EP3795267A1 - Method for operating a rolling mill - Google Patents

Abstract

The invention relates to a method for operating a roll stand 100, to which a first and at least one further control circuit for regulating various control variables are assigned. According to the invention, the temporal course of the setpoint value SMsoll * for the first or master controlled variable is monitored to determine whether the setpoint falls outside a predetermined tolerance range T. If so, the invention provides for the calculation of a corrected, ie reduced or increased, setpoint value for the master controlled variable, which means that the setpoint value returns to the tolerance range. In addition, according to the invention, the calculated correction components for the master controlled variable are also used to calculate a compensation component for the setpoint value of a slave controlled variable. By ensuring according to the invention that the setpoint value remains within the tolerance range, it is ensured that at least one master actuator 132 of a master control loop 130 does not reach its physical performance limits.

Description

The invention relates to a method for operating a roll stand with a pair of work rolls which span a roll gap for rolling a metal strip.

Such roll stands are known in principle in the prior art, such. B. from the Chinese patent CN 102581035 B . The roll stand disclosed there is assigned a first control loop with a first actuator for controlling a first control variable to a time-variable first setpoint value and k further control loops with k = 1-K. Each of the k'th control loops has a k'th actuator for controlling a k'th controlled variable. The setpoint value for the first controlled variable in the prior art is variable over time or has a time variable portion to compensate for changes in process variables during a rolling process. Due to the temporal variability of the setpoint, the actuator of the first control loop can reach its performance limit; please refer Figure 5a : "without correction". This can result in a short travel amount in the first actuator.
In the prior art, this shortfall in travel cannot be adequately compensated for by the known further control loops of the roll stand.

The invention is based on the object of developing a known method for operating a roll stand with a first and at least one further control loop in such a way that the occurrence of a power deficit in the actuator of the first control loop is prevented.

This object of the invention is achieved by the method claimed in claim 1.

The monitoring of the temporal course of the setpoint of the first control variable with regard to the threshold values Min, Max, which are within the performance limits of the first actuator, which is claimed there, advantageously enables a preventive initiation of a countermeasure before the master actuator is set on the basis of a setpoint that is too large reaches its performance limit for the first controlled variable. Specifically, the countermeasure provides that when the minimum or maximum threshold value is reached, i.e. before the lower or upper performance limit of the master actuator is reached, the setpoint for the first controlled variable is increased or decreased by a correction component determined according to the invention. The corrected setpoint value calculated in this way for the first controlled variable is usually smaller in terms of magnitude than the previously provided setpoint value and is specified instead of the previously provided setpoint value for the first control loop. The correction components for the master setpoint SM are measured preventively in such a way that the master actuator is not even driven to its upper or lower performance limit.

The advantages of using the process steps described are basically the improvement of the rolling stability as well as the improvement of the product quality and the reduction of dimensional lengths.

The stability of a rolling mill can be increased by moving actuators to operating points that are favorable for the rolling process in a targeted manner by virtue of the inventive linking of the master-slave control loops. These working points can offer process engineering advantages, such as a targeted control of the actuators in tried and / or pre-calculated working areas.

Advantages can also be achieved in that the actuators, by selecting the threshold values (min, max), are specifically driven into areas in which their behavior is almost linear.

In addition, there are advantages in that the actuators with high dynamic properties are strategically kept in work areas which you can react quickly to any process changes that may occur, such as damage to the incoming material.

In particular, the assignment of the link between master and slave actuators offers additional flexibility. The assignment of the actuators can be different for different process situations and / or types of plant. For example, with a bandwidth r, a different actuator can be defined as the master actuator than with a bandwidth j. The assignment and priorities of the slave actuators can also be changed in real time using the factor a _k for optimal adaptation to current process conditions.

According to a first advantageous embodiment of the method according to the invention, the roll stand has not only one (k = 1), but also additional slave control loops k = 2-K. The method then preferably has the following further step: performing steps ii) analogously in each case for each of the further k = 2-K control loops with their respective k = 2-K'th slave actuators.

The provision of the k further control loops with their respective actuators offers the advantage that a possibly determined power or travel shortfall of the master actuator is not only caused by a first slave actuator, but also by the said further actuators with k = 2 -K of the other control loops can be compensated if necessary.

The method according to the invention can be used both in hot rolling and in cold rolling of metal strip.

Both the master control loop and all slave control loops are operated continuously or iteratively over time. I. E. there is a continuous or continuous regulation of the controlled variable to its respective specified setpoints.

The term "nominal value" used in part in the description and in the claims is representative of a time-variable nominal value signal. Due to the discrete-time consideration that is customary in digital technology, the aforementioned term "setpoint" is also used in the description; However, this setpoint is by no means necessarily to be regarded as constant over time.

Further advantageous configurations of the method according to the invention are the subject of the dependent claims.

Figur 1

einen ersten bzw. Master-Regelkreis zum Regeln einer erste Regelgröße bei einem Walzgerüst;

Figur 2

eine Master-Sollwert-Korrektureinheit zur Berechnung eines korrigierten Master-Sollwertes;

Figur 3

einen dem Walzgerüst zugeordneten k'ten Slave-Regelkreis zum Regeln einer k'ten Regelgröße;

Figur 4

eine Slave-Sollwert-Korrektureinheit zur Berechnung eines korrigierten k'ten Slave-Sollwertes; und

Figuren 5a), 5b) und 5c)

die Ermittlung eines Korrekturanteils y1 und eines Kompensationsanteils ZSL_k bei Durchführung einer erfindungsgemäß notwendigen Korrektur des Master-Sollwertes SM_Soll

zeigt.The description is accompanied by five figures, where

Figure 1

a first or master control loop for controlling a first controlled variable in a roll stand;

Figure 2

a master setpoint correction unit for calculating a corrected master setpoint;

Figure 3

a k'th slave control loop assigned to the roll stand for controlling a k'th controlled variable;

Figure 4

a slave setpoint correction unit for calculating a corrected k'th slave setpoint; and

Figures 5a), 5b) and 5c)

the determination of a correction component y1 and a compensation component ZSL _k when carrying out a correction of the master setpoint value SM _{setpoint that is necessary according to the invention}

shows.

The invention is described in detail below with reference to the figures mentioned in the form of exemplary embodiments. In all figures, the same technical elements are denoted by the same reference symbols.

Figure 1 shows a first or master control circuit 130 for controlling a first control variable in a roll stand 100 to a predetermined master setpoint value SM _{setpoint n *} . For the purpose of regulation, this setpoint is compared with an actual value of the controlled variable SM _{Ist n} . This takes place in a comparator device 134, typically a difference calculator. The result of this comparison is entered as a control deviation in a master controller 133, which generates an actuator for a master actuator 132 at its output. The master actuator influences the controlled system 131 of the first or master control loop 130. The controlled system here consists, for example, of a roll stand 100 for rolling metal strip 120 with the aid of work rolls 110 Work rolls 110 are each assigned to backup rolls. If the roll stand is designed in six-high construction, the roll stand also has intermediate rolls in addition to the work and back-up rolls (in Figure 1 Not shown). According to the in Figure 1 The control loop 130 shown, the controlled variable at the output of the controlled system 131 is detected with the aid of a detection device 136, typically a measuring element. The recorded controlled variable is the said actual value of the controlled variable, which is switched at the output of the detection device 136 to the input of the master comparator device 134.

• Max: einen oberen Schwellenwert für die erste bzw. Master-Regelgröße
• Min: einen unteren Schwellenwert für die erste bzw. Master-Regelgröße
• Cpos_n maximal zulässiger Planheitsfehler oder maximal zulässige Walzspaltprofilkonturänderung, jeweils 2. oder höherer Ordnung, oder die Summe aus beiden, gültig für eine Veränderung des Sollwertes in positiver Richtung;
• Cneg_n minimal zulässiger Planheitsfehler oder minimal zulässige Walzspaltprofilkonturänderung, jeweils 2. oder höherer Ordnung, oder die Summe aus beiden gültig für eine Veränderung des Sollwertes in negativer Richtung;
• dQM_n: Verhältnis von Änderung des Sollwertes der Stellgröße des Masterstellglieds zu Änderung der Planheit 2. und/oder höherer Ordnung des Metallbandes; oder Verhältnis von Änderung des Sollwertes der Stellgröße des Masterstellglieds zu Änderung der Walzspaltkontur 2. und/oder höherer Ordnung.

The subject of the present invention is not so much the described control loop 130, but rather the one in FIG Figure 1 Master setpoint correction device 135 shown. This serves to _{convert an originally or previously provided setpoint SM setpoint n} into a corrected master setpoint value SM _{setpoint n *} in the event that the sum of the previous master setpoint value SM _{setpoint n} and previously calculated correction components y1_n-1 and y2_n-1 should be so large that they bring the master actuator 132 to its performance limits would. In order to calculate the corrected master setpoint value SM _{setpoint n *} , the master setpoint correction device 135 is supplied with various other parameters in _{addition to the previous setpoint value SM setpoint n.} It refers to:

• Max: an upper threshold value for the first or master controlled variable
• Min: a lower threshold value for the first or master controlled variable
• _{Cpos n} maximum permissible flatness error or maximum permissible roll gap profile change, in each case 2nd or higher order, or the sum of both, valid for a change in the setpoint in a positive direction;
• _{Cneg n} minimum permissible flatness error or minimum permissible roll gap profile change, in each case 2nd or higher order, or the sum of both valid for a change in the setpoint in the negative direction;
• dQM _n : ratio of the change in the setpoint of the manipulated variable of the master control element to the change in the flatness of the 2nd and / or higher order of the metal strip; or the ratio of the change in the setpoint of the manipulated variable of the master actuator to the change in the roll gap contour of the 2nd and / or higher order.

Figure 2 shows the structure of said master setpoint correction device 135 in detail. In this correction device, the sum of the previous master setpoint SM _{Soll n} and the previously calculated correction components y1_n-1 and y2_n-1 is monitored in a threshold monitoring device 135-1 to determine whether it exceeds a predetermined upper threshold Max or a predetermined one falls below the lower threshold value Min. The result is provided at the output of the monitoring device 135-1, here by way of example in the form of the output _{signals x 1} , x ₂ , which are for example binary-coded. The signals x ₁ and x ₂ are in fact release signals for releasing a calculation unit 135-2 for a correction component y1 for the master setpoint value or to enable a calculation unit 135-3 for an alternative correction component y2 for the master setpoint value SM _{setpoint n} .

All values or signals used in the present description are time-dependent and are therefore provided with the index n, where n = 1... N represents discrete points in time. These points in time are specified by the clock cycles of the control, that is, the runs of the control loop.

If it is determined during the monitoring in the monitoring device 135 that the setpoint SM _{Soll n} for the first controlled variable exceeds the upper threshold value Max of a tolerance range T, the correction component y1 is either specified process-specifically or system-specifically or it is specified in the calculation unit 135-2 according to calculated using the following formula: $$\mathrm{y}\mathrm{1}\mathrm{n}=\left(\mathrm{y}\mathrm{1}\mathrm{n}-\mathrm{1}\right)-\left(\mathrm{Cposn}*\mathrm{dQMn}\right)$$

Alternatively: If, on the other hand, it is determined in the monitoring device 135-1 that the target value SM _{Soll n} for the first controlled variable falls below the lower threshold value Min of the tolerance range T, a correction component y2 is specified process-specific or system-specific or in the calculation unit 135-3 according to the following Calculated formula: $$\mathrm{y}\mathrm{2}\mathrm{n}=\left(\mathrm{y}\mathrm{2}\mathrm{n}-\mathrm{1}\right)+\left(\mathrm{Cnegn}*\mathrm{dQMn}\right)\mathrm{.}$$

und $$\mathrm{y}\mathrm{2}\mathrm{n}=\mathrm{y}\mathrm{2}\mathrm{n}-\mathrm{1.}$$

Finally, if it is determined during the monitoring in the monitoring device 135-1 that the target value SM _{Soll n} for the first control variable neither exceeds the upper threshold value Max of the tolerance range nor falls below the lower threshold value of the tolerance range T, the correction components y1, y2 for calculates the value of the first controlled variable as follows: $$\mathrm{y}\mathrm{1}\mathrm{n}=\mathrm{y}\mathrm{1}\mathrm{n}-\mathrm{1};$$

and $$\mathrm{y}\mathrm{2}\mathrm{n}=\mathrm{y}\mathrm{2}\mathrm{n}-\mathrm{1.}$$

The correction components y1 and y2 calculated in this way go according to Figure 2 into a calculation unit 135-4 for calculating the corrected setpoint value SM _{setpoint n *} . The calculation unit is typically an addition device which additively adds the correction components y1 or y2 to the previous master setpoint value SM _{setpoint n in} order to calculate said corrected setpoint value signal in this way.

und/oder $$\mathrm{Y}\mathrm{2}\mathrm{n}=\mathrm{Y}\mathrm{2}\mathrm{n}-\mathrm{1.}$$

The correction component y1 is typically negative and the correction component y2 is typically positive. As a result, the sign must be selected in such a way that the target value SM _{target n + 1 is} shifted into the tolerance range. As a result, the corrected target value SM _{target n * is} typically smaller than the previous master target value SM _{target n} . Under certain circumstances, the calculation units 135-2 and 135-3 for the correction components y1 and y2 are individually blocked; this is done with the in Figure 2 _{indicated disable} signals DIS y2 and DIS _y1 .
The following applies in the event of a blocking: $$\mathrm{Y}\mathrm{1}\mathrm{n}=\mathrm{Y}\mathrm{1}\mathrm{n}-\mathrm{1};$$

and or $$\mathrm{Y}\mathrm{2}\mathrm{n}=\mathrm{Y}\mathrm{2}\mathrm{n}-\mathrm{1.}$$

With reference to the Figures 1 and 2 the master control loop 130 has been described so far.

The Figures 3 and 4th describe further control loops 140-k assigned to the roll stand 100 with k = 1-K, so-called slave control loops. According to the invention it is provided that in addition to the master control circuit 130, at least one further slave control circuit 140-k is assigned to the roll stand 100.

Figure 3 illustrates the structure of such a slave control loop 140-k in detail. It has an analog structure for all slaves k. The slave control circuit 140-k is used to regulate _{a slave controlled variable SL k actual n} to a corrected setpoint SL _{k setpoint n *.} For this purpose, the actual value of the controlled variable is detected with the aid of a detection device 146-k and compared with the corrected setpoint SL _{k setpoint n *} in a slave comparator 144-k. The result is fed in the form of a control deviation to the kth controller 143-k, which provides a control signal for a kth slave actuator 142-k at its output. The slave actuator 142-k influences a k'th controlled system 141-k. This slave controlled system 141 - k is typically the same roll stand 100 that also represents the master controlled system 131 of the first control loop 130.

y1, y2

kumulierte Korrekturanteile des Masterstellgliedes

dQS_k

Differenzenquotient, welcher das Verhältnis von Änderung des Sollwertes des k'ten Regelkreises 142-k zu einer Änderung des Sollwertes des ersten bzw. Master-Regelkreises 130 repräsentiert

a_k

Koeffizient mit $\sum _{k=1}^K\mathit{ak}=\mathit{konstant},$

vorzugsweise = 1.

According to the invention, the previous slave setpoint signal SL _{k setpoint n is} corrected or converted _{in said corrected slave setpoint value SL k setpoint n *} with the aid of a setpoint correction device 145-k. For this purpose, the k'th setpoint correction device 145-k receives various input variables; in addition to the said k'th slave setpoint SL _k Solln, the following variables are also involved:

y1, y2

cumulative correction components of the master actuator

dQS _k

Difference quotient, which represents the ratio of a change in the setpoint of the k'th control loop 142-k to a change in the setpoint of the first or master control loop 130

a _k

Coefficient with $\sum _{k=1}^K\mathit{ak}=\mathit{constant},$

preferably = 1.

Figure 4 shows the structure of a k'th setpoint correction device 145-k in detail. Overall, according to the invention, a total of K setpoint correction devices 145-k are provided corresponding to the number of slave control loops 140-k with k = 1-K. The structure of the control loops 140-k and the respectively assigned setpoint correction devices 145-k are basically identical for all k slaves, as in FIG Figure 4 shown. Therefore, for the sake of simplicity, only a first setpoint correction device 145-k = 1 is described in detail by way of example.

mit

k=1... K :

Anzahl der Slave-Stellglieder 142-k.

In addition to the previous slave setpoint SL _{k = 1 setpoint n} , the setpoint correction device 145-k = 1 also receives the correction components y1 and y2 calculated in the master setpoint correction device 135 for correcting the master setpoint. These two correction components are added up in an addition device 145-k = 1-1 and the sum calculated in this way is entered in a calculation unit 145-1-2 for calculating a compensation component ZSL _{k = 1} for slave k. Within this calculation unit, the calculation is carried out according to the following formula: $${\mathrm{ZSL}}_{\mathrm{k}}=\left(\mathrm{<figure-callout\; id="1"\; label="y"\; filenames="imgf0002.png,imgf0004.png"\; state="\{\{state\}\}">y</figure-callout>}\mathrm{1}+\mathrm{y}\mathrm{2}\right)*{\mathrm{dQS}}_{\mathrm{k}}*{\mathrm{a}}_{\mathrm{k}}$$

With

k = 1 ... K:

Number of slave actuators 142-k.

Finally, the corrected slave setpoint value is calculated in a further calculation unit 145-1-3 by adding the previous or previous slave setpoint value SL _{k = 1 setpoint n} and the calculated compensation component ZSL _k .

_{A power deficit Δp k of} the k'th actuator is also determined within the calculation unit 145-k = 1-2 for the compensation component. In the event that the upper or lower performance limit of the k'th slave actuator is reached, the determined travel shortfall is distributed to the remaining slave actuators by appropriately changing the respective coefficients a _{k of} the remaining slave actuators. _{For this purpose, the power deficits Δp k} ascertained in the k slave setpoint correction devices 145-k are also sent to an in Figure 4 The power distribution calculating device 150 shown is input so that, on the basis of the input signals mentioned, it calculates the coefficients a _k for the individual slave setpoint correction devices 145-k updated and also provides the _{disable signals DIS y1} and DIS y2 for the calculation units 135-2 and 135-3 for the correction components y1 and y2. The blocking signals are set to DIS _y1 = 1, DIS _y2 = 1, for example.

In the event that the remaining slave actuators cannot adequately compensate for the short travel amount of the k'th slave actuator, at least one of the correction components of the first controlled variable is kept constant; this is done by said disable signals DIS _y1 and DIS _y2 , which are calculated by the power distribution calculator 150, as above with reference to FIG Figure 4 described.

The method according to the invention is described below with reference to Figures 5a, 5b and 5c described in more detail:
In Figure 5a the upper and lower physical performance limits of the master actuator 132 are entered. They correspond to an upper and / or a lower, positive and / or negative operating limit of the master actuator 132. The invention provides that these performance limits when the master actuator is controlled with the associated control signal S generated by the master controller 133 _{x should} under no circumstances be reached, no matter how great the master setpoint or its change over time. For this purpose, the desired value SM _{Soll n is} monitored according to the invention with the aid of the monitoring device 135-1 with regard to the achievement of lower threshold limit values Max, Min. These limit values are lower in that they are within the upper and lower performance limits of the master actuator. By monitoring these lower threshold values, it is possible to take preventive action even before the upper or lower performance limit is reached, by calculating said correction components y1 and y2 for the master setpoint according to the invention. From a synopsis of the Figures 5a and 5b it can be seen that the master setpoint SM _setpoint when the upper limit value Max is reached at the point in time n is reduced by adjusting the amount of the correction component y1. This results in the corrected master setpoint at time n1. The corrected master setpoint SM _{setpoint n1 *} reduced in this way is further away from the upper performance limit and is also lower and more stable within a tolerance range T spanned by the upper and lower limit values Max, Min. But also this corrected master setpoint at the time n1 is also monitored in the monitoring device 135-1 with regard to reaching the upper or lower limit value. If this is determined at time n2, a new correction takes place, specifically a renewed reduction of its value by a then newly calculated correction component y1. This correction results in another corrected master setpoint value SM _{setpoint n2 *} at time n2.
In Figure 5c the reaction of the slave actuator according to the invention is displayed. This serves to avoid disturbances in the flatness of the strip that would be caused by the preventive procedure of the master actuator. With the aid of the difference quotient dQS _k , the travel paths for the active slave actuators, see Figure 5c , calculated in such a way that the disturbance in the flatness caused by the preventive process of the master actuator is preventively neutralized by a corresponding process of at least one slave actuator.

As a result, the master actuator is moved through the opposing control of at least one slave actuator with only minor flatness disturbances or even flatness-neutral.

• Biegekraft für die Arbeitswalzen und/oder die Zwischenwalzen des Walzgerüstes ;
• Position und/oder Horizontalverschiebung für die Arbeits- und/oder Zwischenwalzen;
• Position, Kraft und/oder Drehwinkel einer Exzentereinrichtung zur Einstellung einer Änderung der Walzspaltkontur; und/oder
• Druck eines Kühlmediums, Durchflussmenge des Kühlmediums, Neigungswinkel einer Zonenkühleinrichtung zur Kühlung einer Arbeitswalze 110 über ihrer Breite zur Einstellung bzw. Änderung der Walzspaltkontur;
• Druck eines Heizmediums, Durchflussmenge des Heizmediums, Neigungswinkel einer Zonenheizeinrichtung zum Aufwärmen einer Arbeitswalze über ihrer Breite zur Einstellung bzw. Änderung der Walzspaltkontur;
• Stromstärke, elektrische Leistung für induktive Walzenerwärmung;
• Differenzposition zwischen Bedien- und Antriebsseite einer hydraulischen Anstellung für die Walzen 110.

The first and each of the second controlled variables for the master and slave control loops are preferably selected from the set of the following variables:

• Bending force for the work rolls and / or the intermediate rolls of the roll stand;
• Position and / or horizontal displacement for the work and / or intermediate rolls;
• Position, force and / or angle of rotation of an eccentric device for setting a change in the roll gap contour; and or
• Pressure of a cooling medium, flow rate of the cooling medium, angle of inclination of a zone cooling device for cooling a work roll 110 over its width for setting or changing the roll gap contour;
• Pressure of a heating medium, flow rate of the heating medium, angle of inclination of a zone heating device for warming up a work roll over its width for setting or changing the roll gap contour;
• Amperage, electrical power for inductive roller heating;
• Difference position between the operating and drive side of a hydraulic adjustment for the rollers 110.

• Biegeeinrichtung für die Arbeitswalzen und/oder die Zwischenwalzen des Walzgerüstes (100);
• Axialverschiebung für die Arbeits- und/oder Zwischenwalzen;-Exzentereinrichtung zur Einstellung einer Änderung der Walzspaltkontur; und/oder
• Zonenkühleinrichtung mit individuell anzusteuernden Ventilen für das Kühleinrichtung zur Kühlung einer Arbeitswalze über ihrer Breite zur Einstellung bzw. Änderung der Walzspaltkontur;
• Zonenheizeinrichtung mit individuell anzusteuernden Ventilen für das Heizmittel zur Aufheizung einer Arbeitswalze über ihrer Breite zur Einstellung bzw. Änderung der Walzspaltkontur;
• induktive Walzenerwärmung;
• Anstellzylinder der hydraulischen Anstellung von insbesondere den Arbeitswalzen (110).

The master 132 and each of the slave actuators 142-k are preferably selected from the set of the following actuators:

• Bending device for the work rolls and / or the intermediate rolls of the roll stand (100);
• Axial displacement for the working and / or intermediate rolls; eccentric device for setting a change in the roll gap contour; and or
• Zone cooling device with individually controllable valves for the cooling device for cooling a work roll across its width for setting or changing the roll gap contour;
• Zone heating device with individually controlled valves for the heating means for heating a work roll across its width for setting or changing the roll gap contour;
• inductive roller heating;
• Adjustment cylinder for the hydraulic adjustment of, in particular, the work rolls (110).

• erste Regelgröße : Biegekraft; und
• k=1'te Regelgröße : Axial-Verschiebung;
  oder
• erste Regelgröße : Axial-Verschiebung und;
• k=1'te Regelgröße : Biegekraft.

If the roll stand 100 is a four-high stand, then the following combination of controlled variables is preferably selected:

• first controlled variable: bending force; and
• k = 1st controlled variable: axial displacement;
  or
• first controlled variable: axial displacement and;
• k = 1st controlled variable: bending force.

For these two alternatives, zone cooling can optionally also be selected as k = 2nd controlled variable.

• erste Regelgröße : Biegekraft für Arbeitswalzen und;
• k=1'te Regelgröße : Biegekraft für Zwischenwalzen und;
• k=2'te Regelgröße : Axialverschiebung der Zwischenwalzen;
  oder
• erste Regelgröße : Biegekraft für Zwischenwalzen; und
• k=1 'te Regelgröße : Biegekraft für Arbeitswalzen und;
• k=2'te Regelgröße : Axialverschiebung der Zwischenwalzen;
  oder
  erste Regelgröße : Axialverschiebung der Zwischenwalzen;
• k=1'te Regelgröße : Biegekraft für Zwischenwalzen; und
• k=2'te Regelgröße : Biegekraft für Arbeitswalzen.

If the roll stand 100 is a six-high stand, then the following combinations of control variables are preferably selected:

• first controlled variable: bending force for work rolls and;
• k = 1st controlled variable: bending force for intermediate rolls and;
• k = 2nd controlled variable: axial displacement of the intermediate rolls;
  or
• first controlled variable: bending force for intermediate rolls; and
• k = 1st controlled variable: bending force for work rolls and;
• k = 2nd controlled variable: axial displacement of the intermediate rolls;
  or
  first controlled variable: axial displacement of the intermediate rolls;
• k = 1st controlled variable: bending force for intermediate rolls; and
• k = 2nd controlled variable: bending force for work rolls.

Each of the mentioned combinations of controlled variables for the six-high stand can also be supplemented by zone cooling as a third controlled variable.

If the width of the metal strip 120 exceeds a predetermined width threshold value, the bending device is preferably specified as the master actuator 132.

In the case of four-high and six-high roll stands, flatness disturbances due to fluctuations in the rolling force are compensated for by a Profile-Gauge Meter PGM. This is state of the art. The functioning of the PGM includes the precontrol of changes in the rolling force on bends in order to keep the roll gap profile and / or the roll gap contour between the work rolls 110 of the roll stand 100 as constant as possible in the event of a fluctuation in the rolling force. The quality of the difference quotients dQM required for the PGM pre-control depends heavily on the current operating point. In addition, the PGM must always have a bending reserve in order to be able to withstand a sudden change in force, e.g. B. to be able to react quickly due to over-pickled areas on steel belts. The bending reserve corresponds to Figure 5a the distance between the upper power limit and the upper limit value Max or the distance between the lower power limit and the lower limit value Min. B. a bending system, as it is specified by the master setpoint for the first control variable, changed and optimized with knowledge of the operating points of the other systems or control variables assigned to the roll stand 100.

In the simple example of a four-high mill stand, the work roll bending is used for the PGM precontrol and is accordingly defined as a master controlled variable with corresponding master setpoint specifications. Depending on the size of the setpoint specification, the associated master actuator 132 can reach its physical limits, ie its upper or lower performance limit. In order to prevent this, according to the invention, one is switched in the background Calculating an allowable error, e.g. B. 4th order, monitor and within its limits a replacement of the work roll bending by z. B. allow an at least partial axial displacement for the work rolls.

In the case of a six-high roll stand, even operating points can be optimized in order to approach the desired operating point despite errors in the calculation of the setting specifications and thus to obtain advantages for the use of calculated difference quotients which then better match the operating point.

As a result, the master actuator is moved through the opposing control of at least one slave actuator with only minor disturbances in flatness or even flatness-neutral.

List of reference symbols

100

Roll stand

110

Work rolls

120

Metal band

130

first control loop

131

Controlled system of the first control loop or the master control loop

132

Master actuator

133

Master controller

134

Master comparator

135

Master setpoint correction device

135-1

Monitoring device

135-2

Calculation unit for correction component y1

135-3

Calculation unit for correction component y2

135-4

Calculation unit for corrected target value

136

Detection device

140-k

k'ter control loop

141-k

k'te controlled system

142-k

kth slave actuator

143-k

k'ter regulator

144-k

k'ter comparator

145-k

k'th slave setpoint correction device

145-k-1

Sumer

145-k-2

Conversion unit

145-k-3

Totalizer of the setpoint

150

Power distribution calculation unit

T

Tolerance range

k

kth slave actuator with k = 1-K

n

discrete point in time, running index

y1

Correction portion

y2

Correction portion

S _x

Control signal for master actuator

*

corrected value

Claims (15)

A method for operating a roll stand (100) which has: a pair of work rolls (110) for tensioning a roll gap for rolling a metal strip (120), a first control circuit (130) with a first actuator (132) for controlling a first controlled variable and k further control loops (140-k) each with a k'th actuator (142-k) for controlling a k'th controlled variable with k = 1 to K,
the method being characterized by the following steps: Establishing that the first actuator (132) function as a master actuator and that the k'th actuators (142-k) each function as a slave actuator; Specifying the setpoint (SM _{Soll n} ) for the first controlled variable; Monitoring the temporal course of the setpoint (SM _{setpoint n} ) for the first control variable to determine whether the setpoint exceeds an upper threshold value (Max) or falls below a lower threshold value (Min), the upper and lower threshold values within one of the upper and lower thresholds lower performance limit of the first actuator are defined tolerance range; if so: i) Determination of at least one correction component (y1, y2) in such a way that the setpoint for the first controlled variable is shifted in the direction of the tolerance range, calculation of a corrected setpoint (SM _{Soll n *} ) for the first controlled variable from the previous setpoint (SM _{Soll n} ) for the first controlled variable taking into account the correction component (y1, y2) and regulating the first controlled variable to the corrected setpoint value (SM _{Soll n *} ) by suitable control of the master actuator (132); and ii) calculating a compensation _{component (ZSL k = 1} ) for the nominal value (SLk = 1 _{nominal n} ) of the k = 1st controlled variable, taking into account the correction component (y1, y2) for the nominal value (SM _{nominal n} ) of the first controlled variable; Calculation of a corrected nominal value (SLk = 1 _{nominal n *} ) for the k = 1st Controlled variable from the previous setpoint (SLk = 1 _{setpoint n} ) for the k = 1st controlled variable taking into account the compensation component (ZSL _{k = 1} ) and regulation of the k = 1st controlled variable to the corrected setpoint (SLk = 1 _{setpoint n *} ) for the k = 1st controlled variable by suitable control of the k = 1st slave actuator (142-1). Method according to claim 1,
characterized,
that the roll stand additionally has further slave control loops (k = 2 to K); and
which the procedure also has the following steps:
Carrying out steps ii) analogously in each case for each of the further k = 2 to K control loops with their respective k = 2 to K'th slave actuator (142-k). Method according to one of the preceding claims,
characterized,
that - if the monitoring determines that the setpoint (SM _{setpoint n} ) for the first controlled variable exceeds the upper threshold value (Max) of the tolerance range (x1 = 1, x2 = 0) - the correction component (y1) is specified specifically for the process or system or is calculated according to the following formula: $$\mathrm{y}\mathrm{1}\mathrm{n}=\left(\mathrm{y}\mathrm{1}\mathrm{n}-\mathrm{1}\right)+\left(\mathrm{Cposn}*\mathrm{dQMn}\right)$$

or
that - if the monitoring determines that the setpoint (SM _{setpoint n} ) for the first controlled variable falls below the lower threshold value (Min) of the tolerance range (x1 = 0, x2 = 1) - the correction component (y2) is specified specifically for the process or system or is calculated according to the following formula: $$\mathrm{y}\mathrm{2}\mathrm{n}=\left(\mathrm{y}\mathrm{2}\mathrm{n}-\mathrm{1}\right)-\left(\mathrm{Cnegn}*\mathrm{dQMn}\right)$$

or
that - if the monitoring determines that the setpoint for the first controlled variable neither exceeds the upper threshold value (Max) of the tolerance range, nor falls below the lower threshold value (Min) of the tolerance range (x1 = 0, x2 = 0) or if the Disable Signals (DIS _y1 and / or DIS _y2 ) from the power distribution calculating device (150) are set - the correction components (y1, y2) for the setpoint (SM _{Soll n} ) of the first controlled variable are calculated as follows: $$\mathrm{Y}\mathrm{1}\mathrm{n}=\mathrm{Y}\mathrm{1}\mathrm{n}-\mathrm{1};\mathrm{and}$$

$$\mathrm{Y}\mathrm{2}\mathrm{n}=\mathrm{Y}\mathrm{2}\mathrm{n}-\mathrm{1}$$

With : n = 1 ... N discrete points in time; _{Cpos n} : Maximum permissible flatness error or maximum permissible roll gap profile change, in each case 2nd or higher order, or the sum of both, valid for a change in the setpoint in a positive direction; _{Cneg n} : minimum permissible flatness error or minimum permissible roll gap profile change, in each case 2nd or higher order, or the sum of both, valid for a change in the setpoint in a negative direction; dQM _n : ratio of the change in the setpoint of the manipulated variable of the master control element to the change in the flatness of the 2nd and / or higher order of the metal strip; or the ratio of the change in the setpoint of the manipulated variable of the master actuator to the change in the roll gap contour 2. and / or higher order. Method according to claim 3,
characterized,
that the corrected setpoint (SM _{setpoint n1 *} ) for the master is calculated as follows: $${\mathrm{SM}}_{\mathrm{Should\; n}\mathrm{1}*}={\mathrm{SM}}_{\mathrm{Should\; n}}+\mathrm{y}\mathrm{1}+\mathrm{y}\mathrm{2}$$

Method according to claim 3 or 4,
characterized,
that the compensation component (ZSL _{k = 2-K} ) for slave k is calculated according to the following formula: $${\mathrm{ZSL}}_{\mathrm{k}}=\left(\mathrm{y}\mathrm{1}+\mathrm{y}\mathrm{2}\right)*{\mathrm{dQS}}_{\mathrm{k}}*{\mathrm{a}}_{\mathrm{k}}$$

With k = 1 ... K: number of slave actuators 142-k a _k : coefficient with $\sum _{k=1}^K\mathit{ak}=\mathit{constant},$

preferably = 1 dQS _k difference quotient: ratio of the change in the setpoint of the k'th control loop (142-k) to the change in the setpoint of the first control loop (130). Method according to one of the preceding claims,
characterized,
that the first and each of the k'th controlled variables is selected from the set of the following variables: Bending force for the work rolls and / or the intermediate rolls of the roll stand; Position and / or horizontal displacement for the work and / or intermediate rolls; Position, force and / or angle of rotation of an eccentric device Setting a change in the roll gap contour; and / or pressure of a cooling medium, flow rate of the cooling medium, angle of inclination of a zone cooling device for cooling a work roll (110) over its width for setting or changing the roll gap contour; Pressure of a heating medium, flow rate of the heating medium, angle of inclination of a zone heating device for warming up a work roll over its width for setting or changing the roll gap contour; Amperage, electrical power for inductive roller heating; Difference position between operating and drive side of a hydraulic adjustment for the rollers (110). Method according to one of the preceding claims,
characterized,
that the master (132) and each of the slave actuators (142-k) are selected from the set of the following actuators: - Bending device for the work rolls and / or the intermediate rolls of the roll stand (100); - Axial displacement for the work and / or intermediate rolls; - Eccentric device for setting a change in the roll gap contour; and or - Zone cooling device with individually controllable valves for the cooling device for cooling a work roll across its width for setting or changing the roll gap contour; - Zone heating device with individually controlled valves for the heating means for heating a work roll across its width for setting or changing the roll gap contour; - inductive roller heating; - Adjustment cylinder of the hydraulic adjustment of, in particular, the Work rolls (110). Method according to one of Claims 6 and 7,
characterized,
that - if the roll stand (100) is a four-high stand - then the following applies: first controlled variable: bending force; and k = 1st controlled variable: axial displacement;
or first controlled variable: axial displacement and; k = 1st controlled variable: bending force. Method according to claim 8,
characterized,
that optionally also applies to both alternatives according to claim 8. k = 2nd controlled variable: zone cooling Method according to one of Claims 6 and 7,
characterized,
that - if the roll stand is a six-high stand - then the following applies: first controlled variable: bending force for work rolls and; k = 1st controlled variable: bending force for intermediate rolls and; k = 2nd controlled variable: axial displacement of the intermediate rolls;
or first controlled variable: bending force for intermediate rolls; and k = 1st controlled variable: bending force for work rolls and; k = 2nd controlled variable: axial displacement of the intermediate rolls;
or first controlled variable: axial displacement of the intermediate rolls; k = 1st controlled variable: bending force for intermediate rolls; and k = 2nd controlled variable: bending force for work rolls. Method according to claim 10,
characterized,
that for all 3 alternatives according to claim 10, optionally also applies. k = 3rd controlled variable: zone cooling Method according to one of the preceding claims,
characterized,
that the rolling is hot rolling or cold rolling. Method according to one of the preceding claims,
characterized by : Monitoring the upper and / or lower power limit of the k'th actuator; Determining a power deficit (Δpk) of the k'th actuator; and in the event that the upper or lower performance limit of the k'th slave actuator is reached: redistribution of the power shortfall to the remaining slave actuators by appropriately changing the respective coefficients a _{k of} the remaining slave actuators. Method according to claim 13,
characterized,
that in the event that the remaining slave actuators cannot adequately compensate for the shortfall in travel of the k'th slave actuator, at least one of the correction components (y1, y2) of the first controlled variable is kept constant. Method according to one of Claims 7 to 14,
characterized,
that when the width of the metal strip (120) exceeds a predetermined width threshold value, the bending device is set as the master actuator (132).

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