JPH05123749A - Method for detecting raw speed in tandem rolling mill - Google Patents

Abstract

PURPOSE:To embody a high accuracy of the plate thickness by a tandem rolling mill composed of plural stands. CONSTITUTION:Plate thickness gages 82-85 and plate speed maters 72-75 are arranged at the inlet and outlet sides of all stands 1-3 of the rolling mill, and a standard plate speed meter is attached at the inlet side of rolling mill. The plate speed correcting operation is constructed in the controlling calculator 90, 91. The plate velocity meter 72 is corrected with the standard plate velocity meter at the inlet side of the rolling mill. About the plate velocity maters 73-75 behind the outlet side of the 1st stand, they are corrected orderly based on the up stream side correct finished plate speed gages 72-74.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for improving the accuracy of detecting a plate speed used for controlling the plate thickness in a tandem rolling mill, improving the control accuracy and preventing erroneous control.

[0002]

2. Description of the Related Art In general, as an important product control index for tandem rolling mills, there is accuracy of rolled sheet thickness. Various control methods have been considered for the purpose of further improving the plate thickness accuracy. In it, the strip rolling speeds on the inlet side and the outlet side of the specific stand of the tandem rolling mill were actually measured using a strip speed detection device, and the measurement signal of the strip thickness gauge installed on the inlet side of the stand was included. By using the three parties, the plate thickness on the outlet side of the stand is predicted in real time from the mass flow conservation law (constant volume rule) that is considered to be established just under the roll of the stand, and this predicted value becomes the target set value. A mass flow AGC (Automati) that changes the roll gap of the stand and the roll peripheral speed of the stand on the upstream side.
c Gauge Control). Therefore, in terms of strip thickness precision control, improvement of strip roll speed measurement precision and precision maintenance control are very important issues. Particularly in recent years, the level of demand for plate thickness accuracy from users tends to become stricter, so that the tolerance of measurement accuracy must be suppressed to the utmost limit. The conventional method of measuring the plate speed has been dealt with by the following method.

This is called a contacting method (measurement roll method), and as shown in FIG. 4, a non-driving roll d which is in mechanical contact with the strip c is arranged between the rolling mill inlet / outlet side and the rolling mill stand. A rotary pulse generator (PLG) is attached to the rotary shaft, and the plate speed is detected by the number of integrated pulses within a fixed time.

This is called a non-contact method (laser Doppler method). As shown in FIG. 3, a laser transmitter a and a detector b are provided between the rolling mill entrance / exit and the stand of the rolling mill, and the stripping from the oscillator a is performed. The reflected wave of the laser light applied to c is detected by the detector b. At this time, the amount of change (Doppler frequency) in which the fundamental frequency of the laser shifts in proportion to the plate speed can be measured, and the plate speed is detected by this.

[0005]

The above-mentioned measuring method has the following problems and the measuring accuracy is limited. Therefore, it is difficult to use the plate thickness control with high accuracy and stability. It was

In the contact method, slipping between the strip and the surface of the non-driving roll is likely to occur. In particular, at the time of accelerating and decelerating rolling of the rolling mill, a phenomenon occurs in which the strip speed and the roll peripheral speed are different due to the inertia of the non-driven roll. Also, since the speed is calculated by integrating the number of pulses within a certain time period from the principle of measurement, the measurement cycle must be made relatively long in order to remove the measurement disturbance such as microslip and improve the measurement accuracy. In that case, the detection upper limit frequency of the plate speed signal cannot be increased. On the contrary, when the detection upper limit frequency of the plate speed signal is set large, the measurement accuracy is deteriorated in proportion thereto.

In the non-contact method, unlike the above-mentioned contact method, the laser Doppler effect is used in the detection principle, and since there is no mechanical contact surface with the strip, there is essentially no measurement error due to the slip phenomenon. However,
Since an optical system is used in this method, very high accuracy is required for focusing the pass line of the strip and the optical system. Therefore, a measurement error occurs due to the relative position of the pass line level during rolling of the strip and the optical system. Further, it may be difficult to measure when there is a large degree of strip pass line fluctuation during rolling and a large strip shape defect. Regarding the calibration of the apparatus, in this method, it is possible to calibrate the proportional relationship of the Doppler frequency and the plate speed in (1) Equation 1 using a reference rotating disk that performs constant speed rotation offline. At present, there is no on-line calibration method, and the measurement error due to the change in the relative position with respect to the optical system at the pass line level cannot be eliminated.

[0008]

Fd = 2V * sin (θ / 2) / λ (1) fd: Doppler frequency V: Plate speed θ: Beam crossing angle λ: Laser emission frequency

In the contact method or the non-contact method, with regard to the mass flow control in which the detected plate speed is used as a parameter to control the plate thickness, the rolling of the control rule (2) is 2 as in (3). This is established on the assumption that there is no change in strip width at the entrance and exit of the stand of the rolling mill. However, in reality, such an assumption holds only approximately, and the error of the condition is observed as a measurement error of the plate speed in the plate thickness control.

[0010]

[Equation 2] W _i = W _i-1 (2) W _i : Width of the _i- th stand output side plate W _i-1 : Width of the _i- th stand input side plate

[0011]

(3) (H _i + ΔH _i ) * V _i = (H _i-1 + ΔH _i-1 ) * V _i-1 (3) H _i : i-th stand output side plate thickness setting value ΔH _i : i-th stand Out-side plate thickness deviation H _i-1 : _i- th stand-in side plate thickness set value ΔH _i-1 : _i- th stand-in side plate thickness deviation V _i : i-th stand out-side plate speed V _i-1 : _i- th stand in-side plate speed

In view of such conventional problems, the present invention provides a means for improving the measurement accuracy and for identifying the location when a measurement abnormality occurs, thereby improving the accuracy and stabilizing the thickness control. It is intended to be used.

[0013]

The gist of the present invention is that the same number of non-contact type plate velocimeters that use the laser Doppler effect as the principle of detecting the rolling strip velocity and the same number of plate thickness gauges that measure the strip thickness are provided before and after the same stand. A tandem rolling mill equipped with two or more stands was equipped with a PLG attached to the roll and a computing device for computing the reference roll wound around the strip on the rolling mill entrance side and the roll peripheral speed as the number of rotation pulses within a certain period of time. A calibrating device consisting of is arranged, and the plate speed measured by this calibrating device is compared with the measurement value of the non-contact type plate speed meter installed on the inlet side of the rolling mill, and based on the result, the non-contact type is measured in real time. The plate speed correction coefficient is calculated so that the measured value of the plate velocimeter matches the reference speed of the calibration device, and the offset error, which is the accumulated error of various measuring systems, is corrected. After that, for at least two or more non-contact type plate speed meters continuously installed in the rolling mill stand from the upstream side of the rolling mill, the measured values are used to calculate from the mass flow conservation law. The offset error of the plate speed meter is estimated from the difference between the mass flow plate thickness and the measurement result of the plate thickness meter corresponding to this, and based on this result,
This is a strip velocity detection method in a tandem rolling mill characterized by determining and compensating a correction coefficient of the strip velocity meter so that the offset error becomes sequentially zero sequentially from the upstream of the stand.

[0014]

In the present invention, as shown in FIG. 1, both the contact type plate speed meter and the non-contact type plate speed meter are installed on the inlet side of the rolling mill. In addition, non-contact type plate speed gauges are continuously installed between the stands of the rolling mill and also on the final exit side of the rolling mill. Further, the same number of plate thickness gauges as the non-contact type plate speed meter are installed between the rolling mill entrance / exit side and the rolling mill stand. In such an observation system, the offset error of the non-contact type plate speed meter on the inlet side of the rolling mill is quantified by comparing the detected plate speed values of both with the contact type plate speed meter as an online reference calibration device. However, as shown in FIG. 4, in both plate velocimeters, one measures the speed of the plate surface and the other measures the peripheral speed of the roll surface. Since there is a speed difference due to the strip plate thickness t, calibration of both detected values is performed. In this case, the plate thickness must be corrected. In order to make the offset error quantified in this way zero, the correction coefficient of the equation (4) is introduced into the detection value detected by the non-contact type plate velocimeter, and this coefficient value is determined. Next, the non-contact type plate speed meter on the entrance side of the rolling mill, which was calibrated in this way, was replaced by No. Used as a reference calibrator for the non-contact plate speedometer on the stand-out side. At this time,
No. The offset error of the non-contact type plate velocimeter on the stand-out side of No. 1 is as shown in Equation (5). The mass flow difference ΔM is introduced and quantified by using the four parameters of the plate thickness detection value and the plate speed detection value for each of the one stand entry / exit side.
Therefore, No. The non-contact type plate speedometer on the stand-out side is
The correction coefficient corresponding to the equation (5) is determined so that this ΔM becomes zero. Similarly, No. Regarding the non-contact type plate speedometer on the 2 stand stand-out side, This time using the non-contact type plate speedometer on the stand 1 exit side, this time No. The plate speed correction coefficient is determined so that the mass flow difference between the two stands in / out side becomes zero. By performing this operation automatically in real time sequentially from the front stand to the rear stand of the rolling mill, the offset error of the non-contact type plate speed meter equipped in the rolling mill of FIG. The accuracy of the detected value will be improved.

[0015]

[Formula 4] V = α * Vm (4) V: Plate speed after calibration Vm: Plate speed indicator value α: Correction coefficient

[0016]

[Number 5] _{ΔM = (H E + ΔH E} ) * V E - (H D + ΔH D) * α * Vm = 0 ... (5) H E: first stand entry side thickness setting value ΔH _E: the first stand input side thickness deviation H _D: first stand delivery side thickness set value [Delta] H _D: first stand delivery side thickness deviation V _E: first stand delivery side speed

In the present invention, the offset error inherent in the non-contact type plate speed meter is quantified by introducing a calculation parameter called mass flow difference starting from the reference contact type plate speed meter and each rolling mill stand. The plate speed correction coefficient is automatically determined in real time so that each offset error becomes zero. Therefore, it is better to use the plate speed corrected by this method than to perform the plate thickness control using the raw plate speed detection value detected by the non-contact plate speed meter, and it changes momentarily during rolling. The influence of the pass line level fluctuation and the strip shape can be removed at any time, and more precise and stable plate thickness control becomes possible. At the same time, an allowable range is set for the plate speed correction coefficient value of each non-contact type plate speed meter, and if the coefficient value obtained by the series of automatic calibration exceeds the allowable range, the plate speed meter is considered to be abnormal. The abnormal position of the plate speedometer can be specified, and the protective measure and the backup measure in the plate thickness control can be automatically performed.

[0018]

Embodiments of the present invention will be described below with reference to the drawings. For simplification of the description, the tandem rolling mill having three stands in FIG. 1 will be described, but the present invention can be generalized, and the tandem rolling mill having N stands can be similarly established.

In the system of FIG. 1, as a plate thickness control, the mass flow AGC is installed in all stands, and the roll speed of the final stand or the (final -1) stand of the final stand according to the plate thickness deviation signal of the plate thickness gauge on the delivery side of the final stand. The final stand is equipped with a tension monitor AGC for correcting the roll speed, and these functions are built in the control computers 90 and 91.

For the sake of explanation, the principle of the mass flow AGC will be briefly described. The AGC concerned is such that the plate thickness deviation ΔH _i-1 of the plate thickness meter installed on the entrance side of the i-th stand is sequentially primary in the computer. At the timing of arrival at the i-th stand of ΔH _i−1 calculated from the rolling speed at that time, the detected plate speeds V _i−1 , V from the non-contact plate speed meter on the input / output side of the i-th stand.
_i is used to estimate the plate thickness deviation ΔH _i on the delivery side of the i-th stand by the equation (6), and the roll speed of the (i−1) -th stand is corrected according to this ΔH _i to reduce the plate thickness variation. It is something to be removed.

[0021]

[Equation 6] ΔH _i = (H _i-1 + ΔH _i-1 ) * V _i-1 / V _i −H _i (6) H _i-1 : Plate thickness setting value H _i on the i-th stand entry side: Plate thickness setting on the output side of i-th stand

At this time, if the measurement errors of the plate velocities V _i-1 and V _i are included, the ratio of the errors directly affects the realization accuracy of the control amount ΔH _i . Therefore, in order to suppress the detection accuracy of the plate speed to the target plate thickness accuracy or less, the offset error of the non-contact plate speed meter is automatically removed during rolling by the following method.

First, the non-contact type plate speed meter 72 on the rolling mill entrance side is calibrated by the contact type plate speed meter 71 installed on the rolling mill entrance side. From the relationship shown in FIG. 4, between the indicated value V _{40 of the} non-contact type plate speed meter 72 and the true plate speed V ₂₀ , and the roll peripheral speed V ₁₀ which is the indicated value of the contact type plate speed meter 71, there are roll diameters. D,
When the plate thickness is t, the equation (7) and the equation (8) are satisfied.

[0024]

[Formula 7] V ₄₀ = (D + t) / D * V ₁₀ (7)

[0025]

V ₂₀ = (D + t / 2) / D * V ₁₀ (8)

As described above, the non-contact plate speed meter 72
Since there is an offset error in the indicated value V ₄₀ in principle, the equation (7) cannot be directly established between the observation amounts of the contact type plate speed meter 71 and the non-contact type plate speed meter 72, Further, since the physical quantity to be observed by the non-contact type plate speed meter 72 in the plate thickness control is the true plate speed V ₂₀ , the correction coefficient α1 is introduced, and the automatic calibration formula of Formula (9) is established. Automatically α1
Is determined, and V ₀ = α1 * V ₄₀ is set as the strip speed on the rolling mill entrance side used for strip thickness control. However, since the observed amount V ₁₀ of the contact type plate speed meter 71 has a measurement error due to the influence of slip,
The automatic correction of the equation (9) is effective only in a steady rolling state in which the rolling speed is constant, and is used after smoothing the measured value N times in order to improve the measurement accuracy.

[0027]

(1 + t / 2D) * ΣV ₁₀ / N−α1 * V ₄₀ = 0 (9)

Secondly, with reference to the automatically calibrated strip speed V ₀ on the inlet side of the rolling mill, No. The non-contact plate speed meter 73 on the stand-out side is automatically calibrated. Therefore, No. A concept called mass flow difference ΔM ₁ which can be defined as a difference between an inflow volume and an outflow volume of a strip before and after one stand per unit time is introduced, and a correction coefficient α 2 as an automatic calibration parameter of the non-contact plate speed meter 73. Is used in the same manner as α1, and α2 is automatically determined so as to satisfy the equation (10).

[0029]

ΔM ₁ = (H ₀ + ΔH ₀ ) * V ₀ − (H ₁ + ΔH ₁ ) * α 2 * V ₁₁ = 0 (10) H ₀ : No. Plate thickness setting on the stand 1 side H ₁ : No. Setting value of plate thickness on stand 1 side ΔH ₀ : No. Thickness deviation ΔH ₁ : No. ₁ output from the thickness gauge on the stand-in side. Plate thickness deviation which is the output of the plate thickness meter on the stand 1 stand side V ₁₁ : Indication value of the non-contact plate speed meter 73

Therefore, No. The plate speed value V ₁ on the plate thickness control on the delivery side of one stand is obtained as V ₁ = α2 * V ₁₁ by using the observation value of the non-contact plate speed meter 73.

Thirdly, this time, with reference to V ₁ , No.
In the automatic calibration of the non-contact type plate speed meter 74 installed on the outlet side of the two stands, the correction coefficient α3 of the non-contact type plate speed meter 74 is automatically adjusted so as to satisfy the equation (11) by the same procedure. To decide.

[0032]

ΔM ₂ = (H ₁ + ΔH ₁ ) * V ₁ − (H ₂ + ΔH ₂ ) * α 3 * V ₂₂ = 0 (11) H ₂ : No. 2 Plate thickness setting value on stand-out side ΔH ₂ : No. 2 Thickness deviation of stand stand-out side V ₂₂ : Observation value of non-contact type plate speed meter 74

Then, No. The plate speed on the control of the 2 stand stand-out side is V ₂ = α3 * V ₂₂ .

[0034] Finally, automatic calibration formula V ₂ as a reference (1
2) No. which satisfies the formula 12 The control plate speed V ₃ on the exit side of the three stands can be obtained.

[0035]

[Equation 12] ΔM ₃ = (H ₂ + ΔH ₂ ) * V ₂ − (H ₃ + ΔH ₃ ) * α4 * V ₃₃ = 0 (12) V ₃ = α4 * V ₃₃ H ₃ : No. Plate thickness setting value on the stand 3 side ΔH ₃ : No. Plate thickness deviation on the stand 3 side V ₃₃ : Observation value of non-contact plate speed meter 75

The above-described series of processes and procedures are performed by the control computer 9
By constructing with No. 1, it is possible to realize automatic calibration of strip speed in a real-time online environment during rolling. Further, by setting the allowable upper and lower limit ranges that can be physically taken for α1, α2, α3, and α4 obtained in the above process, it is possible to identify the abnormal location on the equipment of the plate speedometer. For example, if the laser oscillator of the non-contact type plate speed meter 73 fails and the plate speed cannot be detected, the parameter of α2 will be the upper limit value, so that α2 should be constantly monitored. It is possible to automatically detect the failure.

[0037]

As described above, according to the present invention, the plate speed detection accuracy has been remarkably improved, which was conventionally a constraint condition for the plate thickness realization accuracy in the plate thickness control, and it was impossible in the past. Changes in various rolling conditions (pass line changes, strip shape changes)
Since it is possible to eliminate the fluctuation of the plate speed indicator indicated by the change, it is possible to detect the change in the friction coefficient and the change in the advanced rate, etc., which occur during acceleration / deceleration rolling, etc. Can be realized. FIG. 2 is an example of realizing the plate thickness accuracy according to the present invention, and the effect is clear. Further, since it is possible to automatically detect a failure of the plate speed meter and take measures against it, it is possible to improve reliability when the plate speed meter is used for controlling the plate thickness.

[Brief description of drawings]

1 is a diagram showing an example of an apparatus for carrying out the method of the present invention.

FIG. 2 is a diagram illustrating an effect of the present invention in comparison with a conventional method.

FIG. 3 is an explanatory diagram of a conventional non-contact velocity detection method to which a laser Doppler effect is applied.

FIG. 4 is a diagram illustrating a conventional contact-type speed detection principle.

[Explanation of symbols]

 1 to 3 Rolling mill stand 11 to 13 Rolling mill driving electric motor 21 to 23 Electric motor rotation speed detector 31 to 33 Rolling mill rolling down device 41 Rewinding reel 42 Bridle roll 43, 44 Winding reel 51 Rewinding reel driving electric motor 52 Bridle Roll drive motor 53, 54 Take-up reel drive motor 61 Exit side shear 71 Contact plate speed meter 72-75 Non-contact plate speed meter 82-85 Plate thickness meter 90, 91 Control computer 100 Beam splitter 101 Mirror 102 Backlight probe 103 Irradiated light 104 Scattered light 105 Light receiving probe 106 Light receiving element a Laser oscillator b Detector c Strip d Non-driving roll

Claims (1)

[Claims] 1. A tandem rolling mill comprising two or more non-contact type plate speedometers using the laser Doppler effect as a principle for detecting the rolling strip speed and two or more stand plates equipped with the same number of plate thickness gauges for measuring the strip thickness. A calibration device consisting of a PLG attached to the roll and a calculation device for calculating the peripheral speed of the reference roll wound on the strip at the entrance side of the rolling mill as the number of rotation pulses within a certain period of time is arranged in the roll. The plate speed measured by the device and the measured value of the non-contact type plate speed meter installed on the inlet side of the rolling mill are compared and calculated, and the measured value of the non-contact type plate speed meter is calculated in real time based on the result. The plate speed correction coefficient is arithmetically processed to match the reference speed of No. 1 and the offset error, which is the accumulated error of various measuring systems, is removed. For a non-contact type plate speed meter continuously installed in the stand of the rolling mill from the upstream side of the rolling mill, the mass flow plate thickness calculated from the law of conservation of mass flow using the measured values and the corresponding Estimate the offset error of the plate speed meter from the difference in the measurement results of the plate thickness meter,
Based on this result, a strip velocity detecting method in a tandem rolling mill is characterized in that a correction coefficient of the strip speed meter is determined and compensated so that the offset error becomes sequentially zero from upstream of the stand.