CN104492823A - Method for obtaining constant elongation in states of acceleration and deceleration - Google Patents

Abstract

The invention provides a method for obtaining constant elongation in states of acceleration and deceleration. The method comprises the following steps of respectively acquiring the speed of strip steel of an entrance and the speed of strip steel of an exit; setting a length-variable calculating period; calculating an actual value of the elongation; comparing the actual value of the elongation to a setting value of the elongation to obtain an elongation difference value; using a product of the elongation difference value and an elongation adaptive adjustment factor as an inputting value of a PI (proportional integral) controller; outputting additional controlled quantity of a rolling force control ring and additional controlled quantity of a tension control ring; and superposing the additional controlled quantity of the rolling force control ring, the additional controlled quantity of the tension control ring and a rolling force adaptive adjustment factor to obtain final rolling force adjustment amount. Elongation length calculating periods are set at different speed sections, so that the problem of slipping of strip steel in processes of acceleration and deceleration can be solved. By correlation operation of three-times extraction of a square root of actual speed, elongation fluctuation adjustment in the processes of acceleration and deceleration is accelerated in a feedforward control manner; and adaptive factors are set according to dynamic correction of errors of an actual rolling force and an elongation expected rolling force and relation of thickness, width and elongation, and the control precision and the stability of the elongation in the processes of acceleration and deceleration are improved.

Description

The method of constant percentage elongation is obtained under a kind of acceleration and deceleration state

Technical field

The present invention relates to cold-strip steel planisher production field, under particularly relating to a kind of acceleration and deceleration state, obtain the method for constant percentage elongation.

Background technology

In annealing operation, be with steel due to recrystallization, create strain-aging, in following process, there will be yield point elongation, the band steel after this annealing almost becomes soft state completely, is not suitable for processing; As long as give slightly slight punch process, belt steel surface will produce elongation strain and irregular skid wire.Therefore to carry out slight smooth process to the cold-strip steel after annealing, to eliminate yield point elongation, to improve tensile strength, make it have good band steel mechanical performance, improve belt plate shape, adjustment belt steel surface roughness, obtain satisfactory coil of strip.

In Cold-Rolled Strip Temper Mill, percentage elongation is important technic index, for obtaining constant percentage elongation, by the object regulating roll-force and tension force to reach specific elongation steadily control.But under acceleration and deceleration state, the speed of skin pass mill group, tension force, roll-force, percentage elongation, leveling precision adhesion amount etc. all plays pendulum, and therefore occurs that percentage elongation fluctuation is excessive, makes the smooth section strip steel performance of acceleration and deceleration not meet technological requirement.

Summary of the invention

The technical problem to be solved in the present invention is: a kind of method obtaining constant percentage elongation under providing acceleration and deceleration state, makes the smooth section strip steel performance of acceleration and deceleration meet technological requirement.

The present invention for solving the problems of the technologies described above taked technical scheme is: a kind of method obtaining constant percentage elongation under acceleration and deceleration state, is characterized in that: it comprises the steps:

S1, respectively collection strip steel at entry speed and outlet strip speed, arrange variable-length computing cycle, calculate percentage elongation actual value;

With strip steel at entry speed or outlet strip speed for benchmark, obtain variable-length computing cycle according to its scope, and calculate percentage elongation; Measuring roller rotates girth to be added up to reach the periodic quantity arranged with friction speed section, and as next percentage elongation measured value starting point, namely measuring roller girth often rotates certain distance and calculates a percentage elongation actual value, and this certain distance is relevant with friction speed section;

S2, percentage elongation actual value to be compared with percentage elongation setting value, obtain percentage elongation difference, with percentage elongation self-adaptative adjustment factor gain _aptproduct as the input value of PI controller, export the additional controlled quentity controlled variable of roll-force control loop and tension force control loop; Wherein percentage elongation self-adaptative adjustment factor gain _aptcomputing formula as follows:

$\mathrm{gai}{n}_{\mathrm{apt}}\left(n\right)=\frac{{\mathrm{Width}}_{\mathrm{set}}\×{\mathrm{Thk}}_{\mathrm{set}}}{{\mathrm{Width}}_{\max }\×{\mathrm{Thk}}_{\max }}\×\∫({\mathrm{FR}}_{\mathrm{act}}-100\×\mathrm{ELC}\×\∫{\mathrm{gain}}_{\mathrm{apt}}(n-1))$

In formula, Width _setfor setting strip width, Thk _setsetting belt steel thickness, FR _actfor roll-force actual value, ELC is percentage elongation actual value, Width _maxfor strip width maximum, Thk _maxfor belt steel thickness maximum, n is iterative times, n=1,2,3,

S3, by the additional controlled quentity controlled variable of roll-force control loop and the roll-force self-adaptative adjustment factor superimposed, obtain final roll-force adjustment amount, roll-force adjusted; Wherein the computing formula of roll-force adjustment amount is as follows:

${\mathrm{\ΔFR}}_{\mathrm{corr}}=\left({\mathrm{FR}}_{\mathrm{cal}}\right)\×\frac{\sqrt[3]{V_{\mathrm{act}}}-\sqrt[3]{V_{\mathrm{thread}}}}{\sqrt[3]{V_{\max }}}+\mathrm{\ΔFR}$

In formula, △ FR _corrfor the final adjustment amount of roll-force control loop, △ FR is the additional controlled quentity controlled variable of roll-force control loop, FR _calfor demarcating roll-force, V _actfor the actual strip speed of planisher unit, V _threadfor planisher unit is creeped setting speed, V _maxfor planisher unit maximal rate.

By such scheme, V _maxfor planisher unit maximal rate, Cir _rollfor measuring roller girth, with strip steel at entry speed for benchmark,

If it is less than or equal to n ₁v _max, then measuring roller girth often rotates m ₁cir _rolla percentage elongation actual value is calculated during distance;

If it is greater than n ₁v _maxand be less than or equal to n ₂v _max, then measuring roller girth often rotates m ₂cir _rolla percentage elongation actual value is calculated during distance;

If it is greater than n ₂v _maxand be less than or equal to n ₃v _max, then measuring roller girth often rotates m ₃cir _rolla percentage elongation actual value is calculated during distance;

If it is greater than n ₃v _maxand be less than or equal to n ₄v _max, then measuring roller girth often rotates m ₄cir _rolla percentage elongation actual value is calculated during distance;

If it is greater than n ₄v _max, then measuring roller girth often rotates m ₅cir _rolla percentage elongation actual value is calculated during distance;

Wherein 0<n ₁<n ₂<n ₃<n ₄<1,0<m ₁<m ₂<m ₃<m ₄<m ₅<1.

By such scheme, described percentage elongation actual value is by following formulae discovery:

$\mathrm{ELC}=\frac{{\mathrm{Len}}_{\mathrm{exit}}-{\mathrm{Len}}_{\mathrm{entry}}}{{\mathrm{Len}}_{\mathrm{entry}}}\&times;100\%$

In formula, ELC is percentage elongation actual value, Len _exitfor the strip length passed through in the planisher exporting unit time, Len _entryfor the strip length passed through in the planisher entrance unit time,

Wherein Len _entry=Cir _{roll enters}* Δ t*V _{roll enters}, Cir _{roll enters}for the girth of entrance guide roller, V _{roll enters}for the rotating speed of entrance guide roller, Δ t is the unit time; Len _exitin like manner obtain.

Beneficial effect of the present invention is: by arranging the different percentage elongation length computation cycles in friction speed section, solving in acceleration and deceleration process and being with steel slippage problems; By 3 evolution related operations of actual speed, carry out the adjustment that feedforward control accelerates percentage elongation fluctuation in acceleration and deceleration process; Expected by actual roll-force and percentage elongation and control accuracy and stability that adaptive factor solves percentage elongation in acceleration and deceleration process are set for roll-force error dynamics correction and consider thickness, width and percentage elongation relation; Finally achieve the effect obtaining constant percentage elongation under acceleration and deceleration state.

Accompanying drawing explanation

Fig. 1 is the control principle drawing of one embodiment of the invention.

Fig. 2 is the percentage elongation length computation cyclic graph that friction speed section is arranged.

Fig. 3 is the application principle figure of one embodiment of the invention.

Fig. 4 is the test effect figure of one embodiment of the invention.

Detailed description of the invention

Below in conjunction with instantiation and accompanying drawing, the present invention will be further described.

Fig. 1 is the control principle drawing of one embodiment of the invention, and the present embodiment obtains the method for constant percentage elongation under providing a kind of acceleration and deceleration state, comprise the steps:

S1, respectively collection strip steel at entry speed and outlet strip speed, arrange variable-length computing cycle, calculate percentage elongation actual value;

With strip steel at entry speed or outlet strip speed for benchmark, obtain variable-length computing cycle according to its scope, and calculate percentage elongation; Measuring roller rotates girth to be added up to reach the periodic quantity arranged with friction speed section, as next percentage elongation measured value starting point.Namely measuring roller girth often rotates certain distance (this certain distance is relevant with friction speed section) and calculates a percentage elongation actual value;

Concrete, make V _maxfor planisher unit maximal rate, Cir _rollfor measuring roller girth, can with strip steel at entry speed for benchmark,

If it is less than or equal to n ₁v _max, then measuring roller girth often rotates m ₁cir _rolla percentage elongation actual value is calculated during distance;

If it is greater than n ₁v _maxand be less than or equal to n ₂v _max, then measuring roller girth often rotates m ₂cir _rolla percentage elongation actual value is calculated during distance;

If it is greater than n ₂v _maxand be less than or equal to n ₃v _max, then measuring roller girth often rotates m ₃cir _rolla percentage elongation actual value is calculated during distance;

If it is greater than n ₃v _maxand be less than or equal to n ₄v _max, then measuring roller girth often rotates m ₄cir _rolla percentage elongation actual value is calculated during distance;

If it is greater than n ₄v _max, then measuring roller girth often rotates m ₅cir _rolla percentage elongation actual value is calculated during distance;

Wherein 0<n ₁<n ₂<n ₃<n ₄<1,0<m ₁<m ₂<m ₃<m ₄<m ₅<1.

In the present embodiment, n ₁=0.05, n ₂=0.15, n ₃=0.35, n ₄=0.65; m ₁=0.1, m ₂=0.12, m ₃=0.15, m ₄=0.3, m ₅=0.5.

S2, percentage elongation actual value to be compared with percentage elongation setting value, obtain percentage elongation difference, with percentage elongation self-adaptative adjustment factor gain _aptproduct as the input value of PI controller, export the additional controlled quentity controlled variable of roll-force control loop and tension force control loop; Wherein percentage elongation self-adaptative adjustment factor gain _aptcomputing formula as follows:

$\mathrm{gai}{n}_{\mathrm{apt}}\left(n\right)=\frac{{\mathrm{Width}}_{\mathrm{set}}\&times;{\mathrm{Thk}}_{\mathrm{set}}}{{\mathrm{Width}}_{\max }\&times;{\mathrm{Thk}}_{\max }}\&times;\&Integral;({\mathrm{FR}}_{\mathrm{act}}-100\&times;\mathrm{ELC}\&times;\&Integral;{\mathrm{gain}}_{\mathrm{apt}}(n-1))$

In formula, Width _setfor setting strip width, Thk _setsetting belt steel thickness, FR _actfor roll-force actual value, ELC is percentage elongation actual value, Width _maxfor strip width maximum, Thk _maxfor belt steel thickness maximum, n is iterative times, n=1,2,3 ...

S3, by the additional controlled quentity controlled variable of roll-force control loop and the roll-force self-adaptative adjustment factor superimposed, obtain final roll-force adjustment amount, roll-force adjusted; Wherein the computing formula of roll-force adjustment amount is as follows:

${\mathrm{\&Delta;FR}}_{\mathrm{corr}}=\left({\mathrm{FR}}_{\mathrm{cal}}\right)\&times;\frac{\sqrt[3]{V_{\mathrm{act}}}-\sqrt[3]{V_{\mathrm{thread}}}}{\sqrt[3]{V_{\max }}}+\mathrm{\&Delta;FR}$

In formula, △ FR _corrfor the final adjustment amount of roll-force control loop, △ FR is the additional controlled quentity controlled variable of roll-force control loop, FR _calfor demarcating roll-force, V _actfor the actual strip speed of planisher unit, V _threadfor planisher unit is creeped setting speed, V _maxfor planisher unit maximal rate.

Below in conjunction with principle, the present invention is elaborated.

One, planisher percentage elongation computational methods

Skin pass rolling is last one critical process of producing prime sheet, guaranteeing to be with steel end product quality, it for improving the quality of products, control panel shape, make thin plate have suitable mechanical property according to user's request and surface state plays an important role.In Cold-Rolled Strip Temper Mill, percentage elongation is important technic index, for obtaining constant percentage elongation, by the object regulating roll-force or tension force to reach specific elongation steadily control.

Percentage elongation conventionally calculation formula is

$\mathrm{ELC}=\frac{V_{\mathrm{exit}}-V_{\mathrm{entry}}}{V_{\mathrm{entry}}}\&times;100\%$ (formula 1-1)

In formula, V _exitplanisher outlet strip speed m/s, V _entryplanisher strip steel at entry speed m/s, ELC are percentage elongation actual value.

Due to the smooth secondary deformation for being with steel to carry out light reduction, length direction extends can be ignored, and according to constancy of volume principle, percentage elongation computing formula also can be exchanged into:

$\mathrm{ELC}=\frac{{\mathrm{Len}}_{\mathrm{exit}}-{\mathrm{Len}}_{\mathrm{entry}}}{{\mathrm{Len}}_{\mathrm{entry}}}\&times;100\%$ (formula 1-2)

In formula, ELC is percentage elongation actual value, Len _exitfor the strip length passed through in the planisher exporting unit time, Len _entryfor the strip length passed through in the planisher entrance unit time,

Wherein Len _entry=Cir _{roll enters}* Δ t*V _{roll enters}, Cir _{roll enters}for the girth of entrance guide roller, V _{roll enters}for the rotating speed of entrance guide roller, Δ t is the unit time; Len _exitin like manner obtain.The present invention preferably this mode calculates percentage elongation actual value.

Two, planisher elongation control principle

Elongation control model is controlled by roll-force or is controlled by tension force or roll-force adds tension force control.

According to the size of belt steel thickness, distribute the weight that roll-force controls and tension force controls, when often supplied materials thickness is larger, adopt roll-force control model, time thinner, adopt tension control mode or roll-force to add tension control mode; Working control principle is: percentage elongation actual value is compared difference with setting desired value, and this difference is sent to elongation control device.Elongation control device determines tension value size before and after actual additional roll-force or planisher according to the control model adopted, the rolling force setup value revising pressure or the setting tension value revised before and after planisher.The size of percentage elongation is regulated finally by tension force Controlling model outer shroud before and after pressure roll-force Controlling model or planisher.

Three, constant percentage elongation method is obtained under acceleration and deceleration state

Under acceleration and deceleration state, the speed of skin pass mill group, tension force, roll-force, percentage elongation, leveling precision adhesion amount etc. all plays pendulum, and therefore occurs that percentage elongation fluctuation is excessive, makes the smooth section strip steel of acceleration and deceleration not meet technological requirement.

By groping of percentage elongation debug process in certain planisher Practical Project, invented the fluctuation problem method solving percentage elongation acceleration and deceleration process from three angles, proving effect is good.Percentage elongation detection, by arranging the different percentage elongation length computation cycles in friction speed section, solves in acceleration and deceleration process and is with steel slippage problems; By 3 evolution related operations of actual speed, carry out the adjustment that feedforward control accelerates percentage elongation fluctuation in acceleration and deceleration process; Expected by actual roll-force and percentage elongation and control accuracy and stability that adaptive factor solves percentage elongation in acceleration and deceleration process are set for roll-force error dynamics correction and consider thickness, width and percentage elongation relation.

(1) process of acceleration and deceleration downward-extension rate measured value

The percentage elongation of planisher is generally measured by two laser velocimeters of planisher inlet/outlet or two encoders of inlet/outlet guide roller are measured.Laser velocimeter is vertical with belt steel surface, and direct-detection goes out the linear velocity with steel.Encoder is arranged on the shaft centre line of frame inlet/outlet guide roller respectively, by the linear velocity of guide roller rotating speed conversion inlet/outlet band steel.Laser velocimeter precision is high, and it not the acceleration and deceleration of tape steel skid impact, be planisher percentage elongation instrumentation configuration first-selection.But laser velocimeter is expensive, often need to safeguard, adopt encoder to detect percentage elongation cost performance for medium-sized and small enterprises higher.

Adopt encoder to measure percentage elongation precision lower than laser velocimeter, in this external acceleration and deceleration process, skidding can have influence on the actual strip speed of detection.According to constancy of volume principle, and after smooth, the extension of width can be ignored, and encoder velocity measurement is converted into length value, then adopts percentage elongation length computation formula (1-2), calculates actual percentage elongation.

Because encoder is arranged on inlet/outlet guide roller, it exports as guide roller actual speed, and in working control, the sampling period is 1.6ms, guide roller actual speed, as guide roller actual speed, is then scaled actual strip length by the guide roller rotating speed mean value getting 4 sampling periods.

The slippage problems caused for avoiding velocity variations, improves elongation control precision, the invention provides a kind ofly to measure the measurement of the addition method for percentage elongation, namely eliminates the low impact of encoder certainty of measurement by the length computation cycle.Simultaneously because different strip speed slippery conditions is different, detect measuring roller rotation girth at FM458 controller and add up to reach the percentage elongation length computation periodic quantity arranged with friction speed section, as next percentage elongation measured value starting point, as shown in Figure 2.

(2) feed forward open loop of acceleration and deceleration downward-extension rate controller output quantity regulates.

Consider that velocity variations can cause coefficient of friction to change, acceleration mode percentage elongation actual value when not revising reduces, and deceleration regime percentage elongation actual value when not revising increases.By repeatedly testing, inventing a kind of 3 evolution related operations relevant to actual speed, carrying out feedforward control in advance to percentage elongation fluctuation adjustment in acceleration and deceleration process.

Because feedforward control control accuracy is limited, therefore when carrying out feedforward control, be only added to feedforward preconditioning amount roll-force control loop.

(3) the feedback closed loop Automatic adjusument of acceleration and deceleration downward-extension rate controller.

Detection and feed forward open loop regulate and can adjust percentage elongation in advance when acceleration and deceleration, it is made to fluctuate near setting value, but percentage elongation constant control to be reached under acceleration and deceleration, also need according to actual roll-force, preset roll-force, width and thickness etc. to elongation control device dynamic conditioning, realize self-adapting closed loop and control.

Consider thickness and width and percentage elongation relation, and change of external conditions can cause percentage elongation to change, and then cause roll-force to change, expect that roll-force error is as the percentage elongation self-adaptative adjustment factor according to actual roll-force and percentage elongation.The product of the percentage elongation self-adaptative adjustment factor and percentage elongation difference, as elongation control object, repeatedly iterates adjustment in acceleration and deceleration process.

(4) for specifically to be implemented by the elongation control algorithm designed under acceleration and deceleration state, in FM458, carried out program composition, programming adopts CFC to complete, and programme-control block diagram is as Fig. 3.Five clock cycle as elongation control unit F M458 are set to 1.6ms, 6.4ms, 12.8ms, 51.2ms, 204.8ms respectively, WINCC (process monitoring system that man-machine interface is run) for practical production status display, process data acquisition system iba for gathering, Real time displaying and analysis be from the analog and digital signal of control system and control effects.

Four, actual verification and interpretation of result

Acceleration and deceleration elongation control algorithm of the present invention is tested in actual planisher, and the guarantee value under this planisher elongation control acceleration and deceleration state is ± 0.15%.For verifying validity of the present invention, have employed iba data collecting system, intercepting real data in test process and analyzing, as shown in Figure 4.

As can be seen from data and curves shown in Fig. 4, adopt acceleration and deceleration elongation control algorithm of the present invention, there is higher control accuracy, when percentage elongation setting value is 1%, actual elongation control, in 0.924% ~ 1.075% (accuracy rating-0.076% ~+0.075%), reaches guarantee value requirement far away.This illustrates that controlling plan design is very effective and successful.

Obtain constant percentage elongation method under the acceleration and deceleration state that the present invention proposes and compared with prior art there is following effect: (1) acceleration and deceleration downward-extension rate control accuracy reaches-0.076% ~+0.075%, there is higher control accuracy, reach guarantee value requirement (guarantee value required precision ± 0.15%), the processing performance of smooth band steel during improving acceleration and deceleration; (2) the present invention realizes simply, extending to the electrical control of this type skin pass mill group elongation control system; (3) percentage elongation detection is by arranging the different percentage elongation length superposition cycles in friction speed section, solves in acceleration and deceleration process and is with steel slippage problems; (4) by repeatedly testing, a kind of 3 evolution related operations relevant to actual speed are adopted to carry out feedforward control, by roll-force control loop in advance to percentage elongation fluctuation adjustment in acceleration and deceleration process, improve percentage elongation actual value when accelerating less than normal, percentage elongation actual value problem bigger than normal during deceleration.(5) expect that roll-force error is as the self-adaptative adjustment factor according to actual roll-force and percentage elongation, the product of the self-adaptative adjustment factor and percentage elongation deviation is as elongation control object, in acceleration and deceleration process, repeatedly iterate adjustment, solve control accuracy and the stability problem of percentage elongation in acceleration and deceleration process.

Above embodiment is only for illustration of design philosophy of the present invention and feature, and its object is to enable those skilled in the art understand content of the present invention and implement according to this, protection scope of the present invention is not limited to above-described embodiment.So all equivalent variations of doing according to disclosed principle, mentality of designing or modification, all within protection scope of the present invention.

Claims (3)

1. obtain a method for constant percentage elongation under acceleration and deceleration state, it is characterized in that: it comprises the steps:

S1, respectively collection strip steel at entry speed and outlet strip speed, arrange variable-length computing cycle, calculate percentage elongation actual value;

With strip steel at entry speed or outlet strip speed for benchmark, obtain variable-length computing cycle according to its scope, and calculate percentage elongation; Measuring roller rotates girth to be added up to reach the periodic quantity arranged with friction speed section, and as next percentage elongation measured value starting point, namely measuring roller girth often rotates certain distance and calculates a percentage elongation actual value, and this certain distance is relevant with friction speed section;

S2, percentage elongation actual value to be compared with percentage elongation setting value, obtain percentage elongation difference, with percentage elongation self-adaptative adjustment factor gain _aptproduct as the input value of PI controller, export the additional controlled quentity controlled variable of roll-force control loop and tension force control loop; Wherein percentage elongation self-adaptative adjustment factor gain _aptcomputing formula as follows:

${\mathrm{gain}}_{\mathrm{apt}}\left(n\right)=\frac{{\mathrm{Width}}_{\mathrm{set}}\&times;{\mathrm{Thk}}_{\mathrm{set}}}{{\mathrm{Width}}_{\max }\&times;{\mathrm{Thk}}_{\max }}\&times;\&Integral;({\mathrm{FR}}_{\mathrm{act}}-100\&times;\mathrm{ELC}\&times;\&Integral;{\mathrm{gain}}_{\mathrm{apt}}(n-1))$

In formula, Width _setfor setting strip width, Thk _setsetting belt steel thickness, FR _actfor roll-force actual value, ELC is percentage elongation actual value, Width _maxfor strip width maximum, Thk _maxfor belt steel thickness maximum, n is iterative times, n=1,2,3,

S3, by the additional controlled quentity controlled variable of roll-force control loop and the roll-force self-adaptative adjustment factor superimposed, obtain final roll-force adjustment amount, roll-force adjusted; Wherein the computing formula of roll-force adjustment amount is as follows:

${\mathrm{\&Delta;FR}}_{\mathrm{corr}}=\left({\mathrm{FR}}_{\mathrm{cal}}\right)\&times;\frac{3\sqrt{V_{\mathrm{act}}}-3\sqrt{V_{\mathrm{thredad}}}}{3\sqrt{V_{\max }}}+\mathrm{\&Delta;FR}$

In formula, △ FR _corrfor the final adjustment amount of roll-force control loop, △ FR is the additional controlled quentity controlled variable of roll-force control loop, FR _calfor demarcating roll-force, V _actfor the actual strip speed of planisher unit, V _threadfor planisher unit is creeped setting speed, V _maxfor planisher unit maximal rate.

2. obtain the method for constant percentage elongation under a kind of acceleration and deceleration state according to claim 1, it is characterized in that: make V _maxfor planisher unit maximal rate, Cir _rollfor measuring roller girth, with strip steel at entry speed for benchmark,

If it is less than or equal to n ₁v _max, then measuring roller girth often rotates m ₁cir _rolla percentage elongation actual value is calculated during distance;

If it is greater than n ₁v _maxand be less than or equal to n ₂v _max, then measuring roller girth often rotates m ₂cir _rolla percentage elongation actual value is calculated during distance;

If it is greater than n ₂v _maxand be less than or equal to n ₃v _max, then measuring roller girth often rotates m ₃cir _rolla percentage elongation actual value is calculated during distance;

If it is greater than n ₃v _maxand be less than or equal to n ₄v _max, then measuring roller girth often rotates m ₄cir _rolla percentage elongation actual value is calculated during distance;

If it is greater than n ₄v _max, then measuring roller girth often rotates m ₅cir _rolla percentage elongation actual value is calculated during distance;

Wherein 0<n ₁<n ₂<n ₃<n ₄<1,0<m ₁<m ₂<m ₃<m ₄<m ₅<1.

3. obtain the method for constant percentage elongation under a kind of acceleration and deceleration state according to claim 1, it is characterized in that: described percentage elongation actual value is by following formulae discovery:

$\mathrm{ELC}=\frac{{\mathrm{Len}}_{\mathrm{exit}}-{\mathrm{Len}}_{\mathrm{entry}}}{{\mathrm{Len}}_{\mathrm{entry}}}\&times;100\%$

In formula, ELC is percentage elongation actual value, Len _exitfor the strip length passed through in the planisher exporting unit time, Len _entryfor the strip length passed through in the planisher entrance unit time,

Wherein Len _entry=Cir _{roll enters}* Δ t*V _{roll enters}, Cir _{roll enters}for the girth of entrance guide roller, V _{roll enters}for the rotating speed of entrance guide roller, Δ t is the unit time; Len _exitin like manner obtain.