EP2454033B1 - Ribbon stroke and loop control - Google Patents

Description

The present invention relates to a control method for controlling a Istzuges, which prevails in a clamped between two stands rolling on a debit train and an actual position of an arranged between the two rolling stands, employed on the band loop lifter to a desired position.

The present invention further relates to a computer program which has machine code which can be processed directly by a control device and whose execution by the control device causes the control device to carry out such a control method.

The present invention further relates to a control device which is designed such that it carries out such a control method during operation.

When rolling strips - in particular of metal strips - in multi-stand rolling mills, a strip tension is usually set in the individual strip sections (that is to say in the sections of the strip which are located between each two successive strip rolling mills of the rolling train). For technological reasons - for example, to maintain the thickness and width constancy of the strip - the strip tension should be kept as constant as possible. To set the strip tension, a speed setpoint is usually determined, which acts on one of the two limiting the band section rolling stands. Furthermore, an employment of a loop lifter is set, which is arranged between the two successive rolling stands and is employed on the belt.

Also for detecting the tape tension the looper are often used in the prior art. Hiring the Loop lifter in the prior art by means of an electric drive (less common) or a hydraulic cylinder unit (more often).

The loop lifter not only measures the tension in the belt. Furthermore, an amount of band is set on the deflection of the loop lifter, which is buffered in the respective band section (noose).

Not only the tension prevailing in the belt, but also the position of the looper must be regulated. Thus, in particular, the loop lifter can be brought into its raised position only after the threading of the tape, in which he deflects the tape. Also, the loop lifter must be lowered again before unthreading the tape. As is clear from simple geometrical considerations, an adjustment of the loop lifter directly affects the length of the band located in the band section and thus indirectly the strip tension. The loop control is therefore coupled with the tension control.

From the technical paper " Development of Looper Tension Control Systems for Hot Strip Mill "by CJ Park et al., Proceedings of the IASTED International Conference, Applied Simulation and Modeling 2000, July 24-26, 2000, Banff, Alberta, Canada, pages 423-427 , Is a control method for controlling a Istzuges, which prevails in a clamped between two stands rolling on a debit train and an actual position of an arranged between the two rolling stands, employed on the band looper on a target position is known, comprising a traction controller and a loop controller. The train tension and the actual tension are fed to the tension controller. The loop controller, the target position and the actual position are supplied. Both controllers are designed as PI controllers. Both controllers each determine an output signal. Both output signals act both on the rolling speed of the upstream and downstream roll stand and on the position of the loop lifter. Each of the four effects is set via a corresponding amplification factor.

The technical paper " Application of ILQ control theory to steel rolling processes "by H. Imanari et al., Proceedings of The 7th International Conference on Steel Rolling 1998, Chiba, Japan, pp. 36-41 , a substantially equivalent stored disclosure content can be found.

The control methods known from the technical articles represent an advance over the conventional control methods. They work with a decoupling of the control interventions from one another.

From the EP 0 710 513 A1 a control method is known, by means of which a ruling in a clamped between two stands rolling band Istzug be regulated to a desired train and an actual position of an arranged between the two rolling stands, employed on the belt loop lifter to a desired position. For this purpose, characteristic values are supplied to a tension controller for the desired tension and the actual tension. Furthermore, the desired position and the actual position are fed to a loop controller. The tension controller determines a train compensation signal on the basis of the characteristic values supplied to it. The loop controller determines a loop compensation signal based on the nominal position and the actual position. In response to the train compensation signal and the loop compensation signal, an adjustment speed for the loop lifter and an additional speed setpoint for the upstream or downstream rolling stand are determined. From the EP 0 710 513 A1 is also known that the control of the corresponding rolling stand and the loop lifter influence each other.

The object of the present invention is to provide ways in which it is ensured that interventions of the loop controller no or only a very small Have an effect on the actual train and that the train controller intervenes with high dynamics.

The object is achieved by a control method having the features of claim 1. Advantageous embodiments of the control method according to the invention are the subject of the dependent claims 2 to 8.

The object is further achieved by a computer program having the features of claim 9. Furthermore, the object is achieved by a control device having the features of claim 11.

• dass einem Zugregler für den Sollzug und für den Istzug charakteristische Werte zugeführt werden,
• dass der Zugregler anhand der ihm zugeführten charakteristischen Werte ein Zugausgleichssignal ermittelt, das einen Integralanteil umfasst,
• dass anhand des Integralanteils ein erster Geschwindigkeitszusatzsollwert für mindestens eines der zwei Walzgerüste ermittelt wird,
• dass der Integralanteil zeitlich verzögert wird,
• dass anhand der Differenz von Zugausgleichssignal und verzögertem Integralanteil ein erster Sollverstellgeschwindigkeitsanteil für den Schlingenheber ermittelt wird,
• dass die Sollstellung und die Iststellung einem Schlingenregler zugeführt werden, der anhand der Sollstellung und der Iststellung ein Schlingenausgleichssignal ermittelt,
• dass durch Verzögern des Schlingenausgleichssignals ein zweiter Sollverstellgeschwindigkeitsanteil für den Schlingenheber ermittelt wird,
• dass anhand des Schlingenausgleichssignals ein zweiter Geschwindigkeitszusatzsollwert für das mindestens eine der zwei Walzgerüste ermittelt wird,
• dass die Summe von erstem und zweitem Geschwindigkeitszusatzsollwert an eine Drehzahlregelung für das mindestens eine der zwei Walzgerüste ausgegeben wird und
• dass an eine Verstelleinheit, mittels derer die Stellung des Schlingenhebers eingestellt wird, eine resultierende Sollverstellgeschwindigkeit ausgegeben wird, in die als Summanden der erste und der zweite Sollgeschwindigkeitsanteil eingehen.

In the control method according to the invention, it is provided

• that characteristic values are supplied to a tension controller for the desired tension and for the actual tension,
• the tension controller determines, on the basis of the characteristic values supplied to it, a train compensation signal which comprises an integral component,
• a first additional speed setpoint for at least one of the two rolling stands is determined on the basis of the integral component,
• that the integral part is delayed in time,
• that a first Sollverstellgeschwindigkeitsanteil for the loop lifter is determined based on the difference of train compensation signal and delayed integral component,
• that the desired position and the actual position are fed to a loop controller which determines a loop compensation signal on the basis of the desired position and the actual position,
• in that by delaying the loop compensation signal, a second desired adjustment speed portion for the loop lifter is determined,
• that a second additional speed setpoint for the at least one of the two rolling stands is determined on the basis of the loop compensation signal,
• that the sum of the first and second additional speed setpoint values is output to a speed control for the at least one of the two rolling stands, and
• in that an adjusting unit, by means of which the position of the loop lifter is adjusted, outputs a resulting setpoint adjustment speed, into which the first and second setpoint speed portions are received as summands.

The terms "train compensation signal" and "loop compensation signal" have been chosen because they express from which controller they originate, which deviation they are to counteract and to distinguish them linguistically from each other. A more important meaning is not the word choice. The two signals could also have been referred to as "output signal of the tension controller" and "output signal of the loop controller".

For the correct adaptation of the interventions made by one of the two controllers, it is preferably provided that, in the determination of the additional speed setpoint values relative to the desired adjustment speed components, the derivative the length of the band clamped between the two stands according to the position of the loop lifter.

As part of the determination of the resulting Sollverstellgeschwindigkeit both the integral component of the train compensation signal and the loop output signal are delayed in time. The control method may therefore be simplified by subtracting the instantaneous integral component from a modified loop compensation signal, delaying the resulting difference, and adding the delayed difference to the train compensation signal, wherein the modified loop compensation signal is obtained by scaling the loop compensation signal a value taking into account the derivation is determined.

It is possible that the characteristic value for the actual tension is measured directly. In general, however, the value is either not measurable or at least not easy to measure. In the context of the present invention, it is therefore preferable for the value characteristic of the actual tension to be determined indirectly on the basis of measured variables by means of a tape tension observer. Tape tension observers as such are known to those skilled in the art.

In the resulting Sollverstellgeschwindigkeit - among other things - the first Sollverstellgeschwindigkeitsanteil included, which is determined by the tension controller. In many cases, the tape tension observer continues to be supplied with the resulting desired adjustment speed, that is, the sum of the desired adjustment speed portions. Due to this circumstance, there is a positive feedback within the control. The positive feedback can lead to instability of the tension controller. Therefore, it is preferably provided that a replacement time constant for the tape tension observer is determined dynamically on the basis of variables which are characteristic of the stability of the tension controller, and the tape tension observer determines the characteristic value for the actual tension, taking into account the equivalent time constant determined. Alternatively or additionally, it can be provided that a control gain for the tension controller is determined dynamically on the basis of the variables which are characteristic of the stability of the tension controller, and the tension controller determines the train compensation signal taking into account the control gain.

In a preferred embodiment of the control method according to the invention, it is further provided that a feedforward control is connected in parallel with the tape tension observer. As a result, the dynamics by means of which the value characteristic of the actual tension is determined can be increased.

• dass einem Momentregler der für den Sollzug charakteristische Wert, ein durch den Schlingenheber bewirktes Eigenmoment und ein von einer Verstelleinrichtung für den Schlingenheber bewirktes Verstellmoment zugeführt werden und
• dass der Momentregler einen Zusatzsollverstellgeschwindigkeitsanteil ermittelt, der ebenfalls als Summand in die resultierende Sollverstellgeschwindigkeit eingeht.

In many cases, it is still beneficial

• that a torque controller of the value characteristic value for the train, a self-torque caused by the loop lifter and an adjusting moment caused by an adjusting device for the loop lifter are supplied and
• that the torque controller determines a Zusatzsollverstellgeschwindigkeitsanteil, which also enters as summand in the resulting Sollverstellgeschwindigkeit.

This allows a higher dynamics can be achieved. The torque controller is preferably designed as a P controller (P = proportional) or PD controller (= proportional differential).

The computer program according to the invention is characterized in that the execution of its machine code by a control device causes the control device to carry out a control method according to the invention. The same applies analogously to the control device itself. The computer program can in particular be stored on a data carrier in machine-readable form.

FIG 1

eine mehrgerüstige Walzstraße,

FIG 2

einen einzelnen Bandabschnitt,

FIG 3

eine Zugregelung,

FIG 4

eine Schlingenregelung,

FIG 5

eine mögliche Kombination der Zugregelung von FIG 3 und der Schlingenregelung von FIG 4,

FIG 6

ein Gesamtschaltbild mehrerer Regler,

FIG 7

ein weiteres Gesamtschaltbild mehrerer Regler und

FIG 8

eine mögliche Ergänzung eines Bandzugbeobachters.

Further advantages and details will become apparent from the following description of exemplary embodiments in conjunction with the drawings. In a schematic representation:

FIG. 1

a multi-stand rolling mill,

FIG. 2

a single band section,

FIG. 3

a train regulation,

FIG. 4

a loop control,

FIG. 5

a possible combination of train regulation of FIG. 3 and the loop control of FIG. 4 .

FIG. 6

an overall circuit diagram of several controllers,

FIG. 7

another overall diagram of several controllers and

FIG. 8

a possible addition to a tape tension observer.

According to FIG. 1 For example, a rolling mill has a plurality of rolling stands 1. The rolling mill may in particular be a hot rolling mill. Shown in FIG. 1 a total of three rolling mills 1. In general, however, the rolling mill has more than three rolling mills 1, for example, five to eight mills. In the rolling stands 1, a band 2 is rolled. The band 2 is usually a metal band, for example a steel band, an aluminum band or a copper band. However, it may be made of a different material, such as a non-ferrous metal or a non-metal. The rolling mills 1 are driven to roll the strip 2 at a roll speed v specific to the respective rolling stand 1.

Between each two immediately successive rolling stands 1 a loop 3 is arranged in each case. Each looper 3 has a looper roll 4, which is employed on the band 2. By means of the loop lifter 3, the belt 2 between the rolling stands 1 from a rolling line 5 (that is, the direct line connecting the roll nips of the rolling stands 1 with each other) deflected, usually upwards.

Between the rolling stands 1 (and usually also between a spool 6 and the first of the rolling stands 1 and between the last of the rolling stands 1 and a reel 7), the band 2 is clamped. In band 2, therefore, there is a current Z. The actual Z within each band section is (of course) uniform. In the individual band sections the trains Z may be the same or different from each other.

FIG. 2 shows a single band section including the two the band section limiting rolling stands 1. The two rolling stands 1 are in FIG. 2 The two rolling stands 1 ', 1 "are hereinafter referred to according to their order as a front rolling stand 1' and as a rear rolling stand 1" FIG. 2 section shown around any section.

According to FIG. 2 is a control device 8 available. The control device 8 is designed such that it performs a control method during operation, which will be explained in more detail below.

The control device 8 can be implemented by circuitry. In general, the control device 8, however, according to the representation of FIG. 2 designed as a software programmable control device 8. In this case, the control device 8 is programmed with a computer program 9. The computer program 9 has machine code 10. The machine code 10 can be processed directly by the control device 8. The processing of the machine code 10 by the control device 8 causes the control device 8 carries out the steps of the control method explained below.

The computer program 9 can be supplied to the control device 8 in any manner. For example, it is possible to supply the computer program 9 to the control device 8 via a computer-computer connection, for example a LAN or the Internet. It is also possible to supply the computer program 9 to the control device 8 via a data carrier 11, on which the computer program 9 is stored in machine-readable form. The data carrier 11 can be designed for this purpose as needed. Purely by way of example is in FIG. 2 the disk 11 shown as a USB stick. However, the data carrier 11 could be designed differently, for example as an SD memory card or as a CD-ROM.

According to FIG. 2 the control device 8 is supplied with a desired train Z *. Furthermore, the control device 8 is supplied with a characteristic Z 'characteristic of the actual Z train. Finally, the control device 8 an actual position φ of the loop lifter 3 and a desired position φ * of the loop lifter 3 are supplied. By means of the control device 8, the actual tension Z and the desired tension Z * and the actual position φ are to be regulated to the desired position φ *.

Based on the mentioned variables Z *, Z ', φ, φ *, the control device 8 determines a resulting additional speed setpoint value δv * for the roll stand 1 upstream of the loop lifter 3'. The resulting additional speed setpoint δv * is output to a speed controller 12 for the upstream rolling stand 1 '. Alternatively, the resulting additional speed setpoint value δv * for the roll stand 1 "downstream of the loop lifter 3 could be determined and output to a speed control 13 of this rolling stand 1". This is in FIG. 2 indicated by dashed lines. A division into both rolling stands 1 ', 1 "can be made.

Furthermore, the control device 8 uses the variables Z *, Z ', φ, φ * to determine a resulting setpoint speed ω * for the loop lifter 3. The resulting setpoint speed ω * is output to an adjusting unit 14, by means of which the position of the loop lifter 3 is set , The adjustment unit 14 can operate electrically or - preferably - hydraulically.

The manner of determining the resulting additional speed setpoint value δv * and the resulting desired setpoint speed ω * is the subject of the present invention.

The control device 8 comprises a tension regulator 15. The tension regulator 15 and its mode of action will be described below in connection with FIG. 3 explained in more detail. The control device 8 further comprises a loop regulator 16. The loop regulator 16 and its operation will be described below in connection with FIG. 4 explained in more detail. The entire control device 8 will be described below in connection with FIG. 5 explained again.

The tension controller 15 are according to FIG. 3 a value Z '* characteristic of the reference train Z * and the value Z' characteristic of the actual train Z are supplied. The tension regulator 15 is preferably designed as a PI controller (PI = proportional-integral). On the basis of the characteristic values Z '*, Z' supplied to it, it determines a train compensation signal ZA.

For example, a setpoint determination device 8 'may be present, to which the desired train Z * and further variables are supplied. The further variables may include, for example, the actual position φ of the loop lifter 3, the distances of the loop lifter 3 from the upstream and downstream rolling stand 1 ', 1 "and further geometry parameters, so that the setpoint determination device 8' is able, based on the sizes supplied to it Distances of the looper roll 4 of the rolling stands 1 ', 1 "and the height of the looper roll 4 relative to the rolling line 5 to determine. Furthermore, the setpoint determination device 8 'is supplied with quantities which describe the strip 2, for example its thickness, its width and its elasticity mode. If these quantities are known, the value Z '* characteristic of the desired tension Z * can be determined on the basis of simple geometric calculations. The characteristic value Z '* corresponds in this case to a desired force which the belt 2 should exert on the loop lifter 3, or a setpoint torque which the belt 2 should exert on the loop lifter 3.

Of the variables which are supplied to the setpoint determination device 8 ', at least the desired train Z * and the actual position φ (alternatively the desired position φ *) are variables. Both other sizes may alternatively be variables or parameters. The difference between variables and parameters is that variables in the operation of the control device 8 can vary dynamically, while parameters are set once during the commissioning of the control device 8 and then kept constant.

The setpoint determination device 8 'can be part of the control device 8. Alternatively, it may be arranged outside the control device 8. In the latter case, the control device 8 is supplied with the corresponding characteristic value Z '* instead of the reference pull Z *.

The value Z 'characteristic of the actual pull Z can alternatively be measured or otherwise determined. This will be discussed later.

The tension regulator 15 comprises according to FIG. 3 an integrator 17. The train compensation signal ZA therefore comprises an integral component IA. Furthermore, the tension controller 15 comprises a branch 18, via which a proportional component PA of the train compensation signal ZA is output.

An integration gain kI of the integrator 17 may be a constant. However, it is preferably a variable which increases, inter alia, with increasing control deviation (| Z '* - Z' |).

According to FIG. 3 is determined on the basis of the integral component IA, a first speed additional setpoint δv1 * for the upstream rolling stand 1 '. The first additional speed setpoint δv1 * enters the resulting speed setpoint δv * as one of two summands.

According to FIG. 3 Furthermore, the integral component IA is supplied to a delay element 19, in which the integral component IA is delayed in time. The time-delayed integral component is referred to below as a delayed integral component IA 'to distinguish it from the instantaneous integral component IA.

The time-delayed integral component IA 'is subtracted in a node 20 from the train compensation signal ZA. Based on the resulting difference, a first Sollverstellgeschwindigkeitsanteil ω1 * for the loop lifter 3 is determined. The first Sollverstellgeschwindigkeitsanteil ω1 * enters as one of several summands in the resulting Sollverstellgeschwindigkeit ω *.

The desired position φ * and the actual position φ are according to FIG. 4 fed to the loop controller 16. The loop controller 16 may be formed as a P-controller. He determined based on the desired position φ * and the actual position φ a loop compensation signal SA. The loop compensation signal SA is supplied to a delay element 21 (among others). In the delay element 21, the loop compensation signal SA is delayed in time, thus determining a delayed loop compensation signal SA '. The delayed loop compensation signal SA 'corresponds to a second Sollverstellgeschwindigkeitsanteil ω2 * for the loop lifter 3. Also, the second Sollverstellgeschwindigkeitsanteil ω2 * as summand in the determination of the resulting Sollverstellgeschwindigkeit ω * a.

According to FIG. 4 Furthermore, on the basis of the loop compensation signal SA, a second additional speed setpoint value δv2 * for the upstream roll stand 1 'is determined. The second additional speed setpoint δv2 * is the second summand, which enters the resulting speed setpoint δv *.

According to FIG. 3 a divider link 22 is present. In the divider element 22, the difference between the train compensation signal ZA and the delayed integral component IA 'is divided by a value kL. The value kL corresponds to the derivation of the length of the band 2, which is between the two the band section limiting rolling stands 1 ', 1 ", after the position φ of the loop lifter. 3

In an analogous manner, in determining the second additional speed setpoint value δv2 *, a multiplication with the value kL is undertaken by means of a multiplier element 23 and a division by the value kL is carried out by means of a divider element 24 to compensate for this multiplication during the determination of the second setpoint speed proportion ω2 * , The loop compensation signal multiplied by the value kL is hereinafter referred to as modified loop compensation signal SA ".

By means of the activation of the adjustment unit 14 delayed relative to the output of the resulting additional speed setpoint value δv *, it is achieved that the actual position φ of the loop lifter 3 is not tracked until a corresponding adaptation of the between the rolling stands 1 ', 1 "clamped by the resulting additional speed setpoint value δv * By subtracting the time-delayed integral component IA 'from the train compensation signal ZA is achieved that the integral component IA is not permanently output to the loop lifter 3, but - according to the time delay by the delay element 19 - from looper 3 on the upstream rolling stand '(optionally alternatively or additionally to the downstream rolling stand 1 ") is shifted. Due to the time delay of the delay element 19, the time delay is compensated, which has the regulated path as such. Thereby, the effects of the resulting additional speed setpoint δv * and the resulting target set speed ω * are synchronized with each other.

FIG. 5 shows the total interconnection of the control device 8. The embodiment according to FIG. 5 is functionally completely equivalent to those above in connection with the 3 and 4 explained procedure. Only the order of individual addition, subtraction and delay measures is slightly modified. In particular, in the context of FIG. 5 If the instantaneous integral component IA is subtracted from the modified loop compensation signal SA ", the difference thus determined is delayed and the delayed difference is added to the train compensation signal Z. This procedure is especially computationally simpler because the delay element 21 can be saved.

In principle, it is possible to measure the value Z 'characteristic of the actual Z train. In many cases, however, the measurement is technically complicated or even impossible. For this reason, according to the FIG. 3 and 5 a tape tension observer 25 available. By means of the tape tension observer 25, the value Z 'characteristic of the actual tension Z is determined indirectly on the basis of measured variables. The measured variables may in particular comprise an adjusting moment MV applied by the loop lifter 3. Furthermore, the tape tension observer 25 can be supplied with quantities that are characteristic of the adjustment speed ω of the loop lifter 3 and a self-moment ME caused by the loop lifter 3. At the adjustment speed ω, alternatively, a measured actual value can be used or the resulting desired adjustment speed ω * can be used. The intrinsic moment ME is essentially caused by the weight force of the components of the loop lifter 3 acting on the adjusting unit 14. The intrinsic moment ME may alternatively be constant or be a function of the actual position φ of the loop lifter 3.

The construction and operation of the tape tension observer 25 are well known to those skilled in the art. In particular, the Bandzugbeobachter 25 may be constructed as the load observer who in FIG. 3 the patent application "Load control of a hydraulic cylinder unit with load observer" of the applicant, character of the Applicant 200907995, filed with the European Patent Office on 03 July 2009, official file reference 09 164 521, detailed and in conjunction with This figure is described. Further details can therefore be dispensed with.

The control method according to the invention gives very good results. Through the following in conjunction with the FIGS. 6 to 8 described embodiments, the control method is still further improved. The following in conjunction with the FIGS. 6 to 8 Embodiments described are alternatively realized individually or in combination with each other.

According to FIG. 6 In addition to the tension controller 15 and the loop controller 16, a torque controller 26 is present. The torque controller 26 is supplied with the characteristic Z '*, the characteristic torque ME and the adjusting torque MV characteristic of the reference train Z *. The torque controller 26 uses the quantities Z '*, ME, MV supplied to it to determine an additional target displacement speed component ω3 *. The additional target displacement speed component ω3 * also enters the resulting target displacement speed ω * as a summand. The torque controller 26 may be designed in particular as a P-controller or as a PD controller. It causes a stabilization of the behavior of the entire control device 8.

Additionally, according to FIG. 6 a start-up controller 27 may be present. The approach controller 27 is, if it is present, active only in an initial phase. The approach controller 27 is activated as soon as it is detected that the band 2 has been threaded into the roll stand 1 "downstream of the loop lifter 3. The start-up regulator 27 is switched off when the loop lifter roll 4 contacts the band 2. The switch-off can be performed as a function of the difference of the actual tension Z from the desired tension Z * (or the corresponding characteristic values Z '*, Z') .The approach control 27 ensures that the loop lifter 3 is quickly set against the belt 2 from the lowered position (below the rolling line 5) ,

The control device 8 according to the invention can according to FIG. 7 continue to have a position controller 28. The position controller 28 is used in particular when the loop lifter 3 is to be held in a fixed position when threading or unthreading the strip 2 below the rolling line 5. It is active as an alternative to the tension controller 15 and the loop controller 16 (and possibly also the torque controller 26 and / or the approach controller 27). The switchover takes place - preferably in a sliding manner - as a function of a threading and untangling detection. The position controller 28 is preferably constructed as described in detail in Applicant's patent application "Control Device for a Hydraulic Cylinder Unit", Applicant's Mark 200910164 filed with the European Patent Office on Jul. 03, 2009, Official Gazette No. 09 164 543. In individual cases, the resulting additional speed setpoint δv * can continue to be calculated according to FIG. 6 and 7 delayed by a PT1 delay 31.

FIG. 7 further shows that the control device 8 may have an adaptation device 29. The adaptation device 29 is supplied with quantities which are characteristic of the stability of the tension regulator 15. The adaptation device 29 determines, for example, a replacement time constant T for the tape tension observer 25. If this is the case, the adaptation device 29 outputs the equivalent time constant T to the tape tension observer 25. The tape tension observer 25 determines in this case the value Z 'characteristic of the actual pull Z, taking into account the equivalent time constant T.

Alternatively or additionally, the adaptation device 29 can determine a control gain k for the tension controller 15 on the basis of the variables supplied to it and output it to the tension controller 15. The tension controller 15 determines the train compensation signal ZA in this case, taking into account the control gain k transmitted to it.

The characteristic of the stability of the Zugreglers 15 sizes can be determined as needed. For example, the actual position φ of the loop lifter 3 can be used. Regardless of which sizes the adaptation device 29 determines the equivalent time constant T and / or the control gain k, however, the determination is carried out dynamically, ie during operation of the control device 8. The substitute time constant T and the control gain k are thus variables, not parameters.

According to FIG. 8 Furthermore, a feedforward control 30 can be connected in parallel to the tape tension observer 25. As a result of this refinement, the characteristic Z 'characteristic of the actual pull Z can be determined with greater dynamics. In particular, changes in the value Z 'characteristic of the actual pull Z, which arise as a result of changes in the actual position φ of the loop lifter 3, immediately appear in the characteristic value Z', without the tape tension observer 25 having to settle first. The feedforward control 30 is supplied at least the actual position φ of the loop lifter 3 as a variable.

The present invention has many advantages. In particular, the control method according to the invention is fast and stable. Furthermore, a simple retrofitting of existing control devices is given. Furthermore, the control method according to the invention has superior control results. In particular, a change in the actual position φ of the loop lifter 3 has virtually no effect on the actual pull Z. This is particularly important when lowering the loop lifter 3 before the tape 2 is being unthreaded. Furthermore, deviations of the actual pull Z from the set pull Z * are corrected very quickly. Nevertheless, only a very small excitation of natural vibrations occurs. Another advantage of the control method according to the invention is that no measured value for the adjustment speed ω of the loop lifter 3 is required. There are also no slow, creeping transients, but there is a quick settling.

The above description is only for explanation of the present invention. The scope of the present invention, however, is intended to be determined solely by the appended claims.

Claims (11)

1. Control method for adjusting an actual tension (Z) prevailing in a strip (2) clamped between two roll stands (1', 1") to a setpoint tension (Z*) and an actual position (ϕ) of a looper (3) disposed between the two roll stands (1', 1") and placed against the strip (2) to a setpoint position (ϕ*),

   - wherein characteristic values (Z'*, Z') for the setpoint tension (Z*) and for the actual tension (Z) are supplied to a tension controller (15),

   - wherein on the basis of the characteristic values (Z'*, Z') supplied to it the tension controller (15) determines a tension compensation signal (ZA) which includes an integral component (IA),

   - wherein a first additional speed setpoint value (δv1*) for at least one of the two roll stands (1', 1") is determined on the basis of the integral component (IA),

   - the integral component (IA) is subjected to a time delay,

   - wherein a first setpoint adjustment speed component (ω1*) for the looper (3) is determined on the basis of the difference of tension output signal (ZA) and delayed integral component (IA'),

   - wherein the setpoint position (ϕ*) and the actual position (ϕ) are supplied to a loop controller (16) which determines a loop compensation signal (SA) on the basis of the setpoint position (ϕ*) and the actual position (ϕ),

   - wherein a second setpoint adjustment speed component (ω2*) for the looper (3) is determined by delaying the loop compensation signal (SA),

   - wherein a second additional speed setpoint value (δv2*) for at least one of the two roll stands (1', 1") is determined on the basis of the loop compensation signal (SA),

   - wherein the sum (δv*) of first and second additional speed setpoint value (δv1*, δ2v*) is output to a speed controller (12) for at least one of the two roll stands (1', 1"), and

   - wherein a resulting setpoint adjustment speed (ω*) in which the first and the second setpoint adjustment speed component (ω1*, ω2*) are included as summands is output to an adjustment unit (14) by means of which the position of the looper (3) is set.
2. Control method according to claim 1,
   characterised in that
   at the time of determining the additional speed setpoint values (δv1*, δv2*) relative to the setpoint adjustment speed components (ω1*, ω2*) the derivation of the length of the strip (2) clamped between the two roll stands (1', 1") is taken into account after the position (ϕ) of the looper (3).
3. Control method according to claim 1 or 2,
   characterised in that
   in the course of determining the resulting setpoint adjustment speed (ω*) the undelayed integral component (IA) is subtracted from a modified loop compensation signal (SA"), the resulting difference is delayed and the delayed difference added to the tension output signal (ZA), the modified loop compensation signal (SA") being determined by scaling the loop compensation signal (SA) with a value (kL) taking the derivation into account.
4. Control method according to claim 1, 2 or 3,
   characterised in that
   the characteristic value (Z') for the actual tension (Z) is determined indirectly on the basis of measured quantities (MV) by means of a strip tension monitor (25).
5. Control method according to claim 4, characterised in that

   - an equivalent time constant (T) is determined dynamically for the strip tension monitor (25) on the basis of quantities characteristic of the stability of the tension controller (15) and the strip tension monitor (25) determines the characteristic value (Z') for the actual tension (Z) taking the equivalent time constant (T) into account, and/or

   - a control gain (k) for the tension controller (15) is determined dynamically on the basis of the characteristic quantities for the stability of the tension controller (15) and the tension controller (15) determines the tension compensation signal (ZA) taking the control gain (k) into account.
6. Control method according to claim 4 or 5,
   characterised in that
   a feedforward control (30) is connected in parallel with the strip tension monitor (25).
7. Control method according to one of the above claims,
   characterised in that

   - a torque controller (26) is supplied with the characteristic value (Z'*) for the setpoint tension (Z*), a tare-weight torque (ME) effected by the looper (3) and an adjustment torque (MV) effected for the looper (3) by an adjustment device (14) and

   - the torque controller (26) determines an additional adjustment speed setpoint value component (ω3*) which is also included as a summand in the resulting setpoint adjustment speed (ω*).
8. Control method according to claim 7,
   characterised in that
   the torque controller (26) is embodied as a P controller or as a PD controller.
9. Computer program having machine code (10) which can be processed directly by a control device (8) and the processing of which by the control device (8) causes the control device (8) to perform a control method comprising all the steps of a control method according to one of the above claims.
10. Computer program according to claim 9,
    characterised in that
    it is stored in machine-readable form on a data medium (11).
11. Control device,
    characterised in that
    it is embodied in such a way that during operation it performs a control method comprising all the steps of a control method according to one of the claims 1 to 8.

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