EP0698427A1 - Process for suppressing the influence of roll eccentricities - Google Patents

Abstract

Roll eccentricities are reproduced as an output signal of an oscillator which is used for position or thickness control in the roll stand. The adjustment of the amplitude and phase of the output signal ( DELTA R') are adjusted as follows: (a) the exit thickness (ha) of the rolled material is measured with a delay relative to the thickness reduction in the roll gap; b) a roll adjustment signal (s*) is formed and delayed by an amt. at least approximately equal to the measurement delay; (c) a difference signal (u) is formed at the summing point from the signal (s*) and the signal (h'a) multiplied by an expression involving the stiffness ratio of the rolled material and the roll stand; and (d) the signal ( DELTA R') is modified dependent on its deviation from the signal (u), and is phase-advanced by an amt. equal to the measurement delay.

Description

The invention relates to a method for suppressing the influence of roll eccentricities on the outlet thickness of the rolling stock in a roll stand.

Due to inaccurately manufactured back-up rolls or inaccurate storage of the back-up rolls, there are often eccentricities in rolling stands, which affect the quality of the strip to be rolled, whereby depending on the rigidity of the roll stand and the rolling stock, the eccentricities generally change with the speed of the rolls with eccentricity, usually the back-up rolls , in the band. The frequency spectrum of the eccentricities and the disturbances in the band caused by them essentially contains the fundamental frequencies of the upper and lower support rollers; however, there are also higher harmonics which, however, often only appear with reduced amplitudes. Due to the slightly different diameters and speeds of the upper and lower backup rolls, the frequencies assigned to the backup rolls can differ from one another.

In a method known from EP-B-0 170 016, in order to suppress the influence of roll eccentricities on the runout thickness of the rolling stock in a roll stand, the roll eccentricities of the upper and lower back-up rolls are simulated by the sum of the output signals from two feedback oscillators and a position or thickness control activated for the roll stand. The oscillators work according to the observer principle, the frequencies of their output signals being set as a function of the measured rotational speeds of the rollers; the amplitude and phase position of the output signals is tracked as a function of the deviation between the sum output signal of the two oscillators and a further sum signal, which is composed of the measured rolling force multiplied by the sum of the reciprocal values of the rigidity of the roll stand and the rolling stock and the measured actual value of the roll pitch. The oscillators can be implemented as digital filters, whereby they are coupled to the remaining analog position or thickness control of the roll stand via analog / digital converters and digital / analog converters.

Provided that the dynamics of position control, i.e. H. the dynamics of the control loops and actuators used to control the position of the rollers is negligible, the known method provides a good compensation for the roller eccentricity. However, the measurement of the rolling force and thus the compensation of the roll eccentricity can be impaired by friction in the roll stand.

In a method known from US-A-4 648 257 for compensating for roll eccentricities, the thickness of the rolling stock is measured after it leaves the roll stand and, together with the instantaneous rotation angle also measured, at least one of the rolls is used to continuously calculate estimated values for the changes in thickness of the roll Rolled good used. These estimates are corrected as a function of the measurement delay converted into the corresponding angle of rotation of the roll, which results from the distance of the measuring point for the thickness measurement from the roll gap, that is to say the location of the change in thickness of the rolling stock. The estimated values related to the angle of rotation are then applied to the position or thickness control to compensate for eccentricities. However, the precise detection of the instantaneous angle of rotation on the rolls is to be regarded as relatively complex, in particular with regard to the rough conditions in the vicinity of the roll stand.

The invention has for its object to provide a method for compensating roller eccentricities without this requires a measurement of the rolling force or the instantaneous angle of rotation of rolls.

According to the invention, the object is achieved in that, in order to suppress the influence of roll eccentricities on the outlet thickness of the rolling stock in a roll stand, the roll eccentricities are simulated by the output signal of a feedback oscillator which is applied to a position or thickness control for the roll stand, the frequency the output signal is set as a function of the measured rotational speed of the rolls and the amplitude and phase position of the output signal is set in such a way that the thickness of the rolling stock is measured after its exit from the roll stand with a measurement delay compared to the reduction in thickness taking place in the roll stand, that a signal corresponding to the roll adjustment is formed and at least approximately delayed by the amount of the measurement delay, that a difference signal from the delayed roll adjustment signal and the one with the sum of one and the Qu otients from the rigidity of the rolling stock and the rigidity of the mill stand multiplied thickness measurement signal is formed, that the amplitude and phase of the output signal of the oscillator depending on the deviation between the output signal and the difference signal in the sense of minimizing this deviation is tracked and that the output signal by one the amount corresponding to the measurement delay is shifted in phase in the sense of an advance.

realisieren.In contrast to the method known from EP-B-0 170 016, instead of the rolling force, the thickness of the rolling stock is measured after it exits the rolling stand and is converted into an estimated course of the roll eccentricities using the gauge meter equations. The basic oscillation of the estimated roll eccentricities is simulated by the oscillator and the position or thickness control is applied. The measurement delay in relation to the roll gap that occurs when measuring the thickness of the rolling stock, in which the thickness reduction takes place and the eccentricities in relation to the thickness of the rolling stock take effect, is canceled in the eccentricity compensation by the leading phase shift of the sinusoidal output signal of the oscillator. In the case of an oscillator which, according to FIG. 3 of EP-B-0 170 016, consists of two integrators and supplies a sinusoidal and cosine-shaped signal, this phase shift can be correspondingly very easily $\text{sin (ωt + φ) = cos φ · sin ωt + sin φ · cos ωt}$

realize.

The setpoint of the roll setting is preferably used as the roll setting signal instead of the actual value. This ensures that roll eccentricities are accurate even when the position control dynamics are slow and / or not exactly known. H. completely, to be compensated. With the increasingly slow dynamics of the position control, only the settling time for the compensation of the roller eccentricities is extended.

However, the insensitivity of the eccentricity compensation to the dynamics of the position control no longer applies at high speeds of the rollers, since the entire control loop can become unstable at high speeds and at the same time slow dynamics of the position control. To avoid this effect, it is conceivable to expand the interference observer formed by the oscillator by the dynamics of the position control. However, a dynamic correction of the delay in the position control is simpler by means of a proportional differential element (PD element), via which the thickness measurement signal used to form the difference signal is conducted. As an alternative, the phase-shifted output signal of the oscillator can be fed to the position or thickness control via a proportional differential element (PD element), the roller adjustment signal used to form the difference signal also being guided via a proportional delay element (PT1 element) becomes.

A direct digital implementation of the position or thickness control and the oscillator is preferably provided, the roll setting signal, the thickness measurement signal and the measured speed of the rolls being digital values or being converted into digital values. In contrast to a quasi-continuous implementation, as is proposed for the local oscillators in EP-B-0 170 016 already mentioned, in direct digital control (DDC) a process computer system acts directly on the actuators of the controlled system. No additional hardware is therefore required to implement the observer (oscillator), and in addition the setpoint for the roll adjustment, which is preferably used for tracking the oscillator, is available as a digital value, in contrast to the actual value used in the known method according to EP-B-0 170 016 , so that an analog / digital conversion is not required and the associated, in particular dynamic, errors cannot occur. In contrast to a quasi-continuous implementation, direct digital control also reproduces the roller eccentricities in the correct amplitude and phase, even when the sampling frequency of the observer (oscillator) is not significantly higher than the roller speed, i.e. with a sampling frequency that is only 5 to 10 times higher .

Under the simplifying assumption that the upper and lower rolls of the roll stand have the same speeds, the use of a single oscillator for eccentricity simulation is possible. However, since the speeds of the upper and lower rollers differ in practice - even if only slightly - another feedback oscillator is preferably used, the frequency of the output signal of one of the two oscillators depending on the speed of the upper roller and the frequency of the Output signal of the lower oscillator is set depending on the speed of the lower roller of the roll stand and the output signals of both oscillators are additive be linked together. A series connection of both oscillators is also possible.

To suppress harmonics of the roller eccentricities, further feedback oscillators can also be used, which are also connected in series or whose output signals are additively linked to one another.

According to an advantageous development of the method according to the invention, this is combined with the method known from EP-B-0 170 016, in that the roller eccentricities are additionally simulated by the output signal of at least one additional oscillator, which can be connected to the position or thickness control, the frequency of the output signal as a function of the measured rotational speed of the rolls and the amplitude and phase of the output signal as a function of the deviation between the output signal of the oscillator and the sum signal from the measured rolling force multiplied by the sum of the reciprocal values of the rigidity of the roll stand and the rolling stock and the roll adjustment in order to minimize this deviation. Here, too, the setpoint of the roll adjustment is preferably used to determine the deviation.

FIG 1

ein Beispiel für die Positionsregelung für ein Walzgerüst,

FIG 2

ein Blockschaltbild der von der Positionsregelung und dem Walzgerüst nach FIG 1 gebildeten Regelstrecke mit einem nach dem erfindungsgemäßen Verfahren arbeitenden Störbeobachter,

FIG 3

eine erweiterte Ausführung des in FIG 2 gezeigten Blockschaltbildes,

FIG 4

ein Beispiel für die Ausführung des Störbeobachters mit einem rückgekoppelten Oszillator und

FIG 5

ein weiteres Ausführungsbeispiel des Störbeobachters mit mehreren rückgekoppelten Oszillatoren.

To further explain the invention, reference is made below to the figures of the drawing. Show in detail

FIG. 1

an example of the position control for a roll stand,

FIG 2

2 shows a block diagram of the controlled system formed by the position control and the rolling stand according to FIG. 1 with an interference observer working according to the method according to the invention,

FIG 3

3 shows an expanded version of the block diagram shown in FIG. 2,

FIG 4

an example of the execution of the observer with a feedback oscillator and

FIG 5

another embodiment of the observer with several feedback oscillators.

1 shows an example of the position control of a roll stand 1 with an upper and lower support roll 2 or 3, two work rolls 4 and 5, a hydraulic adjusting device 7, which can be actuated via a control valve 6, for setting the roll position s and a symbolizing the elasticity of the roll stand 1 Spring c _G. The rolling stock 8, to which an equivalent material spring c _M can be assigned in the roll gap, is rolled down by the two work rolls 4 and 5 from an inlet thickness h _e to an outlet thickness h _a . The roll eccentricities can be described by effectively changing the roll radius ΔR.

The roller adjustment s is measured with a position sensor 9 on the adjusting device 7 and compared as an actual value at a summing point 10 with a setpoint s * of the roller adjustment, the comparison result via a position controller 11 and a downstream actuator 12 for actuating the control valve 6 and thus for adjustment the roll adjustment s is used.

As will be explained below, the compensation of the roll eccentricities ΔR requires the measurement of the outlet thickness h _a and the roll speed n and, in the case of the exemplary embodiment shown in FIG. 3, the measurement of the rolling force F _W. The rolling force F _W is measured by means of a pressure sensor 13 on the rolling stand 1.

The measurement of the roller speed n serves to determine the basic vibration of the roller eccentricities. Under the simplifying requirement that the top and bottom rollers of the roll stand 1 rotate at the same speed, it is sufficient to adjust the speed of only one driven roller, e.g. B. the work roll 5 by means of a tachometer 14.

If, as in most cases, the support rollers 2 and 3 are the eccentric rollers, the measured speed of the work roller 5 is in a unit 15 via the ratio of the diameter of the work roller 5 to that of the support roller 3 in the speed n _{u of} the lower Support roller 3 converted. Since, as a rule, the speeds of the upper and lower rollers differ due to slightly different diameters, in the exemplary embodiment shown there is a further tachometer 16 with a subordinate conversion unit 17 for detecting the speed n _{o of} the upper support roller 2.

The outlet thickness h _{a of} the rolling stock 8 is measured by means of a thickness measuring device 18, which is arranged at a distance l behind the roll gap.

In FIG. 2, reference number 19 denotes the simplified block diagram of the control path formed by the position control shown in FIG. 1 and the rolling stand. The position control 20 includes, among other things, the position controller 11 with the summing point 10, the actuator 12, the valve 6 and the hydraulic adjusting device 7 with the roller mass moved by it. The position control 20 supplies the actual value s of the roll adjustment as the output variable. The following relationships for the rolling force F _W can be derived from FIG. 1: $$\begin{array}{c}\begin{array}{c}{\text{F}}_{\text{W}}{\text{= c}}_{\text{G}}{\text{(H}}_{\text{a}}\text{+ ΔR-s) and}\\ {\text{F}}_{\text{W}}{\text{= c}}_{\text{M}}{\text{(H}}_{\text{e}}{\text{-H}}_{\text{a}}\text{).}\end{array}\end{array}$$

die in dem in FIG 2 gezeigten Blockschaltbild der Regelstrecke 19 durch den Summierpunkt 21 mit den Eingangsgrößen h_e, ΔR und -s, den nachgeordneten Funktionsblock 22 mit der Gesamtsteifigkeit c₀ der in Reihe liegenden Gerüstfeder c_G und Materialfeder c_M sowie den nachfolgenden Funktionsblock 23 mit dem negativen Kehrwert der Materialfeder c_M wiedergegeben ist. Am Ausgang des Funktionsblockes 22 erscheint die Walzkraft F_W, deren Meßwert F_W' durch Störungen ΔF_stör, wie z. B. die Reibung im Walzgerüst, beeinflußt ist. Aufgrund der am Ausgang des Funktionsblocks 23 erscheinenden Dickenreduktion h_a-h_e ergibt sich die Austrittsdicke h_a des Walzgutes 8, die mit Hilfe des Dickenmeßgerätes 18 mit einer von der Austrittsgeschwindigkeit v_B des Walzgutes 8 und dem Abstand l zwischen dem Walzspalt und dem Dickenmeßgerät 18 abhängigen Meßverzögerung gemessen wird.This gives rise to relationships $$\begin{array}{c}\begin{array}{c}{\text{F}}_{\text{W}}{\text{= c}}_{\text{0}}{\text{(H}}_{\text{e}}{\text{+ ΔR-s) with c}}_{\text{0}}{\text{= c}}_{\text{M}}{\text{c}}_{\text{G}}{\text{/ (c}}_{\text{M}}{\text{+ c}}_{\text{G}}\text{) and}\\ {\text{H}}_{\text{a}}{\text{-H}}_{\text{e}}{\text{= -F}}_{\text{W}}{\text{/ c}}_{\text{M}}\text{,}\end{array}\end{array}$$

2 in the block diagram of the controlled system 19 through the summing point 21 with the input variables h _e , ΔR and -s, the downstream function block 22 with the overall rigidity cste of the frame spring c _G and material spring c _M lying in series, and the subsequent function block 23 reproduced with the negative reciprocal of the material spring c _M is. At the output of the function block 22, the rolling force F _{W appears} , the measured value F _W 'of disturbances _ΔF , such as. B. the friction in the roll stand is affected. Due to the thickness reduction h _a- h _e appearing at the output of the function block 23, the exit thickness h _{a of} the rolling stock 8 is obtained, which with the aid of the thickness measuring device 18 has a velocity v _{B of} the rolling stock 8 and the distance l between the roll gap and the thickness measuring device 18 dependent measurement delay is measured.

, mit ${\text{n = n}}_{\text{o}}{\text{= n}}_{\text{u}}$

, aufweisen, dient ein Störbeobachter in Form eines gegengekoppelten Oszillators 24, der an seinem Ausgang 25 im eingeschwungenen Zustand die Grundschwingung der Störung, d. h. der Walzenexzentrizitäten ΔR nachbildet. Dabei wird die Frequenz ω des Oszillators 24 in Abhängigkeit von der gemessenen Walzendrehzahl n mit $\text{ω = 2πn}$

eingestellt. Die von dem Oszillator 24 nachgebildete Störung ΔR' wird über einen die Meßverzögerung zwischen dem Walzspalt und dem Dickenmeßgerät 18 kompensierenden Phasendreher 26, ein Proportional-Differential-Glied (PD-Glied) 27 und einen Schalter 28 einem Summierglied 29 zugeführt und dort dem Sollwert s* der Walzenanstellung am Eingang der Regelstrecke 19 aufgeschaltet.To compensate for the roller eccentricities ΔR, which is assumed here to be only a fundamental oscillation $\text{ω = 2πn}$

, With ${\text{n = n}}_{\text{O}}{\text{= n}}_{\text{u}}$

, serves, a disturbance observer in the form of a negative feedback oscillator 24, which simulates the fundamental oscillation of the disturbance, ie the roller eccentricities ΔR, at its output 25 in the steady state. The frequency ω of the oscillator 24 becomes dependent on the measured roller speed n $\text{ω = 2πn}$

set. The disturbance ΔR 'simulated by the oscillator 24 is fed via a phase rotator 26 compensating the measuring delay between the roll gap and the thickness measuring device 18, a proportional differential element (PD element) 27 and a switch 28 to a summing element 29 and there the setpoint s * the roller adjustment switched on at the entrance to the controlled system 19.

wird über ein zu dem PD-Glied 27 komplementäres Proportional-Verzögerungs-Glied (PT1-Glied) 30 und ein Verzögerungsglied 31 mit einer der Meßverzögerung in dem Dickenmeßgerät 18 zumindest annähernd entsprechenden Verzögerung einem Summierpunkt 32 zugeführt. Das von dem Dickenmeßgerät 18 gelieferte Dickenmeßsignal h_a' wird in einem Multiplizierglied 33 mit der Summe aus Eins und dem Quotienten aus den Steifigkeiten c_M' und c_G' des Walzgutes 8 und des Walzgerüsts 1, d. h. mit ${\text{1+c}}_{\text{M}}{\text{'/c}}_{\text{G}}{\text{' = c}}_{\text{M}}{\text{'/c}}_{\text{0}}\text{'}$

multipliziert und mit negativem Vorzeichen ebenfalls dem Summierpunkt 32 zugeführt. Das in dem Summierpunkt 32 erzeugte Differenzsignal u und das Ausgangssignal ΔR' des Oszillators 24 werden an einem weiteren Summierpunkt 34 miteinander verglichen, wobei ein Korrektursignal $\text{e = u-ΔR'}$

gebildet wird, über das der Oszillator 24 an seinem Eingang 35 in Amplitude und Phase so lange nachgeführt wird, bis die nachgebildete Störung ΔR' und das Differenzsignal u übereinstimmen und der Fehler somit zu Null wird.The setpoint of the roll adjustment superimposed with the simulated fault $\text{s * + ΔR '}$

is supplied to a summing point 32 via a proportional delay element (PT1 element) 30, which is complementary to the PD element 27, and a delay element 31 with a delay at least approximately corresponding to the measuring delay in the thickness measuring device 18. The thickness measuring signal h _a 'supplied by the thickness measuring device 18 is in a multiplier 33 with the sum of one and the quotient of the stiffnesses c _M ' and c _G 'of the rolling stock 8 and the rolling stand 1, ie with ${\text{1 + c}}_{\text{M}}{\text{'/ c}}_{\text{G}}{\text{'= c}}_{\text{M}}{\text{'/ c}}_{\text{0}}\text{'}$

multiplied and also fed to the summing point 32 with a negative sign. The difference signal generated in the summing point 32 u and the output signal .DELTA.R 'of the oscillator 24 are compared at a further summing point 34, with a correction signal $\text{e = u-ΔR '}$

is formed, via which the oscillator 24 is adjusted in amplitude and phase at its input 35 until the simulated interference ΔR 'and the difference signal u match and the error thus becomes zero.

Because the summing point 32 is supplied with the setpoint s 'superimposed with the interference simulation ΔR' of the roll adjustment, the respective dynamics of the position control 20 have no influence whatsoever on the compensation of the roll eccentricities ΔR, so that these are asymptotically completely unaffected in their effect on the exit thickness h _{a of} the rolling stock 8 are eliminated. However, this no longer applies at very high speeds of the rollers, since at such high speeds and at the same time slow dynamics of the position control 20, the entire control loop can become unstable. In order to avoid such instabilities, a dynamic correction of the delay of the position control 20 is carried out by means of the PD element 27 already mentioned. So that the disturbance variable compensation continues to take place completely (e = 0), the PT1 element 30 is provided. Instead of the PD element 27 and the PT1 element 30, it is also possible to provide a single PD element in the area of processing the thickness measurement signal h _a 'between the thickness measurement device 18 and the summing point 32.

und der Oszillator 37 in Abhängigkeit von der Drehzahl n_u der Unterwalzen mit ${\text{ω}}_{\text{u}}{\text{= 2πn}}_{\text{u}}$

eingestellt. Die von den beiden Oszillatoren 36 und 37 nachgebildeten Störgrößen ΔR_o' und ΔR_u' werden in einem Summierglied 38 aufsummiert und über den Phasendreher 26, das PD-Glied 27 und den Schalter 28 in dem Summierpunkt 29 dem Sollwert s* der Walzenanstellung aufgeschaltet sowie zur Rückkopplung der beiden Oszillatoren 36 und 37 mit negativem Vorzeichen dem Summierpunkt 34 zugeführt. Im übrigen werden, ebenso wie bei dem in FIG 2 gezeigten Ausführungsbeispiel, der störgrößenbehaftete Sollwert der Walzenanstellung ${\text{s* + ΔR}}_{\text{o}}{\text{' + ΔR}}_{\text{u}}\text{'}$

über das PT1-Glied 30 und das Verzögerungsglied 31 sowie das Dickenmeßsignal h_a' über das Multiplizierglied 33 dem Summierpunkt 32 zur Bildung des Differenzsignals u zugeführt.FIG. 3 shows an expanded embodiment of the block diagram according to FIG. 2, 19 again denoting the controlled system, to which the setpoint s * for the roll adjustment is supplied at the beginning via a digital / analog converter. The controlled system 19 supplies the rolling force measurement signal F _W 'and the thickness measurement signal h _a ' as output signals, both of which are each converted into digital values by means of an analog / digital converter. Both the rolling force F _W and the initial thickness h _{a of} the rolling stock 8 are influenced in the control path 19 by the roll eccentricities which are due to diameter differences for the upper and lower rolls of the roll stand 1 are slightly different and are referred to here as ΔR _o and ΔR _u . To compensate for the roller eccentricities ΔR _o and ΔR _u on the basis of the thickness measurement signal h _a ', two feedback oscillators 36 and 37 are provided, of which the oscillator denoted by 36 simulates the disturbances ΔR _o originating from the upper rollers and the oscillator denoted by 37 the reproduces disturbances ΔR _u originating from the lower rollers. For this purpose, the frequency of the oscillator 36 is dependent on the measured speed n _{o of} the top rollers ${\text{ω}}_{\text{O}}{\text{= 2πn}}_{\text{O}}$

and the oscillator 37 as a function of the speed n _{u of} the lower rollers ${\text{ω}}_{\text{u}}{\text{= 2πn}}_{\text{u}}$

set. The disturbance variables ΔR _o 'and ΔR _u ' simulated by the two oscillators 36 and 37 are added up in a summing element 38 and applied to the setpoint s * of the roll adjustment via the phase rotator 26, the PD element 27 and the switch 28 in the summing point 29 fed to the summing point 34 for the feedback of the two oscillators 36 and 37 with a negative sign. Otherwise, just as in the exemplary embodiment shown in FIG. 2, the setpoint of the roll adjustment, which is subject to interference, becomes ${\text{s * + ΔR}}_{\text{O}}{\text{'+ ΔR}}_{\text{u}}\text{'}$

Via the PT1 element 30 and the delay element 31 and the thickness measurement signal h _a 'via the multiplier 33 to the summing point 32 to form the difference signal u.

wird über ein PT1-Glied 45 einem Summierpunkt 46 zugeführt und dort mit dem in einem Multiplizierglied 47 mit dem berechneten Kehrwert 1/c₀' der Gesamtsteifigkeit der Gerüst- und Materialfeder multiplizierten Walzkraftmeßsignals F_W' zu einem Summensignal u verknüpft. Dieses Summensignal u und das Ausgangssummensignal ΔR_o' + ΔR_u' der beiden Oszillatoren 39 und 40 werden an einem weiteren Summierpunkt 48 miteinander verglichen, wobei mit dem so erhaltenen Korrektursignal e die beiden Oszillatoren 39 und 40 in Amplitude und Phase so lange nachgeführt werden, bis die Summe der nachgebildeten Störungen ΔR_o' + ΔR_u' und das Summensignal u übereinstimmen.In addition, compensation of the roll eccentricities ΔR _o + ΔR _{u is provided} on the basis of the roll force measurement signal F _W '. For this purpose, an oscillator 39 frequency-controlled with ω _o simulates the disturbances ΔR _o originating from the upper rollers, while a further oscillator 40 is frequency-controlled with ω _{u and} simulates the disturbances ΔR _u originating from the lower rollers. The disturbance variables simulated by the two oscillators 39 and 40 are added up in a summing element 41 and applied to the setpoint s * of the roll adjustment via a PD element 42 and a switch 43 in a summing point 44. The setpoint of the roll adjustment superimposed with the simulated faults ${\text{s * + ΔR}}_{\text{O}}{\text{'+ ΔR}}_{\text{u}}\text{'}$

becomes a summing point via a PT1 element 45 46 supplied and linked there with the rolling force measurement signal F _W 'multiplied in a multiplier 47 by the calculated reciprocal 1 / c₀' of the overall rigidity of the frame and material spring to form a sum signal u. This sum signal u and the output sum signal ΔR _o '+ ΔR _u ' of the two oscillators 39 and 40 are compared with one another at a further summing point 48, the amplitude and phase of the two oscillators 39 and 40 being tracked with the correction signal e obtained in this way, until the sum of the simulated disturbances ΔR _o '+ ΔR _u ' and the sum signal u match.

wobei T_ab die Abtastperiode bezeichnet. Ebenso wie bei einer analogen Realisierung des Oszillators bestimmen die Nachführkoeffizienten a und b die Einschwingdynamik des rückgekoppelten Oszillators 24, wobei die Nachführkoeffizienten a und b in Abhängigkeit von der Frequenz ω der Grundschwingung einstellbar sind.4 shows a direct digital implementation of the oscillator 24 shown in FIG. 2 with the downstream phase rotator 26. The transfer function of the digital feedback oscillator 24 shown is $${\text{ΔR '/ u = (a + b) / (z}}^{\text{2nd}}{\text{+ z (a-2cosωT}}_{\text{from}}\text{) + b + 1),}$$

where T _ab denotes the sampling period. Just as with an analog implementation of the oscillator, the tracking coefficients a and b determine the settling dynamics of the feedback oscillator 24, the tracking coefficients a and b being adjustable as a function of the frequency ω of the fundamental oscillation.

in Multipliziergliedern 50 und 51 mit den Faktoren cos φ bzw. sin φ multipliziert und anschließend in einem Summierglied 52 aufsummiert. Unter der Annahme konstanter Geschwindigkeiten gilt für die Phasenverschiebung $${\text{φ = ω · T}}_{\text{tot}}{\text{= (v}}_{\text{W}}{\text{/R)·(l/v}}_{\text{B}}{\text{) = l/((1+k}}_{\text{V}}\text{)R),}$$

wobei T_tot die Meßverzögerung und l den Abstand zwischen dem Walzspalt und dem Dickenmeßgerät 18, v_W die Walzenumlaufgeschwindigkeit, v_B die Austrittsgeschwindigkeit des Walzgutes 8 aus dem Walzspalt, R den Radius der Arbeitswalzen 4 bzw. 5 und k_V die Voreilung mit ${\text{v}}_{\text{B}}{\text{/v}}_{\text{W}}{\text{= 1+k}}_{\text{V}}$

bezeichnen.The sinusoidal output signal generated at the output 25 of the oscillator 24 and a corresponding cosine output signal generated at a node 49 in the oscillator 24 become in accordance with the relationship $$\text{sin (ωt + φ) = cos φ · sin ωt + sin φ · cos ωt}$$

multiplied in multipliers 50 and 51 by the factors cos φ and sin φ and then summed up in a summing element 52. Assuming constant speeds, the following applies to the phase shift $${\text{φ = ω · T}}_{\text{dead}}{\text{= (v}}_{\text{W}}{\text{/ R) · (l / v}}_{\text{B}}{\text{) = l / ((1 + k}}_{\text{V}}\text{) R),}$$

where T _tot the measuring delay and l the distance between the roll gap and the thickness measuring device 18, v _W the roll circulation speed, v _B the exit speed of the rolling stock 8 from the roll gap, R the radius of the work rolls 4 or 5 and k _V the advance with ${\text{v}}_{\text{B}}{\text{/ v}}_{\text{W}}{\text{= 1 + k}}_{\text{V}}$

describe.

5 shows a further exemplary embodiment of the interference observer used to compensate for the roller eccentricities on the basis of the thickness measurement signal h _a '. This contains four oscillators 53, 54, 55 and 56, of which the oscillator 53 the fundamental oscillation ω _o and the oscillator 55 the harmonic 2ω _o of the disturbances originating from the upper rollers and the oscillator 54 the fundamental oscillation ω _u and the oscillator 56 the harmonic 2ω _u of the disturbances emanating from the lower rollers. The structure of the individual oscillators 53 to 56 corresponds to that of the oscillator 24 in FIG. 4. Therefore, only the setting elements 57 for the different tracking coefficients a₁, b₁ to a₄, b₄ are shown here, which on the input side are the same as for the oscillator 24 in FIG. 4, with the deviation e between the difference signal u and the simulated disturbance ΔR '. The simulated interference ΔR 'is formed in a summing point 58 from the sum of the output signals of the oscillators 53 to 56, these output signals, as a comparison of FIGS. 4 and 5 shows, not necessarily having to correspond to the signals present at the circuit points 25 or 49.

In order to compensate for the measurement delay between the roll gap and the thickness gauge 18, each oscillator 53 to 56 is followed by a phase rotator 59, 60, 61 and 62 in the exemplary embodiment shown. The phase rotators 59 and 60, which are used to simulate the fundamental vibration ω _o and ω _u Serving oscillators 53 and 54, each contain two multipliers 63 and 64, in which the sinusoidal signal at the switching point 25 are multiplied by cos φ and the cosine signal at the switching point 49 by sin φ; then both signals are summed in the adder 65. The two phase rotators 61 and 62, which are arranged downstream of the oscillators 55 and 56 used to emulate the harmonics 2ω _o and 2ω _u , also each contain two multipliers 66 and 67, in each of which the sinusoidal signal at switching point 25 is multiplied by cos 2φ and the cosine signal at switching point 49 is multiplied by sin 2φ; then both signals are summed in a summing element 68. The output signals of the phase rotators 59 and 60 are added up in a summing point 69 and the position or thickness control is applied as shown in FIG. 2 or 3. The output signals of the phase rotators 61 and 62 are also added up in a summing point 70 and, if necessary, also applied to the position or thickness control via a switch 71 and a further summing point 72.

Claims (8)

Method for suppressing the influence of roll eccentricities (ΔR) on the runout thickness of the rolling stock (8) in a roll stand (1), in that the roll eccentricities (ΔR) are simulated by the output signal (ΔR ') of a feedback oscillator (24), which corresponds to a position - or thickness control for the roll stand (1) is applied, the frequency (ω) of the output signal (ΔR ') being set as a function of the measured speed (n) of the rolls (2 to 5) and the setting of the amplitude and phase position of the output signal (ΔR ') takes place in _{such a} way that the thickness (h _a ) of the rolling stock (8) after its exit from the roll stand (1) is measured with a measurement delay compared to the thickness reduction taking place in the roll stand (1), that one of the Roll setting (s) corresponding signal is formed and at least approximately delayed by the amount of the measurement delay that a difference signal (u) from the delayed roll setting ungssignal and with the sum of one and the quotient of the stiffness (c _M ') of the rolling stock (8) and the stiffness (c _G ') of the rolling stand (1) multiplied thickness measurement signal (h _a ') is formed that the amplitude and phase position of the output signal (ΔR ') of the oscillator (24) as a function of the deviation between the output signal (ΔR') and the difference signal (u) in the sense of minimizing this deviation (e) and that the output signal (ΔR ') is phase shifted by an amount corresponding to the measurement delay in the sense of an advance. Method according to claim 1,
characterized by
that the setpoint (s *) of the roll setting is used as the roll setting signal. The method of claim 1 or 2,
characterized by
that the thickness measurement signal (h _a ') used to form the difference signal (u) is conducted via a proportional differential element (PD element). The method of claim 1 or 2,
characterized by
that the phase-shifted output signal (ΔR ') of the oscillator (24) is fed to the position or thickness control via a proportional differential element (PD element) (27) and that the roller setting signal (s * used to form the difference signal (u) ) is performed via a proportional delay element (PT1 element) (30). Method according to one of the preceding claims,
characterized by a direct digital implementation of the position or thickness control and the oscillator (24), the roll setting signal (s *), the thickness measuring signal (h _a ') and the measured speed (n _o , n _u ) of the rolls (2 to 5 ) Are digital values or are converted into digital values. Method according to one of the preceding claims,
characterized by
that a further feedback oscillator (37) is used, that the frequency of the output signal (ΔR _o ') one of the two oscillators (36) in dependence on the speed (n _o ) of the upper roller (2) and the frequency of the output signal (ΔR _u ') of the other oscillator (37) as a function of the speed (n _u ) of the lower roller (3) of the roll stand (1) and that the output signals (ΔR _o ', ΔR _u ') of both oscillators (36, 37 ) are additively linked to each other or both oscillators are connected in series. Method according to one of the preceding claims,
characterized by
that further feedback oscillators (55, 56) are used to suppress harmonics of the roller eccentricities, which are connected in series or whose output signals are additively linked. Method according to one of the preceding claims,
characterized by
that the roller eccentricities are additionally simulated by the output signal of at least one additional oscillator (39, 40) which can be connected to the position or thickness control, the frequency of the output signal being set as a function of the measured rotational speed of the rollers (2 to 5) and the Amplitude and phase position of the output signal as a function of the deviation between the output signal of the oscillator (39, 40) and the sum signal from the sum of the reciprocal values of the stiffnesses (c _G ', c _M ') of the roll stand (1) and the rolling stock ( 8) multiplied measured rolling force (F _W ') and the roll pitch (s *) in order to minimize this deviation.

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