CN104307892B - The method of band head correction in tandem rolling crossing process - Google Patents

Abstract

The invention discloses the method for the correction of band head in a kind of tandem rolling crossing process, relate to metal-pressed machine technical field, adopt following steps: A, sampling time point when setting band head arrives each detection position; B, in crossing process, when band head arrives the current detection position until mill stand, by carrying out IMAQ and process to the both sides of the edge curve of band head, judge to calculate band head deflection and skew direction; C, carry out on-line tuning to current in mill stand bilateral roll gap difference; D, carry out presetting to follow-up frame bilateral roll gap difference; E, repetition step C and step D are until profile gauge detects band head, and the band head dual-side contour curve detected by multichannel profile gauge, carries out on-line tuning to finished frame bilateral roll gap difference.In energy Timeliness coverage band tandem rolling crossing process of the present invention, the phenomenon of head generation deflection is gone forward side by side Row sum-equal matrix, causes lumber recovery to decline or threading failure to avoid deflection.

Description

The method of band head correction in tandem rolling crossing process

Technical field

The present invention relates to metal-pressed machine technical field, the method for band head correction in especially a kind of tandem rolling crossing process.

Background technology

Strip is in continuous rolling process, due to the impact of unsymmetrical factors or supplied materials lateral bending, the phenomenon of band head deflection may be produced during threading, this is one of principal element affecting product lumber recovery and reeling quality, even directly may cause threading failure time serious, cause monoblock rolled piece to scrap or device damage.Current domestic calendering factory also rests in the level of Non-follow control in the head correction of band, and often rule of thumb and estimate the object that the band head deflection adjustment both sides roll gap difference obtained realizes rectifying a deviation, control effects is poor for operating personnel.

Summary of the invention

The object of this invention is to provide the method for band head correction in a kind of tandem rolling crossing process, this method can solve the problem of existing Strip band head rectifying effect difference in tandem rolling crossing process.

In order to solve the problem, the technical solution used in the present invention is: in this tandem rolling crossing process the method for band head correction be provided with in each frame of Continuous mill train detect band head roll before the video camera of curve, after finished frame, be provided with multichannel profile gauge; And adopt following steps:

A, sampling time point when setting band head arrives each detection position;

B, in crossing process, when band head arrives the current detection position until mill stand, by carrying out IMAQ and process to the both sides of the edge curve of band head, judge to calculate band head deflection and skew direction;

C, carry out on-line tuning to current in mill stand bilateral roll gap difference;

D, carry out presetting to follow-up frame bilateral roll gap difference;

E, repetition step C and step D are until profile gauge detects band head, and the band head dual-side contour curve detected by multichannel profile gauge, carries out on-line tuning to finished frame bilateral roll gap difference.

In above-mentioned tandem rolling crossing process band head correction method technical scheme in, technical scheme can also be more specifically:

Described video camera is ccd video camera, before the first frame of Continuous mill train, be provided with metal detector, and the test point of described metal detector is positioned at the edge of ccd video camera sample area near the first frame side of described first frame;

In step, the sampling time point of the detection position before band head arrives the first frame is set as that metal detector detects the time of band head; Timing is started, then the video camera sampling time t after the n-th frame when the n-th frame nips band _ncalculating formula be:

$t_n=\frac{L}{V_n}$

Wherein, V _nbe the muzzle velocity of the n-th frame band, unit is mm/second; L is the distance of ccd video camera sample area between the edge of the (n+1)th frame side arrived after the head of band advances to the roll gap of the n-th frame in the (n+1)th frame, and unit is millimeter;

The calculating formula of L is:

$L=\frac{(L_R-L_{de})}{2}+L_{de}$

Wherein, L _rbe the horizontal range of roll gap between two adjacent rack, L _defor the sampling length of ccd video camera on strip-rolling direction, unit is millimeter;

The muzzle velocity V of the n-th frame band _ncalculating formula be:

V _n＝v _n·(1+S _hn)

Wherein, v _nbe the roll real-time speed of the n-th frame, unit is mm/second; S _hnit is the advancing slip value of rolled piece of the n-th frame;

Advancing slip value S _hncalculating formula be:

$S_{hn}={\{tan\[\frac{\mathrm{\π}}{8}\sqrt{\frac{H_n}{R}}\·ln\left(\frac{H_n}{H_{n-1}}\right)+\frac{1}{2}arctan\sqrt{\frac{H_{n-1}}{H_n}-1}\]\}}^2$

Wherein, H _n-1and H _nbe respectively the thickness of nipping and dish out of the n-th frame rolled piece, unit is millimeter; R is the radius of frame working roll, and unit is millimeter;

Start timing when finished frame nips rolled piece, then the multichannel profile gauge after finished frame starts the time t sampled _nscalculating formula be:

$t_{Ns}=\frac{L_W}{V_N}$

The time t that the sampling of multichannel profile gauge terminates _necalculating formula be:

$t_{Ne}=\frac{L_N}{V_N}$

Band head moves to the distance L of multichannel profile gauge sampling end position from finished frame roll gap _ncalculating formula be:

L _N＝L _W+L _df

Wherein, t _nsand t _neunit be second; L _wfor the center line of multichannel profile gauge and the horizontal range of finished frame roll gap, unit is millimeter; L _nunit is millimeter; L _dffor the sampling length of multichannel profile gauge on strip-rolling direction, unit is millimeter; V _nfor the actual muzzle velocity of the band of finished frame, unit is mm/second; The actual muzzle velocity V of the band of finished frame _ncomputational methods and the muzzle velocity V of the n-th frame band _ncomputational methods identical.

Further, the band head deflection of step B and the judgement computational methods of skew direction as follows:

The linear fit of (1) n-th rack outlet band head edge curve

The measure-alike square sample area of the sample area of each ccd video camera or multichannel profile gauge, is denoted as Α, Β, Β respectively by the point at these square sample area four angles ₁and Α ₁, wherein, AB line and A ₁b ₁line is arranged along the rolling direction of band, and AB line is the transmission side of rolling, A ₁b ₁line is the fore side of rolling, Α Α ₁line and Β Β ₁line perpendicular to rolling direction, Α Α ₁the frame of the close rolling of line, Β Β ₁line is near frame to be rolled; Set up rectangular coordinate system to judge band head deflection and skew direction in square sample area, the Y-axis of this rectangular coordinate system overlaps with the center line of rolling, X-axis and Β Β ₁line coincident; The curve that the image curve of the band head side boundary curve that ccd video camera collects is formed in rectangular coordinate system is denoted as camber line AC and camber line A respectively ₁c ₁, camber line AC is band head transmission side edge image curve, camber line A ₁c ₁for band header operations lateral edges image curve, numerical point on the boundary curve of wherein arbitrary side of the band head of the n-th rack outlet is carried out curve fitting, to obtain the function of boundary curve, when the n-th frame threading completes and band head arrives detection position, the set of m numerical point of the band head transmission side edge image curve that the video camera in the (n+1)th frame collects after the n-th frame is: { (x _n1, y _n1), (x _n2, y _n2), (x _n3, y _n3) ... (x _nm, y _nm), wherein require (x _n1, y _n1) for some A coordinate value, namely within sample area near the coordinate value of the n-th frame place strip edge curve sampled point, (x _nm, y _nm) for some C abscissa value, namely within sample area near the coordinate value of the strip edge curve sampled point of the (n+1)th frame, the scope of m is 8≤m≤20;

The function of linear fit expression formula be:

Order then the computational methods of a, b are:

$a=\frac{m\underset{i=1}{\overset{m}{\Σ}}{x}_{ni}{y}_{ni}-\underset{i=1}{\overset{m}{\Σ}}{x}_{ni}\underset{i=1}{\overset{m}{\Σ}}{y}_{ni}}{m\underset{i=1}{\overset{m}{\Σ}}{x}_{ni}^2-{\left(\underset{i=1}{\overset{m}{\Σ}}{x}_{ni}\right)}^2}$

$b=\frac{\underset{i=1}{\overset{m}{\Σ}}{y}_{ni}\underset{i=1}{\overset{m}{\Σ}}{x}_{ni}^2-\underset{i=1}{\overset{m}{\Σ}}{x}_{ni}\underset{i=1}{\overset{m}{\Σ}}{x}_{ni}{y}_{ni}}{m\underset{i=1}{\overset{m}{\Σ}}{x}_{ni}^2-{\left(\underset{i=1}{\overset{m}{\Σ}}{x}_{ni}\right)}^2}$

The linear fit method of band header operations lateral edges image curve is identical with the linear fit method of transmission side edge image curve;

(2) judgement of band head deflection calculates

The straightway obtained after linear fit is denoted as respectively line segment AD and line segment A ₁d ₁the deflection of band head is calculated by the length of the shorter right-angle side of right angled triangle formed AB line, line segment AD and line segment BD and judges, namely calculate the length of line segment BD, suppose that the n-th rack outlet place video camera or multichannel profile gauge samples and the length processing the line segment BD of calculating gained is L _botn, unit is millimeter, by y _n1and y _nmsubstitute into y=ax+b, then L _botnvalue be:

$L_{botn}=|{x_{n1}}^{\′}-{x_{nm}}^{\′}|=|\frac{y_{n1}-b}{a}-\frac{y_{nm}-b}{a}|$

Wherein x _n1', x _nm' be respectively y _n1, y _nmsubstitute into the inverse value after y=ax+b, the numerical value namely gone out by linear function inverse;

L _botnvalue larger, then illustrate that the deflection of the n-th rack outlet place band head is larger; Otherwise, L _botnvalue less, the deflection of the n-th rack outlet place band head is less;

(3) judgement of band head skew direction

When band head edge linear function is increasing function, band head deflection fore side; When band head edge linear function is subtraction function, band head deflection transmission side; Therefore as a>0, band head deflection fore side; As a<0, band head deflection transmission side.

Further, the current on-line tuning method in mill stand bilateral roll gap difference of step C is as follows:

Suppose Δ s _nbe the roll gap difference of the n-th machine frame rolling mill, unit is millimeter, and this value is the difference of mill drive side and fore side roll gap, is:

Δs _n＝s _nds-s _nos

Wherein s _ndsbe the actual roll gap of the n-th frame transmission side, s _nosbe the n-th actual roll gap in gantry operation side, unit is millimeter;

When ccd video camera or multichannel profile gauge detect that skewness appears in the n-th rack outlet band head, adjust as follows:

As 0 < L _botnduring < 10, the n-th frame roll gap difference does not make any adjustments, and is Δ s _n=Δ s _n'+0=Δ s _n';

As 10≤L _botnduring < 40, and when judging band head deflection transmission side, setting roll gap difference Δ s _n=Δ s _n'-0.1f, when judging band head deflection fore side, setting roll gap difference Δ s _n=Δ s _n'+0.1f;

As 40≤L _botnduring < 80, and when judging band head deflection transmission side, setting roll gap difference Δ s _n=Δ s _n'-0.3f, when judging band head deflection fore side, setting roll gap difference Δ s _n=Δ s _n'+0.3f;

As 80≤L _botnduring < 120, and when judging band head deflection transmission side, setting roll gap difference Δ s _n=Δ s _n'-0.5f, when judging band head deflection fore side, setting roll gap difference Δ s _n=Δ s _n'+0.5f;

As 120≤L _botnduring < 170, and when judging band head deflection transmission side, setting roll gap difference Δ s _n=Δ s _n'-0.7f, when judging band head deflection fore side, setting roll gap difference Δ s _n=Δ s _n'+0.7f;

As 170≤L _botnwhen≤220, and when judging band head deflection transmission side, setting roll gap difference Δ s _n=Δ s _n', when judging band head deflection fore side, setting roll gap difference Δ s _n=Δ s _n'+0.9f;

As 220≤L _botnwhen≤300, and when judging band head deflection transmission side, setting roll gap difference Δ s _n=Δ s _n'-1.1f, when judging band head deflection fore side, setting roll gap difference Δ s _n=Δ s _n'+1.1f;

As 300 < L _botntime, because now band head deflection is too serious, if continue threading likely cause production accident, therefore stopped by electric-control system automatic emergency at once; Threading again again after the head of deflection is excised;

Wherein f is the presetting Dynamic gene of bilateral roll gap difference, and its span is 0≤f≤2, and initial value is 1; When band lateral bending being detected first, Δ s _n' be the n-th machine frame rolling mill original bilateral roll gap difference after carrying out mill roll-gap leveling, unit is millimeter, ideally Δ s _n'=0; When for the non-roll gap difference of adjustment first, Δ s _n' be n-th frame the last time adjustment after roll gap difference, unit is millimeter.

Further, the presetting method of the follow-up frame bilateral roll gap difference of step D is as follows:

While carrying out on-line tuning to the bilateral roll gap difference of the n-th frame, to (n+1)th, n-th+2 ... the bilateral roll gap difference of N-1, N frame is carried out presetting, and wherein, N frame is finished frame; For avoiding follow-up frame, especially the bilateral roll gap difference of finished frame causes violent impact, and by the bilateral roll gap difference adjustment amount of the n-th frame, weight assignment is to follow-up each frame; Weight assignment principle is that the weight that preorder frame accounts for is comparatively large, and the weight that postorder frame accounts for is less; When being weighted distribution, total score dosage is Δ s _n-Δ s _n' millimeter, needs the frame quantity M=N-n distributed, then (n+1)th be set as to the bilateral roll gap difference of N frame:

${\mathrm{\&Delta;s}}_{n+1}=\frac{{\mathrm{\&Delta;s}}_n-{{\mathrm{\&Delta;s}}_n}^{\&prime;}}{M~}\&CenterDot;M+{{\mathrm{\&Delta;s}}_{n+1}}^{\&prime;}$

${\mathrm{\&Delta;s}}_{n+2}=\frac{{\mathrm{\&Delta;s}}_n-{{\mathrm{\&Delta;s}}_n}^{\&prime;}}{M~}\&CenterDot;(M-1)+{{\mathrm{\&Delta;s}}_{n+2}}^{\&prime;}$

${\mathrm{\&Delta;s}}_{N-1}=\frac{{\mathrm{\&Delta;s}}_n-{{\mathrm{\&Delta;s}}_n}^{\&prime;}}{M~}\&CenterDot;2+{{\mathrm{\&Delta;s}}_{N-1}}^{\&prime;}$

${\mathrm{\&Delta;s}}_N=\frac{{\mathrm{\&Delta;s}}_n-{{\mathrm{\&Delta;s}}_n}^{\&prime;}}{M~}+{{\mathrm{\&Delta;s}}_N}^{\&prime;}$

The rank of wherein M ~ expression M add;

When the (n+1)th frame band head has been sampled, on-line tuning is carried out to the bilateral roll gap difference of the (n+1)th frame, carry out presetting to the bilateral roll gap difference of follow-up frame simultaneously, the rest may be inferred, when the band head proceeding to N frame and finished frame has been sampled, due to no frame after finished frame, therefore only the bilateral roll gap difference of finished frame is adjusted.

Deviating correcting principle of the present invention is: by the head image of the industrial CCD camera acquisition supplied materials be arranged on tandem mill each frame machine top, and is sent to computer and carries out processing the edge curve obtaining band head, the coordinate of several points on curve can be obtained by edge curve, these points are carried out the linear function that linear fit obtains this curve, suppose head and the roll centre line parallel of band, namely suppose there is not the defect such as tongue and fish tail, by calculating edge straight line during band head generation deflection, the head straight line of band and band head without edge straight line during deflection form the shorter right-angle side length of right angled triangle, can assess the deflection flex degree of band head, shorter right-angle side in this right angled triangle is larger, then deflection is larger, and in conjunction with the judgement in rolled piece deflection flex direction, and then the bilateral roll gap difference of this frame is adjusted, and the bilateral roll gap difference of follow-up institute organic frame is preset, the feedback result of multichannel profile gauge is only for the adjustment of finished frame bilateral roll gap difference.

Owing to have employed technique scheme, the present invention compared with prior art has following beneficial effect: the present invention adopts that band head deflection detects, deflection and the judgement calculating of skew direction, the self-adjusting of milling train bilateral roll gap difference and follow-up frame the steps such as roll gap difference is presetting, can the phenomenon of head generation deflection in Timeliness coverage band tandem rolling crossing process, and take suitable milling train bilateral roll gap difference adjustable strategies, cause product lumber recovery to decline or threading failure to avoid band head deflection.

Accompanying drawing explanation

Fig. 1 is the installation site schematic diagram of ccd video camera of the present invention and multichannel profile gauge.

Fig. 2 illustrates L, L _rand L _dethe schematic diagram of variable implication.

Fig. 3 illustrates L _nand L _wthe schematic diagram of variable implication.

Fig. 4 is the schematic diagram of the relation of each geometry variable in rectangular coordinate system when band head deflection is described.

Detailed description of the invention

Below in conjunction with accompanying drawing embodiment, the invention will be further described:

As shown in Figure 1, the present invention is for four frame tandem mill groups, each frame 3 in Continuous mill train is pushed up and is installed 1 industrial CCD video camera 2, finished frame exit is provided with multichannel profile gauge 4, metal detector 5 is installed before the first frame, the test point that guarantee fund belongs to detector of being sure to during installation is positioned at the sample area of ccd video camera in the first frame near the edge of milling train side, just for detecting the deflection situation of supplied materials head.Ccd video camera is L along the surveyed area length on length of rolled piece direction _de, unit is millimeter, see Fig. 2.Because between each frame, the horizontal range of roll gap is generally no more than 6000 millimeters, should note ensureing sample area length L when therefore camera is installed _debe not more than 4000 millimeters.Send after image digitazation into computer by high speed image data acquisition card, as the object of workpiece measurement identification, computer processes digital picture, obtains the edge contour information of band head.

The correction step of this example is as follows:

Steps A, sampling time point when setting band head arrives each detection position;

When band 1 passes the sample area between frame, the band head obtained by the PLC system process signal that puts in place is collected an image to control industrial CCD video camera and is sent on the computer of IMAQ and data processing, the sampling time point of the detection position before band head arrives the first frame is set as that metal detector detects the time of band head, send signal when metal detector detects band head to PLC system, PLC system sends the instruction of a sampled images immediately to video camera.Put in place the obtain manner of signal of the band head of residue frame is as follows:

Timing is started, then the video camera sampling time t after the n-th frame when the n-th frame nips band _ncalculating formula be:

$t_n=\frac{L}{V_n}$

Wherein, V _nbe the muzzle velocity of the n-th frame band, unit is mm/second; L is the distance of ccd video camera sample area between the edge of the (n+1)th frame side arrived after the head of band advances to the roll gap of the n-th frame in the (n+1)th frame, and unit is millimeter;

The calculating formula of L is:

$L=\frac{(L_R-L_{de})}{2}+L_{de}$

Wherein, L _rbe the horizontal range of roll gap between two adjacent rack, unit is millimeter, and this distance value is determined by each plant configuring condition; L _defor the sampling length of ccd video camera on strip-rolling direction, unit is millimeter; When the distance after the head of band advances to the roll gap of the n-th frame is L, PLC system sends sampled signal control video camera and samples, the value principle of L is: the distance that must be less than roll gap between adjacent two frames, and can ensure that the apical head of rolled piece is positioned at the edge of video camera sample area just, see Fig. 2;

The calculating formula of the muzzle velocity of the n-th frame rolled piece is:

V _n＝v _n·(1+S _hn)

Wherein, v _nbe the roll real-time speed of the n-th frame, unit is mm/second; S _hnit is the advancing slip value of rolled piece of the n-th frame;

Advancing slip value S _hncalculating formula be:

$S_{hn}={\{tan\&lsqb;\frac{\mathrm{\&pi;}}{8}\sqrt{\frac{H_n}{R}}\&CenterDot;ln\left(\frac{H_n}{H_{n-1}}\right)+\frac{1}{2}arctan\sqrt{\frac{H_{n-1}}{H_n}-1}\&rsqb;\}}^2$

Wherein, H _n-1and H _nbe respectively the thickness of nipping and dish out of the n-th frame rolled piece, unit is millimeter; R is the radius of frame working roll, and unit is millimeter;

As shown in Figure 3, L after the head of rolled piece advances to multichannel profile gauge _dfduring length, the curve record after sampling gets off and is sent to computer to process by multichannel profile gauge, L _dffor the sampling length of multichannel profile gauge on strip-rolling direction, unit is millimeter, L _df≤ 4000mm.The center line of multichannel profile gauge and the horizontal range of finished frame roll gap are L _w, unit is millimeter, and this distance value is determined by each plant configuring condition; L after then band head moves to multichannel profile gauge from N frame roll gap _dfdistance, namely band head from finished frame roll gap move to multichannel profile gauge sampling end position distance L _nfor:

L _N＝L _W+L _df

Start timing when finished frame nips rolled piece, then the multichannel profile gauge after finished frame starts the time t sampled _nscalculating formula be:

$t_{Ns}=\frac{L_W}{V_N}$

The time t that the sampling of multichannel profile gauge terminates _necalculating formula be:

$t_{Ne}=\frac{L_N}{V_N}$

Wherein, t _nsand t _neunit be second; V _nfor the actual muzzle velocity of the band of finished frame, unit is mm/second; The actual muzzle velocity V of the band of finished frame _ncomputational methods and the muzzle velocity V of the n-th frame band _ncomputational methods identical.

Step B, in crossing process, when band head arrives the current detection position until mill stand, by carrying out IMAQ and process to the both sides of the edge curve of band head, judge to calculate band head deflection and skew direction; Judge that computational methods are as follows:

The linear fit of (1) n-th rack outlet band head edge curve

The measure-alike square sample area of the sample area of each ccd video camera or multichannel profile gauge, is denoted as Α, Β, Β respectively by the point at these square sample area four angles ₁and Α ₁, wherein, AB line and A ₁b ₁line is arranged along the rolling direction of band, and AB line is the transmission side of rolling, A ₁b ₁line is the fore side of rolling, Α Α ₁line and Β Β ₁line perpendicular to rolling direction, Α Α ₁the frame of the close rolling of line, Β Β ₁line is near frame to be rolled; Set up rectangular coordinate system to judge band head deflection and skew direction in square sample area, the Y-axis of this rectangular coordinate system overlaps with the center line of rolling, X-axis and Β Β ₁line coincident.By computer, the steps such as geometric distortion correction, noise filtering, rim detection, locations of contours, sub-pixel method edge local, planar dimension measurements and calculations are carried out to the shape image of rolled piece, the boundary curve of similar band head as shown in Figure 4 can be obtained after treatment, workpiece front end shape approximation is processed into the straight line being parallel to roll axis, and overlap with X-axis, the unit of reference axis is millimeter; Concrete image detection and processing method can refer to the method in the thesis for the doctorate " research and apply of Plate Rolling Process high accuracy Side Bend Control " of He Chunyu described in chapter 6.Multichannel profile gauge can automatic acquisition band head edge contour curve and be drawn into rectangular coordinate system, without the need to carrying out other process.The curve that the image curve of the band head side boundary curve that ccd video camera collects is formed in rectangular coordinate system is denoted as camber line AC and camber line A respectively ₁c ₁, camber line AC is video camera sampled images band head transmission side edge image curve after treatment, camber line A ₁c ₁for video camera sampled images band header operations lateral edges image curve after treatment, the numerical point on the boundary curve of wherein arbitrary side of the band head of the n-th rack outlet is carried out curve fitting, to obtain the function of boundary curve.Because on rolled piece total length direction, width remains unchanged substantially, can assert that rolled piece fore side edge curve shape should be identical with transmission side edge curve shape, therefore only the situation at band transmission side edge be analyzed below.Due to L _de≤ 4m, according to rolling general knowledge, within the scope of this, the boundary curve of band head can be similar to and regard as straight line, i.e. line segment AD and A ₁d ₁, line segment AD and A ₁d ₁function by camber line AC and A ₁c ₁on numerical point matching out.Dotted line AB and A ₁b ₁be respectively the head edge straight line of band head without transmission side during deflection and fore side.Therefore, linear fit method is adopted to carry out matching to the numerical point that camera acquisition also processes.When the n-th frame threading completes and band head arrives detection position, the set of m numerical point of the band head transmission side edge image curve that the video camera in the (n+1)th frame collects after the n-th frame is: { (x _n1, y _n1), (x _n2, y _n2), (x _n3, y _n3) ... (x _nm, y _nm), wherein require (x _n1, y _n1) for some A coordinate value, namely within sample area near the coordinate value of the n-th frame place strip edge curve sampled point, (x _nm, y _nm) for some C abscissa value, namely within sample area near the coordinate value of the strip edge curve sampled point of the (n+1)th frame, the scope of m is 8≤m≤20;

The function of linear fit expression formula be:

Order then the computational methods of a, b are:

$a=\frac{m\underset{i=1}{\overset{m}{\&Sigma;}}{x}_{ni}{y}_{ni}-\underset{i=1}{\overset{m}{\&Sigma;}}{x}_{ni}\underset{i=1}{\overset{m}{\&Sigma;}}{y}_{ni}}{m\underset{i=1}{\overset{m}{\&Sigma;}}{x}_{ni}^2-{\left(\underset{i=1}{\overset{m}{\&Sigma;}}{x}_{ni}\right)}^2}$

$b=\frac{\underset{i=1}{\overset{m}{\&Sigma;}}{y}_{ni}\underset{i=1}{\overset{m}{\&Sigma;}}{x}_{ni}^2-\underset{i=1}{\overset{m}{\&Sigma;}}{x}_{ni}\underset{i=1}{\overset{m}{\&Sigma;}}{x}_{ni}{y}_{ni}}{m\underset{i=1}{\overset{m}{\&Sigma;}}{x}_{ni}^2-{\left(\underset{i=1}{\overset{m}{\&Sigma;}}{x}_{ni}\right)}^2}$

The linear fit method of band header operations lateral edges image curve is identical with the linear fit method of transmission side edge image curve;

(2) judgement of band head deflection calculates

The deflection of band head is calculated by the length of the shorter right-angle side of right angled triangle formed AB line, line segment AD and line segment BD and judges, namely calculate the length of line segment BD, suppose that the n-th rack outlet place video camera or multichannel profile gauge samples and the length processing the line segment BD of calculating gained is L _botn, unit is millimeter, by y _n1and y _nmsubstitute into y=ax+b, then L _botnvalue be:

$L_{botn}=|{x_{n1}}^{\&prime;}-{x_{nm}}^{\&prime;}|=|\frac{y_{n1}-b}{a}-\frac{y_{nm}-b}{a}|$

Wherein x _n1', x _nm' be respectively y _n1, y _nmsubstitute into the inverse value after y=ax+b, the numerical value namely gone out by linear function inverse;

L _botnvalue larger, then illustrate that the deflection of the n-th rack outlet place band head is larger; Otherwise, L _botnvalue less, the deflection of the n-th rack outlet place band head is less;

(3) judgement of band head skew direction

Linear function after matching is y=ax+b, as shown in Figure 4, when band head edge linear function is increasing function, and band head deflection fore side; When band head edge linear function is subtraction function, band head deflection transmission side; Therefore as a>0, band head deflection fore side; As a<0, band head deflection transmission side.

Step C, carry out on-line tuning to current in mill stand bilateral roll gap difference, method of adjustment is as follows:

Suppose Δ s _nbe the roll gap difference of the n-th machine frame rolling mill, unit is millimeter, and this value is the difference of mill drive side and fore side roll gap, is:

Δs _n＝s _nds-s _nos

Wherein s _ndsbe the actual roll gap of the n-th frame transmission side, s _nosbe the n-th actual roll gap in gantry operation side, unit is millimeter.

When ccd video camera or multichannel profile gauge detect that skewness appears in the n-th rack outlet band head, adjust as follows:

As 0 < L _botnduring < 10, the n-th frame roll gap difference does not make any adjustments, and is Δ s _n=Δ s _n'+0=Δ s _n';

As 10≤L _botnduring < 40, and when judging band head deflection transmission side, setting roll gap difference Δ s _n=Δ s _n'-0.1f, when judging band head deflection fore side, setting roll gap difference Δ s _n=Δ s _n'+0.1f;

As 40≤L _botnduring < 80, and when judging band head deflection transmission side, setting roll gap difference Δ s _n=Δ s _n'-0.3f, when judging band head deflection fore side, setting roll gap difference Δ s _n=Δ s _n'+0.3f;

As 80≤L _botnduring < 120, and when judging band head deflection transmission side, setting roll gap difference Δ s _n=Δ s _n'-0.5f, when judging band head deflection fore side, setting roll gap difference Δ s _n=Δ s _n'+0.5f;

As 120≤L _botnduring < 170, and when judging band head deflection transmission side, setting roll gap difference Δ s _n=Δ s _n'-0.7f, when judging band head deflection fore side, setting roll gap difference Δ s _n=Δ s _n'+0.7f;

As 170≤L _botnwhen≤220, and when judging band head deflection transmission side, setting roll gap difference Δ s _n=Δ s _n', when judging band head deflection fore side, setting roll gap difference Δ s _n=Δ s _n'+0.9f;

As 220≤L _botnwhen≤300, and when judging band head deflection transmission side, setting roll gap difference Δ s _n=Δ s _n'-1.1f, when judging band head deflection fore side, setting roll gap difference Δ s _n=Δ s _n'+1.1f;

As 300 < L _botntime, because now band head deflection is too serious, if continue threading likely cause production accident, therefore stopped by electric-control system automatic emergency at once; Threading again again after the head of deflection is excised;

Wherein f is the presetting Dynamic gene of bilateral roll gap difference, and its span is 0≤f≤2, and initial value is 1; When band lateral bending being detected first, Δ s _n' be the n-th machine frame rolling mill original bilateral roll gap difference after carrying out mill roll-gap leveling, unit is millimeter, ideally Δ s _n'=0; When for the non-roll gap difference of adjustment first, Δ s _n' be n-th frame the last time adjustment after roll gap difference, unit is millimeter.

Step D, carry out presetting to follow-up frame bilateral roll gap difference, presetting method is as follows:

The on-line tuning of the n-th frame bilateral roll gap difference can make the deviation condition of band head no longer aggravate, but the deflection of taking the lead produced needs to eliminate by the bilateral roll gap difference of follow-up frame is presetting.While carrying out on-line tuning to the bilateral roll gap difference of the n-th frame, to (n+1)th, n-th+2 ... the bilateral roll gap difference of N-1, N frame is carried out presetting, and wherein, N frame is finished frame; For avoiding follow-up frame, especially the bilateral roll gap difference of finished frame causes violent impact, and by the bilateral roll gap difference adjustment amount of the n-th frame, weight assignment is to follow-up each frame; Weight assignment principle is that the weight that preorder frame accounts for is comparatively large, and the weight that postorder frame accounts for is less; When being weighted distribution, total score dosage is Δ s _n-Δ s _n' millimeter, needs the frame quantity M=N-n distributed, then (n+1)th be set as to the bilateral roll gap difference of N frame:

${\mathrm{\&Delta;s}}_{n+1}=\frac{{\mathrm{\&Delta;s}}_n-{{\mathrm{\&Delta;s}}_n}^{\&prime;}}{M~}\&CenterDot;M+{{\mathrm{\&Delta;s}}_{n+1}}^{\&prime;}$

${\mathrm{\&Delta;s}}_{n+2}=\frac{{\mathrm{\&Delta;s}}_n-{{\mathrm{\&Delta;s}}_n}^{\&prime;}}{M~}\&CenterDot;(M-1)+{{\mathrm{\&Delta;s}}_{n+2}}^{\&prime;}$

${\mathrm{\&Delta;s}}_{N-1}=\frac{{\mathrm{\&Delta;s}}_n-{{\mathrm{\&Delta;s}}_n}^{\&prime;}}{M~}\&CenterDot;2+{{\mathrm{\&Delta;s}}_{N-1}}^{\&prime;}$

${\mathrm{\&Delta;s}}_N=\frac{{\mathrm{\&Delta;s}}_n-{{\mathrm{\&Delta;s}}_n}^{\&prime;}}{M~}+{{\mathrm{\&Delta;s}}_N}^{\&prime;}$

The rank of wherein M ~ expression M add;

When the (n+1)th frame band head has been sampled, on-line tuning is carried out to the bilateral roll gap difference of the (n+1)th frame, carry out presetting to the bilateral roll gap difference of follow-up frame simultaneously, the rest may be inferred, when the band head proceeding to N frame and finished frame has been sampled, due to no frame after finished frame, therefore only the bilateral roll gap difference of finished frame is adjusted.

When coiling machine spool by the head of band roll up on, and and when forming tension force between finished frame, judged the generation of this tension signal by PLC system, and trigger band head correction process terminate.

Embodiment 1

Because between each frame, the distance of roll gap is generally no more than 6000 millimeters, should note ensureing sample area length L when therefore camera is installed _debe not more than 4000 millimeters, can be taken as L _de=2500 millimeters, get L simultaneously _df=2500 millimeters.Send after image digitazation into computer by high speed image data acquisition card, as the object of workpiece measurement identification, computer processes digital picture, extracts the marginal information of band head, obtains the planar dimension of final rolled piece.When rolled piece is through surveyed area between frame, the band head obtained by the PLC system process signal that puts in place is collected an image to control industrial CCD video camera and is sent on the computer of IMAQ and data processing.Suppose that the frame total quantity of Continuous mill train is 4.The roll driving motor end of frame is provided with speed measuring coder, and the roll real-time speed that can record the 2nd frame is 600 mm/second, and the roll real-time speed of the 4th frame is 1200 mm/second.The thickness of nipping and dish out arranging the 2nd frame rolled piece is respectively 17.5 millimeters and 13.89 millimeters, and the thickness of nipping and dish out of the 4th frame rolled piece is respectively 6 millimeters and 4 millimeters; The radius arranging each frame working roll is 500 millimeters.

The then advancing slip value S of the 2nd frame rolled piece _h2for:

$S_n{\{\tan \&lsqb;\frac{\mathrm{\&pi;}}{8}\sqrt{\frac{13.89}{500}}\&CenterDot;\ln \left(\frac{13.89}{17.5}\right)+\frac{1}{2}\arctan \sqrt{\frac{17.5}{13.89}-1}\&rsqb;\}}^2=0.0577$

The muzzle velocity of the 2nd frame rolled piece is:

V _n=600 (1+0.0577)=634.62 mm/second

The advancing slip value S of the 4th frame rolled piece _h4for:

$S_n={\{tan\&lsqb;\frac{\mathrm{\&pi;}}{8}\sqrt{\frac{4}{500}}\&CenterDot;ln\left(\frac{4}{6}\right)+\frac{1}{2}arctan\sqrt{\frac{6}{4}-1}\&rsqb;\}}^2=0.1008$

The calculating formula of the muzzle velocity of the 4th frame rolled piece is:

V ₄=1200 (1+0.1008)=1320.96 mm/second

The distance arranging roll gap between two frames is 5500 millimeters, then the calculating formula of L is:

Timing is started, then the video camera sampling time t after the 2nd frame when the 2nd frame nips rolled piece ₂for:

The distance of the center line and finished frame roll gap that arrange multichannel profile gauge is 3500 millimeters, then L after band head moves to multichannel profile gauge from the 4th frame roll gap _dftime distance L _nfor:

L _n=3500+2500=6000 millimeter

Start timing when the 4th frame (i.e. finished frame) nips rolled piece, then the multichannel profile gauge after the 4th frame starts the time t sampled _4sfor:

Multichannel profile gauge sampling after 4th frame terminates and is sent to the time t of computer _4efor:

As shown in Figure 4, the region that video camera detects is ABB ₁a ₁, the length in this region is L as previously mentioned _de=2500 millimeters.Rack outlet camber line AC is the boundary curve of band head, carries out curve fitting to the numerical point on band head edge curve, to obtain the function of boundary curve.Y-axis overlaps with the center line of rolling.Suppose that the numerical value of boundary curve is counted as m=9, when the 2nd frame threading completes and head puts in place, the set of the numerical point of band head transmission side (analyzing for transmission side) the edge image curve that video camera collects after the 2nd frame is: { (x ₂₁, y ₂₁), (x ₂₂, y ₂₂), (x ₂₃, y ₂₃) ... (x ₂₉, y ₂₉).Suppose that these 9 numerical points are:

$\left\{\begin{array}{c}(-801,-4000),(-792,-3500),(-776,-3000),(-759,-2500),\\ (-750,-2000),(-711,-1500),(-685,-1000),(-651,-500),(-599,0)\end{array}\right\}$

Wherein require (-801,-4000) be the coordinate value of an A, namely within sample area near the coordinate value of the 2nd frame place strip edge curve sampled point, require (-599,0) for some C coordinate value, namely within sample area near the coordinate value of the strip edge curve sampled point of the 3rd frame.In the diagram, 1 is the roll of the n-th frame, and 2 is band, and camber line AC is video camera sampled images transmission side band head edge curve after treatment; Camber line A ₁c ₁for video camera sampled images fore side side band head edge curve after treatment.Because on rolled piece total length direction, width remains unchanged substantially, can assert that rolled piece fore side edge curve shape should be identical with transmission side edge curve shape, therefore only the situation at band transmission side edge be analyzed below.Due to L _de=2500 millimeters, according to rolling general knowledge, within the scope of this, the boundary curve of band head can be similar to and be judged to be straight line, i.e. straight line AC and A ₁c ₁.Dotted line AB and A ₁b ₁be respectively the head edge straight line of band head without transmission side during deflection and fore side, the area S of dash area Δ ABC _{Δ ABC}be transmission side band head deflection area, unit is square millimeter.Therefore, linear fit method is adopted to carry out matching to the numerical point that camera acquisition also processes.If fitting function expression formula be:

Order then the computational methods of a, b are:

$a=\frac{9\&times;\underset{i=1}{\overset{9}{\&Sigma;}}{x}_{2i}{y}_{2i}-\underset{i=1}{\overset{9}{\&Sigma;}}{x}_{2i}\underset{i=1}{\overset{9}{\&Sigma;}}{y}_{2i}}{9\&times;\underset{i=1}{\overset{9}{\&Sigma;}}{x}_{2i}^2-{\left(\underset{i=1}{\overset{9}{\&Sigma;}}{x}_{2i}\right)}^2}=19.54$

$b=\frac{\underset{i=1}{\overset{9}{\&Sigma;}}{y}_{2i}\underset{i=1}{\overset{9}{\&Sigma;}}{x}_{2i}^2-\underset{i=1}{\overset{9}{\&Sigma;}}{x}_{2i}\underset{i=1}{\overset{9}{\&Sigma;}}{x}_{2i}{y}_{2i}}{9\&times;\underset{i=1}{\overset{9}{\&Sigma;}}{x}_{2i}^2-{\left(\underset{i=1}{\overset{9}{\&Sigma;}}{x}_{2i}\right)}^2}=12136.53$

The linear function expression that can obtain the 2nd rack outlet place band head edge is:

y＝19.54x+12136.53

When the 4th frame threading completes and head puts in place, the set of the numerical point of band head transmission side (analyzing for transmission side) the edge image curve that multichannel profile gauge collects after the 4th frame is: { (x ₄₁, y ₄₁), (x ₄₂, y ₄₂), (x ₄₃, y ₄₃) ... (x ₄₉, y ₄₉).Suppose that these 9 numerical points are:

$\left\{\begin{array}{c}(-700,-4000),(-697,-3500),(-691,-3000),(-682,-2500),\\ (-670,-2000),(-655,-1500),(-637,-1000),(-616,-500),(-592,0)\end{array}\right\}$

Wherein require (-300,-4000) be the coordinate value of some A, namely start the coordinate value of first strip edge curve sampled point when sampling, require (-98,0) for some C coordinate value, namely sample time last strip edge curve sampled point coordinate value.Employing linear fit method is to the collection of multichannel profile gauge and the numerical point of process carries out matching.If fitting function expression formula be:

Order then the computational methods of a, b are:

$a=\frac{9\&times;\underset{i=1}{\overset{9}{\&Sigma;}}{x}_{4i}{y}_{4i}-\underset{i=1}{\overset{9}{\&Sigma;}}{x}_{4i}\underset{i=1}{\overset{9}{\&Sigma;}}{y}_{4i}}{9\&times;\underset{i=1}{\overset{9}{\&Sigma;}}{x}_{4i}^2-{\left(\underset{i=1}{\overset{9}{\&Sigma;}}{x}_{4i}\right)}^2}=34.83$

$b=\frac{\underset{i=1}{\overset{9}{\&Sigma;}}{y}_{4i}\underset{i=1}{\overset{9}{\&Sigma;}}{x}_{4i}^2-\underset{i=1}{\overset{9}{\&Sigma;}}{x}_{4i}\underset{i=1}{\overset{9}{\&Sigma;}}{x}_{4i}{y}_{4i}}{9\&times;\underset{i=1}{\overset{9}{\&Sigma;}}{x}_{4i}^2-{\left(\underset{i=1}{\overset{9}{\&Sigma;}}{x}_{4i}\right)}^2}=20987.616$

The linear function expression that can obtain the 4th rack outlet place band head edge is:

y＝34.83x+20987.616

The shape of the dash area in Fig. 4 is right angled triangle, and the deflection of band head calculates by the right-angle side length shorter to right angled triangle and judges, namely calculates the length of line segment BD.The length supposing the 2nd rack outlet place line segment BD is L _bot2, unit is millimeter, by y ₂₁=-4000 and y ₂₉=0 substitutes into y=19.54x+12136.53, then L _bot2value be:

The length supposing the 4th rack outlet place line segment BD is L _bot4, unit is millimeter, by y ₄₁=-4000 and y ₄₉=0 substitutes into y=34.83x+20987.616, then L _bot4value be:

Known 2nd frame and the linear function of the 4th frame after matching are respectively y=19.54x+12136.53 and y=34.83x+20987.616, the value of a is respectively 19.54 and 34.83, all be greater than zero, therefore the band head at the 2nd, 4 rack outlet places is all partial to fore side.

From calculating above, 170≤L _bot2≤ 220, and judge to take the lead to be partial to fore side, setting roll gap difference Δ s ₂=Δ s ₂'+0.9f; 80≤L _bot4< 120, and when judging to take the lead deflection fore side, setting roll gap difference Δ s ₄=Δ s ₄'+0.5f;

Now desirable initial value is f=1, can think rolled piece lateral bending to be detected, Δ s in the 2nd frame and the 4th rack outlet place first herein ₂' and Δ s ₄' being respectively the 2nd, the original bilateral roll gap difference of 4 machine frame rolling mills after carrying out mill roll-gap leveling, unit is millimeter, desirable Δ s ₂'=Δ s ₄'=0.

Therefore, when the 2nd rack outlet place detects band head generation deflection, be Δ s by the bilateral roll gap difference on-line tuning of the 2nd frame ₂=0+0.9 × 1=0.9 millimeter, i.e. s _2ds-s _2os=0.9 millimeter.Be Δ s by the bilateral roll gap difference on-line tuning of the 4th frame ₄=0+0.5 × 1=0.5 millimeter, i.e. s _4ds-s _4os=0.5 millimeter.

The on-line tuning of the 2nd frame bilateral roll gap difference can make the deviation condition of band head no longer aggravate, but taking the lead of having produced deflection needs by the 3rd, the bilateral roll gap difference of 4 frames is presetting eliminates.For avoiding follow-up frame, especially the bilateral roll gap difference of finished frame causes violent impact, can by the bilateral roll gap difference adjustment amount of the 2nd frame, weight assignment to the 3rd, 4 frames.Total score dosage is 0.9 millimeter, needs the frame quantity M=4-2=2 distributed, Δ s after supposing roll gap difference adjustment (on-line tuning or presetting adjustment) of the 3rd, 4 frame the last times ₃'=Δ s ₄'=0, then the 3rd, the bilateral roll gap difference of 4 frames is set as:

When the 3rd frame band head has been sampled, on-line tuning is carried out to the bilateral roll gap difference of the 3rd frame, has carried out presetting to the bilateral roll gap difference of the 4th frame simultaneously.When the band head proceeding to the 4th frame has been sampled, due to no frame after the 4th frame, therefore only need adjust the bilateral roll gap difference of finished frame.When the head of band is rolled up by the spool of coiling machine, and and when forming tension force between finished frame, judged the generation of this tension signal by PLC system, and signal triggering band head correction process terminates thus.

Claims (5)

1. a method for band head correction in tandem rolling crossing process, is characterized in that: be provided with in each frame of Continuous mill train detect band head roll before the video camera of curve, after finished frame, be provided with multichannel profile gauge; Adopt following steps:

A, sampling time point when setting band head arrives each detection position;

B, in crossing process, when band head arrives the current detection position until mill stand, by carrying out IMAQ and process to the both sides of the edge curve of band head, judge to calculate band head deflection and skew direction;

C, carry out on-line tuning to current in mill stand bilateral roll gap difference;

D, carry out presetting to follow-up frame bilateral roll gap difference;

E, repetition step C and step D are until profile gauge detects band head, and the band head dual-side contour curve detected by multichannel profile gauge, carries out on-line tuning to finished frame bilateral roll gap difference.

2. the method for band head correction in tandem rolling crossing process according to claim 1, it is characterized in that: described video camera is ccd video camera, before the first frame of Continuous mill train, be provided with metal detector, the test point of described metal detector is positioned at the edge of ccd video camera sample area near the first frame side of described first frame;

In step, the sampling time point of the detection position before band head arrives the first frame is set as that metal detector detects the time of band head; Timing is started, then the video camera sampling time t after the n-th frame when the n-th frame nips band _ncalculating formula be:

$t_n=\frac{L}{V_n}$

Wherein, V _nbe the muzzle velocity of the n-th frame band, unit is mm/second; L is the distance of ccd video camera sample area between the edge of the (n+1)th frame side arrived after the head of band advances to the roll gap of the n-th frame in the (n+1)th frame, and unit is millimeter;

The calculating formula of L is:

$L=\frac{(L_R-L_{de})}{2}+L_{de}$

Wherein, L _rbe the horizontal range of roll gap between two adjacent rack, L _defor the sampling length of ccd video camera on strip-rolling direction, unit is millimeter;

The muzzle velocity V of the n-th frame band _ncalculating formula be:

V _n＝v _n·(1+S _hn)

Wherein, v _nbe the roll real-time speed of the n-th frame, unit is mm/second; S _hnit is the advancing slip value of rolled piece of the n-th frame;

Advancing slip value S _hncalculating formula be:

$S_{hn}={\{tan\&lsqb;\frac{\mathrm{\&pi;}}{8}\sqrt{\frac{H_n}{R}}\&CenterDot;ln\left(\frac{H_n}{H_{n-1}}\right)+\frac{1}{2}arctan\sqrt{\frac{H_{n-1}}{H_n}-1}\&rsqb;\}}^2$

Wherein, H _n-1and H _nbe respectively the thickness of nipping and dish out of the n-th frame rolled piece, unit is millimeter; R is the radius of frame working roll, and unit is millimeter;

Start timing when finished frame nips rolled piece, then the multichannel profile gauge after finished frame starts the time t sampled _nscalculating formula be:

$t_{Ns}=\frac{L_W}{V_N}$

The time t that the sampling of multichannel profile gauge terminates _necalculating formula be:

$t_{Ne}=\frac{L_N}{V_N}$

Band head moves to the distance L of multichannel profile gauge sampling end position from finished frame roll gap _ncalculating formula be:

L _N＝L _W+L _df

Wherein, t _nsand t _neunit be second; L _wfor the center line of multichannel profile gauge and the horizontal range of finished frame roll gap, unit is millimeter; L _nunit is millimeter; L _dffor the sampling length of multichannel profile gauge on strip-rolling direction, unit is millimeter; V _nfor the actual muzzle velocity of the band of finished frame, unit is mm/second; The actual muzzle velocity V of the band of finished frame _ncomputational methods and the muzzle velocity V of the n-th frame band _ncomputational methods identical.

3. in tandem rolling crossing process according to claim 2 band head correction method, it is characterized in that: the band head deflection of step B and the judgement computational methods of skew direction as follows:

The linear fit of (1) n-th rack outlet band head edge curve

The measure-alike square sample area of the sample area of each ccd video camera or multichannel profile gauge, is denoted as Α, Β, Β respectively by the point at these square sample area four angles ₁and Α ₁, wherein, AB line and A ₁b ₁line is arranged along the rolling direction of band, and AB line is the transmission side of rolling, A ₁b ₁line is the fore side of rolling, Α Α ₁line and Β Β ₁line perpendicular to rolling direction, Α Α ₁the frame of the close rolling of line, Β Β ₁line is near frame to be rolled; Set up rectangular coordinate system to judge band head deflection and skew direction in square sample area, the Y-axis of this rectangular coordinate system overlaps with the center line of rolling, X-axis and Β Β ₁line coincident; The curve that the image curve of the band head side boundary curve that ccd video camera collects is formed in rectangular coordinate system is denoted as camber line AC and camber line A respectively ₁c ₁, camber line AC is band head transmission side edge image curve, camber line A ₁c ₁for band header operations lateral edges image curve, numerical point on the boundary curve of wherein arbitrary side of the band head of the n-th rack outlet is carried out curve fitting, to obtain the function of boundary curve, when the n-th frame threading completes and band head arrives detection position, the set of m numerical point of the band head transmission side edge image curve that the video camera in the (n+1)th frame collects after the n-th frame is: { (x _n1, y _n1), (x _n2, y _n2), (x _n3, y _n3) ... (x _nm, y _nm), wherein require (x _n1, y _n1) for some A coordinate value, namely within sample area near the coordinate value of the n-th frame place strip edge curve sampled point, (x _nm, y _nm) for some C abscissa value, namely within sample area near the coordinate value of the strip edge curve sampled point of the (n+1)th frame, the scope of m is 8≤m≤20;

The function of linear fit expression formula be:

Order then the computational methods of a, b are:

$a=\frac{m\underset{i=1}{\overset{m}{\&Sigma;}}{x}_{ni}{y}_{ni}-\underset{i=1}{\overset{m}{\&Sigma;}}{x}_{ni}\underset{i=1}{\overset{m}{\&Sigma;}}{y}_{ni}}{m\underset{i=1}{\overset{m}{\&Sigma;}}{x}_{ni}^2-{\left(\underset{i=1}{\overset{m}{\&Sigma;}}{x}_{ni}\right)}^2}$

$b=\frac{\underset{i=1}{\overset{m}{\&Sigma;}}{y}_{ni}\underset{i=1}{\overset{m}{\&Sigma;}}{x}_{ni}^2-\underset{i=1}{\overset{m}{\&Sigma;}}{x}_{ni}\underset{i=1}{\overset{m}{\&Sigma;}}{x}_{ni}{y}_{ni}}{m\underset{i=1}{\overset{m}{\&Sigma;}}{x}_{ni}^2-{\left(\underset{i=1}{\overset{m}{\&Sigma;}}{x}_{ni}\right)}^2}$

The linear fit method of band header operations lateral edges image curve is identical with the linear fit method of transmission side edge image curve;

(2) judgement of band head deflection calculates

The straightway obtained after linear fit is denoted as respectively line segment AD and line segment A ₁d ₁the deflection of band head is calculated by the length of the shorter right-angle side of right angled triangle formed AB line, line segment AD and line segment BD and judges, namely calculate the length of line segment BD, suppose that the n-th rack outlet place video camera or multichannel profile gauge samples and the length processing the line segment BD of calculating gained is L _botn, unit is millimeter, by y _n1and y _nmsubstitute into y=ax+b, then L _botnvalue be:

$L_{botn}=|{x_{n1}}^{\&prime;}-{x_{nm}}^{\&prime;}|=|\frac{y_{n1}-b}{a}-\frac{y_{nm}-b}{a}|$

Wherein x _n1', x _nm' be respectively y _n1, y _nmsubstitute into the inverse value after y=ax+b, the numerical value namely gone out by linear function inverse;

L _botnvalue larger, then illustrate that the deflection of the n-th rack outlet place band head is larger; Otherwise, L _botnvalue less, the deflection of the n-th rack outlet place band head is less;

(3) judgement of band head skew direction

When band head edge linear function is increasing function, band head deflection fore side; When band head edge linear function is subtraction function, band head deflection transmission side; Therefore as a>0, band head deflection fore side; As a<0, band head deflection transmission side.

4. the method for band head correction in tandem rolling crossing process according to claim 3, is characterized in that: the current on-line tuning method in mill stand bilateral roll gap difference of step C is as follows:

Suppose Δ s _nbe the roll gap difference of the n-th machine frame rolling mill, unit is millimeter, and this value is the difference of mill drive side and fore side roll gap, is:

Δs _n＝s _nds-s _nos

Wherein s _ndsbe the actual roll gap of the n-th frame transmission side, s _nosbe the n-th actual roll gap in gantry operation side, unit is millimeter;

When ccd video camera or multichannel profile gauge detect that skewness appears in the n-th rack outlet band head, adjust as follows:

As 0 < L _botnduring < 10, the n-th frame roll gap difference does not make any adjustments, and is Δ s _n=Δ s _n'+0=Δ s _n';

As 10≤L _botnduring < 40, and when judging band head deflection transmission side, setting roll gap difference Δ s _n=Δ s _n'-0.1f, when judging band head deflection fore side, setting roll gap difference Δ s _n=Δ s _n'+0.1f;

As 40≤L _botnduring < 80, and when judging band head deflection transmission side, setting roll gap difference Δ s _n=Δ s _n'-0.3f, when judging band head deflection fore side, setting roll gap difference Δ s _n=Δ s _n'+0.3f;

As 80≤L _botnduring < 120, and when judging band head deflection transmission side, setting roll gap difference Δ s _n=Δ s _n'-0.5f, when judging band head deflection fore side, setting roll gap difference Δ s _n=Δ s _n'+0.5f;

As 120≤L _botnduring < 170, and when judging band head deflection transmission side, setting roll gap difference Δ s _n=Δ s _n'-0.7f, when judging band head deflection fore side, setting roll gap difference Δ s _n=Δ s _n'+0.7f;

As 170≤L _botnwhen≤220, and when judging band head deflection transmission side, setting roll gap difference Δ s _n=Δ s _n', when judging band head deflection fore side, setting roll gap difference Δ s _n=Δ s _n'+0.9f;

As 220≤L _botnwhen≤300, and when judging band head deflection transmission side, setting roll gap difference Δ s _n=Δ s _n'-1.1f, when judging band head deflection fore side, setting roll gap difference Δ s _n=Δ s _n'+1.1f;

As 300 < L _botntime, because now band head deflection is too serious, if continue threading likely cause production accident, therefore stopped by electric-control system automatic emergency at once; Threading again again after the head of deflection is excised;

Wherein f is the presetting Dynamic gene of bilateral roll gap difference, and its span is 0≤f≤2, and initial value is 1; When band lateral bending being detected first, Δ s _n' be the n-th machine frame rolling mill original bilateral roll gap difference after carrying out mill roll-gap leveling, unit is millimeter, ideally Δ s _n'=0; When for the non-roll gap difference of adjustment first, Δ s _n' be n-th frame the last time adjustment after roll gap difference, unit is millimeter.

5. the method for band head correction in tandem rolling crossing process according to claim 4, is characterized in that: the presetting method of the follow-up frame bilateral roll gap difference of step D is as follows:

While carrying out on-line tuning to the bilateral roll gap difference of the n-th frame, to (n+1)th, n-th+2 ... the bilateral roll gap difference of N-1, N frame is carried out presetting, and wherein, N frame is finished frame; For avoiding follow-up frame, especially the bilateral roll gap difference of finished frame causes violent impact, and by the bilateral roll gap difference adjustment amount of the n-th frame, weight assignment is to follow-up each frame; Weight assignment principle is that the weight that preorder frame accounts for is comparatively large, and the weight that postorder frame accounts for is less; When being weighted distribution, total score dosage is Δ s _n-Δ s _n' millimeter, needs the frame quantity M=N-n distributed, then (n+1)th be set as to the bilateral roll gap difference of N frame:

${\mathrm{\&Delta;s}}_{n+1}=\frac{{\mathrm{\&Delta;s}}_n-{{\mathrm{\&Delta;s}}_n}^{\&prime;}}{M~}\&CenterDot;M+{{\mathrm{\&Delta;s}}_{n+1}}^{\&prime;}$

${\mathrm{\&Delta;s}}_{n+2}=\frac{{\mathrm{\&Delta;s}}_n-{{\mathrm{\&Delta;s}}_n}^{\&prime;}}{M~}\&CenterDot;(M-1)+{{\mathrm{\&Delta;s}}_{n+2}}^{\&prime;}$

...

${\mathrm{\&Delta;s}}_{N-1}=\frac{{\mathrm{\&Delta;s}}_n-{{\mathrm{\&Delta;s}}_n}^{\&prime;}}{M~}\&CenterDot;2+{{\mathrm{\&Delta;s}}_{N-1}}^{\&prime;}$

${\mathrm{\&Delta;s}}_N=\frac{{\mathrm{\&Delta;s}}_n-{{\mathrm{\&Delta;s}}_n}^{\&prime;}}{M~}+{{\mathrm{\&Delta;s}}_N}^{\&prime;}$

The rank of wherein M ~ expression M add;

When the (n+1)th frame band head has been sampled, on-line tuning is carried out to the bilateral roll gap difference of the (n+1)th frame, carry out presetting to the bilateral roll gap difference of follow-up frame simultaneously, the rest may be inferred, when the band head proceeding to N frame and finished frame has been sampled, due to no frame after finished frame, therefore only the bilateral roll gap difference of finished frame is adjusted.