REDUCING TENSILE FORCE-INDUCED CHANGES IN THICKNESS DURING ROLLING

Abstract

A position controller that controls an actuator that sets a roll gap of a roll stand by determining an actuating variable (q) for the actuator as a function of a resulting position target value (s*) and a position actual value(s) of the actuator. The (s*) is determined with a resulting base target value (s1*), which is determined as the sum of an initial base target value (s0*) and an additional target value (s1*), which is determined by a determination element with an inlet-end actual tension (ZE) and an inlet-end reference tension (ZER) and/or with an outlet-end actual tension (ZA) and an outlet-end reference tension (ZAR). Instead of (ZE) and (ZA), the corresponding target tensions (ZE*, ZA*) of corresponding tension control operations can also be used. However, in both cases, (ZER) and (ZAR) are variables that differ from (ZE*) and (ZA*).

Claims

1. An operating method for a roll stand for rolling flat metal rolling stock, determining with a position regulator that regulates positioning of an actuator that sets a roll gap of the roll stand, an actuating variable (q) for the actuator as a function of a resulting position target value (s*) and a position actual value (s) of the actuator; and activating, with the position regulator, the actuator accordingly, wherein the resulting position target value (s*) is determined by use of a resulting base target value (s1*), wherein the resulting base target value (s1*) is determined as the sum of an initial base target value (s0*) and an additional target value (s1*), wherein the additional target value (s1*) is determined by a determination element by the use of an inlet-side actual tension (ZE), or a corresponding target tension (ZE*) of an inlet-side tension regulating system, and an inlet-side reference tension (ZER) and/or by the use of an outlet-side actual tension (ZA), or a corresponding target tension (ZA*) of an outlet-side tension regulating system, and an outlet-side reference tension (ZAR), and wherein the inlet-side reference tension (ZER) is a different variable from the inlet-side target tension (ZE*) and/or the outlet-side reference tension (ZAR) is a different variable from an outlet-side target tension (ZA*).

2. The operating method as claimed in claim 1, wherein the roll stand is operated by regulating the roll gap.

3. The operating method as claimed in claim 1, wherein the inlet-side tension regulating system acts on a roll circumferential speed (vU) at which the flat rolling stock is rolled in the roll stand, and/or on a feed speed (vZ) at which the flat rolling stock exits a device arranged upstream from the roll stand, and/or in that the outlet-side tension regulating system acts on the roll circumferential speed (vU) and/or on a discharge speed (vA) at which the flat rolling stock enters a device arranged downstream from the roll stand.

4. The operating method as claimed in claim 1, wherein the additional target value (s1*) is determined by the determination element on the basis of the product of an inlet-side sensitivity (SE) and the difference between the inlet-side actual tension (ZE) or the corresponding target tension (ZE*) and the inlet-side reference tension (ZER) and/or on the basis of the product of the outlet-side sensitivity (SA) and the difference between the outlet-side actual tension (ZA) or the corresponding target tension (ZA*) and the outlet-side reference tension (ZAR).

5. The operating method as claimed in claim 4, wherein the inlet-side sensitivity (SE) and/or the outlet-side sensitivity (SA) are specified for the determination element by a higher-order control device.

6. The operating method as claimed in claim 5, wherein the inlet-side sensitivity (SE) and/or the outlet-side sensitivity (SA) are determined by the higher-order control device as part of a pass schedule calculation by analysis of a rolling model which describes the rolling procedure in the roll stand based on mathematical physical equations.

7. The operating method as claimed in claim 1, wherein the inlet-side reference tension (ZER) and/or the outlet-side reference tension (ZAR) are specified for the determination element by a higher-order control device.

8. The operating method as claimed in claim 7, wherein the higher-order control device determines the initial base target value (s0*) and the inlet-side target tension (ZE*) and/or the outlet-side target tension (ZA*) on the basis of a target thickness (d*) with which the flat rolling stock is to exit the roll stand and the inlet-side reference tension (ZER) and/or the outlet-side reference tension (ZAR), specifies the initial base target value (s0*) of a regulating unit comprising the position regulator and the determination element, and specifies the inlet-side target tension (ZE*) for a front tension regulator which regulates the inlet-side actual tension (ZE) to the inlet-side target tension (ZE*) and/or the outlet-side target tension (ZA*) for a rear tension regulator which regulates the outlet-side actual tension (ZA) to the outlet-side target tension (ZA*).

9. The operating method as claimed in claim 1, wherein the resulting position target value (s*) is determined at least during the rolling of a central portion of the rolling stock by the use of a correction value (s2*) determined by the use of an actual rolling force (F).

10. The operating method as claimed in claim 9, wherein the resulting base target value (s1*) is taken into account as part of the determination of the correction value (s2*) in addition to the actual rolling force (F).

11. The operating method as claimed in claim 1, wherein the resulting position target value (s*) is determined at least during the rolling of a head of the rolling stock and/or a tail of the rolling stock without the use of an actual rolling force (F).

12. The operating method as claimed in claim 1, wherein the resulting position target value (s*) is determined by the use of the deviation of a thickness (d) of the rolling stock, measured at the outlet side of the roll stand, from a target thickness (d*).

13. A control system for a roll stand for rolling a flat rolling stock, wherein the control system is formed by hardware blocks and/or software programs in such a way that during operation it implements an operating method as claimed in claim 1.

14. A rolling unit for rolling flat metal rolling stock, wherein the rolling unit has a roll stand for rolling the flat rolling stock and a control system as claimed in claim 13.

Description

SHORT DESCRIPTION OF THE DRAWINGS

[0044] The abovedescribed properties, features, and advantages of this invention and the manner in which they are achieved will become clearer and more readily understandable in conjunction with the following description of the exemplary embodiments which are explained in detail in connection with the drawings in which, illustrated schematically:

[0045] FIG. 1 shows a roll stand and its control system,

[0046] FIG. 2 shows a roll assembly in a first operating state,

[0047] FIG. 3 shows the roll assembly from FIG. 2 in a second operating state,

[0048] FIG. 4 shows the roll assembly from FIG. 2 in a third operating state,

[0049] FIG. 5 shows the structure of a regulating unit,

[0050] FIG. 6 shows a determination element,

[0051] FIG. 7 shows a supplement to the regulating unit from FIG. 5,

[0052] FIG. 8 shows a modification to the supplement from FIG. 7,

[0053] FIG. 9 shows a time diagram, and

[0054] FIG. 10 shows an embodiment of the regulating unit from FIG. 5.

DESCRIPTION OF THE EMBODIMENTS

[0055] In FIG. 1, rolling stock 2 is to be rolled in a roll stand 1. Only the working rollers of the roll stand 1 are illustrated in FIG. 1 (and, where illustrated, also in the other Figures). However, the roll stand 1 generally has at least back-up rollers in addition to the working rollers (four-high stand), possibly also intermediate rollers, which are arranged between the working rollers and the back-up rollers, in addition to the back-up rollers (six-high stand). The rolling stock 2 is made from metal, often from steel, in many cases from aluminum, rarely from another metal such as, for example, copper. The rolling stock 2 is furthermore flat rolling stock, i.e. a strip (the norm) or a heavy plate (the exception).

[0056] The roll stand 1 is generally operated by regulating the roll gap. Furthermore, the rolling stock 2 is rolled in the roll stand 1 at a roll circumferential speed vU. The associated drives and their activation are not illustrated.

[0057] According to the illustration in FIGS. 2 and 3, the rolling stock 2 can be held in a device 3 upstream from the roll stand 1 whilst it is being rolled in the roll stand 1. In this case, the rolling stock 2 exits the upstream device 3 at a feed speed vZ. Furthermore, an inlet-side actual tension ZE is applied to the rolling stock 2 on the inlet side of the roll stand 1. A loop lifter can be arranged between the upstream device 3 and the roll stand 1. The loop lifter is not illustrated. The upstream device 3 can be designed in accordance with the illustration in FIGS. 2 and 3 in particular as a further roll stand. It can, however, also have a different design, for example as a coiler or as a set of driving rollers. The feed speed vZ is illustrated in FIG. 2 as a circumferential speed. If the upstream device 3 is a roll stand, the forward slip must additionally be taken into account.

[0058] The inlet-side actual tension ZE is generally regulated to a corresponding target tension ZE* by means of a corresponding tension regulating system. In this case, the inlet-side actual tension ZE and the inlet-side target tension ZE* are supplied to a front tension regulator 24. The front tension regulator 24 determines, by the use of the inlet-side actual tension ZE and the inlet-side target tension ZE*, usually by the use of the difference between the two said tensions ZE, ZE*, a front actuating variable vE which is applied to an actuator such that the inlet-side actual tension ZE is aligned to or at least approximated with the inlet-side target tension ZE*. The front actuating variable vE can in particular be a speed additional target value which acts on the roll circumferential speed vU or, with the sign reversed, acts on the feed speed vZ.

[0059] Similarly, the rolling stock 2 can be held, in accordance with the illustration in FIGS. 3 and 4, in a device 4 downstream from the roll stand 1 whilst it is being rolled in the roll stand 1. In this case, the rolling stock 2 enters the downstream device 4 at a discharge speed vA. Furthermore, an outlet-side actual tension ZA is applied to the rolling stock 2 on the outlet 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 not illustrated either. The downstream device 4 can be designed in particular as a further roll stand in accordance with the illustration in FIGS. 3 to 5. It can, however, also have a different design, for example as a coiler or as a set of driving rollers. The discharge speed vA is illustrated in FIGS. 3 and 4 as a circumferential speed. If the downstream device 4 is a roll stand, the backward slip must additionally be taken into account.

[0060] The outlet-side actual tension ZA is generally regulated to a corresponding target tension ZA* by means of a corresponding tension regulating system. In this case, the outlet-side actual tension ZA and the outlet-side target tension ZA* are supplied to a rear tension regulator 25. The rear tension regulator 25 determines, by the use of the outlet-side actual tension ZA and the outlet-side target tension ZA*, usually by the use of the difference between the two said tensions ZA, ZA*, a rear actuating variable vA which is applied to an actuator such that the outlet-side actual tension ZA is aligned to or at least approximated with the outlet-side target tension ZA*. The rear actuating variable vE can in particular be a speed additional target value which acts on the roll circumferential speed vU or, with the sign reversed, acts on the discharge speed vA.

[0061] The roll stand 1 generally has a large number of actuators by means of which the rolling process is influenced. Examples of such actuators are a bending system by means of which a roll bend can be set, a displacement device by means of which a pair of rolls can be displaced axially in opposite directions, a roll cooling system, a roll gap lubrication system, and many others. Within the scope of the present invention, it is essentially an actuator 5 (see FIG. 5) by means of which the roll gap of the roll stand 1 is set. More details will therefore be given below only about this actuator 5 and its activation.

[0062] In order to regulate the positioning of the actuator 5, a position target value s* is specified for a position regulator 6 of a regulating unit 7. An actual value s of the actuator 5 is furthermore supplied to the position regulator 6. As a function of these two variables s*, s, the position regulator 6 determines an actuating variable q for the actuator 5 and controls the actuator 5 accordingly. The regulating unit 7 is an essential constituent part of a control system according to the invention.

[0063] The actuator 5 is generally designed, in accordance with the illustration in FIG. 5, as a hydraulic cylinder unit. In this case, the actuating variable q acts on a hydraulic system 8 by means of which a high working pressure pP (=pump pressure) or a low working pressure pT (=tank pressure) is applied as required to working chambers 9, 10 of the hydraulic cylinder unit. The actuating variable q can in this case be a hydraulic flow to be delivered. In particular in this embodiment, the position regulator 6 can, in accordance with the illustration in FIG. 5, be designed as a proportional regulator (P regulator). In rare cases, alternatively or additionally, adjustment of the roll gap by means of electric drives which act on screws is also possible. In such cases, the position regulator 6 is often designed as a proportional-integral regulator (PI regulator).

[0064] The resulting position target value s* is determined by the use of a resulting base target value s1*. In the embodiment according to FIG. 5, the resulting position target value s* is identical to the resulting base target value s1*. Further variables can, however, also be included in the resulting position target value s*. This will become more apparent from further explanations. The resulting base target value s1* is determined by the use of the inlet-side actual tension ZE and/or the outlet-side actual tension ZA.

[0065] In accordance with the illustration in FIG. 5, the resulting base target value s1* is determined in a node point 11 as the sum of an initial base target value s0* and an additional target value s1*. The initial base target value s0* is, at least generally, independent of the inlet-side actual tension ZE and the outlet-side actual tension ZA. The additional target value s1* is, in contrast, dependent on the inlet-side actual tension ZE and the outlet-side actual tension ZA. In particular, the additional target value s1* is determined by the determination element 13 by the use of an inlet-side actual tension ZE and an inlet-side reference tension ZER. Alternatively or additionally, the additional target value s1* can be determined by the determination element 13 by the use of the outlet-side actual tension ZA and an outlet-side reference tension ZAR.

[0066] In order to determine the additional target value s1*, in accordance with the illustration in FIG. 6, the inlet-side actual tension ZE can be supplied, for example, to a determination block 12 of the determination element 13. In this case, an inlet-side component s1E* of the additional target value s1* is determined in the determination block 12 by the use of the inlet-side actual tension ZE and the inlet-side reference tension ZER. For example, the inlet-side component s1E* can be determined, in accordance with the illustration in FIG. 6, according to the formula

s1E*=SE.Math.(ZEZER)(1)

where SE is an input-side sensitivity. The input-side reference tension ZER can optionally have the value 0. In a particular case, it can even be variable over time. In this case, it is generally also necessary to change the initial base target value to a corresponding extent.

[0067] The input-side sensitivity SE and the input-side reference tension ZER can be specified for the determination element 13, for example, in accordance with the illustration in FIG. 1 by a higher-order control device 14. The control device 14 is, where present, a further essential constituent part of the control system.

[0068] Similarly, in order to determine the additional target value s1*, in accordance with the illustration in FIG. 6, the outlet-side actual tension ZA is supplied, for example, to a determination block 15 of the determination element 13. In this case, an outlet-side component s1A* of the additional target value s1* is determined in the determination block 15 by the use of the outlet-side actual tension ZA and the outlet-side reference tension ZAR. For example, the outlet-side component s1A* can be determined in accordance with the illustration in FIG. 6, according to the formula

s1A*=SA.Math.(ZAZAR)(2)

where SA is an output-side sensitivity. The outlet-side sensitivity SA and the outlet-side reference tension ZAR can likewise be specified for the determination element 13 by the higher-order control device 14 in accordance with the illustration in FIG. 1. The input-side reference tension ZAR can optionally have the value 0. In a particular case, it can even be variable over time. In a similar way to changing the inlet-side reference tension ZER, at one end of the outlet-side reference tension ZAR it may be necessary to change the initial base target value s0* to a corresponding extent.

[0069] It is possible that only one of the two tensions ZE, ZA is used. In this case, the additional target value s1* is identical to the corresponding component s1E*, s1A*. However, generally both tensions ZE, ZA are used. In the case of a linearized determination, the determination element 13 has a node point 16 in which the additional target value s1* is determined as the sum of the two components s1E*, s1A*. It is furthermore possible to use the associated target values ZE*, ZA* instead of the actual values ZE, ZA.

[0070] The target tensions ZE*, ZA*, i.e. the target values ZE*, ZA* supplied to the associated tension regulators 24, 25 and hence valid for the tension regulating systems, are different variables from the reference tensions ZER, ZAR. Although in this approach it can be possible to derive the target tensions ZE*, ZA* from the reference tensions ZER, ZAR, there is, however, no identity between them. Although the specific values can temporarily be the same, this is, however, not systematic and not always the case.

[0071] It is thus, for example, possible that the target tensions ZE*, ZA* are specified by an operator (not illustrated) or can be varied by the operator during the rolling of the flat rolling stock 2. In contrast, the reference tensions ZER, ZAR cannot be changed by the operator. It is furthermore possible that the target tensions ZE*, ZA* are varied over time by the higher-order control device 14 for technological reasons, whilst the reference tensions ZER, ZAR are maintained. This will be explained in detail below with the aid of an example. In this example it is assumed that the upstream device 3 and the downstream device 4 are roll stands and furthermore a roll stand is also arranged upstream from the upstream device 3, and a roll stand is also arranged downstream from the downstream device 4.

[0072] The head 20 of the rolling stock 2 (see FIG. 2) reaches the roll stand 1 at a point in time t1, the downstream device 4 at a point in time t2, and the roll stand arranged downstream from the downstream device 4 at a point in time t3. Similarly, for example, a tail 21 of the rolling stock 2 (see FIG. 4) reaches, for example, the roll stand arranged upstream from the upstream device 3 at a point in time t4, the upstream device 3 at a point in time t5, and the roll stand 1 at a point in time t6. The point in time t4 is generally after the point in time t3.

[0073] FIG. 2 shows the rolling process at the point in time t1 when the rolling stock 2 is being rolled. The inlet-side actual tension ZE can be applied after the point in time t1. In contrast, this is not possible before the point in time t1. The inlet-side actual tension ZE is thus necessarily 0 before the point in time t1. The outlet-side actual tension ZA is likewise 0 because no rolling stock 2 is yet situated on the outlet side of the roll stand 1 and in particular the rolling stock 2 has not reached the downstream device 4.

[0074] Similarly, FIG. 4 shows the rolling process at the point in time t6 when the rolling stock 2 is being rolled. Up until the point in time t6, the outlet-side actual tension ZA can still be applied but after the point in time t6 this is not possible. The actual tension ZA is thus necessarily 0 after the point in time t6. The inlet-side actual tension ZE is also 0 because there is no longer any rolling stock 2 situated at the inlet side of the roll stand 1 and in particular it has exited the upstream device 3 a long time beforehand.

[0075] FIG. 3 shows the rolling process when the rolling stock 2 is being rolled between the points in time t1 and t6, to be more precise between the points in time t2 and t5. The respective actual tension ZE, ZA is applied during this period of time to the rolling stock 2 on at least one side (i.e. on the inlet side or on the outlet side), or even on both sides (i.e. on the inlet side and on the outlet side) during part of this period of time.

[0076] In the static state when the rolling stock 2 is being rolled in all the roll stands of the abovementioned example, the target tensions ZE*, ZA* can correspond to the reference tensions ZER, ZAR, i.e. have the same values. This static state, relative to the specification of the target values ZE*, ZA* for the tension regulators 24, 25, exists between the points in time t3 and t4.

[0077] In contrast, the rear tension regulator 25 can, for example, in principle be inactive in the period of time between the point in time t1 and the point in time t2. This is because the outlet-side actual tension ZA cannot be applied to the rolling stock 2 at the outlet side of the roll stand 1. In contrast, it is absolutely possible to determine the outlet-side component s1A* of the additional target value s1* during this period of time too. Furthermore, although the front tension regulator 24 can be active during this period of time, it is, however, possible that the corresponding target value ZE*=ZER is not supplied immediately to the front tension regulator 24 at the point in time t1 (or shortly thereafter) and instead the target value ZE* is raised by means of a ramp from 0 to the value of the corresponding reference tension ZER.

[0078] It is similarly possible that, although the rear tension regulator 25 is active in the period of time between the point in time t2 and the point in time t3, the corresponding target value ZA*=ZAR is not supplied immediately to the rear tension regulator 25 at the point in time t2 (or shortly thereafter) and instead the target value ZA* is raised by means of a ramp from 0 to the value of the corresponding reference tension ZAR.

[0079] It is similarly possible that, although the front tension regulator 24 is active in the period of time between the point in time t4 and the point in time t5, the target value ZE* supplied to the front tension regulator 24 is, however, lowered by means of a ramp to the value 0 during the said period of time from the value ZE*=ZER present at the beginning of the said period of time.

[0080] Furthermore, the front tension regulator 24 can in principle be inactive in the period of time between the point in time t5 and the point in time t6. This is because the inlet-side actual tension ZE cannot be applied to the rolling stock 2 at the inlet side of the roll stand 1. In contrast, it is absolutely possible to determine the inlet-side component s1E* of the additional target value s1* during this period of time too. Furthermore, although the rear tension regulator 25 can be active during this period of time, it is, however, possible that the target value ZA* supplied to the rear tension regulator 25 is lowered during the said period of time by means of a ramp to the value 0 from the value ZA*=ZAR present at the beginning of the said period of time.

[0081] The inlet-side sensitivity SE and/or the outlet-side sensitivity SA and possibly also further values such as the reference tensions ZER and/or ZAR and/or the initial base target value s0* can be provided by the higher-order control device 14.

[0082] The regulators carry out real-time regulation during the rolling of the rolling stock. The regulators as a whole are usually referred to as an L1 system by experts. The higher-order control device 14 thus functions as a unit which is usually referred to as an L2 system by experts. In accordance with the illustration in FIG. 1, the higher-order 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 which describe the rolling procedure. The higher-order control device 14 determines the said variables SE and/or SA and/or ZER and/or ZAR and/or s0* and possibly also further variables by analyzing the rolling model 17.

[0083] For example, the higher-order control device 14 performs a pass schedule calculation, in which these and if necessary other values are determined, before the rolling stock 2 is rolled in the roll stand 1. The determined values are made available by the higher-order control device 14 to lower-order regulators (for example, to the position regulator 6 of the regulating unit 7). In particular, as part of the pass schedule calculation, the higher-order control device 14 determines the initial base target value s0* and the inlet-side target tension ZE* and/or the outlet-side target tension ZA* on the basis of a target thickness d* (see FIG. 1) with which the flat rolling stock 2 is to exit the roll stand 1, and the inlet-side reference tension ZER and/or the outlet-side reference tension ZAR. The target thickness d* can alternatively be specified for the higher-order control device 14 or be determined independently by the higher-order control device 14. The reference tensions ZER, ZAR are generally set by the higher-order control device 14. Based on these values d*, ZER, ZAR, the higher-order control device 14 determines the required rolling force and the required positioning. The required rolling force corresponds to a reference rolling force FR, and the required positioning to the initial base target value s0*. The initial base target value s0* is specified by the higher-order control device 14 of the regulating unit 7. Also, the higher-order control device 14 specifies the inlet-side target tension ZE* for the front tension regulator 24, and the outlet-side target tension ZA* for the rear tension regulator 25.

[0084] The higher-order control device 14 can determine the inlet-side sensitivity SE, for example, by it determining, for the intended working point of the roll stand 1, the effect of the change in the inlet-side tension ZE on an actual rolling force F and furthermore the effect of the change in the rolling force F on the deflection of the roll stand 1. The product of the two said effects gives the inlet-side sensitivity SE. Similarly, the higher-order control device 14 can determine the outlet-side sensitivity SA by it determining, for the intended working point of the roll stand 1, the effect of the change in the outlet-side tension ZA on the rolling force F and furthermore the effect of the change in the rolling force F on the deflection of the roll stand 1. The product of the two said effects gives the outlet-side sensitivity SA. In a completely equivalent fashion, it is also possible to specify the base variables for the sensitivities SE, SA for the determination element 13, i.e. the effect of the change in the inlet-side tension ZE on the actual rolling force F, the effect of the change in the outlet-side tension ZA on the rolling force F, and the effect of the change in the rolling force F on the deflection of the roll stand 1. In this case, the determination element 13 can determine the sensitivities SE, SA itself. Furthermore, the determination element 13 is in this case in particular also capable of determining a change 5F in the expected rolling force corresponding to changes in the tensions ZE, ZA.

[0085] The resulting position target value s* is generally not identical to the resulting base target value s1* and instead is determined by the use of further correction variables.

[0086] Thus, in accordance with the illustration in FIG. 7, it is, for example, possible that the resulting position target value s* is determined by the use of a correction value s2* determined by the use of the rolling force F. For example, the resulting position target value s* can be determined in a node point 18 as the sum of the resulting base target value s1* and a correction value s2*. The correction value s2* is in this case determined in a determination block 19 by the use of the actual rolling force F. The determination block 19 thus implements an AGC in which an additional deflection of the roll stand 1 is (at least largely) compensated. The additional deflection of the roll stand 1 is caused by the deviation of the actual rolling force F from the reference rolling force FR. For the sake of good order, it should be pointed out that only the additional parts of the regulating unit 7 are illustrated in FIG. 7. FIGS. 5 and 6 should be consulted for the fundamental design of the regulating unit 7.

[0087] In the simplest case, only the actual rolling force F and the reference rolling force FR are supplied to the determination block 19 as input variables. In accordance with the illustration in FIG. 1, the reference rolling force FR is provided by the higher-order control device 14. In many cases, however, in addition to the actual rolling force F, a value is also supplied to the determination block 19 which, apart from the correction value s2* determined by the determination block 19, already corresponds to the resulting position target value s*. For example, the resulting base target value s1* can be supplied to the determination block 19. In this case, as part of the determination of the correction value s2* the determination block 19 additionally also takes into account the resulting base target value s1*. Furthermore, in this case the determination element 13 also determines the associated expected change 5F in the reference rolling force FR in addition to the additional target value s1*. The expected change 5F in the reference rolling force FR is taken into account by the determination block 19 when the correction value s2* is determined. In addition, the position actual value s may also be supplied to the determination block 19.

[0088] It is possible that the procedure explained in connection with FIG. 7 is carried out continuously during the rolling of the rolling stock 2 in the roll stand 1. As part of this, the correction value s2* is determined and updated independently of what portion of the rolling stock 2 is being rolled. In many cases, the correction value s2* is, however, determined and applied whilst a central portion of the rolling stock 2 is being rolled. In contrast, during the rolling of the head 20 and/or tail 21 of the rolling stock, the resulting position target value s* is often determined by the use of the actual rolling force F. This is explained in detail below in connection with FIGS. 8 and 9 with additional reference to FIGS. 2 to 4.

[0089] FIG. 8 is based on the regulating unit 7 from FIG. 7. In FIG. 8, an activation signal A and a reset signal R can be supplied to the determination block 19. The activation signal A has the value 0 or the value 1 in FIG. 9. A value of the activation signal A of 1 causes activation of the determination block 19. In this case, the determination block 19 determines the respective valid correction value s2* by the use of the rolling force F. As a result, the resulting position target value s* is consequently determined by the use of the rolling force F. A value of the activation signal A of 0 causes deactivation of the determination block 19. In this case, the determination block 19 outputs the last determined correction value s2* but does not update the correction value s2* further. As a result, the resulting position target value s* is consequently determined without the use of the rolling force F. The reset signal R is supplied to the determination block 19 only when no rolling stock is being rolled in the roll stand 1. Supplying the reset signal R causes the last determined correction value s2* to be reset to 0.

[0090] The activation signal A varies as a function of time t. Up to the point in time t1, the activation signal A has the zero 0. The activation signal A then increases, generally abruptly, to the value 1. At the point in time t6, the activation signal A falls, again generally abruptly, to the value 0. At a point in time t7, after the point in time t6 in FIG. 9, the reset signal R is specified (for a short period of time).

[0091] FIG. 10 shows a further embodiment of the regulating unit 7 from FIG. 5. The embodiment from FIG. 10 could, however, also be readily based on the embodiment of the regulating unit 7 in FIGS. 7 and 8. In FIG. 10, a thickness d of the rolling stock 2, i.e. its actual value, is measured at the outlet side of the roll stand 2 by means of a corresponding measurement device 22. The thickness d is compared with a target thickness d* in a determination block 23. A correction variable s3* is determined in the determination block 23 on the basis of the deviation of the thickness d of the rolling stock 2 from the target thickness d*. The correction variable s3* is supplied to the node point 18. The resulting position target value s* is consequently also determined by the use of the correction variable s3*. All types of remaining errors can be compensated by this procedure.

[0092] The present invention has many advantages. If and for as long as the AGC is active, i.e. in particular when rolling the central portion of the rolling stock 2, the AGC and also any thickness regulating system based on the measurement of the thickness d no longer have to compensate all the errors in the positioning of the roll stand 1 caused by the change in the rolling force F because partial compensation is effected anyway by the tension-dependent determination of the resulting position target value s*, i.e. by the correction because of the tensions ZE, ZA. If and for as long as the AGC is inactive, i.e. in particular during the initial pass phase and during the final pass phase, correction of thickness errors can be achieved at least partially by the tension-dependent determination of the resulting position target value s*, which otherwise could not be corrected at all. As a result, the initial portion and/or the end portion of the rolling stock 2, the thickness d of which deviates by more than the permissible tolerance from the target thickness d*, can consequently be shortened considerably, often by approximately half. There is furthermore good reason to believe that the structure of the loop regulating system immediately after the initial pass is also improved.

[0093] Although the invention has been illustrated and described in detail by the preferred exemplary embodiment, the invention is not limited to the disclosed examples and other variants can be derived by a person skilled in the art without going beyond the protective scope of the invention.

LIST OF REFERENCE SIGNS

[0094] 1 roll stand [0095] 2 rolling stock [0096] 3, 4 up-/downstream device [0097] 5 actuator [0098] 6 position regulator [0099] 7 regulating unit [0100] 8 hydraulic system [0101] 9, 10 working chambers [0102] 11, 16, 18 node points [0103] 12, 15, 19, 23 determination blocks [0104] 13 determination element [0105] 14 control device [0106] 17 rolling model [0107] 20 head of the rolling stock [0108] 21 tail of the rolling stock [0109] 22 measurement device [0110] 24, 25 tension regulator [0111] A activation signal [0112] d, d* thicknesses (actual and target) [0113] F actual rolling force [0114] FR reference rolling force [0115] pP, pT working pressures [0116] q actuating variable [0117] R reset signal [0118] s position actual value [0119] s* resulting position target value [0120] s0*, s1* base target values [0121] t time [0122] t1 to t7 points in time [0123] vA, vU, vZ speeds [0124] ZA, ZE, ZA*, ZE* tensions (actual and target) [0125] ZAR, ZER reference tensions [0126] s1* additional target value [0127] s1A*, s1E* components [0128] s2* correction value [0129] s3* correction variable [0130] vA, vE actuating variables