Operating method for a production line with prediction of the command speed

Before a first strip point is fed into a production line, an actual energy content at a location in front of the production line and a setpoint energy content at a location behind the production line are received for a first strip point, second strip point, and third strip point. The third strip point, followed by the first strip point, followed by the second strip point, are fed into the production line. A command variable for the first strip point and second strip point(s) is determined prior to feeding in the first strip point. Each command variable is determined based on (a) the actual value and the setpoint value of the strip point currently entering the production line, and (b) the actual value and the setpoint value of at least one strip point having already entered.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a U.S. National Stage Application of International Application No. PCT/EP2011/053513 filed Mar. 9, 2011, which designates the United States of America, and claims priority to EP Patent Application No. 10162135.7 filed May 6, 2010. The contents of which are hereby incorporated by reference in their entirety.

TECHNICAL FIELD

The present disclosure relates to an operating method for a production line for rolling a strip,wherein an actual value and a setpoint value for a first strip point are known to a control computer for the production line at the latest at a time point when said first strip point of the strip is still situated in front of the production line,wherein the actual value is characteristic of the actual energy content of the first strip point and the setpoint value is characteristic of the setpoint energy content of the first strip point,wherein the actual value relates to a location in front of the production line and the setpoint value relates to a location behind the production line,wherein the control computer determines a command variable for the first strip point based on a determining rule before the first strip point is fed into the production line,wherein the control computer determines a command speed based on the command variable and operates the production line at the command speed at the time point when the first strip point is fed into the production line,wherein the actual value and the setpoint value of the strip point entering the production line are input into the determining rule for the command variable.

The present disclosure further relates to a computer program comprising machine code, which can be directly executed by a control computer for a production line for rolling a strip, and whose execution by the control computer causes the control computer to operate the production line in accordance with such an operating method.

The present disclosure further relates to a control computer for a production line for rolling a strip, said control computer being so designed as to operate the production line in accordance with such an operating method.

The present disclosure further relates to a production line for rolling a strip, said production line being equipped with such a control computer.

BACKGROUND

A hot strip mill normally includes at least a production line and a cooling section that is arranged behind the production line. Alternatively or in addition to the cooling section, a blooming train can be arranged in front of the production line if applicable, or a casting device can be arranged in front of the production line.

The production line comprises a number of roll stands. The number of roll stands can be decided as required. Provision is normally made for a plurality of roll stands, e.g. four to seven roll stands. However, just one single roll stand may also be present in specific cases. A setpoint reduction is specified for each reduction stage that is to be performed at each roll stand, irrespective of the number of roll stands. If a plurality of roll stands are present, setpoint tensions are usually specified for the feed and/or delivery sides. If only one roll stand is present, a setpoint tension may be specified for the feed and/or delivery side. However, this is not necessarily required.

One of the target values that must be maintained in a hot strip mill is the final rolling temperature, i.e. the temperature at which the strip is delivered from the production line. As an alternative to the final rolling temperature, it is also possible to use another variable describing the energy content of the strip at this location, e.g. the enthalpy. The target value should be maintained over the whole length of the strip if possible. The target value can either be constant or vary over the length of the strip.

In order to achieve the target value, the command speed of the production line is normally adjusted accordingly. The command speed is a speed from which the strip speed and the circumferential roll speeds occurring within the production line can be clearly determined, possibly in conjunction with the reductions and setpoint tensions that must be adjusted in the production line. For example, it can be a notional speed of the strip head or the rotational speed of the first roll stand in the production line. The command speed can be defined as a function of the location of the strip head, for example.

Further control elements may be provided in the form of inter-stand cooling devices and/or an induction furnace that is arranged in front of the production line. Like the cooling devices of the cooling section, these control elements act only locally on the strip. The presence of these further control elements is however of lesser significance in the context of the present disclosure. Of critical importance is the command speed (or a variable that is characteristic of the command speed, e.g. the mass flow) and the determination thereof.

As mentioned above, a cooling section is usually arranged behind the production line. In the cooling section, the strip is cooled to a coiler temperature (or coiler enthalpy) in a defined manner. The speed at which the strip passes through the cooling section is defined by the command speed. The adjustment of the cooling profiles that are required for the individual strip points is effected by tracking the strip points and activating control valves, which adjust the coolant volume flow, at the correct time in the cooling devices of the cooling section.

The control valves have considerable delay times in practice, often measuring several seconds. In order to allow the control valves to be activated at the correct time in advance, it is therefore necessary to know at the correct time in advance when a specific strip point will be situated in the region of influence of a specific cooling device. In order to be able to calculate exactly when a specific strip point enters and leaves this region of influence, it is necessary to know not only the momentary value of the command speed, but also the future profile of the command speed, at least in the context of the delay time of the control valves. In addition to this, the throughput time itself, i.e. the time required by the respective strip point to pass through the cooling section, also has an influence on the coiler temperature. The throughput time is obviously also influenced by the profile of the command speed.

The prior art discloses a simplified way of determining the command-speed profile. For example, provision is made for predefining an initial value at which the strip head is to pass through the production line. Provision is further made for predefining an acceleration ramp, over which the strip is accelerated to a final speed as soon as the strip head is delivered from the production line. In practice, this procedure is unsuitable for maintaining a predefined setpoint final rolling temperature (or a corresponding temperature profile) with great accuracy.

The prior art also discloses capturing the (actual) final rolling temperature and correcting the command speed in the sense of minimizing the deviation of the actual final rolling temperature from the predefined setpoint final rolling temperature. This correction can be effected by means of conventional control or (as described in e.g. DE 103 21 791 A1) by means of Model Predictive Control. Irrespective of the type of control (conventional or model predictive), the control intervention (i.e. the modification of the command speed) nonetheless takes place at the same time as the command speed is determined. As in the case of the non-controlled procedure, any prediction is limited to predefining an anticipated future acceleration ramp. It is not certain whether, based on the setpoint and actual values of the next control step, the predicted command speed will actually be accepted. Moreover, the prediction applies to a single control step due to the nature of the system.

Admittedly, this procedure is normally suitable in practice for maintaining a predefined setpoint final rolling temperature (or a corresponding profile) with great accuracy. However, this procedure does not allow the actual variation of the command speed in the next control step to be predicted in terms of direction or value. Any prediction is more of a guess than a true determination.

Moreover, even if the prediction were correct or at least approximately correct, it would be essentially restricted to a single control step according to the teaching of DE 103 21 791 A1. This would be wholly unsatisfactory for timely correction of the control signals for the control elements of the cooling section or of inter-stand cooling devices in the production line. As a result of the variation in the command speed, the coolant volumes that are deposited by the control elements of the cooling section are therefore not deposited on the strip points for which said coolant volumes were previously calculated. This causes deviations in the temperature (or the energy content) of the strip points at the end of the cooling section (e.g. at a coiler) from setpoint set values. The precise maintenance of the final rolling temperature in the prior art is therefore achieved at the cost of significant fluctuation of the coiler temperature, for example.

The prior European patent application 09 171 068.1 (filing date Sep. 23, 2009), unpublished at the filing date of the present application, describes a Model Predictive Control which controls both a production line and a cooling section by means of a prognosis. The mass flow is also predicted in this context. This approach requires coolant volumes that are output by control elements of the cooling section, in order to allow the mass flow to be determined. In addition, the mass flow is also always corrected immediately here. This approach therefore likewise fails to solve the problem of allowing a command-speed profile to be determined reliably in advance.

SUMMARY

In one embodiment, an operating method for a production line for rolling a strip is provided, wherein an actual value and a setpoint value for a first strip point, a number of second strip points and a number of third strip points of the strip are known in each case to a control computer for the production line at the latest at a time point when said first strip point of the strip is still situated in front of the production line, wherein the respective actual value is characteristic of the actual energy content of the respective strip point and the respective setpoint value is characteristic of the setpoint energy content of the respective strip point, this applying to each strip point, wherein the respective actual value relates to a location in front of the production line and the respective setpoint value relates to a location behind the production line, this applying to each strip point, wherein the second strip points are fed into the production line after the first strip point and the third strip points are fed into the production line before the first strip point, wherein the control computer determines a command variable in each case for the first strip point and at least a subset of the second strip points based on a determining rule that is specific to the respective strip point and before the first strip point is fed into the production line, wherein the respective command variable is characteristic of the command speed at which the control computer operates the production line at the time point when the respective strip point is fed into the production line, wherein the control computer determines the respective command speed based on the command variable that has been determined for the respective strip point, and operates the production line at the respective command speed at the time point when the respective strip point is fed into the production line, and wherein the actual value and the setpoint value of the strip point currently entering the production line at this time point, and the actual value and the setpoint value of at least one strip point that has already entered the production line at this time point, are input into the determining rule for the respective command variable.

In a further embodiment, the control computer determines each of the command variables based on a multiplicity of individual command variables, each individual command variable relates in each case to one of the strip points whose actual value and setpoint value are input into the determination of the respective command variable, the control computer determines the respective individual command variable for each strip point such that a respective expected value matches the corresponding setpoint value, and the respective expected value is characteristic of an expected energy content that the respective strip point would assume, at that location behind the production line to which the currently corresponding setpoint value relates, if the control computer were to operate the production line at a command speed corresponding to the individual command variable during the entire passage of the respective strip point through the production line.

In a further embodiment, for each strip point whose command variable is determined by the control computer, said control computer: determines an effective actual value based on the actual values that are input into the determination of the command variable for the respective strip point, determines an effective setpoint value based on the setpoint values that are input into the determination of the command variable for the respective strip point, determines an expected value that is characteristic of an expected energy content which the respective strip point would assume, at that location behind the production line to which the effective setpoint value relates, if the control computer were to operate the production line at a command speed corresponding to the command variable for the respective strip point during the entire passage of the respective strip point through the production line, and determines the command variable such that the expected value at that location behind the production line to which the effective setpoint value relates has the effective setpoint value.

In a further embodiment, when determining the command variables, the control computer initially estimates the command variables as provisional values; the control computer determines a respective expected value for the first strip point and at least a subset of the second and third strip points; each expected value is characteristic of an expected energy content that the respective strip point would assume, at that location behind the production line to which the currently corresponding setpoint value relates, if the control computer were to operate the production line at command speeds corresponding to the estimated command variables during the entire passage of the respective strip point through the production line; and the control computer varies the estimated command variables, thereby optimizing a target function into which the amounts of the differences between the expected values and the corresponding setpoint values are input.

In a further embodiment, a penalty term by means of which changes to the command speed are penalized is additionally input into the target function.

In a further embodiment, the control computer creates a data field beforehand, in which, for a multiplicity of possible command speeds and possible actual values, the control computer stores the expected value that is produced for the respective possible actual value in the case of the respective possible command speed, and the control computer determines the command variables for the strip points using the data field.

In a further embodiment, the control computer: determines, for at least a subset of the strip points, a respective expected value which is characteristic of an expected energy content that is expected for the respective strip point, at that location behind the production line to which the currently corresponding setpoint value relates, as a result of the command speeds at which the control computer operates the production line during the entire passage of the respective strip point through the production line; receives, after the passage of the respective strip point through the production line, a measured value which is characteristic of an actual energy content of the respective strip point at that location behind the production line to which the corresponding setpoint value relates; automatically adapts a model of the production line based on a comparison between the expected energy content and the actual energy content; and adapts the model of the production line by adding an offset to the actual values when the data field is used, scaling the command speeds using a scaling factor and/or adding an offset to said command speeds and/or adding an offset to the expected values that were determined using the data field.

In a further embodiment, the actual value and the setpoint value of those strip points that have already entered the production line are only input into the determination of each command variable if these strip points have not yet left the production line at the time point for which the respective command variable is determined.

In a further embodiment, for at least a subset of the strip points, the control computer: determines a respective expected value which is characteristic of an expected energy content that is expected for the respective strip point, at that location behind the production line to which the currently corresponding setpoint value relates, as a result of the command speeds at which the control computer operates the production line during the entire passage of the respective strip point through the production line; receives, after the passage of the respective strip point through the production line, a measured value which is characteristic of an actual energy content of the respective strip point at that location behind the production line to which the corresponding setpoint value relates; and automatically corrects at least a subset of the already determined command variables based on a comparison between the expected energy content and the actual energy content.

In a further embodiment, based on the comparison, the control computer automatically corrects only those command variables that were determined for the strip points having a minimal distance from the entrance to the production line at the time point of the correction.

In a further embodiment, the control computer or another control device uses the determined command variables to determine at least one further actuating variable, that said further actuating variable is delayed by a dead time and acts only locally on the strip, wherein the minimal distance is specified such that a time difference corresponding to the minimal distance is at least as long as the dead time.

In a further embodiment, the control computer or another control device uses the determined command variables to determine at least one further actuating variable; said further actuating variable is delayed by a dead time and acts only locally on the strip; and the first strip point and that subset of the second strip points for which the respective command variable was determined before the first strip point was fed into the production line correspond to a prediction horizon that is at least as long as the dead time.

In a further embodiment, the control computer concatenates the determined command variables or the corresponding command speeds by means of a spline, such that a command-speed profile produced by the concatenation is constant and differentiable.

In a further embodiment, the control computer performs the determination of the command variables in the context of a precalculation online or in real time.

In another embodiment, a computer program comprising machine code, which can be directly executed by a control computer for a production line for rolling a strip and whose execution by the control computer causes the control computer to operate the production line in accordance with an operating method having any or all of the steps disclosed above.

In another embodiment, a control computer for a production line for rolling a strip is provided, wherein the control computer is designed so as to operate the production line in accordance with an operating method having any or all of the steps disclosed above. In another embodiment, a production line for rolling a strip is equipped with such a control computer.

DETAILED DESCRIPTION

According to certain embodiments disclosed below, before a strip point is fed into the production line, the command variable can be determined reliably and realistically for not only this strip point but also for strip points that are fed into the production line after this strip point.

For example, in some embodiments provision is madefor an actual value and a setpoint value for a first strip point, a number of second strip points and a number of third strip points of the strip to be known in each case to a control computer for the production line at the latest at a time point when said first strip point of the strip is still situated in front of the production line,for the respective actual value to be characteristic of the actual energy content of the respective strip point and the respective setpoint value to be characteristic of the setpoint energy content of the respective strip point, this applying to each strip point,for the respective actual value to relate to a location in front of the production line and the respective setpoint value to relate to a location behind the production line, this applying to each strip point,for the second strip points to be fed into the production line after the first strip point and the third strip points to be fed into the production line before the first strip point,for the control computer to determine a command variable in each case for the first strip point and at least a subset of the second strip points based on a determining rule that is specific to the respective strip point and before the first strip point is fed into the production line,for the control computer to determine a command speed in each case based on the command variable that has been determined for the respective strip point, and to operate the production line at the respective command speed at the time point when the respective strip point is fed into the production line,for the actual value and the setpoint value of the strip point currently entering the production line at this time point and the actual value and the setpoint value of at least one strip point that has already entered the production line at this time point to be input into the determining rule for the respective command variable.

For example, provision can be madefor the control computer to determine each of the command variables based on a multiplicity of individual command variables,for each individual command variable to relate in each case to one of the strip points whose actual value and setpoint value are input into the determination of the respective command variable,for the control computer to determine the respective individual command variable for each strip point such that a respective expected value matches the corresponding setpoint value, andfor the respective expected value to be characteristic of an expected energy content that the respective strip point would assume, at that location behind the production line to which the currently corresponding setpoint value relates, if the control computer were to operate the production line at a command speed corresponding to the individual command variable during the entire passage of the respective strip point through the production line.

When determining the respective command variable based on the respective multiplicity of individual command variables, the control computer can implement weighted or unweighted averaging, for example.

Alternatively, for each strip point whose command variable is determined by the control computer, provision can be madefor the control computer to determine an effective actual value based on the actual values that are input into the determination of the command variable for the respective strip point, and to determine an effective setpoint value based on the setpoint values that are input into the determination of the command variable for the respective strip point,for the control computer to determine an expected value that is characteristic of an expected energy content which the respective strip point would assume, at that location behind the production line to which the effective setpoint value relates, if the control computer were to operate the production line at a command speed corresponding to the command variable for the respective strip point during the entire passage of the respective strip point through the production line, andfor the control computer to determine the command variable such that the expected value at that location behind the production line to which the effective setpoint value relates has the effective setpoint value.

The control computer can also implement weighted or unweighted averaging here when determining the effective actual value and the effective setpoint value.

Alternatively, provision can also be madefor the control computer initially to estimate the command variables as provisional values when determining the command variables,for the control computer to determine a respective expected value for the first strip point and at least a subset of the second and third strip points,for each expected value to be characteristic of an expected energy content that the respective strip point would assume, at that location behind the production line to which the currently corresponding setpoint value relates, if the control computer were to operate the production line at command speeds corresponding to the estimated command variables during the entire passage of the respective strip point through the production line, andfor the control computer to vary the estimated command variables, thereby optimizing a target function into which the amounts of the differences between the expected values and the corresponding setpoint values are input.

In the last-mentioned alternative, provision may be made for a penalty term, by means of which changes to the command speed are penalized, to be input into the target function.

Irrespective of which of the three above-cited alternatives is adopted, the operating method disclosed herein may be very computation-intensive. In order to reduce the computing effort, provision may be madefor the control computer beforehand to create a data field in which, for a multiplicity of possible command speeds and possible actual values, the control computer stores the expected value that is produced for the respective possible actual value in the case of the respective possible command speed, andfor the control computer to determine the command variables for the strip points using the data field.

The operating method as described above already works very well. It can be improved even further if the control computerdetermines, for at least a subset of the strip points, a respective expected value which is characteristic of an expected energy content that is expected for the respective strip point, at that location behind the production line to which the currently corresponding setpoint value relates, as a result of the command speeds at which the control computer operates the production line during the entire passage of the respective strip point through the production line,receives, after the passage of the respective strip point through the production line, a measured value which is characteristic of an actual energy content of the respective strip point at that location behind the production line to which the corresponding setpoint value relates, andautomatically adapts a model of the production line (1) based on a comparison between the expected energy content and the actual energy content, andadapts the model of the production line by adding an offset to the actual values when the data field is used, scaling the command speeds using a scaling factor and/or adding an offset to said command speeds and/or adding an offset to the expected values that were determined using the data field.

In one embodiment, the actual value and the setpoint value of those points that have already entered the production line are only input into the determination of each command variable if these strip points have not yet left the production line at the time point for which the respective command variable is determined. In particular, when determining the command variable for a specific strip point, it is possible to input the actual and setpoint values of all strip points that are situated in the production line at the time point when the specific strip point enters the production line.

The operating method as described above already works very well. It can be improved even further if, for at least a subset of the strip points, the control computerdetermines a respective expected value which is characteristic of an expected energy content that is expected for the respective strip point, at that location behind the production line to which the currently corresponding setpoint value relates, as a result of the command speeds at which the control computer operates the production line during the entire passage of the respective strip point through the production line,receives, after the passage of the respective strip point through the production line, a measured value which is characteristic of an actual energy content of the respective strip point at that location behind the production line to which the corresponding setpoint value relates, andautomatically corrects at least a subset of the already determined command variables based on a comparison between the expected energy content and the actual energy content.

If the control computer compares the expected energy content with the actual energy content and corrects the command variables, said comparison could be performed by the computer for all of the strip points one after the other. However, it is sufficient to carry out the comparison for some of the strip points, e.g. for every third or every tenth strip point.

If the control computer corrects the command variables, it obviously takes the modified command-variable profile into comparison when determining expected values.

The control computer could perform the correction for all of the previously determined command variables. However, provision may be made for the control computer, based on the comparison, automatically to correct only those command variables that were determined for the strip points having a minimal distance from the entrance to the production line at the time point of the correction. In particular, this procedure may be advantageous if the control computer or another control device uses the determined command variables to determine at least one further actuating variable and said further actuating variable is delayed by a dead time and acts only locally on the strip. This procedure is optimal if the minimal distance is specified such that a time difference corresponding to the minimal distance is at least as long as the dead time.

In addition to correcting previously determined command variables, the control computer can obviously adapt the determining rule for as yet undetermined command variables. Depending on the situation of the specific case, the adaptation result can be taken into consideration already when determining further command variables of the same strip or only when determining command variables for subsequent strips.

The two last-named procedures, specifically “correcting previously determined command variables” on the one hand and “adapting the determining rule” on the other can be combined, for example, such that the control computer includes a model of the production line, said model being used to determine the temperature that is expected for a strip point on the delivery side of the production line if the respective strip point has a given temperature on the feed side of the production line and passes through the production line while the production line is operated at a given command speed. The model can be adapted immediately in this case. This corresponds to the adaptation of the determining rule. The command variable for at least one of the previously determined command variables is therefore determined again using the adapted model of the production line. This corresponds in terms of approach to the correction of the previously determined command variables. If applicable, a smooth transition can be made from the originally determined command variables to the newly determined command variables.

The operating method disclosed herein may thus represent a significant advance over conventional methods when the prediction horizon is relatively short, e.g., three to five strip points. The operating method disclosed herein may be particularly advantageous when the first strip point and that subset of the second strip points for which the respective command variable was determined before the first strip point was fed into the production line correspond to a prediction horizon that is at least as long as the dead time that applies when the further actuating variable acts on the strip. This may apply in particular when combined with the correction of the previously determined command variables, if the correction is likewise coordinated with the cited dead time.

In one embodiment, provision is further made for the control computer to concatenate the determined command variables or the corresponding command speeds using a spline, such that a command-speed profile produced by the concatenation is constant and differentiable. The resulting advantage takes the form of a smoother and more uniform operation of the production line. This applies in particular if the resulting command-variable profile is not only differentiable, but constantly differentiable.

The control computer may perform the determination of the command variables in the context of a precalculation online or in real time.

Other embodiments provide a computer program embodied such that the control computer performs an operating method comprising any or all of the steps disclosed herein.

Still other embodiments provide a control computer for a production line for rolling a strip, said control computer being programmed to execute such an operating method during operation.

Still other embodiments provide a production line for rolling a strip, said production line being equipped with such a control computer.

As shown inFIG. 1, a hot strip mill comprises at least one production line1. The production line1is used to roll a strip2. The strip2is usually a metal strip, e.g. a steel strip. Alternatively (instead of steel) the strip may comprise copper, brass, aluminum or another metal.

The production line1has a roll stand3or, as illustrated inFIG. 1, a plurality of roll stands3for the purpose of rolling the strip2. Three such roll stands3are illustrated inFIG. 1. The actual number of roll stands3can be three as illustrated. Alternatively, the number may differ from three, upwards in particular. The number of roll stands3is normally four to eight, in particular five to seven. Only the working rolls (2-high) of the roll stands3are illustrated inFIG. 1. In addition to the working rolls, the roll stands3usually also include back-up rolls (4-high), and sometimes even intermediate rolls (6-high).

The production line1can feature a heating device4, e.g. an induction furnace. If the heating device4is present, it is usually situated at the entrance of the production line1. Alternatively or additionally, heating devices can also be present between the roll stands3in the same way as inter-stand cooling devices. If present, the heating device4is considered to be part of the production line1in the context of the present disclosure. Alternatively or in addition to the heating device4, the production line1can feature inter-stand cooling devices5. If the inter-stand cooling devices5are present, each inter-stand cooling device5is straddled by two of the roll stands3. If present, they are part of the production line1. Each inter-stand cooling device5features at least one control valve5′ and at least one spray nozzle5″.

Furthermore, a cooling section6can be arranged behind the production line1. If the cooling section6is present, it features cooling devices7. Each cooling device7features at least one control valve7′ and at least one spray nozzle7″.

The strip2is cooled using a liquid coolant (usually water with or without admixtures) by means of both the inter-stand cooling devices5and the cooling devices7. The difference between the inter-stand cooling devices5and the cooling devices7of the production line6is that the cooling devices7are arranged behind the last roll stand3of the production line1, while the inter-stand cooling devices5are arranged between two of the roll stands3in each case.

As shown inFIG. 1, the production line1is also equipped with a control computer8. The control computer8is used at least to control the production line1, i.e. the roll stands3and, if present, the heating device4and the inter-stand cooling devices5. The control computer8can also control further devices if applicable, e.g. the cooling section6and its cooling devices7. Alternatively, the cooling section6can be controlled by a different control device8′.

The operation of the control computer8is specified by a computer program9, which is supplied to the control computer8via a mobile data medium10, for example. The mobile data medium10can be embodied as required, e.g. as a CD-ROM, a USB memory stick or an SD memory card. The computer program9is stored on the data medium10in machine-readable form, e.g. in electronic form.

The computer program9comprises machine code11by means of which the control computer8is programmed, and which can be directly executed by the control computer8. The execution of the machine code11by the control computer8causes the control computer8to operate the production line1in accordance with an operating method that is explained in greater detail below. The programming by means of the computer program9therefore results in a corresponding embodiment of the control computer8.

In the context of the operating method, in a step S1according toFIG. 2, an actual value G and a setpoint value G* for a first strip point12of the strip2, a number of second strip points13of the strip2and a number of third strip points13′ of the strip2must be known to the control computer8in each case, and at the latest at a time point when the first strip point12is still situated in front of the production line1.

It will become clear from the following explanations that the actual values G and the setpoint values G* for the first strip point12, the second strip points13and the third strip points13′ need not all become known to the control computer8at the same time. However, it will also become clear that they must all be known before the first strip point12is fed into the production line1.

The second strip points13are all situated behind the first strip point12, and therefore fed into the production line1after the first strip point12. The third strip points13′ are fed into the production line1before the first strip point12. Corresponding embodiments are shown inFIG. 3 to 6.

The actual value G of each strip point12,13,13′ is characteristic of the energy content that the respective strip point12,13,13′ has at a location xE in front of the production line1. The actual value G therefore relates to the location xE in front of the production line1. The location xE can be specified as required. In particular, as shown inFIG. 1it can be a location that is situated immediately in front of the first device4,3of the production line1, by means of which the temperature of the strip2is directly or indirectly influenced. It is indeed also possible for a temperature measuring device to be arranged at this location. However, the temperature measuring device14is usually arranged in front of the location Xe.

The setpoint value G* of each strip point12,13,13′ is characteristic of the energy content that the respective strip point12,13,13′ will have at a location xA behind the production line1. The setpoint values G* therefore relate to the location xA behind the production line1. Like the location xE in front of the production line1, the location xA can be specified as required. For example, it can be the location of a temperature measuring device15that is arranged behind the production line1but in front of the cooling section6.

The type of the actual value G and the setpoint value G* can be specified as required. They usually relate to corresponding temperatures. Alternatively, they could relate in particular to an enthalpy.

For the sake of accuracy, it should be noted here that the term “location” in the following always refers to a location that is fixed relative to the production line1. By contrast, the term “strip point” always refers to a point that is fixed relative to the strip2. Distances between the strip points12,13,13′ are not determined by their geometric distances in the context of the present disclosure, since these distances change due to the rolling of the strip2in the production line1. The distances are instead defined by the mass that is situated between the strip points12,13,13′.

The strip points12,13,13′ can be equidistant with reference to the mass of the strip2that is situated between them. Alternatively, the strip points12,13,13′ can be defined by capturing in each case a measured value for the actual value G at temporally equidistant steps, e.g. by means of the temperature measuring device14. The temporal distance between two consecutive strip points12,13,13′ is usually between 100 ms and 500 ms, typically between 150 ms and 300 ms. It may be 200 ms, for example.

In a step S2, the control computer8determines a command variable L* for the first strip point12based on a determining rule, this obviously occurring before the first strip point12is fed into the production line. In a step S3, the control computer8determines a respective command variable L* for at least a subset of the second strip points13likewise based on a determining rule. The step S3is also performed by the control computer8before the first strip point12is fed into the production line1.

The steps S2and S3fromFIG. 2generally form a single unit in practice. The separate representation inFIG. 2merely serves to better explain the present disclosure.

In the context of the step S3, the control computer8may determine a respective command variable L* for all of the second strip points13that are situated within a predefined prediction horizon H relative to the first strip point12. Therefore if a command variable L* is determined for a specific second strip point13in the context of the step S3, the respective command variables L* are normally also determined for all other second strip points13between the first strip point12and the specific second strip point13.

The determined command variables L* are characteristic in each case of the command speed vL at which the control computer8operates the production line1when the strip point12,13for which the respective command variable L* was determined is fed into the production line1. For example, the command speed vL can be the speed at which the strip2is fed into the production line1. Alternatively, it can be the speed at which the strip2is delivered from the production line1. Other variables are also possible, e.g. specifying the mass flow or a rotational speed or circumferential speed of a roll. The essential provision is that all of the strip speeds and circumferential roll speeds occurring in the production line1are unambiguously specified by means of the command speed vL, possibly in conjunction with reductions and setpoint tensions.

In a step S4, the control computer8determines the corresponding command speeds vL based on the command variables L* if required. In a step S5, the control computer8operates the production line1in accordance with the command speeds vL that were determined in the step S4. Therefore the control computer8continuously adjusts the command speed vL such that at any time point the production line1is operated at precisely that command speed vL which corresponds to the command variable L* of the strip point12,13currently entering the production line1.

The determining rule for determining the command variables L* is specific to the respective strip point12,13in each case. It is therefore not readily possible, from the determined value of the command variable L* for a specific strip point12,13, to deduce the value of the command variable L* for another strip point12,13. In particular, the actual value G and the setpoint value G* of the corresponding strip point12,13are initially input into the determining rule for the command variable L* for a specific strip point12,13. The actual values G and the setpoint values G* of at least one further strip point12,13,13′, which has already entered the production line1at the time point when the examined strip point12,13enters the production line1, are also input into the respective determining rule. This fact is clearly explained below with reference toFIG. 7.

By way of example,FIG. 7shows a snapshot of the production line1while the strip2is being rolled in the production line1. In connection with the explanations forFIG. 7, the strip points12,13are designated as strip points Pi (i=1, 2, 3, . . . ).

In accordance with the illustration inFIG. 7, it is assumed that the strip points P5to P30are currently in the production line1. In this case, the strip points P1to P4have already emerged from the production line1, and have therefore already left the production line1again. The strip points P31to P35are still in front of the production line1. In this case, the strip point P31will enter the production line1next. After the strip point P31, the strip points P32, P33, P34and P35will enter the production line1consecutively. It is assumed that the actual and setpoint values G, G* as far as and including the strip point P35are known.

In the situation illustrated inFIG. 7, the determination of the command variable L* for the strip point P4must already have been completed some time ago, since the strip point P4has not only already entered the production line1, but has actually already left the production line1again. The command variable L* that was used to operate the production line1at the time point when the strip point P4entered the production line1may be determined using inputs as follows:the actual value G and the setpoint value G* for the strip point P4, andthe actual value and the setpoint value G, G* for at least one of the strip points P1, P2and P3.

Assuming that the prediction horizon H corresponds to four strip points, the determination of the command variable L* for the strip point P4must have been completed one time cycle before the time point when the strip point P1entered the production line1.

Similarly, the command variable L* for the strip point P7was determined using inputs as follows:the actual value and the setpoint value G, G* for the strip point P7, andthe actual value and the setpoint value G, G* for at least one of the strip points P1to P6.

This determination must have been completed at the latest at the time point of the entry of the strip point P3.

The strip point P30is the strip point that has just entered the production line1. The determination of the command variable L*, which must have been completed at the latest at the time point of the entry of the strip point P26, used inputs as follows:the actual value and the setpoint value G, G* for the strip point P30, andthe actual value and the setpoint value G, G* for at least one of the strip points P1to P29.

As a rule, for the purpose of determining the command variable L* for the strip point P30, it is sufficient to consider the actual and setpoint values G, G* of the strip points P5to P30, i.e. those strip points which are currently situated in the production line1according to the illustration inFIG. 7.

The command variables L* for the strip points P31to P35are specified similarly. In the illustration according toFIG. 7, the strip point P31corresponds to the first strip point12, and the strip points P32to P35correspond to the second strip points13. The determination of the command variables L* for these strip points P31to P35must be completed at the latest at the time point when the strip points P27to P31respectively enter the production line1. The strip points P1to P30correspond to the third strip points13′.

The command variable L* for the strip point P31is determined using inputs as follows:the actual value and the setpoint value G, G* for the strip point P31, andthe actual and setpoint values G, G* for at least one of the strip points P1to P30, e.g., for at least one of the strip points P6to P30.

The latter applies in particular because the strip points P1to P5have already left the production line1again at the time point when the strip point P31enters the production line1.

The command variables L* for the strip points P32to P35can be specified in a similar manner. For example, the command variable L* for the strip point P35is determined using inputs as follows:the actual value and the setpoint value G, G* for the strip point P35andthe actual and setpoint values G, G* for at least one of the strip points P1to P34.

The actual and setpoint values G, G* for the strip points P1to P9can be ignored in this case, because the strip points P1to P9have already left the production line1again at the time point when the strip point P35enters the production line1.

Similar explanations apply to the remaining strip points P32, P33and P34.

In one embodiment, the command variable L* for each strip point12,13entering the production line1, e.g. for the strip point P31according toFIG. 7, is therefore specified based on the actual and setpoint values G, G* of those strip points12,13,13′ which are currently situated in the production line1at this time point, i.e. have not yet left the production line1.

A multiplicity of strip points12,13,13′ are usually situated in the production line1concurrently. They typically number between 10 and 200, e.g. between 50 and 100. Of the strip points12,13,13′ that are currently situated in the production line1at a specific time point, it is possible to consider only a subset of strip points12,13,13′, e.g. every second or every fourth strip point12,13,13′. This procedure produces a reduced computing effort and gives results that are nonetheless acceptable. However, the determination of the command variable L* for a specific strip point12,13may take into consideration the actual and setpoint values G, G* of all of the strip points12,13,13′ that are already situated in the production line1at the time point when the strip point12,13whose command variable L* is being determined enters the production line1.

It is obvious that the illustration shown inFIG. 7is purely exemplary. Therefore e.g. the number of (third) strip points13′ situated in the production line1is purely exemplary. The number of (second) strip points13, whose command variable L* is being predicted (the strip points P32to P35here), is likewise purely exemplary. The prediction horizon H is also purely exemplary. In particular, the prediction horizon H can be some seconds in practical applications, wherein a time cycle of e.g. 200 ms per capture of the actual value G as a measured value signifies a five-fold number of strip points12,13correspondingly. A prediction horizon H of up to a minute and more is even possible in some cases, corresponding to a prediction horizon H of 300 strip points and more in the case of a time cycle of 200 ms.

It is possible for the actual and setpoint values G, G* for all strip points12,13,13′ of the (entire) strip2to be known to the control computer8in the step S1fromFIG. 2. In this case, it is possible for the control computer8to process the steps S2and S3only once, and to determine the command variables L* of all strip points12,13,13′ of the strip2in the steps S2and S3in a single stroke, so to speak. In this case, the control computer8performs the determination of the command variables L* in the context of a precalculation online.

Alternatively, it is possible for the actual and setpoint values G, G* for all strip points12,13,13′ of the entire strip2to be known to the control computer8in the context of the step S1fromFIG. 2, but for the control computer8only ever to determine the command variables L* for some of the strip points12,13,13′ in the steps S2and S3fromFIG. 2. In this case, the steps S2and S3are integrated into a loop as indicated by a broken line inFIG. 2. In this case, the control computer8performs the determination of the command variables L* in real time with the activation of the production line1. In this case, the control computer8determines the command variables L* in advance as far as the prediction horizon H, so to speak.

As indicated likewise by a broken line inFIG. 2, it is even possible for the step S1also to be integrated into the loop. In this case also, the control computer8performs the determination of the command variables L* in real time.

If the step S1is also integrated into the loop, only the actual and setpoint values G, G* of strip points12,13that have not yet entered the production line1are known to the control computer8during a specific pass through the loop. The actual and setpoint values G, G* of the strip points13′ that have already been fed into the production line1are nonetheless known to the control computer8in this case due to previous passes through the loop. In this case, it is therefore only necessary for the control computer8to “remember” the “old” actual and setpoint values G, G*.

Various procedures can be used when determining the command variables L* for a specific strip point12,13, i.e. when implementing the steps S2and S3fromFIG. 2. The various alternatives are explained in greater detail below in turn with reference to theFIGS. 8, 9 and 10.FIG. 7should also be referred to in this context if required.

In a first possible embodiment of the steps S2and S3fromFIG. 2, one of the strip points12,13whose actual and setpoint values G, G* are already known to the control computer8is initially selected by the control computer8in a step S11according toFIG. 8. For example, the control computer8selects the strip point P31fromFIG. 7.

In a step S12, the control computer8determines all of the strip points12,13,13′ whose actual and setpoint values G, G* are used as inputs when determining the command variable L* for the strip point12,13which the control computer8selected in the step S11. For example, the control computer8can determine the strip points P6to P31for the strip point P31(seeFIG. 7). Similarly, the control computer in the step S12would determine e.g. the strip points P7to P32for the strip point P32, the strip points P8to P33for the strip point P33, etc.

In a step S13, the control computer8selects one of the strip points12,13,13′ that was determined in the step S12. In a step S14, the control computer8determines an individual command variable l* for the strip point12,13,13′ that was selected in the step S13, e.g. for the strip point P6. Only the actual value G and the setpoint value G* of the strip point12,13,13′ that was selected in the step S13are used as inputs for determining the individual command variable l*. The respective individual command variable l* therefore relates to this one strip point12,13,13′.

The individual command variable l* specifies a corresponding command speed vL. The control computer8assumes that the strip point12,13,13′ examined in the step S14is passing through the production line1, and the production line1is operated constantly at this command speed vL, specified by the corresponding individual command variable l*, during the entire passage of the examined strip point12,13,13′ through the production line1, i.e. from the time point when it is fed into the production line1until the time point when it is delivered from the production line1. An energy content to which the setpoint value G* of the examined strip point12,13,13′ relates is expected for the examined strip point12,13,13′ at the location xA in this case. The control computer8determines this expected energy content. The expected energy content can be determined by the control computer8by means of a production line model, for example. Suitable production line models as such are known. They are used to determine the final rolling temperature, for example, as per DE 103 21 791 A1 cited above.

The expected energy content is characterized by a corresponding expected value GE. The expected value GE can be either the temperature or the enthalpy, in the same way as the actual and setpoint values G, G*. The control computer8determines the individual command variable l* for the examined strip point12,13,13′ in the step S14such that the expected value GE matches the setpoint value G* for the examined strip point12,13,13′.

In a step S15, the control computer8checks whether it has already performed the step S14for all of the relevant strip points12,13,13′. If this is not the case, the control computer8returns to the step S13. When the step S13is performed again, the control computer8obviously selects a different and previously unexamined strip point12,13,13′ that is to be used as an input for determining the required command variable L*, e.g. the strip point P7.

If in the step S15the control computer8finds that it has already determined all of the required individual command variables l*, the control computer8moves on to a step S16. In the step S16, based on all of the individual command variables l* it determined during the repeated execution of the step S14, the control computer8determines the command variable L* for the strip point12,13that was selected in the step S11. For example, the control computer8can form the weighted or unweighted average of the individual command variables l*.

In a step S17, the control computer8checks whether it has already performed the steps S11to S16for all of the strip points12,13whose command variables L* are to be calculated. If this is not the case, the control computer8returns to the step S11. There the control computer8obviously selects a different and previously unexamined strip point12,13. Otherwise, the method according toFIG. 8ends.

In practice, the procedure according toFIG. 8is implemented in a slightly different manner to that described above, as the individual command variable l* for a specific strip point12,13,13′ (e.g. for the strip point P28inFIG. 7) is used as an input when determining the command variable L* for a plurality of strip points12,13,13′, e.g. when determining the strip points P28, P29, . . . P53in the context ofFIG. 7. It is obviously possible and may even be preferable to determine and then store the respective individual command variable l* just once, such that it can simply be retrieved from the memory for subsequent use.

As an alternative to the procedure according toFIG. 8, it is possible as shown inFIG. 9to replace the steps S13to S16fromFIG. 8with steps S21to S23as perFIG. 9. The steps S11, S12and S17inFIG. 8are carried over fromFIG. 8into the procedure according toFIG. 9.

In the step S21, the control computer8determines an effective actual value G′ based on the actual values G of the strip points12,13,13′ that were determined in the step S12. In the step S22, the control computer8similarly determines an effective setpoint value G′* based on the setpoint values G* of the strip points12,13,13′ that were determined in the step S12. For example, the control computer8can implement weighted or unweighted averaging in the steps S21and S22. Irrespective of the procedure that is adopted, the procedures in steps S21and S22should nonetheless correspond to each other.

In the step S23, the control computer8determines the command variable L* for the strip point12,13that was selected in the step S11.

The command variable L* that is determined in the step S23corresponds to a corresponding command speed vL. If the strip point12,13selected in the step S11were to exhibit the effective actual value G′ at the location xE, to which the actual value G of the strip point12,13selected in the step S11relates, and the control computer8were to operate the production line1at said command speed vL during the entire passage of the strip point12,13selected in the step S11, an actual energy content that is characterized by an expected value GE would be expected for this strip point12,13at the location xA, to which the setpoint value G* of the strip point12,13selected in the step S11relates. The control computer8determines the command variable L* in the step S23such that the determined expected value GE matches the effective setpoint value G′*. In the same way as the procedure in step14according toFIG. 8, the expected value GE can be determined by means of a corresponding production line model that is known per se.

As an alternative to the procedures according toFIGS. 8 and 9, the command variables L* can be determined as perFIG. 10as follows:

As shown inFIG. 10, in a step S31the control computer8initially estimates the command variables L* that it is to determine (i.e. the command variables L* for the first strip point12and for at least a subset of the second strip points13) as provisional values.

In a step S32, the control computer8determines a respective expected value GE for the strip points12,13examined in the step S31. The expected values GE determined in the step S32are characteristic in each case of that expected energy content, of the corresponding strip point12,13in each case, which is expected for the respective strip point12,13when the respective strip point12,13passes through the production line1in accordance with the estimated profile of the command speed vL as defined by the sequence of the command variables L*. The expected energy contents GE relate in each case to that location xA to which the setpoint values G* for the strip points12,13relate.

In a step S33, the control computer8generates a target function Z. The inputs for the target function Z comprise at least the amounts of the differences between the expected values GE and the corresponding setpoint values G*. The target function Z can contain a sum, for example, each summand being the square of the difference between an expected value GE and the corresponding setpoint value G* as per the illustration inFIG. 10.

The above described target function Z can be used in the way that has been described previously. However, the target function Z may have further input variables. In particular, a penalty term by means of which changes to the command speed vL are penalized can also be input into the target function Z. For example, the target function Z can therefore take the following form:

Different indices i, j are used in the two sums in this case because the indices i and j relate to different ranges. αiand βjare weighting factors, being freely selectable in principle and not negative.

In a step S34, the control computer8varies the estimated command variables L* with the objective of optimizing the target function Z, i.e. minimizing it in accordance with the embodiment above. In the context of a corresponding different layout of the target function Z, maximizing would also be applicable.

The procedures inFIGS. 8 and 9can be applied irrespective of whether, as a result of executing the steps S2and S3inFIG. 2once, only a few command variables L* are determined or the command variables L* for all strip points12,13,13′ of the strip2are determined in advance. By contrast, the procedure according toFIG. 10usually provides meaningful results only if the prediction horizon H covers the whole strip2or (provided the strip2is long enough) is sufficiently long. When using the procedure according toFIG. 10in respect of a long strip2, the prediction horizon H should be in particular so long that it corresponds at least to the effective length of the production line, and may be at least twice as long. The effective length of the production line is determined by the maximal number of strip points12,13,13′ situated in the production line1concurrently.

Expected values GE must be determined in the context of the procedure according toFIG. 8and in the context of the procedure according toFIG. 9and in the context of the procedure according toFIG. 10. The determination of the expected values GE is effected, in terms of approach, by means of a model of the production line1, which models the thermal events (heat conduction and heat transmission, and possibly also phase conversion and structural formation) in the production line1. Such models are known per se; see DE 103 21 791 A1.

This type of model can also be used as such in the steps S14, S23and S32. As per the illustration inFIG. 11, however, the control computer8may create a data field in advance in a step S41, i.e. before the command variables L* are determined. In a step S42, for a multiplicity of possible command speeds vL and possible actual values G, the control computer8stores the expected value GE that is produced in the case of the respective possible actual value G and the respective possible command speed vL, in the data field, as the control computer8can then determine the command variables L* for the strip points12,13using the data field in the context of the correspondingly configured steps S2and S3fromFIG. 2(or the steps S14, S23and S32). In the procedure according toFIG. 8, the control computer8determines the individual command variables l* using the data field, such that the use of the data field is indirect by nature. In the procedure according toFIG. 9, the respective command variable L* is determined directly. In the procedure according toFIG. 10, the data field is used to determine the expected values GE that are produced in each case.

Considerable acceleration can be achieved as a result of using the data field. Admittedly, the data field must also be determined in the context of a precalculation, i.e. when the hot strip2is already available for rolling in the production line1. The data field cannot therefore be determined offline. Instead, the data field must be determined online, i.e. after the strip data has been specified to the control computer8. Therefore only a few seconds are available for the purpose of determining the data field. Considerable acceleration is nonetheless achieved, as only relatively few values within the scope of the data field need to be fully examined by means of the model of the production line1, e.g. for 10 possible actual values G and 10 possible command speeds vL in each case, such that the model calculation has to be performed for a total of 100 values. However, this is still considerably quicker than constantly determining the expected value GE for each individual strip point12,13,13′ subsequently by means of the model of the production line1in the context of the steps S14, S23, S32.

The way in which the data field is incorporated into the procedures according toFIGS. 8 and 9is immediately apparent, since the actual value G is known to the control computer8and the relationship between the possible command speed vL and the expected value GE is that of one-to-one correspondence (the greater the command speed vL for a given actual value G, the greater the expected energy content of the corresponding strip point12,13,13′). However, the data field can also be applied in connection with the procedure according toFIG. 10, as the average of all command variables G* and/or all command speeds vL for a specific strip point12,13,13′ can be generated in a first approximation, which is generally already very good, and used to operate the production line1during the passage of the relevant strip point12,13,13′ through the production line1. This average can be taken as an effective command speed vL. The data field can therefore be evaluated at this point in order to determine the expected value GE for the corresponding strip point12,13,13′.

The data field can be configured as required. For example, it can be a simple interpolation node field comprising e.g. 5, 8, 10, . . . interpolation nodes per dimension. Linear or non-linear interpolation (e.g. using splines) between individual interpolation nodes can be performed in this case. Alternatively, the data field can be configured as a neural network, for example.

If the actual value G is based on a measured value, e.g. captured by means of the temperature measuring device14, the measured values can be processed directly. However, the location xE in front of the production line1, to which the actual values G relate, is normally situated behind the temperature measuring device14. It is therefore necessary to convert the measured values into the actual values G (which relate to the location xE). This is relatively easy, as only an air gap has to be calculated. Input values for the air gap are the temperature value that was measured by means of the temperature measuring device14and the time that is required by the respective strip point12,13,13′ before the corresponding strip point12,13,13′ reaches the location xE in front of the production line1. The time for each strip point12,13,13′ is derived from the command speeds of the preceding strip points12,13,13′.

This produces a feedback problem. In order to solve this problem, a provisional profile of the command speed vL is estimated initially. Assuming that this estimated profile is suitable, the actual values G relating to the location xE in front of the production line1are determined. Using the actual values G that have now been determined, the profile of the command speed vL is determined. The determined profile of the command speed vL is in turn used to determine the actual values G again. In practice, the procedure converges very quickly. Only a few iterations, e.g. three to five iterations, are usually required to achieve sufficiently stable results.

In the context of the foregoing explanations of the present disclosure, it has been assumed that the production line1features neither an input-side heating device4nor inter-stand cooling devices5. If the heating device4and/or the inter-stand cooling devices5are present, the operating method can be adapted accordingly. The necessary adaptations are explained below in connection with a single inter-stand cooling device5. However, the corresponding explanations are also readily applicable to embodiments of the production line1having more than one inter-stand cooling device5and/or one input-side heating device4, wherein the heating device4may be present as an alternative to or in addition to the inter-stand cooling devices5.

Let it therefore be assumed that the production line1features a single inter-stand cooling device5, e.g. between the second and the third roll stand3according to the illustration inFIG. 1. In this case, it is immediately apparent that the model of the production line1can be divided into three partial models, which are designated partial model TM1, partial model TM2and partial model TM3inFIG. 12.

In terms of approach, the partial model TM1corresponds to a model of a production line1as assumed previously, i.e. a model of a production line1without inter-stand cooling devices. It models the behavior of the strip2in the production line1as far as the inter-stand cooling device5. The partial model TM1receives the actual value G of a strip point12,13,13′ and its command speed vL or the corresponding command-speed profile as input variables. The partial model TM1delivers an output variable in the form of an expected value TE, which corresponds to an expected energy content of the corresponding strip point12,13,13′ when this is fed into the inter-stand cooling device5. The partial model TM1is two-dimensional, since it has two input variables, namely the actual value G and the command speed vL. The partial model TM2models the inter-stand cooling device5itself. As input variables, it receives the expected value TE that is delivered from the partial model TM1, the command speed vL at which the relevant strip point12,13,13′ passes through the inter-stand cooling device5, and a given coolant volume M to which the strip2is exposed per time unit. The coolant volume M per time unit may be defined as a function of that material volume of the strip2which has already passed through the inter-stand cooling device5. Alternatively, the coolant volume M per time unit can be defined e.g. as a function of the relevant strip point12,13,13′ that is currently feeding into the inter-stand cooling device5.

Unlike a model of a production line1without inter-stand cooling devices, the partial model TM2therefore has three input variables. The creation of a corresponding three-dimensional data field for the three-dimensional partial model TM2is still possible depending on the computing power available. However, the partial model TM2may be split into two submodels TM2′, TM2″ that are multiplicatively associated, as a three-dimensional function f that specifies an expected value TA behind the inter-stand cooling device5as a function of the expected value TE in front of the inter-stand cooling device5, the command speed vL and the coolant volume M per time unit, can be represented with sufficient accuracy as the product of a two-dimensional function g and a one-dimensional function h. The function g here is dependent on the expected value TE (which is supplied by the partial model TM1) and the command speed vL. The function h is dependent only on the coolant volume M per time unit. It therefore applies that
TA=f(TE,vL,M)=g(TE,vL)·h(M)
whereTA designates the expected value for the energy content of the examined strip point12,13,13′ behind the inter-stand cooling device5,TE designates the expected value for the energy content of the examined strip point12,13,13′ in front of the inter-stand cooling device5,vL designates the command speed, andM designates the volume of coolant that is deposited onto the strip2per time unit.

In terms of approach, the partial model TM3has the same structure as the partial model TM1. It models that part of the production line1which is arranged behind the inter-stand cooling device5.

The partial models TM1to TM3are interconnected and concatenated such that the output variables of the one partial model TM1, TM2represent input variables of the next model TM2, TM3respectively. By virtue of said concatenation of the partial models TM1to TM3, it is already possible significantly to reduce the dimensionality of the modeling problem, specifically to the examination of one three-dimensional problem and two two-dimensional problems. As a result of splitting the three-dimensional problem (i.e. the partial model TM2) into one one-dimensional and one two-dimensional function, the complexity can be reduced further. In particular, this reduction in the complexity of the three-dimensional problem allows the realtime and online capability to be maintained even when the inter-stand cooling devices5and/or the heating device4are present.

If the inter-stand cooling devices5and/or the heating device4are present, it is therefore possible to calculate the command variables L* assuming that the profile of the coolant volume M per time unit is given. In a second step, using the profile of the command variables L* that is now known, it is then possible to vary the volume M for each inter-stand cooling device5, in order to approximate the expected energy contents of the strip points12,13,13′ as far as possible to the corresponding setpoint energy contents of the strip points12,13,13′. The determination of the correct volumes M is similar in every respect to the determination of the correct volumes of coolant for the cooling devices7of the cooling section6.

It is possible for the control computer8to control the production line1without capturing a measured value GM that is characteristic of the actual energy content of the strip points12,13,13′ behind the production line1. However, in one embodiment and obviously after the respective strip points12,13,13′ have passed through the production line1in this case, the control computer8receives a corresponding measured value GM in each case for the corresponding strip points12,13,13′ in a step S51as perFIG. 13. For example, the control computer8can receive a corresponding temperature measured value that was captured by means of the temperature measuring device15.

Furthermore, in a step S52according toFIG. 13, the control computer8determines an expected value GE′ in each case for at least a subset of the strip points12,13,13′, or for all of the strip points12,13,13′. As a rule, the control computer8determines the relevant expected value GE′ for each strip point12,13,13′ while the respective strip point12,13,13′ is passing through the production line1. However, it is alternatively possible for the control computer8to determine the corresponding expected value GE′ before the respective strip point12,13,13′ passes through the production line1. Each such determined expected value GE′ is characteristic of the energy content that is expected for the respective strip point12,13,13′ at the location xA to which the setpoint values G* relate. The control computer8determines the expected values GE′ using the command-speed profile according to which the respective strip point12,13,13′ actually passes through the production line1.

If the model of the production line1is error-free, irrespective of the precise type of model of the production line1, the actual energy contents of the strip points12,13,13′ as determined in the step S52correspond exactly to the actual energy contents that are specified by the corresponding measured values GM. In many cases, however, the model of the production line1is erroneous. The reasons for this can be very varied. For example, the modeling may be based on excessively simple estimates or the model may have a systematic error such as e.g. incorrect modeling of the heat transmission. In a step S53, the control computer8therefore compares the energy content according to the measured value GM with the energy content according to the corresponding expected value GE′. Depending on the comparison in the step S53, a step S54provides for the control computer8automatically to correct at least a subset of the command variables L* that the control computer8has already determined at the time point of the comparison.

Within the context of step S54, the correction of the command variables L* obviously relates only to those command variables L* which have already been determined but have not yet been implemented at this time point. The step S54is therefore only carried out for command variables L* that have been determined for strip points12,13which have not yet been fed into the production line1at the time point of the correction.

It is possible for all of the corrected command variables L* to be immediately corrected to the full extent. However, a gradual transition may be preferred. For example, the first corrected command variable L* can be corrected by 10% of its change, the second corrected command variable by 20% of its change, the third corrected command variable L* by 30% of its change, etc.

Alternatively or in addition to the inclusion of the step S54, provision can be made in a step S55for the control computer8, based on the comparison, to adapt the very determining rule that is used to determine the command variables L*. This results in an improved determination of command variables L* that will be determined in the future and have not yet been determined at the time point of the comparison in the step S53. The adaptation of the determining rule can comprise in particular an adaptation of the model of the production line1, and of the heat transmission model in particular here.

In particular, if the expected values GE, GE′ are determined by means of the data field cited above, the adaptation of the model of the production line1can be performed in a simple manner for the strip2that is currently passing through the production line1, as in this case the adaptation can be effected e.g. by adding an offset to the actual values G before they are used as input variables of the data field. Alternatively or in addition to this, the command speed vL can be scaled using a factor and/or an offset can be added to it before it is used as an input variable of the data field. Alternatively or in addition to this, an offset can be added to the expected value GE, GE′ that is determined using the data field in each case. In particular, the realtime capability of the operating method is maintained when using this simplified manner of adapting the model of the production line1.

In the context of the step S54, it is possible to correct all of the command variables L* that have already been determined but have not yet been implemented at this time point, thus including the command variable L* for the (first) strip point12that will enter the production line1next, for example. However, provision may be made for the control computer8, based on the comparison in the step S53, automatically to correct only those command variables L* which were determined for (second) strip points13that have a minimal distance MIN (seeFIG. 14) from the entrance of the production line1at the time point of the correction.

As illustrated inFIG. 14, the operating method has a prediction horizon H in relation to the command-variable profile. The prediction horizon H is specified by the second strip point13whose command variable L* has already been determined and which, of the second strip points13whose command variables L* have already been determined, is farthest from the production line1. It can be beneficial if the control computer8, based on the comparison, automatically corrects only those command variables L* which have been determined for the second strip points13that have the minimal distance MIN from the entrance of the production line1at the time point of the correction. This is explained below with reference toFIG. 7.

According to the illustration according toFIG. 7,the strip points P1to P4have already left the production line1,the strip points P5, P6, P7, . . . P30are situated in the production line1,the strip point P31is the next to enter the production line1, andthe prediction horizon H, starting from the strip point P31, extends to the strip point P35.

Based on the actual temperature of the strip point P2in front of the production line1, for example, and based on the profile of the command-speed at which the strip point P2passed through the production line1, the control computer8determines the temperature that is expected for the strip point P2at the exit of the production line1(i.e. at the location xA). This corresponds to the step S52fromFIG. 13. The control computer8also receives the actual temperature that is measured for the strip point P2, from the temperature measuring device15. This corresponds to the step S51fromFIG. 13. Let it be assumed that the comparison in the step S53reveals a deviation. In spite of the deviation, for example, the control computer8leaves the previously determined command variables L* for the strip points P31to P34unchanged. Based on the comparison in the step S53, it corrects only the command variable L* of the strip point P35in the step S54. The command variables L* for subsequent strip points P36, P37, . . . , which have not yet been determined at this time point, are determined by the control computer8based on a determining rule that it adapts in the step S55based on the comparison in the step S53.

It may still be permitted in specific cases also to change the command variables L* of the strip points P31to P34. In this case, the modification of the corresponding command variables L* is not performed based on the comparison in the step S53, however, but based on a supervisory control intervention that is specified to the control computer8by a different control device, e.g. the control device8′, or by an operator.

As mentioned above, a cooling section6is usually arranged behind the production line1. The cooling section6comprises cooling devices7. Each cooling device has at least one control valve7′ and a number of spray nozzles7″ that are assigned to the respective control valve7′. The quantity of cooling liquid that is released locally onto the strip2is adjusted by means of the respective control valve7′. The control valves7′ react relatively slowly. Between the time point at which a control valve7′ is activated using a modified actuating variable S, and the time point at which the modified activation has an effect on the strip2, there is a dead time T that often measures several seconds. Dead times of two to five seconds are perfectly normal. Furthermore, the profile of the command speed vL also influences the throughput time of the strip points12,13,13′ through the cooling section6. Therefore the control device8′, which performs the activation of the cooling devices7of the cooling section6, must know not only the momentary value of the command speed vL, but also its future profile, as only then can the control device8′ of the cooling section6react at the correct time in advance to any changes in the command speed vL that may apply in the future. The control device8′ of the cooling section6must therefore use the command variable L*, and indeed any command variables L* that may apply in the future, to determine the actuating variables S for the control valves7′ if the correct coolant volumes are to be deposited at the “correct” positions on the strip2. This obviously also applies analogously if the control of the cooling section6is performed by the control computer8.

In the event that inter-stand cooling devices5are present, similar dead times occur at the inter-stand cooling devices5. Therefore the command-variable profile should also be used here when determining the actuating variables S for the inter-stand cooling devices5, such that it is possible to react at the correct time in advance to any changes in the command speed vL that may apply in the future. Therefore the prediction horizon H according toFIG. 14may be at least as long as the dead time T described above. The prediction horizon H may be even longer than the dead time T. If the dead time T corresponds to the strip points P31to P33as perFIG. 7, for example, the prediction horizon H should extend over more than two strip points, e.g. over four strip points as per the illustration inFIG. 7.

For essentially the same reasons, the minimal distance MIN, within which the correction of the command variables L* is suppressed, should be at least as long as the dead time T, e.g. three strip points as perFIG. 7.

In terms of approach, the command variables L* are determined at specific points for the individual strip points12,13. When determining a continuous command-speed profile, the step S4is developed in the form of a step S61according toFIG. 15. In the step S61, the control computer8concatenates the determined command variables L* by means of a spline, whereby the concatenation produces a command-variable profile that is constant and differentiable. The corresponding command-speed profile determined thus is also constant and differentiable.

A step S62could be provided as an alternative to the step S61. In the step S62, the control computer8determines the corresponding command speeds vL at specific points based on the command variables L* that are determined at specific points. In this case, the control computer8concatenates the corresponding command speeds vL by means of a spline, such that a constant and differentiable command-speed profile is produced by the concatenation.

The steps S61and S62represent alternatives. Although both are shown inFIG. 15, they are therefore both marked only by a broken line.

The above described operating method for the production line1(initially) supplies command speeds vL until the last strip point13of the strip2has been fed into the production line1. However, the command speed vL must continue to be defined for as long as at least one strip point12,13is situated in the production line1, even if no further strip points12,13are being fed into the production line1. The procedure can easily be extended accordingly. For this purpose, in addition to the strip points12,13,13′ relating to the physical strip2, provision is simply made for virtual strip points to be taken into consideration within the control computer8, said virtual strip points being appended to the first-cited strip points. A corresponding command variable L* is also determined for these virtual strip points. However, neither an actual value G nor a setpoint value G* is assigned to the virtual strip points, and therefore the virtual strip points themselves do not contribute to the determination of the corresponding command variables L*.

In the context of the explanation of the present disclosure, the command variable L* has been explained in each case with reference to the strip points12,13that are fed into the production line1at specific time points. However, this does not mean that the corresponding command variables L* are permanently assigned to the corresponding strip points12,13, as the corresponding command variable L* acts globally on the entire strip2. Of critical importance is solely therefore the assignment of the respective command variable L* to a specific time point, said time point being defined as that time point at which the corresponding strip point12,13is fed into the production line1.

Embodiments of the present disclosure may provide various advantages. for example, it may allow the prediction of a command-variable profile or command-speed profile that is actually also maintained subsequently during the operation of the production line1. This is associated with improved accuracy in the maintenance of the setpoint energy content on the delivery side of the production line1, and with improved accuracy (even significantly improved accuracy) in the control of the cooling section6. It is thus possible to maintain both a final rolling temperature (on the delivery side of the production line1) and a coiler temperature (on the delivery side of the cooling section6) with great accuracy.

The foregoing description serves merely to explain the present invention. The scope of protection of the present invention is defined exclusively by the appended claims.