JP7729896B2 - Reduction of tension-induced changes in thickness during rolling - Google Patents

Description

The present invention is based on a method of operating a roll stand for rolling flat metal stock, in which a position regulator for adjusting the positioning of an actuator for setting the roll gap of the roll stand determines an actuation variable for the actuator as a function of an obtained position target value and an actual position value of the actuator and actuates the actuator accordingly, the obtained position target value being determined by use of an obtained reference target value, and the obtained reference target value being determined as the sum of an initial reference target value and an additional target value.

In the simplest case, the resulting position target value is identical to the resulting reference target value. The initial reference target value is generally independent of the inlet and outlet tensions.

The present invention is further based on a control system for a roll stand for rolling flat metal strips, the control system being formed by hardware blocks and/or software programs so as to implement such an operating method during operation.

The present invention is further based on a rolling unit for rolling flat metal stock, the rolling unit having a roll stand for rolling the flat metal stock, and such a control system.

When rolling flat metal stock, one of the basic requirements of the rolling process consists in producing a flat stock with a thickness that corresponds as closely as possible to a predetermined target thickness. The thickness of the stock leaving the roll stand is set, inter alia, via the roll gap. The size of the roll gap is then set by the corresponding setting of the actuator to a specific position.

The size of the roll gap, and therefore the thickness of the existing rolled material, is not, however, fixed solely by the position of the actuator. Instead, the deflection of the roll stand must be taken into account, in addition to wear, thermal crowning, roll displacement, and possibly other effects. The deflection is the result of the rolling force and other forces acting on the roll stand, such as bending forces.

Often, roll stands are operated by adjusting the roll gap. In such cases, the exit thickness to which the rolled material will be rolled in the roll stand is initially determined in a pass schedule. The associated predicted rolling force is further determined taking into account the parameters of the rolled material (e.g., its width, its entry thickness, its temperature, and other variables). The associated deflection of the roll stand is determined through the use of a spring model of the roll stand. Position target values for the actuators are then determined taking into account the deflection of the roll stand and other variables, such as, for example, wear-induced and/or temperature-induced crowning.

When rolling stock, the actual rolling force is measured directly or determined based on measured variables. A correction value is determined by the AGC (Automatic Gauge Control). The correction value is determined within the AGC via a spring model of the roll stand.

Flat metal stock is often rolled such that, while being rolled in a roll stand, the stock is tensioned in an upstream device upstream from the roll stand and/or in a downstream device downstream from the roll stand. Consequently, entry tension can be applied to the stock upstream from the roll stand, and exit tension can be applied to the stock downstream from the roll stand. To better maintain entry and exit tension, respective loop lifters can be located upstream and/or downstream from the roll stand. If the roll stand is part of a multi-stand rolling line but is not the first roll stand in the rolling line, the upstream device can also be another roll stand in the multi-stand rolling line. Similarly, if the roll stand is part of a multi-stand rolling line but is not the last roll stand in the rolling line, the downstream device can also be another roll stand in the multi-stand rolling line. In other designs, the upstream and/or downstream device can also be a coiler, for example, in the case of a Steckel mill. Other embodiments are possible.

The exit tension, and to an even greater extent the entry tension, have an influence on the rolling force. In particular, the higher the tension, the lower the required rolling force. The roll stand deflects less at lower rolling forces. If the reduced deflection is not taken into account, the tension therefore influences the thickness to which the rolled material is rolled in the roll stand.

In principle, this does not present a problem, since changes in the rolling force are measured and the deflection changes affected by these changes are corrected via the AGC already described. However, the AGC requires a considerable period of time to correct the deflection of the roll stand. The correction value is therefore only applied with a delay. Furthermore, compensation by the AGC is often only taken into account in a damped manner, since otherwise there is a risk of simultaneously correcting the positioning by the AGC and updating the tension by the tensioning system, which could cause vibrations and instability. Finally, the correction value determined by the AGC is often subject to errors, for example, due to frictional hardening in the roll stand or due to dead zones.

Furthermore, it is common practice to switch on the AGC only after the initial pass, i.e., with a delay. During the initial pass, the outlet tension is zero because the leading edge of the rolled material has not yet reached the downstream device that, in conjunction with the roll stand, can apply outlet tension to the rolled material. However, it is entirely possible for the inlet tension to have a value other than zero. If the inlet tension changes in such a case, this will affect the rolling force and therefore the deflection of the roll stand. However, because the AGC is switched on only after the initial pass, changes in the thickness at which the rolled material is rolled within the roll stand, caused by the changed deflection of the roll stand, are not corrected during the initial pass.

Similarly, it is common practice to freeze the AGC (i.e., the correction value determined at the time of freezing is no longer updated) before the initial pass, or to limit the time during which the correction value changes. During the final pass, the entry tension is zero because the tail of the rolled material has already exited the upstream device, which, together with the roll stand, can apply entry tension to the rolled material. However, there is a full possibility that the exit tension will have a value other than zero. If the exit tension changes in such a case, this will affect the rolling force and therefore the deflection of the roll stand. However, because the AGC is frozen before the final pass and the time during which the correction value determined by the AGC changes is limited, changes in the thickness of the rolled material rolled in the roll stand, caused by the changed deflection of the roll stand, will not be corrected, or will only be insufficiently corrected, during the final pass.

Patent Document 1 discloses an operating method of the type mentioned at the beginning. In this operating method, the additional target positioning value added to the actual target positioning value is determined by a tension regulator that adjusts the actual input tension to the target input tension. The actual target positioning value is the target roll gap value.

Patent Document 2 also discloses an operating method of the type described at the beginning. In this operating method, the additional target positioning value added to the actual target positioning value is determined by a tension regulator that adjusts the actual output tension to the target output tension. The actual target positioning value is the target roll gap value.

Patent document 3 also discloses a method for operating a roll stand for rolling flat metal stock. This method involves, in part, adjusting the mass flow rate, which acts on the roll stand's positioning system. The thickness of the rolled stock exiting the roll stand is set as a result. In this method, a tension regulator, which adjusts the input-side actual tension to the input-side target value, acts on the roll stand's positioning system.

EP3231522A1 JP 2003-164906 EP2620233A1

"On the theory of rolling" by J. M. Alexander, published in the Proceedings of the Royal Society of London, Vol. 326, pp. 535-563 (1972)

The object of the present invention is to provide an option that makes it possible to ensure better maintenance of the thickness of the rolled material at the exit side of the roll stand.

This object is achieved by an operating method having the characteristics of claim 1. Advantageous embodiments of the operating method are the subject of dependent claims 2 to 12.

According to the present invention, an operating method of the type described at the beginning is configured such that the additional target value is determined by a determining element using the inlet-side actual tension or a corresponding target tension and the inlet-side reference tension of the inlet-side tensioning system, and/or using the outlet-side actual tension or a corresponding target tension and the outlet-side reference tension of the outlet-side tensioning system, the inlet-side reference tension being a variable different from the inlet-side target tension and/or the outlet-side reference tension being a variable different from the outlet-side target tension.

The actual inlet tension and/or the actual outlet tension may be actual values measured using measurement techniques, or values determined based on values measured using measurement techniques. Tensioning systems generally have sufficiently high power and quality that the actual and target values coincide to a sufficient extent, allowing the use of either the actual or target values.

The roll stands are generally operated by adjusting the roll gap. Furthermore, the inlet tensioning system generally acts on the roll peripheral speed at which the flat rolled material is rolled in the roll stand and/or on the feed speed at which the flat rolled material leaves a device located upstream from the roll stand. Similarly, the outlet tensioning system generally acts on the roll peripheral speed and/or on the discharge speed at which the flat rolled material enters a device located downstream from the roll stand. The tensioning system generally acts on only one device in each case, i.e., either the upstream device or the roll stand, or either the roll stand or the downstream device.

If there is a dependence of the additional target value on the inlet-side tension state (target or actual), the additional target value is preferably determined by a determination element based on the product of the inlet-side sensitivity and the difference between the inlet-side actual tension or the corresponding target tension and the inlet-side reference tension. Similarly, if there is a dependence of the additional target value on the outlet-side tension state, the additional target value is preferably determined by a determination element based on the product of the outlet-side sensitivity and the difference between the outlet-side actual tension or the corresponding target tension and the outlet-side reference tension. The determination of the additional target value, and thus the resulting basic target value, is therefore particularly simply configured.

The additional target value is preferably determined by the determining element based on the product of the inlet-side sensitivity and the difference between the inlet-side actual tension or the corresponding target tension and the inlet-side reference tension, and/or based on the product of the outlet-side sensitivity and the difference between the outlet-side actual tension or the corresponding target tension and the outlet-side reference tension. In this way, the additional target value can be determined particularly simply and reliably.

It is preferred that the inlet sensitivity and/or outlet sensitivity be specified for the determining element by a higher-level control device.

The corresponding sensitivities can be stored in the high-level control device, for example in the form of a table. The corresponding sensitivities can be stored in the table according to the geometry and other properties of the rolled material (for example, its chemical composition and its temperature). However, it is preferred if the entry and/or exit sensitivities are determined by the high-level control device as part of the pass schedule calculation by analysis of a rolling model. The rolling model is based on mathematical physical equations that describe the rolling procedure in the roll stand. Therefore, a very accurate determination of the entry and/or exit sensitivities is possible. The rolling model can be adapted iteratively as needed.

The mathematical physical equations of the rolling model are generally differential and/or algebraic equations. Such models are widely known to those skilled in the art. As a mere example, reference may be made to "Rock Mill Models: A New Approach to Rolling Models," by John S. Bauer, ...

Similarly, the inlet reference tension and/or the outlet reference tension can also be specified for the determining element by a higher-level control device. The corresponding reference tensions can be determined or set by the higher-level control device as part of the pass schedule calculation.

The operating method is preferably configured such that the high-level control device, for example as part of a pass schedule calculation, determines an initial reference target value and an inlet-side target tension and/or an outlet-side target tension based on the target thickness at which the flat rolled material leaves the roll stand and the inlet-side reference tension and/or the outlet-side reference tension, assigns the initial reference target value to an adjustment unit having a position regulator and a determination element, assigns the inlet-side target tension to a pre-tension regulator that adjusts the inlet-side actual tension to the inlet-side target tension, and/or assigns the outlet-side target tension to a post-tension regulator that adjusts the outlet-side actual tension to the outlet-side target tension.

The resulting target position value is preferably determined during rolling at least the center of the rolled material by using a correction value determined by using the actual rolling force. Therefore, AGC is implemented. Therefore, the operating method according to the present invention can be combined with AGC.

The resulting reference target value is preferably taken into account as part of determining the correction value in addition to the actual rolling force. Power can be improved as a result when determining the correction value.

The resulting target position value is preferably determined during rolling of at least the head and/or tail of the rolled material without using the actual rolling force. In this case, the invention also compensates for tension and rolling force changes that occur when the AGC is not activated.

The latter procedure can also be combined with a procedure in which the AGC is active during rolling, in particular during rolling of the center of the rolled material. In this case, the AGC can alternatively be switched on at the transition from rolling the head of the rolled material to rolling the center. Similarly, the AGC can be switched off (frozen or limited in its changes) at the transition from rolling the center to rolling the tail of the rolled material.

The resulting position target value is preferably determined by using the deviation of the thickness of the rolled material measured at the exit side of the roll stand from the target thickness. Any remaining errors can be corrected as a result.

The object is further achieved by a control system having the characteristics of claim 13. According to the invention, the control system implements the operating method according to the invention during operation using hardware blocks and/or software programs.

The object is further achieved by a rolling unit having the characteristics of claim 14. According to the invention, the control system is designed as a control system according to the invention for a rolling unit of the type described at the beginning.

The above-mentioned features, characteristics and advantages of the present invention, and the manner in which they are achieved, will become more apparent and more easily understood in conjunction with the following detailed description of exemplary embodiments, which are set forth in conjunction with the diagrammatic drawings.

FIG. 1 shows a roll stand and its control system. FIG. 2 illustrates the roll assembly in a first operational state. FIG. 3 shows the roll assembly from FIG. 2 in a second operational state. FIG. 3 shows the roll assembly from FIG. 2 in a third operational state. FIG. 2 is a diagram showing the structure of an adjustment unit. FIG. 1 illustrates decision elements. FIG. 6 shows additions to the adjustment unit from FIG. 5 . FIG. 8 shows a modification to the addition from FIG. 7. FIG. FIG. 6 shows an embodiment of the adjustment unit from FIG. 5 .

In FIG. 1, the rolled material 2 is rolled in a roll stand 1. Only the working rollers of the roll stand 1 are shown in FIG. 1 (and may be shown in other figures). However, the roll stand 1 generally has at least a backup roller in addition to the working rollers (4 high stand), possibly intermediate rollers located between the working rollers, and a backup roller in addition to the backup rollers (6 high stand). The rolled material 2 is often made of metal, often steel, often aluminum, and rarely another metal, such as copper. The rolled material 2 may also be flat rolled material, i.e., strip (standard) or plate (exceptional).

The roll stand 1 is generally operated by adjusting the roll gap. Furthermore, the rolled material 2 is rolled in the roll stand 1 at a rolling surface speed vU. The associated drives and their operation are not shown.

2 and 3, the rolled material 2 can be held in device 3 upstream from roll stand 1 while being rolled in roll stand 1. In this case, the rolled material 2 leaves upstream device 3 at a feed speed vZ. Furthermore, an inlet effective tension ZE is applied to the rolled material 2 at the inlet side of roll stand 1. A loop lifter can be arranged between upstream device 3 and roll stand 1. The loop lifter is not shown. The upstream device 3 can be designed according to the diagrams of FIGS. 2 and 3, in particular as a separate roll stand. However, it can have a different design, for example as a coiler or as a set of drive rollers. The feed speed vZ is shown as a peripheral speed in FIG. 2. If the upstream device 3 is a roll stand, forward slip must additionally be taken into account.

The actual inlet tension ZE is generally adjusted to a corresponding target tension ZE* by a corresponding tension adjustment system. In this case, the actual inlet tension ZE and the target inlet tension ZE* are supplied to the pre-tension regulator 24. Using the actual inlet tension ZE and the target inlet tension ZE*, and usually the distance between the two tensions ZE and ZE*, the pre-tension regulator 24 determines a pre-actuation variable δvE applied to the actuator so that the actual inlet tension ZE is the same as or at least approximates the target inlet tension ZE*. The pre-actuation variable δvE may in particular be a speed additive target value acting on the roll peripheral speed vU or, in the reverse representation, on the feed speed vZ.

Similarly, the rolled material 2 can be held in a device 4 downstream from the roll stand 1 while being rolled in the roll stand 1, as shown in Figures 3 and 4. In this case, the rolled material 2 enters the downstream device 4 with a discharge speed vA. Furthermore, an exit-side actual tension ZA is applied to the rolled material 2 at the exit side of the roll stand 1. A loop lifter can also be arranged between the roll stand 1 and the downstream device 4. This loop lifter is also not shown. The downstream device 4 can be designed in particular as a separate roll stand according to the diagrams in Figures 3 to 5. However, it can have a different design, for example as a coiler or as a set of drive rollers. The discharge speed vA is shown as a peripheral speed in Figures 3 and 4. If the downstream device 4 is a roll stand, rear slip must additionally be taken into account.

The actual exit tension ZA is generally adjusted to a corresponding target tension ZA* by a corresponding tension adjustment system. In this case, the actual exit tension ZA and the target exit tension ZA* are supplied to the post-tension regulator 25. Using the actual exit tension ZA and the target exit tension ZA*, and usually the distance between the two tensions ZA and ZA*, the post-tension regulator 25 determines a post-actuating variable δvA applied to the actuator so that the actual exit tension ZA is the same as or at least approximates the target exit tension ZA*. The post-actuating variable δvA may in particular be a speed additive target value acting on the roll peripheral speed vU or, in the reverse representation, on the discharge speed vA.

The roll stand 1 generally has a number of actuators that influence the rolling process. Examples of such actuators are a bending system capable of setting the roll bending, a displacement device capable of axially displacing a pair of rolls in opposite directions, a roll cooling system, a roll gap lubrication system, and many others. Within the scope of the present invention, this is essentially the actuator 5 (see Figure 5) that sets the roll gap of the roll stand 1. Therefore, more details are given below only regarding this actuator 5 and its operation.

To regulate the positioning of the actuator 5, a position target value s* is specified to the position regulator 6 of the regulating unit 7. The actual value s of the actuator 5 is further supplied to the position regulator 6. As a function of these two variables s* and s, the position regulator 6 determines an actuation variable q for the actuator 5 and controls the actuator 5 accordingly. The regulating unit 7 is an essential component of the control system according to the invention.

The actuator 5 is generally designed as a hydraulic cylinder unit according to the diagram in FIG. 5. In this case, the actuation variable q acts on the hydraulic system 8, which applies a high actuation pressure pP (= pump pressure) or a low actuation pressure pT (= tank pressure) to the actuation chambers 9, 10 of the hydraulic cylinder unit as required. In this case, the actuation variable q can be the conveyed hydraulic flow. In particular, in this embodiment, the position regulator 6 can be designed as a proportional regulator (P regulator) according to the diagram in FIG. 5. In rare cases, it is alternatively or additionally possible to adjust the roll gap by means of an electric drive acting on the screw. In such cases, the position regulator 6 is often designed as a proportional-integral regulator (PI regulator).

The resulting position target value s* is determined by using the resulting reference target value s1*. In the embodiment according to FIG. 5, the resulting position target value s* is identical to the resulting reference target value s1*. However, other variables can also be included in the resulting position target value s*. This will become more clear from further explanations. The resulting reference target value s1* is determined by using the inlet actual tension ZE and/or the outer actual tension ZA.

According to the diagram of FIG. 5, the resulting reference target value s1* is determined in node point 11 as the sum of the initial reference target value s0* and the additional target value δs1*. The initial reference target value s0* is, at least generally, independent of the actual inlet tension ZE and the actual outlet tension ZA. In contrast, the additional target value δs1* depends on the actual inlet tension ZE and the actual outlet tension ZA. In particular, the additional target value δs1* is determined by the determination element 13 using the actual inlet tension ZE and the reference inlet tension ZER. Alternatively or additionally, the additional target value δs1* can be determined by the determination element 13 using the actual outlet tension ZA and the reference outlet tension ZAR.

To determine the additional setpoint value δs1*, the inlet actual tension ZE can be supplied, for example, to decision block 12 of decision element 13, according to the diagram of Fig. 6. In this case, the inlet component δs1E* of the additional setpoint value δs1* is determined in decision block 12 using the inlet actual tension ZE and the inlet reference tension ZER. For example, the inlet component δs1E* can be determined according to the diagram of Fig. 6 by the following formula:
δs1E*=SE・(ZE-ZER) (1)
where SE is the input sensitivity. The input reference tension ZER can optionally have a value of 0. In certain cases, it may be more variable over time. In this case, it is generally also necessary to change the initial reference target value to the corresponding range.

The input sensitivity SE and input reference tension ZER can be specified to the determining element 13 by a higher-level control device 14, for example according to the diagram in Figure 1. The control device 14, if present, is another basic component of the control system.

Similarly, in order to determine the additional setpoint value δs1*, the outlet-side actual tension ZA is supplied, for example, to a decision block 15 of the decision element 13, according to the diagram of Fig. 6. In this case, the outlet-side component δs1A* of the additional setpoint value δs1* is determined in the decision block 15 by use of the outlet-side actual tension ZA and the outlet-side reference tension ZAR. For example, the outlet-side component δs1A* can be determined according to the diagram of Fig. 6 by the following formula:
δs1A*=SA・(ZA−ZAR) (2)
where SA is the output-side sensitivity. The outlet-side sensitivity SA and the outlet-side reference tension ZAR can likewise be specified to the decision element 13 by the high-level control device 14 according to the diagram of FIG. 1. The input-side reference tension ZAR can optionally have a value of 0. In certain cases, it may be more variable over time. A similar method of changing the input-side reference tension ZER may require changing the initial reference target value s0* at one end of the outlet-side reference tension ZAR by a corresponding range.

It is also possible to use only one of the two tensions ZE, ZA. In this case, the additional setpoint δs1* is identical to the corresponding components δs1E*, δs1A*. However, typically both tensions ZE, ZA are used. In the case of linearized determination, the determination element 13 has a nodal point 16 at which the additional setpoint δs1* is determined as the sum of the two components δs1E*, δs1A*. Furthermore, instead of the actual values ZE, ZA, it is possible to use the associated setpoints ZE*, ZA*.

The target tensions ZE*, ZA*, i.e., the target values ZE*, ZA*, supplied to the associated tension regulators 24, 25 and therefore effective in the tension adjustment system, are variables that differ from the reference tensions ZER, ZAR. While this approach allows for the target tensions ZE*, ZA* to be derived from the reference tensions ZER, ZAR, there is no identity between them. Specific values may be the same temporarily, but this is not systematically or consistently the case.

Thus, for example, the target tensions ZE*, ZA* can be specified by an operator (not shown) or can be changed by the operator during rolling of the flat rolled material 2. In contrast, the reference tensions ZER, ZAR cannot be changed by the operator. Furthermore, while maintaining the reference tensions ZER, ZAR, the target tensions ZE*, ZA* can be changed over time by the higher-level control device 14 for technical reasons. This will be explained in more detail below with the help of an example. In this example, the upstream device 3 and the downstream device 4 are roll stands, which are also arranged upstream from the upstream device 3 and downstream from the downstream device 4.

The leading edge 20 of the rolled material 2 (see FIG. 2) reaches roll stand 1 at time t1, the downstream device 4 at time t2, and a roll stand located downstream from the downstream device 4 at time t3. Similarly, for example, the tail 21 of the rolled material 2 (see FIG. 4) reaches a roll stand located upstream from the upstream device 3 at time t4, the upstream device 3 at time t5, and a roll stand at time t6. Time t4 is generally after time t3.

Figure 2 shows the rolling process at time t1 when the rolled material 2 is being rolled. The actual inlet tension ZE can be applied after time t1, but not before time t1. The actual inlet tension ZE is therefore always 0 before time t1. The actual outlet tension ZA is also 0, since the rolled material 2 has not yet been placed at the outlet of the roll stand 1, in particular, the rolled material 2 has not yet reached the downstream device 4.

Similarly, Figure 4 shows the rolling process at time t6 when the rolled material 2 is being rolled. Up until time t6, further application of the exit-side actual tension ZA is possible, but not after time t6. The actual tension ZA is therefore always zero after time t6. Since the rolled material 2 at the entrance side of the roll stand 1 is gone, in particular having left the upstream device 3 a long time ago, the entrance-side actual tension ZE is also zero.

Figure 3 shows a rolling process in which the rolled material 2 is being rolled between times t1 and t6, or more precisely, between times t2 and t5. Respective actual tensions ZE, ZA are applied to the rolled material 2 on at least one side (i.e., the inlet side or the outlet side) during this period, and further on both sides (i.e., the inlet side and the outlet side) during part of this period.

In a static state in which the rolled material 2 is being rolled in all of the roll stands in the above example, the target tensions ZE* and ZA* correspond to the reference tensions ZER and ZAR, i.e., can have the same value. This static state for the specification of the target values ZE* and ZA* for the tension regulators 24 and 25 exists between times t3 and t4.

On the other hand, the rear tension regulator 25 may, for example, essentially not be operating during the period between time t1 and time t2. This is because the actual outlet tension ZA cannot be applied to the rolled material 2 at the outlet side of the roll stand 1. On the other hand, it is absolutely possible to determine the outlet component δs1A* of the additional setpoint value δs1* even during this period. Furthermore, although the front tension regulator 24 may operate during this period, the corresponding setpoint value ZE* = ZER is not immediately supplied to the front tension regulator 24 at time t1 (or shortly thereafter); instead, the setpoint value ZE* may be ramped up from 0 to the value of the corresponding reference tension ZER.

Similarly, the rear tension regulator 25 operates during the period between time t2 and time t3, but the corresponding target value ZA* = ZAR is not immediately supplied to the rear tension regulator 25 at time t2 (or shortly thereafter); instead, the target value ZA* may be ramped up from 0 to the value of the corresponding reference tension ZAR.

Similarly, the front tension regulator 24 operates during the period between time t4 and time t5, but the target value ZE* supplied to the front tension regulator 24 may be ramped down from a value ZE* = ZER present at the beginning of the period to a value of 0 during the period.

Furthermore, the front tension regulator 24 may not operate during the period between times t5 and t6, since the actual inlet tension ZE cannot be applied to the rolled material 2 at the inlet side of the roll stand 1. However, it is absolutely possible to determine the inlet component δs1E* of the additional setpoint value δs1* during this period. Furthermore, the rear tension regulator 25 may operate during this period, but the setpoint value ZA* supplied to the rear tension regulator 25 may be reduced during this period by a ramp from the value ZA* = ZAR present at the beginning of the period to the value 0.

Further values such as the inlet sensitivity SE and/or outlet sensitivity SA, and possibly the reference tension ZER and/or ZAR and/or the initial reference target value s0*, may also be provided by the high-level control device 14.

The regulator makes real-time adjustments while the material is being rolled. The regulator as a whole is usually referred to by experts as the L1 system. The high-level control device 14 therefore acts as a unit usually referred to by experts as the L2 system. According to the diagram in Figure 1, the high-level control device 14 comprises, inter alia, a rolling model 17 in which the rolling procedure in the roll stand 1 is modeled. The rolling model 17 is based on mathematical physical equations that describe the rolling procedure. By analyzing the rolling model 17, the high-level control device 14 determines the variables SE and/or SA and/or ZER and/or ZAR and/or s0*, and possibly also further variables.

For example, the high-level control device 14 performs a pass schedule calculation in which these and other values, as needed, are determined before the rolled stock 2 is rolled in the roll stand 1. The determined values are made available by the high-level control device 14 to a lower-level regulator (e.g., to the position regulator 6 of the regulating unit 7). In particular, as part of the pass schedule calculation, the high-level control device 14 determines an initial reference target value s0* and an entry target tension ZE* and/or an exit target tension ZA* based on the target thickness d* (see FIG. 1) at which the flat rolled stock 2 will exit the roll stand 1, as well as the entry reference tension ZER and/or the exit reference tension ZAR. The target thickness d* may alternatively be specified to the high-level control device 14 or may be determined independently by the high-level control device 14. The reference tensions ZER and ZAR are generally set by the high-level control device 14. Based on these values d*, ZER, and ZAR, the high-level control device 14 determines the required rolling force and required positioning. The required rolling force corresponds to the reference rolling force FR, and the required positioning corresponds to the initial reference target value s0*. The initial reference target value s0* is specified by the high-level control device 14 of the adjustment unit 7. The high-level control device 14 also specifies the entrance target tension ZE* for the front tension regulator 24 and the exit target tension ZA* for the rear tension regulator 25.

The high-level control device 14 can determine the entry-side sensitivity SE, for example, by determining the intended operating point of the roll stand 1, the effect of changes in the entry-side tension ZE on the actual rolling force F, and the effect of changes in the rolling force F on the deflection of the roll stand 1. The product of these two effects gives the entry-side sensitivity SE. Similarly, the high-level control device 14 can determine the exit-side sensitivity SA by determining the intended operating point of the roll stand 1, the effect of changes in the exit-side tension ZA on the rolling force F, and the effect of changes in the rolling force F on the deflection of the roll stand 1. The product of these two effects gives the exit-side sensitivity SA. In a completely equivalent manner, it is also possible to specify the basic variables for the sensitivity SE and SA for the determination element 13, namely, the effect of changes in the entry-side tension ZE on the actual rolling force F, the effect of changes in the exit-side tension ZA on the rolling force F, and the effect of changes in the rolling force F on the deflection of the roll stand 1. In this case, the determining element 13 can determine the sensitivities SE, SA themselves. Furthermore, the determining element 13 can in this case also determine, in particular, the change δF in the predicted rolling force corresponding to a change in the tensions ZE, ZA.

The resulting position target value s* is generally not identical to the resulting reference target value s1*, but instead is determined by the use of another correction variable.

Thus, according to the diagram of FIG. 7, for example, the resulting position target value s* can be determined by using a correction value δs2* determined by using the rolling force F. For example, the resulting position target value s* can be determined at node 18 as the sum of the resulting reference target value s1* and the correction value δs2*. The correction value δs2* is then determined in decision block 19 by using the actual rolling force F. Decision block 19 therefore implements an AGC, whereby additional deflections of the roll stand 1 are (at least largely) compensated for. The additional deflections of the roll stand 1 result from the deviation of the actual rolling force F from the reference rolling force FR. Note that for clarity, only additional parts of the adjustment unit 7 are shown in FIG. 7. FIGS. 5 and 6 should be used as references for the basic design of the adjustment unit 7.

In the simplest case, only the actual rolling force F and the reference rolling force FR are provided as input variables to decision block 19. According to the diagram in FIG. 1, the reference rolling force FR is provided by the high-level control device 14. However, in many cases, in addition to the actual rolling force F, a value is also provided to decision block 19 that already corresponds to the obtained position target value s*, separate from the correction value δs2* determined by decision block 19. For example, the obtained reference target value s1* can be provided to decision block 19. In this case, as part of determining the correction value δs2*, decision block 19 also takes into account the obtained reference target value s1*. Furthermore, in this case, decision element 13 also determines the associated predicted change δF in the reference rolling force FR in addition to the additional target value δs1*. The predicted change δF in the reference rolling force FR is taken into account by decision block 19 when determining the correction value δs2*. In addition, the position actual value s may also be provided to decision block 19.

The procedure described in connection with FIG. 7 is carried out continuously within the roll stand 1 while the stock 2 is being rolled. As part of this, the correction value δs2* is determined and updated independently of whether this portion of the stock 2 is being rolled. However, in many cases, the correction value δs2* is determined and applied while the center portion of the stock 2 is being rolled. In contrast, during rolling of the head 20 and/or tail 21 of the stock, the resulting position target value s* is often determined by use of the actual rolling force F. This is described in more detail below with reference to FIGS. 8 and 9, with additional reference to FIGS. 2 to 4.

8 is based on the regulating unit 7 from FIG. 7. In FIG. 8, an actuation signal A and a reset signal R can be supplied to the decision block 19. The actuation signal A has the value 0 or 1 in FIG. 9. A value of 1 for the actuation signal A results in the activation of the decision block 19. In this case, the decision block 19 determines the respective effective correction value δs2* using the rolling force F. As a result, the resulting position target value s* is therefore determined using the rolling force F. A value of 0 for the actuation signal A results in the deactivation of the decision block 19. In this case, the decision block 19 outputs the last determined correction value δs2* but does not further update the correction value δs2*. As a result, the resulting position target value s* is therefore determined without using the rolling force F. The reset signal R is supplied to the decision block 19 only if the rolled material is not being rolled in the roll stand 1. Supplying the reset signal R resets the last determined correction value δs2* to 0.

The actuation signal A varies as a function of time t. Up to time t1, the actuation signal A has a value of zero (0). It then rises, typically abruptly, to a value of one (1). At time t6, the actuation signal A again falls, typically abruptly, to a value of zero. At time t7, after time t6 in Figure 9, the reset signal R is asserted (for a short period of time).

Figure 10 shows another embodiment of the adjustment unit 7 from Figure 5. However, the embodiment from Figure 10 can also be based directly on the embodiment of the adjustment unit 7 from Figures 7 and 8. In Figure 10, the thickness d of the rolled material 2, i.e., its actual value, is measured at the exit side of the roll stand 1 by a corresponding measuring device 22. The thickness d is compared with the target thickness d* in decision block 23. A correction variable δs3* is determined in decision block 23 based on the deviation of the thickness d of the rolled material 2 from the target thickness d*. The correction variable δs3* is supplied to node point 18. The resulting position target value s* is therefore also determined using the correction variable δs3*. Residual errors of all types can be compensated for by this procedure.

The present invention has many advantages. When and as long as the AGC is active, i.e., especially when rolling the center of the rolled material 2, the AGC, and thus any thickness adjustment system based on measuring the thickness d, does not have to compensate for all errors in the positioning of the roll stand 1 caused by changes in the rolling force F, since partial compensation is achieved somehow through the tension-dependent determination of the resulting position target value s*, i.e., through correction by the tensions ZE and ZA. When and as long as the AGC is not active, i.e., especially during the initial and final pass phases, correction of thickness errors can be achieved at least partially through the tension-dependent determination of the resulting position target value s*, which would otherwise not be correctable at all. As a result, thicknesses d in the initial and/or final sections of the rolled material 2 that deviate more than the permitted tolerance from the target thickness d* can subsequently be significantly shortened, often by about half. Furthermore, there is good reason to believe that the design of the loop adjustment system immediately after the initial pass could also be improved.

Although the present invention has been shown and described in detail by means of preferred exemplary embodiments, the present invention is not limited to the disclosed examples, and other modifications may be devised by those skilled in the art without going beyond the scope of protection of the present invention.

1 Roll stand 2 Rolled stock 3, 4 Upstream/downstream device 5 Actuator 6 Position regulator 7 Regulating unit 8 Hydraulic system 9, 10 Working chamber 11, 16, 18 Nodal points 12, 15, 19, 23 Decision block 13 Decision element 14 Control device 17 Rolling model 20 Head of rolled stock 21 Tail of rolled stock 22 Measuring device 24, 25 Tension regulator A Actuation signal d, d* Thickness (actual and target)
F actual rolling force FR reference rolling force pP, pT working pressure q working variable R reset signal s actual position value s* obtained position setpoint s0*, s1* reference setpoint t time t1 to t7 time points vA, vU, vZ speed ZA, ZE, ZA*, ZE* tension (actual and setpoint)
ZAR, ZER Reference tension δs1* Additional target value δs1A*, δs1E* Components δs2* Correction value δs3* Correction variable δvA, δvE Operation variable

Claims (14)

A method of operating a roll stand (1) for rolling a flat metal strip (2), comprising the steps of:
a position regulator (6) for adjusting the positioning of an actuator (5) for setting the roll gap of the roll stand (1) determines an actuation variable (q) for the actuator (5) as a function of the resulting position target value (s*) and position actual value (s) of the actuator (5) and actuates the actuator (5) accordingly;
the obtained position target value (s*) is determined using the obtained reference target value (s1*);
said resulting reference target value (s1*) being determined as the sum of an initial reference target value (s0*) and an additional target value (δs1*) determined by a higher level control device (14) ;
the additional target value (δs1*) is determined by a determining element (13) using the actual inlet tension (ZE) or the inlet target tension (ZE*) of an inlet tensioning system , which is a tension that can be set during operation of the roll stand (1), and the inlet reference tension (ZER), which is a tension that is set before operation of the roll stand (1), and/or using the actual outlet tension (ZA) or the outlet target tension (ZA*) of an outlet tensioning system, which is a tension that can be set during operation of the roll stand (1), and the outlet reference tension (ZAR), which is a tension that is set before operation of the roll stand (1),
An operating method in which the inlet-side reference tension (ZER) is a variable different from the inlet-side target tension (ZE*), and the outlet-side reference tension (ZAR) is a variable different from the outlet-side target tension (ZA*). The operating method described in claim 1, characterized in that the roll stand (1) is operated by adjusting the roll gap. The method of claim 1 or 2, characterized in that the inlet tensioning system acts on the roll peripheral speed (vU) at which the flat rolled material (2) is rolled in the roll stand (1) and/or on the feed speed (vZ) at which the flat rolled material (2) exits a device (3) arranged upstream from the roll stand (1), and/or the outlet tensioning system acts on the roll peripheral speed (vU) and/or on the discharge speed (vA) at which the flat rolled material (2) enters a device (4) arranged downstream from the roll stand (1). The operating method according to claim 1, 2 or 3, characterized in that the additional target value (δs1*) is determined by the determining element (13) based on the product of an inlet-side sensitivity (SE) and the difference between the inlet-side actual tension (ZE) or the inlet-side target tension (ZE*) and the inlet-side reference tension (ZER) and/or based on the product of an outlet-side sensitivity (SA) and the difference between the outlet-side actual tension (ZA) or the outlet-side target tension (ZA*) and the outlet-side reference tension (ZAR). 5. A method according to claim 4, characterized in that the high-level control device (14) determines the inlet sensitivity (SE) and/or the outlet sensitivity (SA). The operating method described in claim 5, characterized in that the entrance sensitivity (SE) and/or the exit sensitivity (SA) are determined by the high-level control device (14) as part of a pass schedule calculation by analyzing a rolling model (22) that describes the rolling procedure in the roll stand (1) based on mathematical physical equations. 7. A method according to any one of claims 1 to 6, characterized in that a high-level control device (14) determines the inlet reference tension (ZER) and/or the outlet reference tension (ZAR). The high-level control device (14)
determining the initial reference target value (s0*) and the entrance-side target tension (ZE*) and/or the exit-side target tension (ZA*) based on a target thickness (d*) of the flat rolled material (2) exiting the roll stand (1) and the entrance-side reference tension (ZER) and/or the exit-side reference tension (ZAR);
specifying the initial reference target value (s0*) of the regulating unit (7) comprising the position regulator (6) and the determining element (13);
8. The operating method according to claim 7, wherein the inlet-side target tension (ZE*) is designated for a front tension regulator (24) that adjusts the inlet-side actual tension (ZE), and/or the outlet-side target tension (ZA*) is designated for a rear tension regulator (25) that adjusts the outlet-side actual tension (ZA), to the outlet-side target tension (ZA*). 9. The method according to claim 1, wherein the obtained position target value (s*) is determined during rolling of at least the central portion of the rolled material (2) by using a correction value (δs2*) determined on the basis of the actual rolling force (F) and used to take into account the influence of changes in the rolling force (F) on the deflection of the roll stand (1). 10. The operating method according to claim 9, characterized in that the correction value (δs2*) is determined based on the obtained reference target value (s1*) and the actual rolling force (F) . 9. The method according to claim 1, wherein the obtained position target value (s*) is determined during rolling of at least the head (20) of the rolled material and/or the tail (21) of the rolled material without using an actual rolling force (F) . 9. The method according to claim 1, wherein the resulting position target value (s*) is determined by using the deviation of the thickness (d) of the rolled material (2) measured at the exit side of the roll stand ( 1) from the target thickness (d* ). A control system for a roll stand (1) for rolling flat rolled material (2), formed by hardware blocks and/or software programs, so as to implement, during operation, the operating method described in any one of claims 1 to 12. A rolling unit for rolling a flat metal strip (2), comprising a roll stand (1) for rolling the flat metal strip (2) and a control system as described in claim 13.