CN1020868C

CN1020868C - Thickness gauge type thickness setting and measuring method for agc system

Info

Publication number: CN1020868C
Application number: CN 88100750
Authority: CN
Inventors: 张进之
Original assignee: Central Iron and Steel Research Institute
Current assignee: Central Iron and Steel Research Institute
Priority date: 1988-02-23
Filing date: 1988-02-23
Publication date: 1993-05-26
Anticipated expiration: 2003-02-23
Also published as: CN88100750A

Abstract

The present invention relates to a thickness setting method and a thickness gauging method for a high precision board-rolling thickness gauge type automatic gauge control (AGC) system, which proves that a setting thickness h1 is different from a rolled thickness h by analysis, the difference of the setting thickness h1 and the rolled thickness h is particularly determined by a control system of a rolling mill and mechanical characteristics, which can be expressed by a mathematic expression that h 1 = h-(P <1>-P<0>) / Mc. In on-line prediction, the indirect thickness measured value h2 of a board is gotten by rolling pressure and a roll gap value.

Description

Thickness gauge type thickness setting and measuring method for AGC system

The present invention relates to the thickness setting method and the method for measuring thickness of the rolling pachometer type of a kind of high accuracy sheet material automatic thickness control (AGC) system, it sets thickness and to shut out thickness different, and particularly its difference is determined by the control system (KB) of milling train and the characteristic of mechanical (M); In online forecasting, can obtain the indirect thickness measurements of sheet material by draught pressure and roll gap.It is applicable to computer implemented DDC-AGC system, also can be used for simulating the AGC system.

In order to improve the vertical tolerance of steel plate, guarantee the thickness hit rate, pachometer type AGC system has been carried out a large amount of research both at home and abroad, Japanese MSaito carries out high accuracy and rolls in the plate thickness control application on the plate mill of fan island, adopt a kind of AGC system of absolute value mode, forecast thickness with spring equation, this system disposition absolute thickness of slab regulate and high-speed hydraulic is depressed, realized that the high-precision plate thickness that rolls controls.Directly adopt pressure signal, roll gap signal on the jobbing sheet-rolling mill of China steel mill, calculate one-tenth-value thickness 1/10 by spring equation, set an one-tenth-value thickness 1/10 at the adder place, calculated thickness is regulated roll gap with the difference of setting thickness through PID adjuster, amplifier control electrohydraulic servo valve, equate until indirect thickness measuring and setting thickness, be the two difference when being output as zero, roll gap is just constant.More than the thickness prediction computational methods of two kinds of methods be identical in itself, its computing formula is:

h=φ + (P ₂-P _O)/(KB) + A

H is the rolled piece exit thickness in the formula;

φ is a gap values between rollers;

P ₂Be the draught pressure measured value;

P ₀For pressing the fixed roll seam setting pressure (pressing pressure) at zero point;

K _BFor the rolled piece width for B the mill stiffness of time control default;

A is a constant, and is relevant with zero point, roll wear, thermal expansion and other errors.

With AGC steel rolling the time, must set an one-tenth-value thickness 1/10 h.Before stinging steel, draught pressure is zero, and roll gap φ must swing very big.In order before stinging steel, to transfer a suitable roll gap, have only force value of artificial setting, when steel is nipped and reach normal width, again the force value of artificial setting is transformed on the observed pressure signal.The technical difficulty of doing like this is very big, because one is that suitable stinging steel setup pressure value, the 2nd, the moment of the pressure signal of controlling well conversion will be arranged.These two setting values and steel grade, specification, rolling pass are relevant, for the numerous and diverse working condition of description, are difficult to draw suitable setting value.

Thickness setting also is very difficult, because the setting rigidity in real mill stiffness and the control system can not be in full accord, so the thickness of setting out is not exclusively the same with the actual thickness that shuts out.The way of Japan and some factory of China all is to revise constant A, but can not improve the thickness hit rate well.Because to the product of a description, the pressure between each passage is unequal, and the accurate finished product of required thickness road, the preceding road of finished product, its draught pressure changes bigger; To different descriptions, the difference of draught pressure is just bigger between each passage, and it is undesirable therefore to solve problem with the correction constant A.Technological difficulties in the steel rolling of above full dose method (absolute value) pachometer type AGC system have influenced the raising of thickness prediction hit rate.

The objective of the invention is at above-mentioned technological difficulties, propose the thickness setting method and the method for measuring thickness of the rolling pachometer type of a kind of high accuracy sheet material AGC system.Considered the influence of mill control system characteristic and mechanical property in the method, from having solved the method for forecast of high accuracy thickness and thickness setting in essence, rather than leaned on the way of correction factor thickness prediction and thickness setting.Overcome the difficult point of traditional method, improved thickness prediction precision and hit rate greatly, thereby improved production efficiency and board quality.

Above-mentioned purpose realizes in the following manner:

Utilize draught pressure can measure the thickness h of rolled piece indirectly ₂, its rule is generally described by spring equation:

h ₂=φ + (P ₂-P _O)/(K _B) + A（1）

And find between forecast thickness and actual (real) thickness bigger difference is always arranged in the production practices, so adopt the method for revising constant A.This method fails to embody all sidedly the characteristic of control system and milling train.

In the AGC system, control system and milling train associating characteristic are described by the equivalent stiffness value of milling train, and the equivalent stiffness computing formula of absolute value pachometer type AGC system is

MC＝ (KB·M)/(KB-M) （2）

M is the milling train true stiffness in the formula, generally is difficult for recording its exact value, but its physical quantity that to be objective reality;

The MC equivalent stiffness;

K _BWhen the rolled piece width is B, the mill stiffness that control system is set.

Replace setting rigidity with true stiffness M, in order to obtain the sheet material that thickness is h, gap values between rollers should be

φ=h (P ₂-P _O)/(M) - A （3）

In control system, the predicted value of rolled piece exit thickness is h ',

h ^′=φ + (P ₂-P _O)/(K _B) + A（4）

Because M ≠ K _BSo h ' ≠ h(forecasts one-tenth-value thickness 1/10 ≠ one-tenth-value thickness 1/10).

With (3) formula substitution (4) formula

h′＝h+ (KB-M)/(MKB) P ₀- (KB-M)/(MKB) P ₂（5）

Equivalent stiffness formula (2) substitution (5) formula is got

h ^′=h + (P ₂-P _O)/(M _C) （6）

(6) formula shows, obtain the rolled piece that thickness is h, and when with the steel rolling of AGC system, the thickness setting value of this system should not be h, but the h ' that calculates by (6) formula.

With (6) formula substitution (4) formula because this moment h=h ₂, h ₂Be indirect measurement,

h ₂=φ + (P ₂-P _O)/(KB) + (P ₂-P _O)/(M _C) + A （7）

(7) formula shows in online forecasting, can be obtained the indirect thickness measurements h of sheet material by draught pressure and roll gap ₂, its essence is accurate spring equation.It will reflect the setting rigidity value K of control system characteristic _BWith the natural rigidity value M of milling train, MC joins together by equivalent stiffness, will reflect that dexterously the two-parameter of control system characteristic and milling equipment characteristic is introduced in the equation, obtained accurate spring method.Because (P ₂-P _O)/(K _B) be the function of draught pressure, so, if it is incorporated in the A constant term, realize the self adaptation of A parameter realizing that it is unapproachable making the purpose of spring equation precision by modern control theory and measuring technique.

In sum, in order to obtain the rolled piece that thickness is h, in the thickness setting method of this pachometer type AGC system, set thickness h ₁With to shut out thickness different, its difference is determined by the equivalent stiffness MC of reflection mill control system and mechanical property, and is represented by following mathematical expression:

h ₁=h (P ₂-P _O)/(M _C) （8）

H in the formula ₁For setting thickness

P ₁Be forecast pressure

And the formula of accurately measuring rolled piece thickness is (7) formula.

The present invention is suitable for computer implemented DDC-AGC system most, and analog circuit also can be realized.

Below in conjunction with description of drawings line map of the invention process.

Fig. 1 realizes schematic diagram of the present invention,

Fig. 2 is the schematic diagram of existing AGC system,

Among this two figure, the 1st, pressure-measuring head, the 2nd, working roll, the 3rd, rolled piece, the 4th, support roller, the 5th, plunger, the 6th, differential transformer, the 7th, oil cylinder, the 8th, servo valve, the 9th, roll gap is measured, and the 10th, adder, the 11st, pressure measxurement.

In Fig. 1, thickness setting is tried to achieve h by (8) formula ₁That's all, A is set at constant, and this method has realized thickness control and two functions of thickness prediction automatically.

Fig. 2 is the diagram that prevailing system is realized, by changing control and the forecast that the A coefficient value reaches thickness.By foregoing reason as can be known, the way that changes the A coefficient can not adapt to the production status of many descriptions, in fact can not improve the accuracy of system.

Comparison diagram 1 and Fig. 2, method of the present invention is little with the difference of existing out-of-date methods in realization, but method of the present invention simplified on coefficient A, and A is a constant, and has increased the circuit of equivalent stiffness MC part, and the calculating of MC is realized by (2) formula.

Method of the present invention also can realize becoming rigidity control except that improving the control system precision.In the operation of rolling of a slab, the front passage can be rolling with the APC system, i.e. MC=M; Pony-roughing pass is rolling with the AGC system, gets hard rigidity, as gets MC=3000 ton/millimeter, can be calculated the setting stiffness K of system by (2) formula _B; For final pass, good for guaranteeing plate shape, can adopt soft rigidity, as MC=0.8M, can calculate corresponding K by (2) formula _BValue.So just make the realization of absolute value pachometer type AGC system more free.

Utilize method of the present invention, use accurate spring equation, owing to reflected of the influence of control system characteristic,, will inevitably improve thickness hit rate and thickness prediction precision from having solved the problem of forecast of high accuracy thickness and thickness setting in essence to thickness prediction and thickness setting.For example, in the application of the rolling band steel for shadow mask of steekle mill, roll into 2.5 * 1050 millimeters by 14 * 1050 millimeters, utilize this method, rolling by five passages, first block of steel just hit the thickness targets value.The actual observation record of first three piece steel rolling is as shown in table 1, and it is as shown in table 2 to set specification.

Annotate: this system is that analog line realizes that each parameter is not accurately measured and demarcated, and comprises the part value of A in thickness setting, so setting value h ₁Bigger.

In the shadow mask steel band operation of rolling, K _B＞M, and finished product passage draught pressure is less than P ₀(P ₀=1920 tons/millimeter).The setting thickness h that (8) formula of pressing calculates ₁Should be greater than required thickness h(h=2.5 millimeter), the AGC default thickness that physical record gets off is also all greater than the required thickness value.

First three piece steel rolling record of table 1

1 2 3

Passage h ₁P passage h ₁P passage h ₁P

Remember 1 9.2 2,000 1 9.0 2,100 1 8.8 2100

2 6.6 1900 2 6.3 2000 2 6.3 2000

Record 3 5.0 1,700 3 5.0 1,700 3 5.0 1500

4 4.7 1500 4 4.7 1500 4 4.7 1200

Be worth 5 4.5 1,400 5 4.4 1,300 5 4.7 800

Table 2 five passage rolling procedures

Passage 12345

h ₁9.0 6.5 4.8 4.5 4.3

P 2200 2000 1700 1500 1000

Claims

1, the thickness setting method of a kind of AGC system is characterized in that described thickness setting value h ₁Calculate h according to following formula ₁=h-(P ₂-P _O)/(m _c), P wherein ₁For pre-pressure measurement is a power, P ₀For pressing pressure, h is a target thickness, the equivalent stiffness M of milling train _c(KB-M)/(KB-M), K _BSet rigidity for control system, M is the milling train true stiffness.

2, a kind of AGC system shut out method for measuring thickness, it is characterized in that shutting out thickness measurements h ₂Calculate h according to following formula ₂=φ+(P ₂-P _O)/(K _B)+(P ₂-P _O)/(m _c)+A(1) wherein Φ is actual measurement roll gap, P ₂Be observed pressure, A is given constant.