the figure, block 51 is a coefficient unit related to armature inductance, block 52 is a coefficient unit related to armature time constant, and block 53.5 is an embodiment of the (IOB) formula.
4 is a coefficient unit regarding the time constant of the observer, block 55
is a storage device that stores the value of the previous step for one sampling time Δt, and block 56 is a divider, and the output of this divider 56 becomes the back electromotive force coefficient Φ, which is applied to the rolling torque calculation section 30.

In the above embodiments, the basic equations for simulating the electric motor and rolling mill system and the basic equations for simulating the electric motor are transformed into discretized state equations, respectively, assuming digital calculation, and then the minimum dimension observer is Although formulas transformed according to theory are used, when performing analog calculations, it is possible to transform the basic formula directly according to the theory of the minimum dimension observer and use an arithmetic device that embodies this transformed form to achieve similar accuracy. It is possible to calculate the back electromotive force coefficient Φ, the rolling torque G, and the speed correction amount ΔN1.

〔Effect of the invention〕

As is clear from the above explanation, according to the present invention, the rolling torque is determined using a formula that accurately simulates the rolling system, and the speed correction amount is calculated using this rolling torque. Tension between stands can be controlled without detection delay.

In addition, by adding a calculation unit that calculates the back electromotive force coefficient of the motor, it is possible to accurately estimate the rolling torque even with ripples in the armature current that occur in the case of field weakening. Inter-stand tension control becomes possible.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing a schematic structure of an embodiment corresponding to the first invention of this application, FIG. 2 is a block diagram showing a detailed structure of the embodiment, and FIG. FIG. 4 is a block diagram showing the structure of an embodiment corresponding to the invention; FIG. 4 is a block diagram showing the structure of a conventional inter-stand tension control device; FIG.
The figure is a block diagram showing the detailed configuration of the device. 1.2... Rolling stand, 3, 4... Electric motor, 5,
6... Speed detector, 7, 8... Speed control device, 9,
10...Adder, 14...Load detector, 15...
Current detector, 16... Voltage detector, 30... Rolling torque calculation section, 40... Speed correction amount calculation section, 50...
Back electromotive force coefficient calculation section. Applicant's representative Mr. Sato 1: Rolling stand Figure 3 Figure 5

Claims (1)

[Scope of Claims] 1. An inter-stand tension control device for a continuous rolling mill that corrects the speed standard of an electric motor that drives the rolling mill so that the inter-stand tension is constant; a first arithmetic circuit that receives a signal and calculates the rolling torque using a minimum dimension observer of a basic equation that simulates a system consisting of the rolling mill and the electric motor; a rolling load signal of the rolling mill; and a speed of the electric motor; a second method for determining a speed correction amount for correcting the speed reference based on the signal and the rolling torque determined by the first calculation circuit;
An inter-stand tension control device for a continuous rolling mill, characterized in that it is equipped with an arithmetic circuit. 2. The continuity system according to claim 1, wherein the first arithmetic circuit creates a state equation by discretizing the basic equation by sampling time, and constitutes a minimum dimension observer of this state equation. Tension control device between stands of rolling mill. 3. In an inter-stand tension control device for a continuous rolling mill that corrects the speed standard of an electric motor that drives the rolling mill so that the inter-stand tension is constant, an armature current signal, an armature voltage signal, and a speed signal of the electric motor are provided. a first calculation circuit that calculates a back electromotive force coefficient of the motor using a minimum dimension observer of a basic equation that simulates the motor, and an armature current signal and a speed signal of the motor; a second arithmetic circuit that calculates the rolling torque using a minimum dimension observer of a relational expression that simulates a system consisting of the rolling mill and the electric motor; a rolling load signal of the rolling mill; a speed signal of the electric motor; An inter-stand tension control device for a continuous rolling mill, comprising: a third calculation circuit that calculates a speed correction amount for correcting the speed reference based on the rolling torque calculated by the calculation circuit. 4. The first and second arithmetic circuits each create a state equation by discretizing the basic equation by sampling time, and constitute a minimum dimension observer of this state equation. An inter-stand tension control device for a continuous rolling mill as described in 2.