Method and control loop for operating a roll stand

Abstract

The invention relates to a method and a control loop for operating a roll stand for rolling a preferably metal rolled material. The method and the control loop are used in particular to set the roll gap of the roll stand to allow the rolled material to reliably run straight through the roll stand. For this purpose, the control signals for actuators (120) for setting the roll gap of the roll stand have a previously determined basic swivel value applied to them. To remove the need for manual correction settings pertaining to the basic swivel values for, or during, a rolling process, which settings were traditionally additionally necessary, the method according to the invention and a control loop according to the invention provide for a continuous swivel value characteristic to be determined when the rolled material (i) is rolled and for this swivel value characteristic (x) to be assessed to determine an actual swivel value for the beginning and / or end of the rolled material in light of the previously generated basic swivel value.

Description

[0001] Method and control circuit for operating a rolling stand

[0002] The invention relates to a method and a control loop for operating a rolling stand for rolling and reducing the thickness of a preferably metallic rolled stock, for example a metal strip or a flat product or sheet. The method and the control loop are used in particular for adjusting the roll gap of the rolling stand to ensure that the rolled stock runs straight through the rolling stand. Furthermore, the invention relates to a rolling stand with such a control loop. The invention can be used in rolling stands for hot rolling or cold rolling of the rolled stock. The rolling stand can be a single stand or a rolling stand in a rolling mill, e.g. a tandem mill. The rolling stand can be, for example, a roughing stand in the rolling mill, a splitting mill stand or a reversing mill stand. Finally, the invention also relates to a rolling stand and various uses for basic pivoting values ​​determined according to the invention.

[0003] Methods and control circuits for adjusting the roll gap between the work rolls of a rolling stand are generally known in the prior art. They serve to achieve straight running, i.e., stable passage of the rolled stock through the rolling stand. They can also be used to adjust the tapered shape, i.e., a wedge-shaped cross-section, of the rolled stock. Deviations from the straight running may result in the rolled stock not reaching a downstream processing unit at the head of the rolling stock. At the end of the rolling stock, the rolled stock may drift sideways, with the end of the rolled stock then touching guides installed in front of the rolling stand, for example, and possibly causing mechanical damage.

[0004] In order to ensure sufficiently stable straight run-out, it is known that the work rolls of the rolling stand, i.e. the roll gap, are pre-adjusted with so-called basic swivel settings before the rolling of the rolled stock. The swivel setting is the differential position between the drive and operator side in the adjustment device of a stand. This differential position may result in a non-constant roll gap height between the drive and operator sides. Such an adjustment is particularly necessary after a roll change or after calibrating the work rolls, because in this case a new, suitable swivel state usually first has to be found. The basic swivel settings are then generally retained during the subsequent rolling process and are traditionally only changed when necessary by an operator or automatic control of the rolling stand.

[0005] Depending on the boundary conditions of the roughing mill or the incoming rolling stock, different basic swivel settings are often provided for its head and its end.

[0006] The patent literature describes various methods that describe the automatic pivoting of work rolls in rolling stands:

[0007] EP 0875303A2 describes the swivel control to a precisely calculated differential rolling force.

[0008] DE 3837101A1 describes the principle of control for a strip position measurement.

[0009] JP 2004237313A describes the control by means of strip position measurement by adapting the swivel state, in particular for the strip end after threading out of the previous stand.

[0010] EP 3202502A1 describes the predictive control based on a strip position measurement for the strip head until it reaches the subsequent stand.

[0011] The known methods for controlling the swivel state based on differential rolling force or strip position measurement significantly improve the situation. These respond to a given measured value by changing the gap setting. However, even a control system with a precisely calculated differential rolling force fails to keep the system and the controls within the typical operating range.

[0012] The same applies to slewing controls with strip position measurement. This can only intervene for the strip head when the first measured value is available, i.e., approximately after passing through half of the inter-stand area. Until then, the strip has been rolled without control based on the basic slewing value by the operator, possibly under suboptimal conditions.

[0013] The same applies to the belt end. Here, a swivel control can intervene as soon as a change in the belt position is detected by the measurement. A change in the belt position occurs, for example, if the base swivel value of the stand was not optimal.

[0014] The invention is based on the object of developing a known method and a known control circuit for operating a rolling stand, in particular for adjusting the roll gap of the rolling stand, as well as a correspondingly known rolling stand and a known use of basic pivot values ​​in such a way that the at least one basic pivot value for adjusting the roll gap is determined in such a way that additional manual settings or corrections of the basic pivot value for a rolling process are no longer necessary.

[0015] This object is achieved with respect to the method by the method claimed in patent claim 1. This method is characterized in that a continuous swivel value curve is determined for the rolling stock i, and that the actual swivel value for the rolling stock head and / or for the rolling stock end is determined by evaluating the continuous swivel value curve, taking into account the basic swivel value for the head and / or for the end of the rolling stock i.

[0016] The term "rolled stock" refers specifically to a metal strip or a metallic flat product. The term "basic tilt value" represents the tilt setting to be made or made on the rolling stand, as defined above in the description of the prior art.

[0017] The term “actual swivel value” means an evaluated swivel value curve for the head and / or for the end of the rolling stock i.

[0018] The claimed inventive method describes an automatic control system in which basic swivel values ​​for the head and / or for the end of the rolling stock are determined as control variables for an actuator for adjusting the roll gap in the rolling stand. Within the scope of this control system, at least one target swivel value is compared with at least one actual swivel value in order to determine any swivel error, i.e., a control deviation. A control device then uses this swivel error to determine the required basic swivel value for adjusting the roll gap. The special feature of the inventive method lies in the determination of said actual swivel value. This actual swivel value is determined according to the invention by the said characterizing method steps.This particular procedure according to the invention for determining the actual swivel value advantageously enables a fully automatic and so precise determination of the basic swivel value that corrective manual intervention by an operator of the rolling stand is no longer necessary.

[0019] The method according to the invention enables the automatic determination of the basic pivot value for the head of the rolled stock, to which the roll stand is set before rolling begins. Alternatively or additionally, the method according to the invention enables the determination of the basic pivot value for the end of the rolled stock, whereby this basic pivot value is then set at the roll stand before the rolled stock leaves at least the current roll stand. Two different basic pivot values ​​can be determined for the head and the end of the rolled stock. Controls of the roll gap of the roll stand for thickness reduction for the head, fillet and end of the rolled stock are carried out independently of the method according to the invention for determining the basic pivot values. The determination and setting of at least one basic pivot value serve exclusively to ensure that the rolled stock travels straight through the roll stand.The setting of the basic swivel value is subordinate to or superimposed on the control of the roll gap of the rolling stand for thickness reduction.

[0020] Therefore, in the context of this description, the term "actuator control signal" refers only to that portion of the overall actuator control signal that concerns ensuring the straight running of the rolled stock using the basic pivot values. The term "actuator control signal" does not refer to any thickness reduction of the rolled stock.

[0021] In the event of significant changes in the operating status of the rolling stand, the basic swivel value can always be reset to predefined values. This is advantageous, for example, during a roll change or when switching to coil box operation.

[0022] According to a first exemplary embodiment of the method according to the invention, the continuous swivel value curve for the rolling stock i, as required for the inventive determination of the actual swivel value, can be determined in three different ways. For the determination according to at least one of these three alternatives, the output signal of a swivel controller is used, whereby this swivel controller can in turn be designed in various ways according to a second exemplary embodiment of the invention. For example, the swivel controller can be based on the differential rolling force and / or on a strip position measurement; in any case, the swivel controller evaluates process variables supplied to it to determine its output signal. A third exemplary embodiment relates to the procedure for evaluating the continuous swivel value curve to determine the actual swivel value.

[0023] The rolling stand may, for example, be a reversing rolling stand; in this case, it is recommended to carry out the method according to the invention not only for a forward rolling direction, but also for a reversing, i.e., backward rolling direction, independently of one another, in order to generate separate basic pivot values ​​not only for the head and / or for the end of the rolling stock, but also for a forward pass and a backward pass of the rolling stock.

[0024] The transition between two different basic swivel value settings should be smooth, particularly ramp-like, to ensure a smooth transition. The basic swivel value for the head of the rolling stock should be maintained at least until the rolling stock has reached, for example, a subsequent rolling stand in a rolling mill. The basic swivel value for the end of the rolling stock should remain active until the rolling stock has threaded out of the current stand.

[0025] The above-mentioned object of the invention is further achieved by a control circuit according to claim 8, a rolling stand according to claim 9, and a use according to claim 10. The advantages of these solutions correspond to the advantages mentioned above with reference to the claimed method.

[0026] Further advantageous embodiments of the method according to the invention, the control circuit and the rolling stand are the subject of the dependent claims.

[0027] The method according to the invention is intended for individual application to a specific rolling stand. When several rolling stands are arranged in a rolling mill, the method according to the invention and the control loop according to the invention are applied independently of one another for individual rolling stands. Using the method according to the invention, the basic pivoting values ​​are initially determined during rolling and for rolling a current rolling stock in a current rolling stand. According to the invention, the basic pivoting values ​​determined in this way can then be used as follows. For example, these basic values ​​can be used to preset a downstream rolling stand in a rolling mill before the same rolling stock passes through this stand. Alternatively, the basic values ​​determined in this way are retained as a preset for the same current rolling stand for rolling a subsequent identical or at least similar rolling stock in the same rolling direction as the current rolling stock.Alternatively, if the rolling stand is a reversing rolling stand, the basic pivot values ​​determined according to the invention can be retained as a preset for the same current rolling stand for re-rolling the current rolling stock in the opposite, i.e., reversing, rolling direction. The term "presetting a rolling stand with a basic pivot value" means that, based on the basic pivot values, a control signal is generated for an actuator for adjusting the roll gap in the rolling stand, and the actuator is controlled with the control signal.

[0028] Seven figures are attached to the description, where

[0029] Figure 1 shows the control circuit according to the invention in a simplified representation;

[0030] Figure 2 shows the control circuit according to the invention in a more detailed representation;

[0031] Figure 3 shows an embodiment of a swivel controller;

[0032] Figure 4 shows the determination of a basic swivel value for the head of the rolling stock according to the invention;

[0033] Figure 5 shows the inventive determination of a basic pivot value for the end of the rolling stock; Figure 6 shows the determination of new basic pivot values ​​for the head and the end of a subsequent rolling stock i+1 based on the pivot value curves x for a currently rolled rolling stock i, when the current rolling stock and the subsequent rolling stock are rolled in the same current rolling stand; and

[0034] Figure 7 shows the determination of new basic swivel values ​​for the head and the end of a subsequent rolling stock i+1 based on the basic swivel values ​​for a currently rolled rolling stock i, if the current rolling stock is rolled in at least one subsequent rolling stand after leaving the current rolling stand.

[0035] The invention is described in detail below with reference to the figures mentioned in the form of exemplary embodiments. In all figures, identical technical elements are designated by identical reference numerals.

[0036] All values, errors, and signals are actually time-dependent signals, i.e., signal waveforms, even if their reference symbols are not explicitly marked as time-dependent (t). Constant values ​​correspond to a temporally constant signal waveform.

[0037] Fig. 1 shows a control circuit 100 according to the invention for operating a rolling stand FJ with two work rolls spanning a roll gap, for rolling a rolling stock i, in particular a metal strip. The control circuit 100 consists of an actuator 120 for adjusting the roll gap and a control device 110 for generating at least one basic swivel value delta sk_i, delta se_i for the head and / or for the tail of the rolling stock i as the basis for a control signal for the actuator 120. The control device 110 determines the basic swivel value delta sk_i, delta se_i according to a received swivel error e_delta sk_i, e_delta se_i such that the swivel error, which corresponds to a control difference, becomes zero as far as possible.The swivel error is determined by a comparator 160, which is also part of the control circuit 100, as the difference between a predetermined target swivel value delta sk_w, delta se_w for the head and / or for the end of the rolling stock i and an actual swivel value delta sk'_i, delta se'_i for the rolling stock head and / or for the rolling stock end.

[0038] Furthermore, the control loop 100 includes an evaluation device 140 for determining the actual pivot value. The evaluation device 140 determines the actual pivot value delta sk'_i, delta se'_i for the rolling stock head and / or for the rolling stock end by evaluating a received continuous pivot value curve x, taking into account the basic pivot value delta sk_i, delta se_i for the head and / or for the end of the rolling stock i.

[0039] Fig. 2 shows various variants for determining or selecting the continuous slewing curve. Specifically, various representative signals can be seen, each of which can be selected as the continuous slewing value curve x. For example, the following can be selected as the representative signal or as the continuous slewing value curve:

[0040] - the time course of the control signal delta s_i(t) for the actuator 120; or

[0041] - the continuously measured output signal delta sr_i(t) of the actuator 120; or

[0042] - the continuous course delta sgj (t) of the roll gap geometry in the rolling stand FJ for the rolling stock i.

[0043] To evaluate the selected continuous swivel value curve x, the evaluation device 140 carries out, for example, the following sub-steps:

[0044] - Forming the mean value of the continuous swivel value curve (x) over a defined period of time or over a rolled defined length section of the rolling stock i, wherein the period of time or the length section relates, for example, to the head, the fillet area or the end of the rolling stock i;

[0045] - Forming the difference between the basic swivel value delta sk_i, delta se_i for the head and / or for the end of the rolling stock i and / or for the fillet area of ​​the rolling stock i and the mean value; and

[0046] - Weighting the difference with a predetermined factor. The weighted difference then corresponds to the actual tilt value delta sk , delta se'_i to be generated.

[0047] When carrying out the first sub-step according to the first mirror line, the following variants must be distinguished:

[0048] In the event that a subsequent stand FJ+1 is arranged downstream of the rolling stand FJ in the rolling direction, the time required by the rolling stock i from piercing in the considered rolling stand FJ to piercing in the subsequent stand FJ+1 can be chosen as the period for calculating the mean value.

[0049] Alternatively or additionally, in the event that a previous roll stand FJ-1 is arranged upstream of the roll stand FJ in the rolling direction, the time required by the rolling stock i from leaving the previous roll stand FJ-1 to leaving the roll stand FJ in question can be selected as the period for calculating the mean value.

[0050] Fig. 2 further illustrates that the control signal delta sj(t) for the actuator 120 can be formed by means of an adder 170 as the sum of the basic swivel value delta skj, delta sej for the rolling stock head and / or for the rolling stock end and a time-continuous total output signal delta scj(t) of a swivel controller 150.

[0051] Figure 3 illustrates an embodiment of the tilt controller 150. It is generally known in the prior art. It consists of one or more partial tilt controllers 150-1 ... N, whose output signals can optionally be added to the continuous-time total output signal delta scj(t). The partial tilt controllers can, for example, be

[0052] - a swivel controller based on a differential force curve delta F(t), determined as the difference between the curve of the setting force on the operating side and the curve of the setting force on the drive side of the rolling stand;

[0053] - a tilt controller based on the center position of the rolling stock delta x(t); and / or

[0054] - a swivel controller based on other process variables delta nn(t).

[0055] Furthermore, the swivel controller 150 can optionally also take into account operator interventions of a rolling stand operator when determining the overall output signal delta scj(t). The following Figures 4 to 7 illustrate the inventive generation of the basic swivel values ​​and the advantageous effects of their application in various applications.

[0056] Figure 4 is divided into an upper and a lower half. The upper half shows rolling of the rolled stock without the inventive adjustment of the basic pivot value. The lower half, in contrast, illustrates the positive effects on preventing lateral wandering of the rolled stock when using the inventive basic pivot value. In each of the two halves, two rolling stands of a rolling train FJ+1 are shown, arranged one behind the other in the rolling direction, each symbolized by two thicker, vertically aligned rolls. The rolling direction is indicated by the black arrow pointing to the right. As an example, a support roller or roller table is arranged between the rolling stands, symbolized by a slimmer roller. This arrangement of the rolling stands is shown three times next to one another in the horizontal direction, with each representation showing a different time t1, t2, t3 during the rolling of a rolling stock i that is currently to be rolled.In the first illustration, the rolling stock i is just entering the first rolling stand FJ. In the second illustration t2, the rolling stock i has passed the first rolling stand FJ and is supported on the support roller or roller table before reaching the subsequent rolling stand. In doing so, it shears upwards, i.e., to the left in the rolling direction. The third illustration t3 shows the further path of the shearing rolling stock i. It can be seen that, due to its lateral path, the rolling stock no longer hits the subsequent rolling stand FJ+1 centrally, but offset to the side. This is undesirable.

[0057] Below the three aforementioned representations of the rolling stands, the corresponding curve of the control signal for the actuator of the roll gap of the first rolling stand FJ is shown, insofar as the control signal concerns a correction of the straight-line running of the rolled stock. As long as the rolling stock i has not yet passed the two rolling stands FJ and FJ+1, there is initially no reason to significantly change the control signal delta sj(t) for the rolling stands or to apply a basic swivel value. However, as soon as the lateral deviation of the head of the rolling stock i after passing the first rolling stand FJ is detected in the second representation t2, an attempt is made to counteract this by a corresponding change in the control signal delta s_i(t), represented by the dotted curve.The strong change in the control signal shown is essentially brought about by the swivel controller 150, which detects the lateral deviation of the head of the rolling stock, as shown in the second representation t2. The swivel controller 150 then changes its overall output signal, which automatically leads to a corresponding change in the control signal delta s_i(t) for the actuator 120. As a consequence, the lateral deviation of the rolling stock i weakens somewhat, as shown in the third representation t3. This decrease in the lateral deviation is also detected and leads to a corresponding reduction in the amplitude of the control signal. Despite the very strong change in the control signal shown, it is often not possible to correct the lateral deviation of the head of the rolling stock sufficiently for the head to enter the center of the subsequent rolling stand FJ+1; i.e., stable straight-line travel of the rolling stock i is not yet ensured.

[0058] This is where the present invention comes in, in particular with the method according to the invention. As shown by way of example in the lower half of Figure 4, the time profile of the actuating signal delta s_i(t) for the actuator 120 is used here as an example to represent a continuous swivel value profile x and is used as a control variable for regulating the settings of the roll gap of a rolling stand with a view to ensuring that the rolled stock travels straight through the rolling stand. For this purpose, the method according to the invention provides that the actuating signal, i.e. the continuous swivel value profile x, is first evaluated taking into account the basic swivel value delta sk_i, delta sej for the head of the rolling stock i. The evaluation takes place in the evaluation device 140 in the manner as explained in detail above in the description of Figure 1.

[0059] The result of the evaluation is an actual swivel value delta sk'_i for the head of the rolling stock. Within the scope of the method and the control according to the invention, this actual swivel value is compared with a predetermined target swivel value for the head of the rolling stock, which is zero by default, using the comparator 160 in order to determine any control deviation in the form of the swivel error e_delta skj for the head of the rolling stock. This swivel error is input as an input signal to the controller 110 to determine the basic swivel value delta skj for a subsequent rolling pass, either in the subsequent rolling stand FJ+1 or - in the case of a reversing rolling stand - in the same rolling stand FJ.

[0060] The lower half of Figure 4 illustrates the advantageous effects when the basic swivel value previously determined according to the invention for the rolling stock i is now used for the presetting of the rolling stands for rolling a subsequent rolling stock i+1. The control signal for the rolling stands FJ and FJ+1 are already subjected to the basic swivel value delta skj+1 previously determined according to the invention for the rolling stock i+1 before rolling begins. This basic swivel value is constant here, for example, and is preferably maintained as long as the rolling stock i+1 passes through the two rolling stands. The positive effect of this presetting is evident at the second time t2' shown in the second illustration, where it can be seen that the lateral deviation of the head of the rolling stock i+1 is significantly less than the lateral deviation of the rolling stock i in the upper figure at time t2.Nevertheless, even this minor lateral deflection is detected, for example, by the swivel controller 150 and leads to a further correction of the control signal delta sj+1 (t), as shown by the dotted curve in the lower illustration of Figure 4. Advantageously, due to the preventive application of the basic swivel value determined according to the invention to the control signal delta sj+1 from t1', only a relatively small change or correction of the control signal is required from the second time t2', as shown by the dotted line in Figure 4. This is significantly more advantageous for process stability than the very strong change in the signal curve, as was still necessary in the upper time diagram of Figure 4.The control signal now driven according to the invention, consisting of the said portion of the basic swivel value and the said smaller correction according to the dash-dotted line, causes overall a significant reduction in the lateral movement of the head of the rolling stock i+1 between the rolling stands FJ and FJ+1, as shown in the third representation t3' in the lower half of Figure 4.

[0061] The temporal profiles of the actuating signal in the upper and lower halves of Figure 4 each apply only to the rolling stand FJ, but for different rolling stock i and i+1. For the subsequent rolling stand FJ+1, the method according to the invention is carried out separately again, and the basic pivoting values ​​during rolling of the rolling stock i on the rolling stand FJ+1 are recalculated for the rolling stock i+1 to be subsequently rolled on the rolling stand FJ+1. Accordingly, the actuating signal for the actuator of the subsequent rolling stand FJ+1 is also recalculated, and the actuator 120 or the roll gap for rolling the rolling stock i+1 is accordingly re-adjusted.

[0062] The description of Figure 5 applies analogously to Figure 4, but with the essential difference that it illustrates the method according to the invention for determining the basic pivot values ​​not for the head of the rolling stock, but for its end. The lateral deviation of the end of the rolling stock i is not detected here at time t2 before the rolling stand FJ, but only when the rolling stock i has already passed the rolling stand FJ and has also already been partially rolled in the subsequent rolling stand FJ+1. This detection is also carried out here, for example, by the pivot controller 150 and leads to the necessary significant change in the control signal delta sJ(t)FJ+1 for the subsequent rolling stand FJ+1, shown in the upper half of Figure 5. After the rolling stock i has passed the subsequent rolling stand FJ+1, the control signal drops abruptly to zero again after its previous significant change.

[0063] In this exemplary embodiment, too, the course of the actuating signal delta sj(t) is evaluated by the evaluation device 140 to determine the actual swivel value delta se J. The actual swivel value is compared with a predetermined target swivel value for the end of the rolling stock i using the comparator 160. Any swivel error e_delta sej that may result from this is converted into a basic swivel value delta sej+1 for the end of the rolling stock i+1 using the controller 110. This basic swivel value determined in this way is also preventively applied to the actuating signal for the actuator 120 of the rolling stand FJ+1 as soon as the rolling stock i+1 has passed the first rolling stand FJ. Here, too, this basic swivel value remains constant over time, preferably maintained at least until the rolling stock i+1 has passed the rolling stand FJ+1 at time t3'.As can be seen in the lower temporal course of the control signal, the control signal can, in addition to the temporally constant basic swivel value, also contain temporary deviations, as shown by the dotted course of the control signal, if even smaller lateral breakouts of the end of the rolling stock i+1 are detected when passing through the rolling stands FJ and FJ+1.

[0064] Figure 6 illustrates the change in the curve of the control signal, significantly influenced by a change in the basic swivel values ​​when the rolling stock i passes through the rolling stand FJ. The change in the signal curve of the control signal results from the fact that the basic swivel values ​​for the head and the end of the rolling stock are different. The signal component of the control signal shown with a black solid line represents the change in the time profiles of the basic swivel values ​​for the head of the rolling stock delta skj and for the end of the rolling stock delta sej. The actual curve of the control signal delta sj(t) for the actuator 120 of the rolling stand FJ is shown by the dotted curve and can temporarily deviate from the superimposed basic swivel values. This deviation results, as already described above, from any lateral movement of the rolling stock i that may have been detected in the meantime as it passed through the stand FJ.It can be seen that the selected basic swivel value for the control signal for the rolling stock i for its head is first switched on before the roll stand FJ starts and then switched off again later, even before the rolling stock i has completely passed the roll stand FJ. Before the end of the rolling stock i enters the roll stand FJ, the previously determined basic swivel value detla sej for the end of the rolling stock i is already switched on to the control signal, which has the effect that after the basic swivel value component delta sk_i for the roll head is switched off at time t4, the control signal is not reduced to zero, but is greater than zero, as shown in the upper illustration of Figure 6; see the signal level for the control signal delta sej.

[0065] According to the method according to the invention, this signal curve is used to determine new basic pivot values ​​for the head and for the end of the rolling stock i+1 to be subsequently rolled. This is done separately for the head and the end of the rolling stock using the evaluation device 140, the comparator 160, and the control device 110. Applying the method according to the invention results in new basic pivot values ​​delta sk_i+1 and delta se_i+1 for the rolling stock i+1 to be subsequently rolled. These new basic pivot values, in turn, form the basis for the control signal delta s_i+1 (t) for controlling the actuator 120 for the rolling stand F_j when it is rolling the subsequent rolling stock i+1 (see the lower half of Figure 6).Analogous to the explanation of the signal curve in the upper figure of Figure 6, the control signal delta s_i+1 (t) is also essentially generated by a time-shifted superposition of the swivel values ​​for the head and the end of the rolling stock i+1.

[0066] The use of ramps results in smooth switching between the basic swivel values ​​for the head and tail of the rolling stock, which is beneficial for process stability. As mentioned, to determine the basic swivel values ​​for the head and tail of the rolling stock, the corresponding curves of the control signals delta s_i(t) are evaluated. A reasonable limitation of the time signals could be the first 5 m of the rolled stock for the head of the rolling stock and the last 5 m of the rolled stock for the tail of the rolling stock.

[0067] The description for Figure 6 applies analogously to Figure 7. In contrast to Figure 6, Figure 7 illustrates the course of the control signal delta s_i(t) for the current rolling stand FJ in the case where the rolling stock i has already passed a previous rolling stand FJ-1 before passing the rolling stand FJ and subsequently passes a subsequent stand FJ+1.

[0068] 100 control loop

[0069] 110 basic controller swivel value 120 actuator

[0070] 140 Assessment Facility

[0071] 150 swivel controllers

[0072] 160 comparators

[0073] 170 Adder delta sk_w: Target swivel value at the belt head (zero by default) delta se_w: Target swivel value at the belt end (zero by default) e_delta sk_i: Swivel error at the belt head for belt i e_delta sej: Swivel error at the belt end for belt i delta skj: Basic swivel value at the belt head for belt i delta se_i: Basic swivel value at the belt end for belt i Process variables: Multi-dimensional signal with all existing process variables delta sc_i(t): Continuous total output signal as a sum signal from all swivel controllers for belt i including operator interventions delta s_i(t): Time course of the control signal for the actuator as

[0074] Representative signal for the continuous swivel value curve for band i delta sr_i(t): continuously measured output signal of the actuator as a representative signal for the continuous swivel value curve for band i

[0075] Disturbances: Multidimensional signal of measurable and non-measurable disturbances of the rolling process delta sg_i(t): Time course of the roll gap geometry for strip i as a representative signal for the continuous swivel value course for strip i delta sk'_i: Evaluated swivel value course at the strip head for strip i (=actual swivel value for the head of the rolling stock i) delta se'_i: Evaluated swivel value course at the strip end for strip i

[0076] (= actual swivel value for the end of the rolling stock i) delta F(t): continuous differential rolling force curve delta x(t): continuous strip position curve delta nn(t): continuous measurement curve of other process variables (e.g.

[0077] Forces of the inlet guides, axial forces of the work rolls...) delta s_F(t): continuous swivel value curve of the

[0078] Differential rolling force controller delta s_x(t): continuous swivel value curve of the strip position controller delta s_nn(t): continuous swivel value curve of other controllers delta s_Bed(t): continuous swivel value curve through operator intervention delta sk_i-1 : basic swivel value at the strip head for strip i-1 delta se_i-1 : basic swivel value at the strip end for strip i-1

[0079] F_j-1 previous rolling stand

[0080] Rolling stand

[0081] FJ+1 following rolling stand (=follow-up stand) i-1 previously rolled rolling stock i currently rolled rolling stock i+1 subsequently rolled rolling stock x continuous swing value curve for strip i t1, t2, t3, t4 different times during rolling of the rolling stock t1', t2', t3', t4' different times during rolling of the rolling stock

Claims

Patent claims: 1 . A method for operating a rolling stand (FJ) for rolling a rolling stock i, in particular a metal strip, wherein the rolling stand (FJ) is assigned a control circuit (100) with an actuator (120) for adjusting the roll gap of the rolling stand and with a control device (110) for generating a basic pivot value for controlling the actuator, and wherein the method comprises the following steps: - Specifying a target swivel value (delta sk_w) for the head of the rolling stock i and / or a target swivel value (delta se_w) for the end of the rolling stock i; - comparing the target swivel value (delta sk_w, delta se_w) for the head and / or for the end of the rolling stock i with an actual swivel value (delta sk , delta se ) for the rolling stock head and / or for the rolling stock end in order to determine a swivel error (e_delta sk , e_delta se ) for the rolling stock head and / or for the rolling stock end; - generating the basic swivel value (delta skj, delta sej) for the head and / or for the end of the rolling stock i with the aid of the control device (110) in response to the swivel error such that the swivel error becomes zero as far as possible; characterized in that a continuous swivel value curve (x) is determined during the rolling of the rolling stock i; that the actual swivel value (delta sk , delta se ) for the rolling stock head and / or for the rolling stock end is determined in each case by evaluating the continuous swivel value curve (x) taking into account the basic swivel value (delta skj, delta sej) for the head and / or for the end of the rolling stock i.

2. Method according to claim 1, characterized in that one of the following signals is selected and determined as a representative signal for the continuous swivel value curve (x): - the time course of a control signal (delta s_i(t)) for the actuator 120, formed with the aid of an adder (170) as the sum of the basic swivel value (delta sk_i, delta se_i) for the rolling stock head and / or for the rolling stock end and a time-continuous total output signal (delta sc_i(t)) of a swivel controller (150); or - the continuously measured output signal (delta sr_i(t)) of the actuator (120); or - the continuous course (delta sg_i(t)) of the roll gap geometry in the rolling stand (F_j) for the rolling stock i.

3. Method according to claim 2, characterized in that the at least one swivel controller (150) is - a swivel controller based on a differential force curve, determined as the difference between the curve of the setting force on the operating side and the curve of the setting force on the drive side of the rolling stand; - a swivel controller based on the center position of the rolling stock as it passes through; and / or - a swivel controller based on other process variables.

4. Method according to one of the preceding claims, characterized in that the evaluation of the continuous swivel value curve (x) comprises the following sub-steps: - Forming the mean value of the continuous swing value curve (x) over a defined period of time or over a rolled defined length section of the rolling stock i, wherein the period of time or the length section includes, for example, the head, the fillet area or the end of the rolling stock i concerns; - Forming the difference between the basic swivel value (delta sk_i, delta se_i) for the head and / or for the tail of the rolling stock i and / or for the fillet area of the rolling stock i and the mean value; and - Weighting the difference with a predetermined factor to generate the actual swivel value (delta sk , delta se'_i).

5. Method according to claim 4, characterized in that for determining the actual pivot value at the rolling stock head - in the event that a subsequent stand (FJ+1) is arranged downstream of the rolling stand (FJ) in the rolling direction - the time required by the rolling stock i from piercing in the considered rolling stand (FJ) to piercing in the subsequent stand (FJ+1) is selected as the period for forming the mean value; and / or that for determining the actual pivot value at the rolling stock end - in the event that a previous rolling stand (FJ-1) is arranged upstream of the rolling stand (FJ) in the rolling direction - the time required by the rolling stock i from leaving the previous rolling stand (FJ-1) to leaving the considered rolling stand (FJ) is selected as the period for forming the mean value.

6. Method according to one of the preceding claims, characterized in that the rolling stand (FJ) is a reversing rolling stand; and in that the method is carried out independently of one another for a forward rolling direction and a reversing rolling direction to generate separate basic pivot values (delta skj, delta sej) not only for the head and / or for the end of the rolling stock i, but also for a forward pass and a reverse pass of the rolling stock (i).

7. Method according to one of the preceding claims, characterized in that that a change in the setting of the basic swivel value in the rolling stand from a previous value to a new value occurs continuously, in particular in a ramp-like manner, during ongoing rolling operation.

8. A control circuit (100) for operating a rolling stand (FJ) with two work rolls spanning a roll gap, for rolling a rolled stock i, in particular a metal strip, comprising: an actuator (120) for adjusting the roll gap in the rolling stand (FJ) for rolling a rolled stock i; a comparator (160) for determining a swivel error (e_delta skj, e_delta se_i) as the difference between a desired and an actual swivel value, respectively for the head and / or for the end of the rolled stock i; a control device (110) for generating a basic swivel value for the head and / or for the end of the rolling stock i as a basis for a control signal for the actuator (120) in accordance with a swivel error, characterized in that the control circuit (100) has an evaluation device (140) for determining the actual swivel value for the rolling stock head and / or for the rolling stock end;and that the control circuit with the evaluation device is designed to carry out the method according to one of the preceding claims.; 9. Roll stand with two work rolls spanning a roll gap for rolling a rolling stock i, in particular a metal strip, characterized by an associated control circuit (100) according to claim 8.

10. Use of the basic swivel value (delta sk , delta se ) generated by the method according to one of claims 1 to 7 on the rolling stand (FJ) for the head and / or for the end of the rolling stock i for generating a control signal (delta sj(t)) for the following applications: - for controlling an actuator of a rolling stand (FJ) in a Rolling mill downstream stand (FJ+1) for rolling the same rolling stock i after passing through the rolling stand (F_j), or - for controlling the actuator (120) of the rolling stand (F_j) for rolling the rolling stock i or a subsequent rolling stock i+1 in the same rolling direction as the rolling stock i, or — if the rolling stand is a reversing rolling stand - for controlling the actuator (120) of the rolling stand (FJ) for re-rolling the rolling stock i in the opposite rolling direction.

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