Model-predictive setting of the thermal crowning of a roll of a rolling stand

Abstract

A control device (3) of a rolling line for rolling a flat rolling material (2) made of metal receives a temporal profile of rolling-material data (D) for a rolling time period (T1) during which the rolling material (2) should be rolled in a rolling stand (1). Furthermore, a temporal profile of rolling-stand data (D') of the rolling stand (1) is known to the control device for the rolling time period (T1), and initial data (D") of the rolling stand (1) is known to the control device for the start of a determination time period (T2) which comprises at least the rolling time period (T1). The rolling-material data (D) of a particular time (ti) of the rolling time period (T1) describes the state of a particular portion (14i) of the rolling material (2) that should be rolled in the rolling stand (1) at the particular time (ti), immediately before the rolling. The rolling-stand data (D') of a particular time (ti) of the rolling time period (T1) describes the state of the rolling stand (1) with which the rolling stand (1) should be operated at the particular time (ti). The initial data (D") describes a state of rolls (6) of the rolling stand (1) at the start of the determination time period (T2). Before the determination time period (T2), the control device (3) uses the temporal profile of the rolling-material data (D'), the rolling-stand data (D') and the initial data (D") for the determination time period (T2) to determine a temporal profile of cooling control (x9). The cooling control (x9) is the control of a cooling device (9) by means of which the rolls (6) are cooled location-dependently with respect to location over a barrel length of the rolls (6). To determine the temporal profile of the cooling control (x9), the control device (3) sets up and solves an optimization problem. The optimization problem involves the rolling-material data (D) and the rolling-stand data (D') of the rolling time period (T1) and the initial data (D") of the rolling stand (1) as input variables and the cooling control (x9) during the determination time period (T2) as a variable to be determined. The control device (3) determines the temporal profile of the cooling control (x9) such that a predefined optimization objective is achieved as best as possible. During the determination time period (T2), the control device (3) controls the cooling device (9) according to the determined cooling control (x9).

Description

[0001] Description

[0002] Title of the invention

[0003] Model-predictive adjustment of the thermal crowning of a roll of a rolling stand

[0004] field of technology

[0005] The present invention is based on a control method for a rolling mill with at least one rolling stand for rolling a flat rolled metal product,

[0006] - wherein a control device of the rolling mill receives a time profile of rolling stock data for a rolling period during which the rolling stock is to be rolled in the rolling stand, and the control device receives a time profile of rolling stand data of the rolling stand for the rolling period and initial data of the rolling stand for the beginning of a determination period comprising at least the rolling period,

[0007] - wherein the rolling stock data of a respective point in time of the rolling period describe the condition of a respective section of the rolling stock to be rolled in the rolling stand at the respective point in time, immediately before rolling in the rolling stand,

[0008] - where the rolling stand data of a particular point in time during the rolling period describe the state of the rolling stand with which the rolling stand is to be operated at that particular point in time,

[0009] - where the initial data describe a condition of rolls of the rolling mill at the beginning of the investigation period.

[0010] The present invention further relates to a control program for a control device for controlling a rolling mill having at least one rolling stand for rolling a flat rolled metal stock, wherein the control program comprises machine code which can be directly processed by the control device, wherein the processing of the machine code by the control device causes the control device to carry out such a control method.

[0011] The present invention further relates to a control device for controlling a rolling mill having at least one rolling stand for rolling a flat rolled metal stock, wherein the control device is programmed with such a control program, so that the control device executes such a control method during operation.

[0012] The present invention further relates to a rolling mill with at least one rolling stand for rolling a flat rolled metal product,

[0013] - wherein the rolling stand has a cooling device by means of which rolls of the rolling stand are cooled over the barrel length of the rolls, - wherein the rolling mill has a control device,

[0014] - wherein the control device is programmed with such a control program, so that the control device executes such a control method during operation.

[0015] State of the art

[0016] DE 29 11 621 A1 discloses determining a tensile stress distribution in a flat rolled stock on the exit side of a rolling stand and (among other things) controlling local cooling devices to ensure uniform tensile stress distribution. A similar disclosure can be found in EP 0 063 605 A1.

[0017] From US 2006 / 0 156 778 A1 it is known to provide cooling devices in a rolling stand which are controlled individually and in a controlled manner in order to regulate profile or flatness.

[0018] From KR 2016 0 142 956 A it is known to adjust a roll cooling system in such a way that a reduction in the diameter of the rolls of a rolling stand is compensated by adjusting the cooling of the rolls of the rolling stand.

[0019] EP3691806 B1 describes a method for determining control variables for flatness actuators. Possible flatness actuators include a backbending device, by means of which backbending forces can be exerted on the work rolls, or the work rolls can be axially displaced, or a cooling device for local cooling of the work rolls. A measuring device is arranged downstream of the rolling stand, which records flatness measurements, which are fed to the control device as initial flatness values. An optimizer is implemented in the control device, which determines a set of flatness values ​​and considers linear constraints when determining the current correction variables. The control device then determines the control variables for the flatness actuators from the current correction variables.

[0020] Summary of the invention

[0021] The contour, i.e. the thickness distribution across the width of the rolled stock, is an important quality feature of flat rolled stock such as heavy plate and especially strip. The contour is influenced by many factors in the rolling process, for example roll deflection, which occurs due to the rolling force acting on the rolled stock. Other factors include roll flattening, roll grinding, and roll crown caused by temperature and wear. The latter is commonly referred to as TWO (temperature-wear-crown) in technical circles. It is known that the contour can be influenced by a number of control elements. Examples of such control elements are roll bending or - with appropriately ground rolls - the opposing axial displacement of the rolls and also a so-called pair crossing. The resulting influence on the contour is generally close to a quadratic function.

[0022] Roll stands also typically feature a cooling system for cooling the rolls, by means of which a cooling medium is applied to the rolls of the roll stand. In many cases, the coolant will be water, or at least contain water as its main component. In the latter case, it may be a water-oil mixture, for example. However, other cooling media are also possible, such as dual-fluid cooling, in which water is atomized in air. The cooling system usually acts at least on the work rolls.

[0023] In simple designs, the extent of cooling is not regulated; the cooling device is simply switched on. Other designs have segmented cooling devices. In this case, the cooling device comprises, for example, several active devices, each controlled by its own valve and acting on a specific section of the rollers along the length of the rollers. Alternatively, the cooling device can comprise several active devices, each acting along the entire length of the rollers, but with a different functional cooling pattern across the length of the rollers.For example, there may be three cooling beams, with one of the cooling beams providing essentially uniform cooling across the barrel length, another cooling beam providing center-biased cooling across the barrel length, and another cooling beam providing edge-biased cooling. If B denotes the barrel length of the rolls and x denotes the location in the axial direction of the rolls, where x = 0 denotes a location in the center of the roll barrel, and a factor C has the value 2TT / B, then, for example, center-biased cooling can occur according to the functional relationship 1 + cos Cx, and edge-biased cooling can occur according to the functional relationship 1 - cos 2Cx.For example, a cooling system with active devices in which one of the cooling beams provides essentially uniform cooling along the bale length, another cooling beam provides center-emphasized cooling along the bale length, and another cooling beam provides edge-emphasized cooling, is offered by the applicant under the name Dynamic Work Roll Cooling. These cooling beams are commonly referred to as basic cooling, add1, and add2.

[0024] It is known in the prior art to read setpoints for controlling the cooling system from tables based on the rolling stock to be rolled and to specify them depending on whether or not rolling stock is currently being rolled in the rolling stand. It is also known to specify the setpoints manually via an operator interface. Furthermore, it is known to determine and update the setpoints as part of a control system for the flatness of the rolled stock.

[0025] The object of the present invention is to create possibilities by means of which the roll gap profile and thus the contour and / or the flatness of the rolled stock can be influenced as positively as possible after rolling in the rolling mill.

[0026] The object is achieved by a control method having the features of claim 1. Advantageous embodiments of the control method are the subject of dependent claims 2 to 10.

[0027] According to the invention, a control method of the type mentioned at the outset is designed in that

[0028] - that the control device determines a temporal progression of a cooling control before the start of the determination period by utilising the temporal progression of the rolling stock data, the rolling stand data and the initial data for the determination period,

[0029] - that the cooling control is the control of a cooling device by means of which the rollers are cooled over a barrel length of the rollers,

[0030] - that the control device sets and solves an optimization problem to determine the time course of the cooling control,

[0031] - that the rolling stock data and the rolling stand data of the rolling period and the initial data of the rolling stand are included as input variables in the optimization problem and the cooling control during the determination period is included as a variable to be determined,

[0032] - wherein the control device determines the time course of the cooling control in such a way that a predetermined optimization target is achieved as well as possible and

[0033] - wherein the control device controls the cooling device during the determination period in accordance with the determined cooling control.

[0034] By setting and solving an optimization problem within which the entire investigation period is considered, the effects of control interventions on future conditions can also be taken into account.

[0035] Preferably, the control device determines wear occurring on the rolls of the rolling stand as part of the optimization problem and takes this wear into account when determining the cooling control. This yields even better results.

[0036] In many cases, the rolling stand includes an actuator that acts on the chocks of the rolls of the rolling stand and whose control allows the roll gap profile of the rolling stand to be adjusted across the entire barrel width. In this case, it is possible for the rolling stand data to include an actuator control for the actuator. Possible actuators are roll bending, axial roll displacement, and a so-called pair crossing. If the aforementioned actuator is present, it is alternatively possible to

[0037] - that the control device determines not only a time profile of the cooling control but also a time profile of an actuator control before rolling the rolling stock in the rolling stand for the determination period,

[0038] - that the actuator control is the control of such an actuator,

[0039] - that the control device sets and solves a uniform optimization problem to determine the time course of the cooling control and the actuator control,

[0040] - that in addition to the cooling control, the actuator control during the determination period is also included in the optimization problem as a variable to be determined and

[0041] - that the control device controls the actuator at least during the rolling period based on the determined actuator control.

[0042] In this case, the predetermined optimization goal can, in particular, include maintaining the actuator within a predetermined subrange of its possible adjustment range. This can, in particular, be a middle adjustment range, i.e., an adjustment range that is at a minimum distance from the limits of the possible adjustment range. This ensures sufficient control reserve during subsequent rolling in the rolling stand, allowing for response to unforeseen events and malfunctions. Alternatively, the subrange can be specified by an operator.

[0043] Alternatively or additionally, it is possible for the predetermined optimization objective to include achieving a predetermined target contour and / or a predetermined target flatness of the sections of the rolled stock after rolling in the rolling mill. In this case, the optimization directly influences compliance with specified limits for the contour and / or flatness of the final product.

[0044] Alternatively or additionally, it is possible for the predetermined optimization objective to comprise achieving a predetermined target contour and / or a predetermined target flatness of the sections of the rolling stock after rolling in the rolling stand.

[0045] This criterion is not necessarily identical to the previously mentioned criterion. Identicalness only exists if the roll stand under consideration is the last roll stand in the rolling mill. Otherwise, this criterion can be used to ensure that contour and / or flatness limits are maintained between the roll stand under consideration and the subsequent roll stand, thereby avoiding problems during rolling in the subsequent roll stand. Preferably, the control device considers at least one of the following conditions as boundary conditions when solving the optimization problem:

[0046] - for each effective device of the cooling system, a minimum cooling effect is not undercut and / or a maximum cooling effect is not exceeded,

[0047] - a minimum cooling effect is not undercut and / or a maximum cooling effect is not exceeded across the entire range of effective devices,

[0048] - for each active device, the minimum adjustment speed of the respective active device is not undercut and / or the maximum adjustment speed of the respective active device is not exceeded.

[0049] This allows technological issues to be taken into account, especially when solving the optimization problem.

[0050] The statement that a minimum adjustment speed of the respective active device is not undercut does not imply that the respective active device must be continuously adjusted. The respective active device can therefore also be maintained at a certain setting. However, if a respective active device is adjusted, it will be adjusted at least at the minimum adjustment speed.

[0051] Typically, valves are assigned to the active devices, which are used to adjust the cooling effect. Furthermore, the valves are usually control valves, i.e., valves that can be continuously controlled and adjusted across their control range. However, the valves can also be switching valves, i.e., valves that are only fully open or fully closed.

[0052] Preferably, the minimum cooling effect and / or the maximum cooling effect depend on the rolling temperature of the rolls and / or the rolling temperature of the rolled material. This allows the boundary conditions to be adapted to the specific condition of the rolls in the rolling stand or the specific condition of the rolled material.

[0053] At a minimum, the recording period is identical to the rolling period. Preferably, however, the determination period also includes an additional period preceding the rolling period. This allows, for example, proactively influencing the cooling of the rolls during a rolling break before the rolling of the rolled stock. It is therefore possible to cool the rolls before the rolling of the rolled stock in such a way that the best possible result is achieved.

[0054] In the simplest case, uniform cooling occurs across the entire length of the roller barrel. Preferably, however, the rollers are cooled location-dependently across the entire length of the roller barrel using the cooling system, and the extent of the location-dependent cooling is adjusted using the cooling control.

[0055] After the rolling stock has been rolled in the rolling mill, the profile, contour, and / or flatness of the rolled stock can be recorded using standard measuring devices. Such measured values ​​can be used to adapt the models used by the control system. Corresponding procedures are generally known. If the rolling of rear sections of the rolled stock has not yet been completed when the front sections of the rolled stock reach the measuring devices, correction values ​​for the cooling control and, if applicable, the actuator control can also be determined during rolling and fed to the cooling system or actuator. Due to the inertia of the cooling of the rolls in the rolling stand, the actuator control is generally given priority, if the actuator is present. Furthermore, specifications from the control operator can also be taken into account for both controls during rolling.Such requirements will be given priority.

[0056] The object is further achieved by a control program having the features of claim 12. According to the invention, the processing of the machine code by the control device causes the control device to execute a control method according to the invention.

[0057] The object is further achieved by a control device having the features of claim 13. According to the invention, the control device is programmed with a control program according to the invention, so that the control device executes a control method according to the invention during operation.

[0058] The object is further achieved by a rolling mill having the features of claim 14. According to the invention, in a rolling mill of the type mentioned at the outset, the control device is designed as a control device according to the invention and programmed with a control program according to the invention, so that the control device executes a control method according to the invention during operation.

[0059] The rolling stand preferably has an actuator that acts on chocks of the rolls of the rolling stand and whose control allows a roll gap profile to be adjusted exclusively over the roll barrel length. Alternatively or additionally, the rolling stand preferably has a cooling device by means of which the rolls are cooled location-dependently over the roll barrel length.

[0060] Brief Description of the Drawings The above-described properties, features, and advantages of this invention, as well as the manner in which they are achieved, will become clearer and more readily understood in connection with the following description of an embodiment, which is explained in more detail in conjunction with the drawings.

[0061] FIG 1 a rolling mill,

[0062] FIG 2 a rolled product,

[0063] FIG 3 a rolling stand

[0064] FIG 4 a flow chart,

[0065] FIG 5 a timing diagram and

[0066] FIG 6 a flow chart.

[0067] Description of the embodiments

[0068] According to FIG 1, a rolling mill comprises a number of rolling stands 1. In a minimal configuration, only a single rolling stand 1 is present. As a rule, several rolling stands 1 are present, as shown in FIG 1. In the rolling stands 1 of the rolling mill, a rolled stock 2 is rolled. In the case of several rolling stands 1, the rolled stock 2 usually passes through the rolling stands 1 sequentially one after the other, i.e. not in reverse. The rolled stock 2 is, as shown in FIG 2, a flat rolled stock made of metal, for example a metal strip or a longer or shorter section of a metal strip. The rolled stock 2 has a rolled stock width b. The material of the rolled stock 2 can be, for example, steel or aluminum.

[0069] The rolling mill is controlled by a control device 3. The control device 3 is programmed with a control program 4. The control program 4 includes machine code 5, which can be directly executed by the control device 3. Programming the control device 3 with the control program 4 or executing the machine code 5 by the control device 3 causes the control device 3 to execute a control method, which is explained in more detail below.

[0070] The control method is explained below in connection with a single rolling stand 1 of the rolling mill. This rolling stand can be the frontmost rolling stand 1, the rearmost rolling stand 1, or a middle rolling stand 1 between the frontmost and rearmost rolling stands 1. However, the control method can also be applied to several of the rolling stands 1. Furthermore, the structural design of the rolling stand 1 under consideration is explained below in connection with FIG. 3, insofar as it is relevant here.

[0071] According to FIG 3, the rolling stand 1 has work rolls 6. The rolling stock 2 is rolled between the work rolls 6. The work rolls 6 are mounted in chocks 7. In many cases, the rolling stand 1 has (at least) one actuator 8 that acts on the chocks 7 and, by controlling which, a roll gap profile can be adjusted exclusively across the entire barrel width - i.e., not just locally. According to FIG 3, there are even two such actuators 8a, 8b. One actuator 8a is a bending device by means of which the chocks 7 and, with them, the rolls 6, can be pressed apart. The other actuator 8b is a sliding device by means of which the chocks 7 and, with them, the rolls 6, can be axially displaced in opposite directions to one another. The specific design of such actuators and their effect are generally known to those skilled in the art.Experts are also aware of other actuators 8 which have the properties mentioned, i.e. which influence the roll gap profile over the entire barrel width of the work rolls 6 by acting on the chocks 7.

[0072] The rolling stand 1 further comprises a cooling device 9. The work rolls 6 are cooled by means of the cooling device 9. The cooling device 9 is preferably designed such that the rolls 6 are cooled location-dependently over the barrel length by means of the cooling device 9. In this case, the cooling device 9 comprises a plurality of individually controllable actuating devices 10. For example, an individually controllable valve 11 and / or an individually controllable pump 12 can be arranged upstream of each actuating device 10. The actuating devices 10 generally act on the rolls 6 by applying a liquid cooling medium 13 to the rolls 6. The liquid cooling medium 13 is generally water or at least contains water as its main component. However, other configurations of the actuating devices 10 are also conceivable.

[0073] In the simplest case, only a single knitting device 10 is present. In the case of multiple knitting devices 10, the knitting devices 10 can each act locally on a single section of the rollers 6, viewed along the bale length. However, it is also possible for multiple knitting devices 10 to be present and for the cooling effect of the knitting devices 10 to extend over the entire bale length, but for the functional progression of the cooling effect to be different from one knitting device 10 to the next. One such configuration is, for example, the applicant's aforementioned Dynamic Work Roll Cooling.

[0074] According to FIG 4, the control device 3 carries out the following control procedure:

[0075] In a step S1, the control device 3 receives a temporal profile of rolling stock data D for a rolling period T1. According to FIG. 5, the rolling period T1 is the period in the future during which the rolling stock 2 is to be rolled in the rolling stand 1. The rolling stock data D of a respective point in time t1 (where i = 1, 2, 3 ... n) describe the state of a respective section 14i (where i = 1, 2, 3 ... n) of the rolling stock 2. The respective rolling stock data D relate to the state of the corresponding section 14i immediately before the rolling of the corresponding section 14i in the rolling stand 1. The rolling stock data D can include, for example, the rolling stock width b, the thickness d, the temperature, the material strength, the contour and more of the corresponding section 14i. They can be specified individually for the individual sections 14i or uniformly for all sections 14i.

[0076] In a step S2, roll stand data D' of roll stand 1 is made known to control device 3. Roll stand data D' can, for example, be specified to control device 3 or determined by control device 3 itself. Roll stand data D' at a respective time t1 of rolling period T1 describe the state of roll stand 1 at which roll stand 1 is to be operated at the respective time t1. For example, roll stand data D' can include the setting, the rolling force, the roll gap in the center of roll stand 1, the roll gap profile across the width of roll stand 1, the rolling force, and more. If roll stand 1 includes actuator 8, roll stand data D' can also include an actuator control x8. Actuator control x8 is the control of actuator 8.

[0077] In a step S3, the control device 3 receives information about the initial data D" of the rolling stand 1. The initial data D" relate to the beginning of the determination period T2. They describe a state of rolls 6 of the rolling stand 1 at the beginning of the determination period T2. The initial data D" of the rolling stand 1 can, in particular, comprise the thermal state of the rolls 6 at the beginning of a determination period T2. The initial data D" can, if necessary, also comprise a wear state of the work rolls 6. The determination period T2 comprises at least the rolling period T1. However, according to FIG 5, it can also comprise an additional period T3 preceding the rolling period T1. In this case, the additional period T3 directly adjoins the rolling period T1.

[0078] The length of the additional period T3 can be determined as required, provided that the additional period T3 exists. Often, the length of the additional period T3 corresponds to the period from the end of rolling of the immediately preceding rolled stock to the start of rolling of the rolling stock 2 now under consideration (= rolling break). However, other lengths are also possible, both shorter and longer. In the case of longer lengths, the additional period T3 can, for example, correspond to the rolling break between the end of rolling of the immediately preceding rolled stock and the start of rolling of the rolling stock 2 now under consideration, plus the rolling period required for rolling the immediately preceding rolled stock. The additional period T3 can also include additional rolling breaks and additional rolling periods.

[0079] In a step S4, the control device 3 sets up an optimization problem. The optimization problem uses the rolling stock data D of the rolling stock 2 and the roll stand data D' of the roll stand 1 during the rolling period T1 and the initial data D" of the roll stand 1 at the beginning of the determination period T2 as input variables. The optimization problem also includes the temporal profile of the control of the cooling device 9 as a variable to be determined. The control of the cooling device 9 is referred to below as the cooling control and is provided with the reference symbol x9. The temporal profile of the cooling control x9 is set by the control device 3 for the determination period T2.

[0080] Setting up an optimization problem implies setting up a cost function. Minimizing the cost function is the optimization goal. Depending on the specific situation, various variables can be included in the cost function. Some variables that can be included in the cost function are explained below.

[0081] For example, the cost function for each time point ti can include the deviation of the resulting contour of the corresponding section 14i after rolling in the rolling mill. In this case, the influence of the cooling control x9 on the final product, i.e., the rolled stock 2 after rolling of the rolled stock 2 in all rolling stands 1 of the rolling mill, is considered. The optimization objective in this case is that the sections 14i of the rolled stock 2 have a predetermined target contour after rolling in the rolling mill (if possible).

[0082] Alternatively or additionally, the cost function for the times ti can include the deviation of the resulting contour of the corresponding section 14i after rolling in the rolling stand 1. In this case, the influence of the cooling control x9 on an intermediate product, i.e., the rolling stock 2 immediately after rolling in the rolling stand 1, is considered. The optimization objective in this case is that the sections 14i of the rolling stock 2 have a predetermined target contour after rolling in the rolling stand 1 (if possible).

[0083] In both cases, the flatness of the rolled stock 2 can also be considered alternatively or in addition to the contour.

[0084] The individual criteria are included in the cost function. Typically, they are each included as a summand. The individual summands can be weighted with a respective weighting factor. It is possible for the cost function to contain only a single summand. In this case, the weighting factor can be omitted.

[0085] In step S5, control device 3 solves the optimization problem applied in step S4. It thereby determines the temporal progression of the cooling control x9. The optimization problem in step S5 is solved in such a way that the optimization goal is achieved as effectively as possible. Accordingly, control device 3 determines the temporal progression of the cooling control x9. Corresponding optimizers are known to experts. Purely as an example, reference can be made to the entries "branch and bound" in the German and English Wikipedia, accessed on December 17, 2023. In the case of switching valves, the corresponding optimizer can operate according to the so-called branch-and-bound method.

[0086] The models by means of which the resulting roll gap and the exit-side contour and / or flatness can be determined by taking into account the data D, the roll stand data D', the initial data D" and the cooling control x9 as well as, if necessary, other data and settings of the roll stand 1 (e.g., the roll grind, the inlet-side tension, the outlet-side tension, etc.) are also generally known to those skilled in the art. In particular, models can be used that are usually used in the context of pass schedule calculations for rolling mills. For example, there are also models that not only determine and take into account the so-called thermal crown of the rolls 6, but also additionally determine any wear occurring on the rolls 6 of the roll stand 1. In this case, the optimizer can take the wear into account when determining the cooling control x9.

[0087] With such models, it is readily possible to determine the values ​​included in the cost function depending on the variables to be determined. By considering the relevant boundary and secondary conditions when determining the optimal solution, compliance with the relevant boundary and secondary conditions can also be ensured. Depending on the cost function and the relevant boundary and secondary conditions, the contour and / or flatness at the exit side of roll stand 1 and / or the exit side of the rolling mill can be adapted as closely as possible to the corresponding target values, as required.

[0088] In a step S6, the control device 3 controls the cooling device 9 according to the determined cooling control x9. The cooling device 9 is controlled during the entire determination period T2.

[0089] Due to the fact that in step S6, the cooling device 9 is to be controlled according to the cooling control x9 determined in step S5, steps S1 to S5 must be executed before the start of the determination period T2. In particular, step S5 must also be completed.

[0090] FIG 6 shows a modification of the procedure of FIG 4. FIG 6 comprises steps S11 to S16. In the case of the embodiment according to FIG 6, it is necessary for the rolling stand 1 to comprise the actuator 8. In step S11, the control device 3 receives the time profile of rolling stock data D for the rolling period T1. In step S12, the rolling stand data D' are made known to the control device 3. In step S13, the initial data D" are made known to the control device 3. Steps S11 to S13 correspond to steps S1 to S3 of FIG 4. It is important, however, that the rolling stand data D do not include the actuator control x8.

[0091] In step S14, the control device 3 sets up an optimization problem analogously to step S4. Analogously to step S4, the optimization problem uses the rolling stock data D of the rolling stock 2 and the roll stand data D' of the rolling stock 1 during the rolling period T1 and the initial data D" of the roll stand 1 at the beginning of the determination period T2 as input variables. However, the optimization problem not only includes the temporal profile of the control of the cooling device 9 as a variable to be determined. Rather, the actuator control x8 during the determination period T2 is also included in the optimization problem as a variable to be determined. The optimization problem is thus designed as a unified optimization problem.

[0092] In step S15, the control device 3 solves the uniform optimization problem applied in step S14. The approach of step S15 corresponds to step S5 of FIG. 4. However, in step S15, the control device 3 determines not only the temporal profile of the cooling control x9, but also the temporal profile of the actuator control x8. The optimization problem is solved in step S15 analogously to step S5 in such a way that the optimization goal is achieved as effectively as possible. Accordingly, the control device 3 determines the temporal profile of the cooling control x9 and the temporal profile of the actuator control x8.

[0093] In step S16, the control device 3 controls the cooling device 9 according to the determined cooling control x9. The cooling device 9 is controlled during the entire determination period T2. Furthermore, in step S16, the control device 3 controls the actuator 8 at least during the rolling period T1 based on the determined actuator control x8. The control of the actuator 8 during the additional period T3 may be irrelevant if the rolling stock 2 is not rolled in the rolling stand 1 during the additional period.

[0094] Within the scope of the embodiment of FIG 6, it is possible - alternatively or in addition to the optimization objectives mentioned above in connection with FIG 4 - for the predetermined optimization objective to comprise keeping the actuator 8 within a predetermined sub-range of its possible actuating range, i.e., the actuator control x8 moves within a predetermined sub-range so that a sufficient control reserve remains to compensate for disturbances. Alternatively or additionally, the distance that the actuator 8 has from its minimum and / or maximum actuation, i.e., the distance from the actuating limits of the actuator 8, can be included in the cost function for the times ti. In this case, a corresponding evaluation in the cost function "penalizes" if the actuator control x8 comes close to the respective minimum and / or maximum actuation.Thus, in this case too, the optimization objective includes keeping the actuator 8 in a predetermined (usually middle) sub-range of its possible adjustment range.

[0095] To maintain actuator 8 within a predetermined sub-range of its possible control range, it is also possible to specify corresponding inequality constraints that prevent the control x8 of actuator 8 from falling below a predetermined distance from its minimum and / or maximum control. In this case, too, the optimization objective can include maintaining actuator 8 within a predetermined (usually central) sub-range of its possible control range. The inequality constraints are generally specified as an alternative to, but in exceptional cases also in addition to, taking into account the distance from the control x8 of actuator 8 to its minimum and / or maximum control in the cost function.

[0096] Such inequality constraints are taken into account by the control device 3 when solving the optimization problem. If necessary, other constraints can also be specified in both the embodiment shown in FIG. 4 and the embodiment shown in FIG. 6. Some possible constraints that can be considered when solving the optimization problem are explained below.

[0097] It is possible to specify as a boundary condition for the individual knitting devices 10 that a minimum cooling effect is not undershot. This can, for example, ensure that a minimum cooling of the rollers 6 is always guaranteed. For the same purpose—in some cases additionally, but usually alternatively—it can also be specified for the entire knitting devices 10 that a minimum cooling effect is not undershot.

[0098] It is also possible to specify as a boundary condition for the individual active devices 10 that a maximum cooling effect is not exceeded. This can ensure, for example, that the permissible control limits of the active devices 10 are adhered to. Alternatively or additionally, for the same purpose, it can also be specified that a maximum cooling effect is not exceeded across the active devices 10 as a whole. This allows, for example, in the case of individually controlled valves 11 fed by a common pump 12, a maximum flow rate of the pump 12 to be taken into account.

[0099] It is possible to specify as a boundary condition for the individual active devices 10 that a maximum adjustment speed of the respective active device 10 is not exceeded. This allows the speed with which an active device 10 can respond to a request for a changed cooling effect to be taken into account.

[0100] Finally, it is possible to specify as a boundary condition for the individual active devices 10 that a minimum adjustment speed of the respective active device 10 is not undercut. This may be sensible for energy-saving reasons.

[0101] As far as the minimum and maximum cooling effect is concerned, these can be fixed. However, they can also depend on the rolling temperature of rolls 6 and / or the rolling temperature of the rolled stock 2.

[0102] The precise manner of controlling the actuator 8 and the cooling device 9 is no longer the subject of the present invention. For example, coolant flows can be detected with respect to the cooling device 9 and controlled according to the cooling control x9. This is equally possible with (continuously adjustable) control valves and with pure switching valves (open-closed).

[0103] Due to the fact that the determination period T2 can include the additional period T3 in addition to the rolling period T1, it is possible, both in the embodiment of FIG 4 and in the embodiment of FIG 6, to begin with the thermal adjustment of the roll contour before the rolling stock 2 is rolled. This is particularly advantageous because the thermal adjustment is often very slow. Ideally, the additional period T3 begins at the time at which a rolling stock rolled before the rolling stock 2 under consideration runs out of the relevant roll stand 1. This is because it is from this time onwards that the thermal influencing of the rolls 6 for the rolling stock 2 under consideration can take place. Ideally, the execution of steps S1 to S5 or S11 to S15 is therefore completed shortly before the rolling stock rolled before the rolling stock 2 under consideration runs out of the relevant roll stand 1, so that the execution of step S6 orof step S16. However, the additional period T3 can also begin at a later time. Furthermore, in such a case, the actuator control x8 continues to act on the chocks 7 and thus on the rolls 6. However, during the additional period T3, the rolling stock 2 is not yet being rolled in the rolling stand 1. The actuator control x8 is therefore irrelevant during the additional period.

[0104] The control method according to the invention is repeatedly executed. It is possible to perform the execution at a fixed time interval, for example, every 20 seconds. It is also possible to repeat the control method each time the control device 3 receives the rolling stock data D of a new rolling stock 2 or when a triggering is triggered in another way, for example, by a load change in a rolling stand 1. It is even possible to repeatedly execute the control method according to the invention at a relatively short time interval. In this case, the control device 3 acts as a model-predictive controller.

[0105] It is also possible to carry out the control method alternatively for a single rolling stand 1 or for several of the rolling stands 1 of the rolling mill.

[0106] The present invention has many advantages. In particular, superior control of the rolling stand 1 can be achieved. Although the invention has been illustrated and described in detail using the preferred embodiments, the invention is not limited to the disclosed examples, and other variations may be derived therefrom by those skilled in the art without departing from the scope of the invention.

[0107] List of reference symbols

[0108] 1 rolling stands

[0109] 2 Rolled goods

[0110] 3 Control device

[0111] 4 Control program

[0112] 5 Machine code

[0113] 6 rollers 7 chocks

[0114] 8, 8a, 8b Actuators 9 Cooling device

[0115] 10 active devices

[0116] 11 valves

[0117] 12 pumps

[0118] 13 Cooling medium 14i Sections b Rolled stock width d Thickness

[0119] D Rolled stock data

[0120] D' Roll stand data

[0121] D" Initial data

[0122] S1 to S16 steps

[0123] T1 rolling period

[0124] T2 Investigation period

[0125] T3 additional period ti times x8, x9 controls

Claims

Claims 1 . Control method for a rolling mill with at least one rolling stand (1) for rolling a flat rolled product (2) made of metal, - wherein a control device (3) of the rolling mill receives a time profile of rolling stock data (D) for a rolling period (T1) during which the rolling stock (2) is to be rolled in the rolling stand (1), and the control device (3) receives a time profile of rolling stand data (D') of the rolling stand (1) for the rolling period (T1) and initial data (D") of the rolling stand (1) for the beginning of a determination period (T2) comprising at least the rolling period (T1), - wherein the rolling stock data (D) of a respective time (ti) of the rolling period (T1) describe the state of a respective section (14i) of the rolling stock (2) which is to be rolled in the rolling stand (1) at the respective time (ti), immediately before rolling in the rolling stand (1), - wherein the rolling stand data (D') of a respective time (ti) of the rolling period (T1) describe the state of the rolling stand (1) with which the rolling stand (1) is to be operated at the respective time (ti), - wherein the initial data (D") describe a state of rolls (6) of the rolling stand (1) at the beginning of the determination period (T2), - wherein the control device (3) determines a temporal progression of a cooling control (x9) before the start of the determination period (T2) by utilizing the temporal progression of the rolling stock data (D), the roll stand data (D') and the initial data (D") for the determination period (T2), - wherein the cooling control (x9) is the control of a cooling device (9) by means of which the rollers (6) are cooled over a barrel length of the rollers (6), - wherein the control device (3) sets and solves an optimization problem to determine the time course of the cooling control (x9), - wherein the rolling stock data (D) and the rolling stand data (D') of the rolling stand (1) of the rolling period (T 1 ) and the initial data (D") of the rolling stand (1) are included as input variables in the optimization problem and the cooling control (x9) during the determination period (T2) is included as a variable to be determined, - wherein the control device (3) determines the time course of the cooling control (x9) in such a way that a predetermined optimization target is achieved as well as possible and - wherein the control device (3) controls the cooling device (9) during the determination period (T2) in accordance with the determined cooling control (x9).

2. Control method according to claim 1, characterized in that the control device (3) within the framework of the optimization problem, a on the rollers (6) of the rolling stand (1) is determined and the wear is taken into account when determining the cooling control (x9).

3. Control method according to claim 1 or 2, characterized in that the rolling stand comprises an actuator (8) which acts on chocks (7) of the rolls (6) of the rolling stand (1) and by the control of which a roll gap profile of the rolling stand (1) can be adjusted over the entire barrel width, and in that the rolling stand data (D') comprise an actuator control (x8) for the actuator (8).

4. Control method according to claim 1 or 2, characterized in that - that the control device (3) determines not only a time profile of the cooling control (x9) but also a time profile of an actuator control (x8) for the determination period (T2) before the rolling of the rolling stock (2) in the rolling stand (1), - that the actuator control (x8) is the control of an actuator (8) acting on chocks (7) of the rolls (6) of the rolling stand (1), by the control of which a roll gap profile can be adjusted over the entire barrel width, - that the control device (3) sets and solves a uniform optimization problem for determining the time course of the cooling control (x9) and the actuator control (x8), - that in addition to the cooling control (x9), the actuator control (x8) is also included in the optimization problem as a variable to be determined during the determination period (T2) and - that the control device (3) controls the actuator (8) at least during the rolling period (T1) based on the determined actuator control (x8).

5. Control method according to claim 4, characterized in that the predetermined optimization goal comprises keeping the actuator (8) in a predetermined subrange of its possible adjustment range.

6. Control method according to one of the above claims, characterized in that the predetermined optimization objective comprises achieving a predetermined desired contour and / or a predetermined desired flatness of the sections (14i) of the rolling stock (2) after rolling in the rolling train.

7. Control method according to one of the above claims, characterized in that that the control device (3) takes into account at least one of the following conditions as boundary conditions when solving the optimization problem: - for each active device (10) of the cooling device (9), a minimum cooling effect is not undercut and / or a maximum cooling effect is not exceeded, - over the entirety of the active devices (10), a minimum cooling effect is not undercut and / or a maximum cooling effect is not exceeded, - for each active device (10), a minimum adjustment speed of the respective active device (10) is not undercut and / or a maximum adjustment speed of the respective active device (10) is not exceeded.

8. Control method according to claim 7, characterized in that the minimum cooling effect and / or the maximum cooling effect depend on the rolling temperature of the rolls (6) and / or the rolling temperature of the rolling stock (2).

9. Control method according to one of the above claims, characterized in that the determination period (T2) also includes an additional period (T3) preceding the rolling period (T1).

10. Control method according to one of the above claims, characterized in that the rollers (6) are cooled by means of the cooling device (9) in a location-dependent manner over a barrel length of the rollers (6), and in that the extent of the location-dependent cooling is adjusted by means of the cooling control (x9).

11. Control program for a control device (3) for controlling a rolling train with at least one rolling stand (1) for rolling a flat rolled stock (2) made of metal, wherein the control program comprises machine code (5) which can be processed directly by the control device (3), wherein the processing of the machine code (5) by the control device (3) causes the control device (3) to carry out a control method according to one of the above claims.

12. Control device for controlling a rolling mill with at least one rolling stand (1) for rolling a flat rolled stock (2) made of metal, wherein the control device is programmed with a control program (4) according to claim 12, so that the control device carries out a control method according to one of claims 1 to 10 during operation.

13. Rolling mill with at least one rolling stand (1) for rolling a flat rolled product (2) made of metal, - wherein the rolling stand (1) has a cooling device (9) by means of which rolls (6) of the rolling stand (1) are cooled in a location-dependent manner over the barrel length of the rolls (6), - wherein the rolling mill has a control device (3), - wherein the control device (3) is programmed with a control program (4) according to claim 12, so that the control device (3) in operation carries out a control method according to one of the Claims 1 to 10.

14. Rolling mill according to claim 13, characterized in that the rolling stand (1) has an actuator (8) which acts on chocks (7) of rolls (6) of the rolling stand (1) and by the control of which a roll gap profile can be adjusted exclusively over a barrel length of the rolls (6), and / or that the rolling stand (1) has a cooling device (9) by means of which the rolls (6) are cooled in a location-dependent manner over a barrel length of the rolls (6).

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