US3568637A - Tandem mill force feed forward adaptive system - Google Patents

Tandem mill force feed forward adaptive system Download PDF

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Publication number
US3568637A
US3568637A US728469A US3568637DA US3568637A US 3568637 A US3568637 A US 3568637A US 728469 A US728469 A US 728469A US 3568637D A US3568637D A US 3568637DA US 3568637 A US3568637 A US 3568637A
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workpiece
stand
roll
pass
correction factor
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US728469A
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Andrew W Smith Jr
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Westinghouse Electric Corp
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Westinghouse Electric Corp
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21B—ROLLING OF METAL
    • B21B37/00—Control devices or methods specially adapted for metal-rolling mills or the work produced thereby
    • B21B37/16—Control of thickness, width, diameter or other transverse dimensions

Definitions

  • the present invention relates to rolling mills and, more particularly, to provision of improved setup conditions based on workpiece history in cooperation with an online monitoring of predetermined mill parameters.
  • both the unloaded roll opening and the speed for each tandem mill speed are set up either by an operator or by a computer to provide successive workpiece (strip or plate) reduction resulting in an on-gauge finished work product. It may be assumed that the loaded roll opening at a stand equals the stand delivery gauge since there is little or no elastic workpiece recovery.
  • a stand gauge control system must be employed to closely control the stand delivery gauge.
  • a stand gauge control system is normally used for a reversing mill stand and for predetermined stands in tandem rolling mills.
  • the roll force gauge control system uses Hookes law in controlling the screwdown position at a rolling stand, i.e., the loaded roll opening under rolling conditions equals the unloaded roll opening (screwdown position) plus the mill spring stretch caused by a separating force supplied to the rolls by the workpiece.
  • a load call or other force detector measures the roll separating force. The screwdown position is then controlled to balance the roll force changes from a reference or setpoint value and thereby hold the loaded roll opening at a substantially constant value.
  • mill setup parameters have been set either by the operator or by a computer. But, as the rolling mill parameters have increased both in number and complexity, the computer has played the dominant role in determining mill setup with the operator serving as backup.
  • the credibility of the computer has been established by causing it to monitor certain inputs according to a predetermined model and then, through functional relationships between these inputs, to provide proper operating conditions.
  • information is gathered from the various inputs which serve to improve the setup conditions for the rolling of the next workpiece.
  • Such a system has proved satisfactory in that, even if the original setup conditions are poor, eventually the system will adapt to a proper setup by learning from the rolling of each previous workpiece. It should be noted, however, that the rolling of a workpiece is inherently dependent on information gained from previous rollings and that any error in conditions for that particular piece would go uncorrected for that particular piece.
  • a further object of the present invention is to provide a new and improved head-end gauge control system wherein changes in the setup conditions for the workpiece being rolled may occur from information received from the last rougher and first finishing stand of the rolling mill.
  • An additional object of the present invention is to provide a new and improved head-end gauge control system wherein ratios between predicted and actual force are made at the last roughing stands and at the finishing stands to provide setup information for rolling of the next workpiece.
  • a still further object of the present invention is to provide a new and improved head-end gauge control system whereby subsequent stands are responsive to feed forward information for providing an on-gauge workpiece strip.
  • Yet a further object of the present invention is to provide a new and improved head-end gauge control system which is compatible with apparatus required in a conventional computer-controlled roll force gauge control system.
  • a tandem strip rolling mill is under the control of a process computer for providing an on-gauge workpiece strip.
  • a force feed forward system is operating whereby the pattern for the head end is held in storage whereby the pattern for the head end is held in storage ash is rolled to the last roughing stand and then the finishing stands. Measurements are then made on the head end of the next piece to determine whether the general force level will be higher or lower and corrections are made in the later stand screwdown references to compensate for the predicted change in roll separating force.
  • the target thickness to be delivered from each stand is maintained the same as determined from the original schedule calculation so no change is required in the speed of the stands.
  • FIG. 1 shows a schematic diagram of the last stand of a roughing mill and a portion of the finishing mill in a tandem hot steel strip rolling mill illustrating the inputs and outputs requisite to the head-end gauge control system which is the subject of this invention.
  • FIG. 2 represents the system operation for the rolling of a new workpiece from the time it enters the last rougher until the entire mill is full.
  • FIGS. 3 and i set forth the system operation in accordance with the head end of the workpiece entering certain predetermined stands within the rolling mill.
  • FIG. l a portion of a continuous strip rolling mill is shown and designated generally by the numeral ill.
  • the last stand of the roughing mill is shown by the symbol R followed by the first two and the last stands of a finishing line designated respectively by the symbols El, E2 and EN
  • Each of the rolling stands includes a pair of work rolls l2 and M. These work rolls are caused to provide a strip reduction as the workpiece 16 passes successively through each of the several stands.
  • a set of backup rolls 1% and 20 provides pressure on the work rolls l2 and 14 in response to the operation of a screwdown 22.
  • the regulation of the applied pressure is through a screwdown motor 24 whose operation is controlled by a position regulator 26.
  • Screwdown position detectors 28 monitor the position of the screwdowns 22 by detecting the number of revolutions of the screwdown motors 24 and transmitting an output signal representative thereof. Following the last stand FN in the finishing mill, an X-ray gauge 30 is so positioned to detect the actual finished gauge of the workpiece and to provide a signal proportional thereto. Associated with each of the respective rolling stands is a load cell 32 which measures the separating roll force at each of the respective stands.
  • Control of the rolling process is provided by a process control computer 34 which provides communication between the rolling mill inputs and outputs in a predetermined manner.
  • the exact mode of control is provided by an externally provided program which functionally relates an input or combination of inputs to provide controlled output signals which are commensurate with an on-gauge workpiece strip.
  • the functional relationship between and among certain inputs as seems to exist within the process computer 34 will be discussed in detail herein.
  • Other apparatus and structure necessary for the proper operation of a rolling mill is purposely left out for ease of illustration and would necessarily include such items as drive motors, potentiometers, speed controllers, temperature sensors etc.
  • Accurate online gauge control and regulation of the workpiece head end is achieved by the provision of reference signals from the process control computer 34 to the respective position regulators 26 corresponding to all the finishing stands when the workpiece is being measured in the last rougher and the third to last finishing stands when the workpiece is being measured in the first finishing stand.
  • the reference signals are developed through a mathematical model provided in the process control computer 34 which is responsive to the analogue signals resulting from the respective load cells 32, the screwdown position detectors 28, and the X-ray gauge 30 as well as digital inputs pertaining to the strip characteristic shown in block 36 to effect adequate gauge control on the workpiece 316 until the mill becomes full.
  • the process control computer 34 is then free to provide control under a gauge control system as previously referenced in above-referenced Eggers et al. copending patent application. It is only upon the beginning of the rolling of another workpiece that the head-end gauge control system is again activated to provide proper on-gauge strip until the mill is once again full.
  • the digital inputs relating to the strip characteristics in block 36 contains such items as strip width, desired or target gauge, and the type of strip alloy.
  • FIG. 2 a flow chart illustrating the timing sequence of the head-end gauge control system is illustrated.
  • System operation is initiated at the start block 109 at some time as the workpiece is progressing through the roughing mill.
  • the last rougher is interrogated in block 110 to see if the workpiece has entered the rougher R. If not a finite delay period is initiated in block 12'! whereupon a return is then made to block 110 to again interrogate to see if the workpiece has now entered the last rougher.
  • a counter in the process control computer 34 which represents the stand number is set in block to the stand number corresponding to the last rougher R whereupon the system then progresses to that part of the gauge control system corresponding to updating of the screwdown references while in the last roughing stand.
  • This function is illustrated in block by referring to the routine as shown in FIG. 3 progressing from the enter block proceeding through the exit block and then returning to block which then interrogates the first finishing stand F1 to determine whether the workpiece has entered. If not, a finite delay is initiated in block following which return is made to block 140 for a further interrogation of the first finishing stand F1.
  • the stand counter in the process control computer 34 is then set to the stand number for the first finisher in block as a prelude to again traversing through the system of FIG. 3 as shown in block which provides updating of the screwdown following the entry of the workpiece into the first finishing stand Fl.
  • FIG. 3 illustrates the operation of the head-end gauge control system at such times when the workpiece has either entered the last rougher stand R or the first finisher stand Fl. As previously mentioned this occurs at the blocks 130 and 170 of FIG. 2.
  • the first block of FIG. 3 is block 200 which is the entry point to this segment of head-end gauge control system.
  • the stand counter is set to the proper stand number.
  • the stand is interrogated to see if it is actually producing a reduction in the strip gauge or on the other hand if it is merely providing a dummy operation.
  • the mill spring is calculated using the measured force FMn as determined from the load cell 32 corresponding to the stand number in the counter n.
  • the mill spring Xn is equal to the negative of the fraction F, /I( where F, is the measured force and K is equal to the mill spring constant. for that particular stand.
  • F is the measured force
  • K is equal to the mill spring constant. for that particular stand.
  • a previously determined screwdown offset OS which acts as a correction factor to steady state gauge errors is then added to the just-calculated mill spring K and the screwdown position SDM, as determined by the screwdown position detector 28 of FIG. 1 to provide a calculated gauge H which corresponds to the actual thickness or the workpiece delivery gauge of the stand n. This calculation is represented by the block 206.
  • Block 208 then predicts a force F corresponding to the stand in as a function of the entry gauge Pi the delivery gauge H the width of the strip W, and the strip temperature T Had the stand :1 been inoperable as determined in block 202 the exit gauge would then have been set equal to the entry gauge as shown in block 210.
  • Blocks 202 through 210 are initiated each time that data has been collected on the head end of the workpiece in either the last rougher stand R or the first finishing stand F1. in this procedure, any difference between the measured roll force and screwdown setting and the predicted roll force and screwdown setting will cause a difference between the actual gauge delivered from the stand and the desired gauge.
  • Blocks 2% through 210 calculate the scrum gauge delivered from the particular stand and repredict the rail separating force for the actual draft taken in that stand.
  • interrogation is made in block 21 .2 to determine whether the stand counter is set for the last rougher stand or the first finishing stand.
  • interrogation is made in block 214 to determine whether the piece now being rolled is of the same alloy content as the previous piece.
  • a check is made in block 216 to determine whether the ratio of the final target gauge l-lT for the previous piece to the final target gauge l-lT,,-, of the previous piece is within percent. if the limit check in block 216 is satisfied,
  • the procedure then follows to block 226 for a calculation of force correction factor.
  • the stand correction factor SCFn is set equal to l for all stands. The same procedure is followed if the limit condition suggested in block 216 is not satisfied.
  • the action of block 213 serves to set the stand correction factor for the last rougher equal to l in block 220 the stand counter is. interrogated to see if it is presently equal to the stand number of the last finisher and if not the stand number n is increased by l in block 222 and return is then made to block 218 which then sets the current stand correction factor equal to-l This same process continues until the last finisher is detected in block 2258 whereupon the stand number is again set to its initial position as that of the last rougher in block 224.
  • the stand correction factor for all the finishing stands are reset to l and are not dependent on any past history.
  • a force correction factor FCF which is equal to the fraction (FMJI CFM (E).
  • the force correction factor is set equal to 1 in block 232 before preceeding to the next sequential block 234.
  • the stand counter n is equal to the stand number for the last rougher as determined in block 2% the stand counter would be increased by l in bloclt 244i and now be equal to the stand number for the first finisher. if this stand is operating and not dummied as determined in block sea, the force E ⁇ .
  • the stand number n is then interrogated to determine whether it is at that of the last finish stand FN and if so, the procedure is completed at block 252.
  • the stand number is increased by l in block 2 30 and a determination as to whether the second finishing stand is operating as made in block 242. It necessariing finishing stands in the mill. For any finishing stand that is inoperable as determined in block 242 the stand number is increased by l in block 254 and no updated screwdown reference is calculated for that inoperative stand.
  • block 1176 again calls for the return to the system procedure of H6. 3 with the only difference being that the stand number n is now equal to that of the first finishing stand Fl.
  • the same procedure beginning at block 200 is followed as when n was equal to the stand number of the last rougher except that beginning in block 2R2, if the stand number is equal to that of the first finisher the procedure immediately skips to block 226 for calculation of a force correction factor without providing any recomputation of the stand correction factor.
  • the stand correction factor SCF will remain as calculated previously from the system sequence when the mill was full on the previous piece.
  • a second variance in the procedure occurs following the computation of the force correction factor whereupon in block 234 n is now equal to the stand number for the first finisher and proceeds to block 255 which increases the stand number by l and is thus now equal to that of the second finishing stand F2.
  • the procedure advances immediately to block 2% where new roll force and screwdown setting are determined for the remaining finishing stands as previously described. If, however, the second finishing stand is in operation as determined in block 256 the mill spring is again recalculated in block 258 using the predicted force F,,. Then, in block 260 gauge thickness 1H,, is predicted out of the next stand using the unadjusted screw setting.
  • l-lT equals the target exit gauge from the present stand
  • ll-lT,,- equals the target entry gauge at the present stand.
  • the stand number is again increased by l in block 262 and a check is made in block 264 to see if this new stand is operating. If the stand is inoperable, the stand number is again increased and interrogated until some stand number is found to be operating.
  • a roll force F is predicted using the predicted entry H 'q and the target exit gauge ET,, the force correction factor PCP and the stand correction factor SCF,,.
  • block 211 makes reference to the system procedure of FIG. 4 when the stand number has been set to that for the first finishing stand Fl.
  • blocks 2% through Zill are exactly equivalent to that of FIG. 3 and serve to predict a force for that particular stand n in block 302 an offset factor OS, is calculated-for stand n which corresponds to a correction factor for offsetting the setting gauge error.
  • OS offset factor
  • stand n is then interrogated in block 3% to see if it is operating. If not, no new stand correction factor is provided and in block 312 interrogation is made as to whether n is equal to the number of the last finishing stand.
  • this invention provides a system and method of making force measurement in all of these stands in a rolling mill as a piece is being rolled. Ratio comparisons are made between the measured force in each stand and predicted force and these ratios are then used to better predict forces for the rolling of the next workpiece.
  • the measured force in an early stand as the next piece is being rolled is compared with the predicted force and this ratio along with the ratios calculated for each stand while rolling the previous piece are used to better predict the force roll opening to thus obtain a good mill setup and produce a proper on-gauge finish workpiece.
  • a gauge control system for a rolling mill having at least one roll stand with a screwdown-controlled roll opening through which a first pass of a present workpiece is transported comprising:
  • gauge control system as set forth in claim 11, wherein said system includes:
  • the gauge control system as set forth in claim 1, including means for determining a correction factor according to the equation FCF (SCF) (F) where FCF is the determined force correction factor for subsequent passes of said present workpiece, FM is the measured roll force of said one roll stand during said first pass of the present workpiece through said stand SCF is the stand correction factor in relation to a previous similar workpiece for said one roll stand, and F is the predicted roll force for said one roll stand in accordance with the actual reduction made in the gauge of the present workpiece by said stand, and wherein said correction factor is used to determine the respective corrective screwdown movements for subsequent passes in relation to said present workpiece.
  • FCF the determined force correction factor for subsequent passes of said present workpiece
  • FM the measured roll force of said one roll stand during said first pass of the present workpiece through said stand
  • SCF is the stand correction factor in relation to a previous similar workpiece for said one roll stand
  • F is the predicted roll force for said one roll stand in accordance with the actual reduction made in the gauge of the present workpiece by said stand
  • said means for determining a predicted roll force includes a digital computer, said computer having an input coupled to said actual roll force sensing means and an output coupled to said means for determining a screwdown movement.
  • the gauge control system as set forth in claim 8 including means for providing a unity correction factor when said correction factor is beyond predetermined value limits.
  • means for determining a stand operation correction factor for the latter roll stand in accordance with a ratio between the earlier pass actual roll force and the earlier pass predicted roll force relative to said previous workpiece with said means for determining the roll opening being responsive to said stand operation correction factor when determining the roll opening of the latter roll stand.
  • screwdown-controlled should be screwdown controlled line 53, line 73,

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  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Control Of Metal Rolling (AREA)
US728469A 1968-05-13 1968-05-13 Tandem mill force feed forward adaptive system Expired - Lifetime US3568637A (en)

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Cited By (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3766761A (en) * 1971-10-07 1973-10-23 Wean United Inc Rolling mill control
US3802236A (en) * 1972-01-06 1974-04-09 Westinghouse Electric Corp Gauge control method and apparatus including workpiece gauge deviation correction for metal rolling mills
US3813908A (en) * 1972-12-18 1974-06-04 Gen Electric Method of adaptive thread
US3906765A (en) * 1974-11-20 1975-09-23 Boeing Co Numerically controlled contour forming machine
US4125004A (en) * 1977-07-12 1978-11-14 Amtel, Inc. Rolling mill gauge control system
US4753093A (en) * 1984-08-16 1988-06-28 Mannesmann Ag Planarity control in the rolling of flat stock
WO2004085087A3 (en) * 2003-03-28 2005-01-20 Tata Iron And Steel Company Lt A system and method for on-line property prediction for hot rolled coil in a hot strip mill
US7110840B1 (en) * 1999-04-01 2006-09-19 Siemens Aktiengesellschaft Master control system for a rolling mill

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3186201A (en) * 1961-06-21 1965-06-01 Steelworks Automation Ltd Production of metal strip
US3332263A (en) * 1963-12-10 1967-07-25 Gen Electric Computer control system for metals rolling mill
US3357217A (en) * 1965-05-12 1967-12-12 Westinghouse Electric Corp Slave gauge control system for a rolling mill

Family Cites Families (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB984001A (en) * 1960-06-08 1965-02-24 Steelworks Automation Ltd Improvements in or relating to the production of metal strip
US3186200A (en) * 1961-10-31 1965-06-01 Gen Electric Automatic thickness regulator for strip rolling mills
BE637694A (enrdf_load_stackoverflow) * 1962-09-21
GB1243806A (en) * 1967-10-23 1971-08-25 Westinghouse Electric Corp Apparatus for controlling a rolling mill

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3186201A (en) * 1961-06-21 1965-06-01 Steelworks Automation Ltd Production of metal strip
US3332263A (en) * 1963-12-10 1967-07-25 Gen Electric Computer control system for metals rolling mill
US3357217A (en) * 1965-05-12 1967-12-12 Westinghouse Electric Corp Slave gauge control system for a rolling mill

Cited By (11)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3766761A (en) * 1971-10-07 1973-10-23 Wean United Inc Rolling mill control
US3802236A (en) * 1972-01-06 1974-04-09 Westinghouse Electric Corp Gauge control method and apparatus including workpiece gauge deviation correction for metal rolling mills
US3813908A (en) * 1972-12-18 1974-06-04 Gen Electric Method of adaptive thread
US3906765A (en) * 1974-11-20 1975-09-23 Boeing Co Numerically controlled contour forming machine
US4125004A (en) * 1977-07-12 1978-11-14 Amtel, Inc. Rolling mill gauge control system
US4753093A (en) * 1984-08-16 1988-06-28 Mannesmann Ag Planarity control in the rolling of flat stock
US7110840B1 (en) * 1999-04-01 2006-09-19 Siemens Aktiengesellschaft Master control system for a rolling mill
WO2004085087A3 (en) * 2003-03-28 2005-01-20 Tata Iron And Steel Company Lt A system and method for on-line property prediction for hot rolled coil in a hot strip mill
US20070106400A1 (en) * 2003-03-28 2007-05-10 Tata Steel Limited System and method for online property prediction for hot rlled coil in a hot strip mill
US8108064B2 (en) 2003-03-28 2012-01-31 Tata Steel Limited System and method for on-line property prediction for hot rolled coil in a hot strip mill
EP1608472B1 (en) 2003-03-28 2016-09-07 Tata Steel Limited A system for on-line property prediction for hot rolled coil in a hot strip mill

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FR2008428A1 (enrdf_load_stackoverflow) 1970-01-23

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