EP1986795B1 - 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 which passes through a roll stand, wherein the roll eccentricities are identified using a process model and taken into account in determining a correction signal for at least one control device for an actuator of the rolling stand.

In rolling stands are often found, for example, by inaccurately machined support rollers or by non-exact storage of the support rollers conditional eccentricities affecting the quality of the rolled strip, depending on the rigidity of the rolling mill and the rolling Walzenxzentrizitäten with the speed of the eccentric rollers, in the rule of the backup rolls, in the tape map. The frequency spectrum of the eccentricities and the disturbances they cause in the band essentially comprises the fundamental frequencies of the upper and lower support rollers; but there are also higher harmonic harmonics, but often occur only with reduced amplitudes in appearance. Due to slightly different diameters and speeds of the upper and lower support roller, the frequencies assigned to the support rollers may differ from one another.

The EP 0 170 016 B1 describes a method of the type mentioned above, wherein the influence of roll eccentricities in the position or thickness control of rolling stands is compensated, wherein the roll eccentricities are identified on the basis of a measurement of the rolling force in the roll stand. To measure the rolling force oil pressure sensors are usually used, the measured values are significantly distorted by friction influences. This requires that no sufficient Reliable and effective suppression of the influence of roller eccentricities can be done with the help of the measuring instruments. More reliable and accurate measuring methods for the rolling force are too expensive and too expensive.

From the EP 0 698 427 B1 It is known to use in a method for suppressing the influence of Walzenexzentrizitäten the outlet thickness of the rolling stock instead of the rolling force as a measured value. Thickness encoders, however, are very expensive and therefore generally only provided in front of and behind the first and after the last rolling mill in multi-stand rolling trains.

From the US 4,656,854 A is a method for suppressing the influence of Walzenexzentrizitäten on the outlet thickness of a rolling stock is known, wherein the rolling stock passes through a roll stand. The roll eccentricities are identified using a process model and taken into account in the determination of a correction signal for a control device for an actuator of the mill 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 roller eccentricities, which avoids the known from the prior art and in particular the disadvantages described above.

The object is achieved by a method for suppressing the influence of Walzenexzentrizitäten on the outlet thickness of a rolling stock having the features of claim 1. Advantageous embodiments of this method are the subject of the dependent claims 2 to 5.

The object underlying the invention is also achieved by a computer program product according to claim 6.

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.

Hereinafter, advantages and details of the invention will be described by way of example and with reference to the drawings. Show it:

FIG. 1

a rolling stand in conjunction 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 rolling mill 1 of a rolling train for rolling a rolled material 10. The rolling mill for rolling the rolling stock 10 has one or more such rolling stands 1 on. Before or after the roll stand 1, a further roll stand, a reel device, a cooling device and / or another device, for example for thermal and / or mechanical Walzgutbeeinflussung and / or means for transporting the rolling stock 10 may be provided. The rolling stock 10 is preferably a band, a profile, a wire or a slab. For example, the rolling stock 10 may be a metal strip, for example a steel strip, a non-ferrous metal strip or an aluminum strip.

A rolling stand 1 has at least one upper support roller 4 with a radius R _o and at least one lower support roller 5 with a radius R _u . The rolling stand 1 shown has at least one upper work roll 2 and at least one lower work roll 3, wherein the diameter of the work rolls 2 and 3 is usually smaller than the diameter of the support rollers 4 and 5. In the example shown is for controlling the setting position of the roll stand 1, an actuatable via a control valve 6 hydraulic adjusting device 7 is provided. Alternatively or additionally, an electromechanical adjusting system can also be provided. The adjusting device 7 and the Anstellsystem not shown serve to adjust the roller adjustment s. The hydraulic adjustment 7 is supported on the scaffolding frame. The elastic scaffolding is symbolically represented by a spring with the spring constant C _G.

The rolling stand 1 is traversed by the rolling stock 10, wherein the thickness of the rolling stock 10 is reduced when passing through the roll gap with the aid of the work rolls 2, 3 of the inlet thickness h _e to the outlet thickness h _a . The rolling stock 10, which is assigned an equivalent material spring with the spring constant C _M 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 roll eccentricities of the upper back-up roll 4 and the lower back-up roll 5, respectively, may be due to uneven roll wear, deformation due to thermal stresses, and / or the deviations of the geometric cylinder axis of the rolls from the operationally-setting rotation axes. The roll eccentricities are denoted by ΔR _o or ΔR _u , ie deviations from the ideal back-up roll radii R _o or R _u .

The measurement of the rolling speed n _o or n _{u of} the upper and lower support rollers 4 and 5 is used to determine the fundamental vibration of Walzenexzentrizitäten. Under the simplifying condition that the upper and lower rollers of the roll stand 1 rotate at the same speed, it is sufficient to detect the speed of only one driven roller, eg the lower work roll 3, by means of a tachometer 11.

Are, as in most cases, the support rollers 4 and 5, the eccentricity-bearing rollers, so in at least one conversion unit 14 and 12, the measured speed of the work roll 2 and 3 on the ratio of the diameter of the Work roll 2 or 3 to the diameter of the support roller 4 and 5 in the speed n _o or n _{u of} the support roller 4 and 5 converted. Since in general the speeds of the upper rollers 4, 2 and the lower rollers 5, 3 are different due to slightly different diameters, in the embodiment shown, both a tachometer 13 above the rolling stock 10 and a tachometer 11 below the rolling stock 10, respectively subordinate conversion unit 14 or 12 for detecting the rotational speed n _o or n _u provided.

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

For the identification and / or suppression of 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 frequency guided by means of the rolling speed, ie, for example, using the determined rolling speeds n _o or n _u . The time course of the disturbances to be modeled is periodic, but not purely sinusoidal. This means that the vibration to be modeled consists of a fundamental vibration and several harmonics.

In the process model 27 sinusoidal correction target values 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 The correction setpoint values can be given via a control device 19 and optionally via a control valve 6 to the adjusting device 7 or to a positioning system. By using the measured tensile force F _z , the required strip thickness, ie the outlet thickness h _{a of} the rolling stock 10, can be set extremely uniformly with the aid of the regulating device 18. Thickness deviations caused by the roll eccentricity ΔR _o or ΔR _u can thus be avoided.

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

Alternatively or additionally, the thickness of the rolling stock 10, for example the outlet thickness h _a , can be measured by means of a thickness gauge 16.

FIG. 2 shows schematically and exemplarily the structure used for the identification of roll eccentricities according to the observer principle. In this case, a desired value s * of the setting position both a real process 29, as it expires, for example, in one of a rolling stock 10 continuous rolling stand 1 (see FIG. 1 ), as well as an observer module 30 supplied. The observer module 30 has the process model 27, by means of which roll eccentricities can be identified and with the aid of which the identified roll eccentricities ΔR _i can be provided for compensation purposes. With the aid of the process model 27, an identified run-out thickness h _ai can preferably be determined, which can be linked to the measured tensile force F _z to determine an observer error e. The measured tensile force F _z is first fed to a module 21 in the measuring channel, which takes into account the transmission behavior from the outlet thickness to the strip tension inverse. With the aid of the module 21, the measured value of the tensile force F _z is thus 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 constitutes the observer error e. The states of the process model 27 are corrected, taking account of the observer error e, until the measurement and the model at least largely coincide and the observer error e is sufficiently low 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 FIG. 1 ) match existing roll eccentricities. The identified by the observer module 30 identified Walzenexzentrizitäten .DELTA.R _i allow extremely reliable and accurate eccentricity compensation.

As in the FIG. 3 shown example, can be made by means of a switch 20 to see whether the process model 27, the outlet thickness h _a , the rolling force F _w or the tensile force F _{z should be considered} in the identification of Walzenexzentrizitäten.

FIG. 3 shows by way of example how the transmission behavior from the setting position to the strip tension can be taken into account when using the tensile force F _z for identifying and suppressing roll eccentricities. Thus, in the example shown, a module 21 is preferably provided in the measuring channel, which takes into account the transmission behavior from the outlet thickness to the strip tension inverse. Preferably, the measured values of the tensile force F _{z are} linked to the corresponding transfer function H _zug . This can be done, for example, by multiplication with a factor which corresponds to the inverse transfer function H _zug . In addition, an adaptation circuit can be provided which takes into account the dependence on the rolling stock speed V _B. Preferably, the value present at the output of the module 21, the was determined with the aid of the tensile force F _z , the process model 27 supplied.

As well as in FIG. 2 illustrated example, the process model 27 is preferably the behavior of the process 29 of the setting position s or from the setpoint s * the setting position to the outlet thickness h _a after. If, alternatively 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, then 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. In this case, a thickness gauge 17 is provided in front of the roll stand 1, by means of which a measured inlet thickness h _{em is} detected. The shown inlet thickness compensation module 22 has a tape tracking module 23. By means of the tape tracking module 23, the measured inlet thickness h _{em is} traced to the mill stand 1. With the aid of the inlet velocity v _SE , a tracked inlet thickness h _{ev is} determined. The tape tracking module 23 preferably operates 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 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 a compensation model 24 for the use of the outlet thickness h _a as the measured variable m _E , 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 the measured variable m _E provided. The compensation signal given by the inlet thickness compensation module 22 is included in FIG the corresponding measured value of the measured variable m _E linked 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 underlying the invention 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, wherein the roll eccentricities are identified using a process model 27 and in determining a correction signal for at least one actuator, preferably an actuator are taken into account for the setting position of the roll stand 1, wherein the process model 27, the measured tensile force F _z in the rolling stock 10 is supplied to identify the Walzenexzentrizitäten. According to the invention, traction fluctuations are purposefully attributed to the reduction of the effects of periodic rolling eccentricities on the rolling stock 10, whereas all other sources of fluctuation are excluded. Based on the observer principle, the process model 27 of the roll gap and the rolls 2 to 5 generates reliable data about the roll eccentricities, eg with the aid of the measured tensile force F _z , the roll adjustment s and the roll speed or the roll speed. According to the invention, predetermined dimensions of the rolling stock 10 are achieved more uniformly than hitherto. Tensile measuring devices 8 work very accurately and dynamically compared to measuring devices for the thickness h _e and h _{a of} the rolling stock 10 and compared to measuring devices for the rolling force F _w . Preferably, the periodic vibration components contained in the tension fluctuation and caused by the roll eccentricity are used specifically for reducing the eccentricity-related, unwanted change in thickness in the rolling stock 10. On fluctuation parts with other frequencies not equal to the eccentricity frequencies is not reacted.

Periodic thickness variations resulting from the inlet thickness with frequencies nearly equal to the eccentricity frequencies can disturb the identification of the roll eccentricities. Therefore, it is possible to provide an inlet thickness compensation which determines and compensates the influence of the inlet thickness fluctuations on the measured variable m _{E used} and thus eliminates this type of disturbance.

Due to their limited dynamics, only a small rolling speed and only at the front stands of the tandem road can avoid some of the effects on the thickness caused by the eccentricities in known control concepts of a rolling train designed as a tandem mill. An inventively designed control device 18 for suppressing the influence of Walzenexzentrizitäten, which is fed to the rolling stock 10 measured tensile force F _z , can take on a rolling stand 1, the compensation of the eccentricity and thus completely relieve conventional tension regulator.

Claims (6)

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.
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 (s) 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_ai) of the rolling stock item (10) is determined on the basis of the captured tensile force (F_z),

   - 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. Method according to one of claims 1 to 4, wherein the process model (27) describes at least the rolling nip and the rolls of the rolling stand (1).
6. 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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