DE4040360A1 - Multiple-stand strip rolling control - uses model comparisons and converging parameters to maintain strip profile and flatness - Google Patents

Abstract

In the control system for a multiple-stand and/or cold rolling strip mill, the process control has a pass plan with the start and end dimensions, material data and roller temps. and setting systems to maintain nominal values. Separate controls are provided for variable function values at the separate stands and a computer compares models under converging parameter matching at the actual parameters to bring the individual controls into nominal values. A closed circuit gives profile and flatness control by altering the load distribution at the separate stands, by acting on the roller back bending, the camber and, if required, the roller sliding and/or setting. ADVANTAGE - By acting on all the working points of the strands the strip quality is accurately controlled.

Description

The invention relates to a regulation in the manufacture of Rolling strip using a multi-stand hot and / or cold strip Rolling mill, which is a superordinate process control system, the one Rolling program with the initial and final dimensions, with material data, rolling temperatures etc. and a guide system for setpoint control of subordinate, decoupled individual controller for the variable function variables of the individual roll scaffolding, e.g. B. roller setting, speed, axial tension, etc. on points, whereby through a calculation process using model equations with converging model parameter adjustment to the actual parameters determine the setpoints of the individual controllers be that a control behavior corresponding to a closed loop results.

Under constant cost pressure it is with increasing quality requirements necessary, rolling mills in relation to the process optimize leadership. This is flexible, in particular the profile and flatness of the product created visual, fast regulation necessary. General have therefor control systems with controlled adaptation, e.g. B. of the type like defined under 2.7 of VDI / VDE guidelines 3685, enforced.

A correspondingly quick regulation for rolling mills is z. B. known from DE 30 26 229 A1. The well-known regulation however, works particularly with regard to that in the individual Scaffold accessible belt profile, which for the further work is very important, because in particular the flatness of the Finished tape is dependent on this, insufficient. The back Visible influences allow even when using empirical Factors do not adjust to the actual dependencies  of the individual mill stands from each other. This forces one to part development of the rolling stock in thickness classes, so that there is a regulation in stages. The tape quality produced leaves something to be desired left.

It is an object of the invention to provide a scheme for more to specify a scaffolding rolling mill, which is opposite to a increased control accuracy of the rolling mill components in all Working points of the scaffolding and thus to an improved Tape quality leads. In particular, the main influencing factors on the essential properties of the tape, d. H. first Line the band flatness and the band profile, on relatively simple and quickly responding way self-adapting continuously be managed.

The task is essentially solved in that a Adaptation of the model equations to the actual dependent the profile of the individual variables by changing the load distribution on the individual scaffolds, by influencing the roll bending, crowning and if necessary, the roller displacement and / or limitation such takes place that the function of a closed control loop results.

In adaptation to the conditions in hot rolling mills, the band profile up to the critical framework behind which there is a relative profile constancy, controlled influenced and then essentially taking into account the flatness conditions linearly reduced. So there is a flow condition conditions the steel adjusted during rolling, at which is particularly advantageous if a correction of the Control parameters according to the roll wear and Roll heating takes place.

By observing the load distribution and its change, the Has consequences for the roll deflection and possibly the change in  Roll contour, e.g. B. by hydraulic or thermal means (segmented work roll cooling), or the roll shift exercise and / or setting there is an influence on the profile, which leads to a flat strip profile at the end of the rolling mill. Such a tape particularly meets the requirement that its individual sections remain flat even after a division. It is advantageous if the rolling force and the nip shape of the individual scaffolds depending on the one in front of the scaffolds existing band profile and flatness is regulated. So there is an improvement in the strip profile and flatness from scaffolding to scaffolding leading to an ongoing improvement of the Ribbon shape leads. The determination of the band profile and given if the band flatness by the well-known mechani can, radiometric, optical or US measuring devices take place advantageously at a particularly favorable place, e.g. B. in front of the critical framework. This framework is then called Used the scaffolding from which the corresponding values, in particular the rolling force distribution with its individual values, e.g. B. band tension and deformation force is set. Here, a route model is advantageously used, the Sensors such as B. photocells that provide variable data.

The converging parameter adjustment is advantageously carried out by Equations of the type as set out in claims 5, 6 and 7 are reproduced. These equations result in a fast convergence with little computation.

To ensure a flawless production process further provided that when the specified framework is exceeded limits, advantageously in the host computer, an optimized Recalculation of the pass schedule is done in such a way that in the new Pass schedule the limits are met. So is advantageous ensures that always the characteristics of the rolling mill taking into account the pass schedule, to which the Initial parameters are given in the size to be expected.  

The result is a safe process control with an acceptable level Computing effort.

By averaging taking into account the measured value scattering, e.g. B. via a gain factor, the requirement the safety of the scheme and takes into account the fact that all measured values, especially measured values in a hot mode, with one not too negligible measurement errors. In particular one Measured value drift cannot be excluded.

To adapt the models to the physical processes to achieve during rolling, the measured value acquisition must the Adap Provide measurement values that can be assigned to the This means the different measured values (e.g. rolling force, Temperature, strip thickness) must be recorded in relation to the strip section will.

This is achieved by dividing the volume into so-called Band segments. For each band segment are passed through the rolling mill collected all measured values. After the tape exits segments from the rolling mill are followed by a segment-related follow-up calculation and thus an improvement of the rolling model.

Further advantages and details emerge from the following description of an embodiment, using the Drawing and in connection with the subclaims.

In detail show:

FIG. 1 shows a schematic roll stand, stating the main sizes

Fig. 2, the control technology linkage of the rolling stands in a portion of the rolling mill,

Fig. 3 shows the measurement, control and regulation structure of a rolling mill and

Fig. 4 shows the material flow conditions during the rolling of hot strip.

In Fig. 1 the deformed strip 1 denotes behind the frame, while the work rolls 2 and the back-up rolls are indicated by 3. 4 denotes the undeformed band part in front of the frame. The tape sizes in front of the scaffold are labeled i-1 and behind the scaffold i. The belt speed is in front of the stand V _i-1 and behind the stand V _i . The sizes and forces present on the scaffold and the belt ( 1, 4 ) behave as they pass through the scaffold as in the following, e.g. B. known from lectures and specialist articles, reproduced equations.

• 1) h _{iV i} = h _i- 1V _i-1 (volume constancy)
• 2) V _i = (1 + _i + r _vi ) V _wi (forward slip)
• 3) S _i = h _i - C _i (B) F _i - Roll Flattening (F _i , h _i , h _i , h _i-1 ) - Bearing Oil Film Thickness (F _i , V _i ) + r _Si ( Screwdown)
• 4) F _i = f (r _fi , K _f , B, h _i-1 , h _i , _{Zi-1, Zi} , V _i ,) (Roll Separating Force)
• 5) M _i = m (r _mi , K _f , B, h _h-1 , h _i , T _i , _{Zi-1, Zi} , V _i ,) (Rolling Torque)
• 6) T _i = t (r _ti , T _i-1 , M _-1 (Heat Losses (Rolling Time, Transport Time)) (Initial Pass Temperature, Deformation Energy)

The relationship of the results from the individual equations individual sizes.  

The setpoints of the individual variables are linked to one another in order to achieve an optimized rolling process, which is shown in FIG. 2. Here, too, the names known from publications and lectures have been chosen.

In Fig. 2, 5 denotes the control system and 6 , 7 , 8 the roll stands with their measuring devices 10 , 11 , 12 , for example position, torque and force measuring devices. The measuring devices 10 , 11 , 12 give signals to the individual controllers 16 , 17 , 18 , which in turn are based on the various scaffold drives 13 , 14 , 15 , e.g. B. for the delivery, the torque, etc., act. From the individual controllers 16 , 17 , 18 signals of the variable process variables 22 as well as signals of the process variables from the measuring devices 10 , 11 and 12 are transmitted as output signals to the control system 5 .

The target system 5 , the target variables as well as material data and additional rolling conditions are also entered by the symbolically represented signal 19 . This corresponds to the reference variable W of the standard. The control system 5 , in which the model equations are calculated, as exemplified in the explanation of FIG. 1 and in the claims, subjects the input process data, both the measured data and the variable data, to statistical processing and adaptation and carries out the adaptation of the model equations to the actual rolling process. The control system 5 uses the model equations to carry out the optimization, in particular the rolling force and thickness reduction distribution and the calculation of the setpoints for the individual controllers.

The setpoints for the individual controllers are given to the individual controllers 16 , 17 , 18 via the signals 20 . This results in a quasi-closed control loop for the individual controllers 16 , 17 , 18 via the control system 5 .

In Fig. 3 with 23 the individual stands of a rolling mill and with 24 the individual measuring devices, not only the individual stands 23 , but also other function blocks, for. B. for the rolling good picture, the thickness and flatness measurement etc., referred to net. The measured values of the measuring devices 24 are given to a measured value adaptation 25 , after which they arrive in the statistical preparation 26 , from which the adapted and prepared measured values are fed to a subsequent calculation. In the recalculation 27 , the essential process variables z. B. the final thickness, the final temperature, the decrease in thickness, the framework force, the driving force, the relative decrease in thickness, etc. calculated in a control-optimized manner. With the standard deviations of the prepared measured values, the gain of the resulting feedback circles is changed.

The values of the recalculation 27 arrive at the adaptation and learning procedure 28 , from where they are made available to the model equations in 29. From here, the determined values are fed back to recalculation 27 in a very substantial manner in order to be able to carry out the necessary adaptation and the necessary learning steps. Together with inputs 30 of the general rolling conditions, the results from the calculation of the model equations are then subjected to a pre- and post-calculation 31 , from which the new setpoints for the individual controllers are then determined.

Fig. 4 illustrates the relationship that exists in rolling mills between the strip thickness and the profile profile changes. Depending on the possibility of cross-material flow, in the thickness range below approx. 12 mm rapidly decreasing, essentially only a longitudinal material flow, ie a linear decrease in thickness, is possible. The critical framework on which the final relative profile profile must be reached in order to produce a flat finished product is therefore between 6 and 12 mm thick. The critical stand is advantageously used as a guide stand for the distribution of rolling force, crowning, roll displacement etc. of the stands in front of it. Together with the setpoint adjustment, this results in a control of a hot strip mill that makes optimal use of the possibilities of a hot rolling process. Behind the critical stand, the control is essentially the same as for cold rolling, ie the reduction in thickness, the roll crown, the load distribution on the different stands etc., as well as the stitch acceptance, are aligned with the optimal flatness of the finished product. For optimal flatness, the belt must have a uniform residual stress curve so that flat sections are obtained even after belt division. The residual stress distribution is advantageously checked with a known measuring roller and, if necessary, corrected by suitable means (scaffold adjustment, bending device, cooling, lubrication during cold rolling).

The states are also advantageously included in the control, that arise on the furnace side and the cooling section. The Regulation works accordingly. a. with a total temperature model and single temperature models. In addition come from the Literature known rolling process models, e.g. B. a rolling force model, a moment of deformation model, a rolling temperature model, an employment zero point model, a load distribution model, a track model, a rolling time model and models the work rolls, e.g. B. bending model, heating model and Wear model.

All profile-relevant parameters are therefore very advantageous taken into account by a network of self-adapting models.

Claims (13)

1. Regulation in the manufacture of rolled strip by means of a multi-stand hot and / or cold strip rolling mill, which is an over orderly process control system, which is a pass schedule with the beginning and final dimensions, with material data, rolling temperatures etc. is specified and a control system for setpoint control subordinate, decoupled individual controller for the variable Functional sizes of the individual roll stands, e.g. B. Rollers tion, speed, axial tension, etc., with a Calculation process using model equations under converging Adjustment of parameters to the actual parameters, the setpoints the individual controller can be determined so that there is a rule behaves according to a closed control loop and wherein a profile and flatness control by changing the Load distribution on the individual scaffolding, by influencing the Roll back bending, crowning and possibly the Roll displacement and / or restriction takes place. 2. Regulation according to claim 1, characterized records that hot strip up to the critical framework, behind which there is a relative profile constancy, profile influenced and then to maintain flatness the profile cross section is reduced substantially linearly. 3. Regulation according to claim 1 or 2, characterized ge indicates that in addition to the parameter fit a permanent correction of the model equation parameters according to the abrasion of the rolls and the heating of the rolls. 4. Regulation according to claim 1, 2 or 3, characterized ge indicates that the rolling force and roll gap shape of the individual scaffolds depending on the current volume profile and the current flatness is regulated.   5. Control according to claim 1, 2, 3 or 4, characterized in that the converging parameter adjustment from an output equation of the type r _Si = S _i - h _i + C _Ri F _i
r _fi = -a _Ri h _i-1 + a _Ri h _i + F _i , where r represents the parameters. 6. Regulation according to claim 5, characterized in that the converging parameters adapt with equations of the type is continued, with the corrected parameters. 7. Control according to claim 5 and 6, characterized in that the converging parameters adapt with the equations is continued and the framework variables are determined from it. 8. Regulation according to claim 1, 2, 3, 4, 5, 6 or 7, characterized characterized that the profile and flatness determination behind the critical framework with back calculation the critical framework is made. 9. Regulation according to one or more of the preceding Claims, characterized, that the critical framework is taking place. 9. Regulation according to one or more of the preceding Claims, characterized, that when predetermined framework limits are exceeded in one  Host computer a recalculation of the pass schedule is carried out in such a way that the limit values are met in the new pass schedule. 10. Regulation according to claim 9, characterized shows that the pass schedule calculation and the adap tion of the converging parameters in the host computer. 11. Regulation according to one or more of the preceding Claims, characterized, that it is done with a gain factor that is dependent speed of the measured value spread taking into account the respective current position of the measuring point on the tape is determined. 12. Regulation according to one or more of the preceding Claims, characterized, that the profile control of a multi-stand roller mill Load redistribution between the individual scaffolds with new ones Working points for the load roll gap control, the roll back bending controls and the roller displacement and / or setting regulations.