EP1986795B2 - Method for suppressing the influence of roll eccentricities - Google Patents

Description

The invention relates to a method for suppressing the influence of roll eccentricities on the outlet thickness of a rolling stock passing through a roll stand, the roll eccentricities being identified using a process model and being taken into account when determining a correction signal for at least one control device for an actuator of the roll stand.

In rolling stands, eccentricities of the rolls caused by imprecisely machined back-up rolls or imprecise mounting of the back-up rolls are often found, which impair the quality of the rolled strip, whereby depending on the rigidity of the roll stand and the rolled stock, the roll eccentricities with the speed of the eccentric rolls, in the rule of the backup rolls, map in the belt. The frequency spectrum of the eccentricities and the disturbances caused by them in the strip essentially contains the fundamental frequencies of the upper and lower backup rolls; but there are also higher harmonic oscillations, which, however, often only appear with reduced amplitudes. Because of the slightly different diameters and speeds of the upper and lower backup rollers, the frequencies assigned to the backup rollers can differ from one another.

The EP 0 170 016 B1 describes a method of the type mentioned at the outset, wherein the influence of roll eccentricities in the position or thickness control of roll stands is compensated, the roll eccentricities being identified on the basis of a measurement of the rolling force in the roll stand. Oil pressure transducers are generally used to measure the rolling force, the measured values of which are significantly falsified by the effects of friction. This means that the influence of roller eccentricities cannot be suppressed in a sufficiently reliable and effective manner with the aid of the measuring devices. More reliable and more accurate measuring methods for the rolling force are too expensive and too complex.

From the EP 0 698 427 B1 it is known, in a method for suppressing the influence of roll eccentricities, to use the outlet thickness of the rolling stock instead of the rolling force as a measured value. Thickness gauges are very expensive, however, and are therefore usually only provided in front of and behind the first and after the last roll stand in multi-stand rolling lines.

From the U.S. 4,656,854 A a method for suppressing the influence of roll eccentricities on the outlet thickness of a rolling stock is known, the rolling stock passing through a roll stand. The roll eccentricities are identified using a process model and taken into account when determining a correction signal for a control device for an actuator of the roll stand. To identify the roll eccentricities, measured values of the tensile force prevailing in the rolling stock are fed to the process model.

Of the JP 04 200 915 A a similar disclosure can be found.

The object of the invention is to provide a method for suppressing the influence of roll eccentricities which avoids the disadvantages known from the prior art and in particular the disadvantages described above.

The object is achieved by a method for suppressing the influence of roll eccentricities on the outlet thickness of a rolling stock having the features of claim 1. Advantageous refinements of this method are the subject matter of the dependent claims 2 to 4.

The object on which the invention is based is also achieved by a computer program product according to patent claim 5.

FIG 1

ein Walzgerüst in Verbindung mit einer Regelvorrichtung mit einem Prozessmodell,

FIG 2

eine schematische Darstellung des zum Identifizieren der Walzenexzentrizitäten verwendeten Beobachter-Prinzips,

FIG 3

die Ankopplung der Zugmessung an das Prozessmodell,

FIG 4

eine Einlaufdickenkompensation für die verwendeten Messwerte.

Advantages and details of the invention are described below by way of example and with reference to the drawings. Show it:

FIG 1

a roll stand in connection with a control device with a process model,

FIG 2

a schematic representation of the observer principle used to identify the roller eccentricities,

FIG 3

the coupling of the tension measurement to the process model,

FIG 4

an inlet thickness compensation for the measured values used.

FIG 1 shows schematically and by way of example a roll stand 1 of a rolling train for rolling a rolling stock 10. The rolling train for rolling the rolling stock 10 has one or more such rolling stands 1. Before or after the roll stand 1, another roll stand, a reel device, a cooling device and / or another device, for example for thermal and / or mechanical influencing of the rolling stock and / or a device for transporting the rolling stock 10, can be provided. The rolling stock 10 is preferably a strip, a profile, a wire or a slab. For example, the rolling stock 10 can be a metal strip, for example a steel strip, a non-ferrous metal strip or an aluminum strip.

A roll stand 1 has at least one upper backup roll 4 with a radius R _o and at least one lower backup roll 5 with a radius R _u . The roll stand 1 shown has at least one upper work roll 2 and at least one lower work roll 3, the diameter of the work rolls 2 and 3, as a rule, being smaller than the diameter of the backup rolls 4 and 5. In the example shown, the setting position is used to regulate of the roll stand 1, a hydraulic adjusting device 7 which can be actuated via a control valve 6 is provided. Alternatively or in addition, an electromechanical adjustment system can also be provided. The adjusting device 7 or that not in more detail Adjustment system shown are used to adjust the roll adjustment s. The hydraulic adjustment 7 is supported on the scaffolding frame. The elastic scaffolding frame is symbolically represented by a spring with the spring constant C _G.

The rolling stand 1 is passed through by the rolling stock 10, the thickness of the rolling stock 10 being reduced from the inlet thickness h _e to the outlet thickness h _a with the aid of the work rolls 2, 3 as it passes through the roll gap. The rolling stock 10, to which an equivalent material spring with the spring constant C _{M is} assigned in the roll gap, enters the roll gap at the entry speed v _SE and leaves the roll gap at the exit speed v _SL .

The roller eccentricities of the upper support roller 4 or the lower support roller 5 can be caused by uneven roller wear, deformations due to thermal stresses and / or the deviations of the geometrical cylinder axis of the rollers from the operationally established rotation axes. The roll eccentricities are denoted by ΔR _o and ΔR _u , ie as deviations from the ideal backup roll radii R _o and R _u .

The measurement of the roll speed n _o or n _{u of} the upper or lower backup roll 4 or 5 is used to determine the fundamental oscillation of the roll eccentricities. Under the simplifying prerequisite that the upper and lower rolls of the roll stand 1 rotate at the same speed, it is sufficient to detect the speed of only one driven roll, for example the lower work roll 3, by means of a tachometer 11.

If, as in most cases, the back-up rolls 4 and 5 are the eccentric rolls, then in at least one conversion unit 14 and 12, the measured speed of the work roll 2 or 3 via the ratio of the diameter of the work roll 2 or 3 to the diameter of the Support roll 4 or 5 converted into the speed n _o or n _{u of} the support roll 4 or 5, respectively. Since the speeds of the upper rollers 4, 2 and the lower rollers 5, 3 are usually different due to slightly different diameters, both a tachometer 13 above the rolling stock 10 and a tachometer 11 below the rolling stock 10 are each with downstream conversion unit 14 or 12 for detecting the speed n _o or n _u .

The roll adjustment s is measured with a position sensor 9 on the adjustment device 7 or on the adjustment system. The roll adjustment s is fed to a control device 18. For roll eccentricity identification and suppression, at least one roll speed n _o or n _{u is} fed to the control device 18. Furthermore, a tensile measuring device 8 for measuring the tensile force F _z prevailing in the rolling stock 10 is provided in front of the roll stand 1. The tension measuring device 8 can as in FIG 1 indicated, have a measuring roller for tension measurement. This measuring roller can preferably be segmented. The tension measuring device 8 can also be designed as a contactless tension measuring device. A corresponding device for contactless measurement of the tensile force F _z in a rolled stock 10 designed as a metal strip is for example in FIG DE 198 39 286 B4 described.

In order to identify and / or suppress roll eccentricities, the control device 18 has a process model 27. The process model 27 is based on an observer and models the behavior of the roll gap and the rolls 2 to 5. The process model 27 is controlled in terms of frequency with the help of the rolling speed, ie for example with the help of the determined roll speeds n _o or n _u . The time course of the disturbances to be modeled is periodic, but not purely sinusoidal. In other words, the oscillation to be modeled consists of a fundamental oscillation and several harmonics.

In the process model 27, sinusoidal correction setpoints assigned to the eccentricity frequencies are calculated for an actuator of the roll stand 1 with the appropriate phase position and amplitude for the position of the roll gap control. As in FIG 1 As shown, the correction setpoints can be given via a control device 19 and possibly via a control valve 6 to the adjusting device 7 or to a adjusting system. By using the measured tensile force F _z , the required strip thickness, that is to say the outlet thickness h _{a of} the rolling stock 10, can be set extremely uniformly with the aid of the control device 18. Deviations in thickness caused by the roll eccentricity ΔR _o or ΔR _u can be avoided in this way.

Alternatively or additionally, it is possible, for example, to measure the rolling force F _w by means of a pressure sensor 15 and to take it into account when identifying and suppressing roll eccentricities.

As an alternative or in addition, the thickness of the rolling stock 10, for example the outlet thickness h _a , can be measured by means of a thickness measuring device 16.

FIG 2 shows schematically and by way of example the structure used to identify roller eccentricities according to the observer principle. In this case, a setpoint value s * of the setting position is used both in a real process 29, as it runs, for example, in a rolling stand 1 through which a rolling stock 10 passes (see FIG FIG 1 ), as well as an observer module 30. The observer module 30 has the process model 27, with the aid of which roller eccentricities can be identified and with the aid of which the identified roller eccentricities ΔR _i can be provided for compensation purposes. With the aid of the process model 27, an identified runout thickness h _ai can preferably be determined, which can be linked to the measured tensile force F _z in order to determine an observer error e. The measured tensile force F _z is first fed to a module 21 in the measuring channel, which inversely takes into account the transmission behavior from the outlet thickness to the strip tension. With With the help of the module 21, the measured value of the tensile force F _{z is converted} to the outlet thickness and compared with the identified outlet thickness h _ai determined with the aid of the process model 27. The difference e resulting from this comparison forms the observer error e. The states of the process model 27 are corrected taking into account the observer error e until the measurement and model at least largely agree and the observer error e is sufficiently small or zero. Then the roll eccentricities ΔR _i identified in the process model 27 also agree with those actually in the roll stand 1 (see FIG 1 ) existing roller eccentricities. The identified roller eccentricities ΔR _i ascertained in this way by the observer module 30 enable an extremely reliable and precise eccentricity compensation.

As in the in FIG 3 As shown in the example shown, a selection can be made by means of a switch 20 as to whether the process model 27 should take into account the outlet thickness h _a , the rolling force F _w or the tensile force F _z when identifying roller eccentricities.

FIG 3 shows an example of how the transfer behavior from the adjustment position to the strip tension can be taken into account when using the tensile force F _z to identify and suppress roller eccentricities. In the example shown, a module 21 is preferably provided in the measuring channel which inversely takes into account the transfer behavior from the outlet thickness to the strip tension. The measured values of the tensile force F _z are preferably linked with the corresponding transfer function H _zug . This can be done, for example, by multiplication by a factor which corresponds to the inverse transfer function H _train . In addition, an adaptation circuit can be provided which takes into account the dependence on the rolling stock speed v _B. The value present at the output of module 21, which was determined with the aid of tensile force F _z , is preferably fed to process model 27.

Like the one in FIG 2 As can be seen in the example shown, the process model 27 preferably simulates the behavior of the process 29 from the contact position s or from the setpoint s * of the contact position up to the outlet thickness h _a . If, as an alternative or in addition to the tensile force F _z, the rolling force F _{w is to be} taken into account in the process model 27, it is expedient to provide a module 28 in the measuring channel of the rolling force F _w which has a suitable transfer characteristic.

FIG 4 shows an example of the use of an inlet thickness compensation in connection with the method according to the invention. A thickness measuring sensor 17 is provided in front of the roll stand 1, with the aid of which a measured inlet thickness h _{em is} recorded. The shown inlet thickness compensation module 22 has a strip tracking module 23. With the aid of the strip tracking module 23, the measured inlet thickness h _{em is} tracked down to the roll stand 1. With the aid of the inlet speed v _SE , a tracked inlet thickness h _{ev is} determined. The tape tracking module 23 is preferably model-based.

In the example shown, the inlet thickness compensation module 22 has at least one compensation model 24, 25, 26 with the aid of which the influence of the inlet thickness h _e on the outlet thickness h _{a is} determined as _a function of the measured variable m _{E used} or the corresponding measured value. Since the quality of the inlet thickness compensation depends essentially on the compensation model (s) 24, 25, 26 used, in the example shown there are a compensation model 24 for using the outlet thickness h _a as the measured variable m _E , and a compensation model 25 for the use of the rolling force F _w as the measured variable m _E and a compensation model 24 for the use of the tensile force F _z as measured variable m _{E is} provided. The compensation signal given by the inlet thickness compensation module 22 is linked to the corresponding measured value of the measured variable m _E to form a compensated measured variable m _K.

• Die Erfindung betrifft ein Verfahren zur Unterdrückung des Einflusses von Walzenexzentrizitäten auf die Auslaufdicke h_a eines Walzgutes 10, welches ein Walzgerüst 1 durchläuft, wobei die Walzenexzentrizitäten unter Verwendung eines Prozessmodells 27 identifiziert werden und bei der Ermittlung eines Korrektursignals für mindestens ein Stellglied, vorzugsweise ein Stellglied für die Anstellposition, des Walzgerüstes 1 berücksichtigt werden, wobei zur Identifizierung der Walzenexzentrizitäten dem Prozessmodell 27 die gemessene Zugkraft F_z im Walzgut 10 zugeführt wird. Erfindungsgemäß werden Zugkraftschwankungen zielgerichtet zur Reduktion der Auswirkungen periodischer Walzenexzentrizitäten auf das Walzgut 10 zurückgeführt, wohingegen alle anderen Schwankungsquellen ausgeschlossen werden. Das auf dem Beobachter-Prinzip basierende Prozessmodell 27 des Walzspaltes und der Walzen 2 bis 5 erzeugt, z.B. unter Zuhilfenahme der gemessenen Zugkraft F_z, der Walzenanstellung s und der Walzengeschwindigkeit bzw. der Walzendrehzahl, zuverlässige Daten über die Walzenexzentrizitäten. Erfindungsgemäß werden vorgegebene Abmessungen des Walzguts 10 gleichmäßiger als bisher erreicht. Zugmessvorrichtungen 8 arbeiten im Vergleich zu Messvorrichtungen für die Dicke h_e bzw. h_a des Walzgutes 10 und im Vergleich zu Messvorrichtungen für die Walzkraft F_w sehr genau und dynamisch. Vorzugsweise werden die in der Zugkraftschwankung enthaltenen und von der Walzenexzentrizität verursachten periodischen Schwingungsanteile gezielt zur Reduktion der exzentrizitätsbedingten, ungewünschten Dickenveränderung im Walzgut 10 verwendet. Auf Schwankungsanteile mit anderen Frequenzen ungleich der Exzentrizitätsfrequenzen wird nicht reagiert.

An essential idea on which the invention is based can be summarized as follows:

• The invention relates to a method for suppressing the influence of roll eccentricities on the outlet thickness h _{a of} a rolling stock 10 which passes through a roll stand 1, the roll eccentricities being identified using a process model 27 and when determining a correction signal for at least one actuator, preferably one actuator for the setting position of the roll stand 1, the measured tensile force F _z in the rolling stock 10 being fed to the process model 27 to identify the roll eccentricities. According to the invention, fluctuations in the tensile force are returned in a targeted manner in order to reduce the effects of periodic roll eccentricities on the rolling stock 10, whereas all other sources of fluctuation are excluded. The process model 27 of the roll gap and rolls 2 to 5 based on the observer principle generates reliable data on the roll eccentricities, for example with the aid of the measured tensile force F _z , the roll pitch s and the roll speed or the roll speed. According to the invention, predetermined dimensions of the rolling stock 10 are achieved more evenly than before. Tension measuring devices 8 work very precisely and dynamically in comparison to measuring devices for the thickness h _e or h _{a of} the rolling stock 10 and in comparison to measuring devices for the rolling force F _w . Preferably, the periodic vibration components contained in the tensile force fluctuation and caused by the roll eccentricity are targeted to reduce the undesired change in thickness caused by the eccentricity used in rolling stock 10. There is no reaction to fluctuations with other frequencies unequal to the eccentricity frequencies.

Periodic thickness fluctuations resulting from the inlet thickness with frequencies that are almost equal to the eccentricity frequencies can interfere with the identification of the roll eccentricities. An inlet thickness compensation can therefore be provided, which determines and compensates for the influence of the inlet thickness fluctuations on the measured variable m _{E used} and thus eliminates this type of disturbance.

The tension regulators present in known control concepts of a rolling mill designed as a tandem mill, for example, can avoid part of the effects on the thickness caused by the eccentricities due to their limited dynamics only at low rolling speeds and only on the front stands of the tandem mill. A control device 18 designed according to the invention for suppressing the influence of roll eccentricities, to which the tensile force F _z measured on the rolling stock 10 is supplied, can compensate for the eccentricity frequencies on a roll stand 1 and thus completely relieve conventional tension regulators.

Claims (5)

1. Method for suppressing the influence of roll eccentricities on the run-out thickness (h_a) of a rolling stock item (10), which passes through a rolling stand (1), wherein the roll eccentricities are identified by the use of a process model (27) and are taken into account in the determination of a correction signal for at least one control device (19) for a final control element of the rolling stand (1), wherein measured values (m_E) for the tensile force (F_z) prevailing in the rolling stock item (10) are fed to said at least one process model (27) to identify the roll eccentricities, wherein a run-in thickness compensation is effected on the measured values (m_E) used to identify the roll eccentricities, wherein the process model (27) describes at least the rolling nip and the rolls of the rolling stand (1).
2. Method according to claim 1, wherein the tensile force (F_z) is measured upstream or downstream of the rolling stand (1).
3. Method according to claim 1 or 2,

   - wherein a target value (s*) for the screwdown position (s) is fed to a real process (29), such as e.g. takes place in the rolling stand (1),

   - wherein the target value (s*) for the screwdown position is also fed to the model (27),

   - wherein the model (27) determines an identified run-out thickness (h_ai) by taking account of the identified roll eccentricities,

   - wherein the measured values (m_E) for the tensile force (F_z) are fed to a module (21) which takes inverse account of the transfer behaviour of the tensile force (F_z) prevailing in the rolling stock item (10) as a function of the screwdown position (s), so that a run-out thickness (h_a) of the rolling stock item (10) is determined on the basis of the captured tensile force (Fz),

   - wherein an observer error (e) is determined on the basis of the difference between the identified run-out thickness (h_ai) determined on the basis of the model (27) and the run-out thickness (h_a) determined on the basis of the captured tensile force (F_Z),

   - wherein the observer error (e) is fed to the model (27),

   - wherein the roll eccentricities are corrected on the basis of the observer error (e), until the observer error (e) is sufficiently small or zero.
4. Method according to claim 3, wherein the dependency on the strip speed (v_B) is taken into account in an adaptive manner in the determination of the determined run-out thickness (h_a).
5. Computer program product encompassing program code means suitable for carrying out all the steps of a method according to one of the preceding claims whenever the computer program product is executed on a data processing system.

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