US3928994A - Thickness control system for a rolling mill - Google Patents

Thickness control system for a rolling mill Download PDF

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Publication number
US3928994A
US3928994A US515030A US51503074A US3928994A US 3928994 A US3928994 A US 3928994A US 515030 A US515030 A US 515030A US 51503074 A US51503074 A US 51503074A US 3928994 A US3928994 A US 3928994A
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Prior art keywords
thickness
roll eccentricity
roll
strip thickness
control system
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Expired - Lifetime
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US515030A
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English (en)
Inventor
Ken Ichiryu
Masayuki Shigeta
Ichiro Nakamura
Toshiyuki Kajiwara
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Hitachi Ltd
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Hitachi Ltd
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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
    • B21B37/58—Roll-force control; Roll-gap control
    • B21B37/66—Roll eccentricity compensation systems

Definitions

  • ABSTRACT A system for controlling strip thickness in a rolling mill in which the rolling pressure applied to material is continuously measured or the strip thickness on the output side is continuously detected as a parameter of the outgoing thickness of the rolled strip and the result of measurement or detection of the parameter is used to obtain an autocorrelation.
  • the power spectra for the entire region and a predetermined region covered by the autocorrelation are produced, so that the ratio of roll eccentricity component to the entire variation is obtained from the ratio between the two spectra.
  • the roll eccentricity component is applied to a feedback loop of the control system in order to eliminate the effect of the roll eccentricity component on the automatic thickness control system.
  • FIG. 1 A first figure.
  • the present invention relates to a thickness control system for a rolling mill, or more in particular to a thickness control method aimed at removing the influence of the roll eccentricity.
  • This gagemeter type automatic thickness control system controls values such as a thickness command hd, no-load roll gap S, rolling pressure P, and mill modulus Km so as to satisfy the following equation:
  • hd( S+P/Km) Those values are essential for controlling thickness of strips in a rolling mill.
  • the gagemeter type automatic thickness control system has suffered from disadvantages in that the presence of eccentricity in respective rolls leads to the failure to maintain the roll gap constant as well as to meet the objectives of the thickness control.
  • the gagemeter type control system in case the rolling pressure is increased, it is so designed that no-load roll gap S be decreased on the assumption that the increase in the rolling pressure has been caused by the increase in thickness of a strip on the input side.
  • the rolling pressure in case the roll gap is decreased due to roll eccentricity, the rolling pressure will be increased, so that contrary to the need to increase the roll gap, the aforesaid control system will function so as to decrease the roll gap. Accordingly, it is an important problem imposed on the gagemeter type automatic thickness control system to remove or avoid the influence of roll eccentricity.
  • the so-called resonance type filter adapted to tune with a roll eccentricity frequency fe has a given band width (sensitive zone width), thereby presenting shortcoming of passing signals whose frequencies are close to that of the signal intended to be passed therethrough.
  • the disturbance in the roll system occurs in a work roll section, as well, presenting a complicated pattern, including its frequency component. For this reason, the desired accuracy can not be obtained merely by detecting and compensating for the eccentricity component of a single roll according to the aforesaid system.
  • a parameter relating to the thickness on the output side is continuously measured and the result of the measurement is used to detect external disturbance due to the roll eccentricity by statistical techniques based on the correlation, thus eliminating the external disturbance from the thickness control system.
  • the present invention is characterized in that the autocorrelation function R P of the thickness parameter on the output side is obtained, so that the roll eccentricity component is taken out of the all variation components by obtaining the power spectra 4),, and 4),, respectively from the entire region and a predetermined region associated with the auto correlation function R,,.
  • the roll eccentricity component thus taken out is applied as a command to the automatic thickness control.
  • FIG. 1 is a schematic diagram showing a typical automatic thickness control system of gagemeter type according to the present invention.
  • FIG. 2 shows a block diagram of a circuit for detecting the roll eccentricity by the method of thickness control according to the invention.
  • FIG. 3 is a diagram showing an example of the autocorrelation function of rolling pressure.
  • FIG. 4 is a block diagram showing a flow chart for calculating the phase relation of the roll eccentricity against the rotation of the reinforcing roll on the basis of rolling pressure.
  • FIG. 5 is a block diagram showing an automatic thickness control system of gagemeter type according to an embodiment of the invention.
  • FIG. 6 is a block diagram showing a flow chart for calculating the phase relation of the roll eccentricity on the basis of thickness variation on the output side.
  • FIG. 1 there is shown a diagram of a gagemeter type automatic thickness control system.
  • a rolling mill consists of a work roll 2 adapted to directly roll a strip 1, and a backup roll 3 externally supporting the work roll 2.
  • the roll screw-down operation of the rolling mill is accomplished by means of a hydraulic jack provided at the ends of the lefthand and righthand rolls.
  • the hydraulic jack consists of a hydraulic cylinder 5 and a ram 6 and is so designed as to adjust the roll gap by adjusting the amount of oil within the hydraulic jack with the aid of a servo-valve 4.
  • the displacement S of the ram 6 is measured by means of a displacement meter 7, and then a measurement thus obtained is negatively fed back to be compared with the thickness command hd.
  • rolling pressure P is measured by a pressure gage 8, and then the measurement value is divided by a mill constant Km at a coefficient multiplier 9 and then the value thus obtained is applied to the summing point 10 to be negatively fed back to the thickness command hd.
  • the aforesaid respective values are controlled so as to meet the relationship, hd (S P/Km) 0, thereby maintaining the thickness of the rolled strip constant.
  • the thickness variation of the output side is generally attributable to the thickness variation on the input side and roll eccentricity.
  • the thickness variation on the input side is an irregular one in most cases given by statistically random signal whereas the roll eccentricity is subjected to periodical variation.
  • the rolling pressure which is closely related to the thickness variation on the output side and easily measured is continuously detected and the autocorrelation function R (1') of the result P(t) of detection is obtained.
  • an autocorrelation function R is defined as where r is a delay time. As shown in FIG. 3, this autocorrelation function R ('r) varies with the delay time 1'. Where the delay time 1- is close to zero, that is O 5 1' 7R1 or 0 g 17 7R in the drawing, for example, the correlation function R indicates the irregularity of the rolling pressure generally corresponding to the irregular components of the thickness variation on the input side.
  • FIG. 2 showing a block diagram for calculating a component corresponding to the roll eccentricity from the rolling pressure detector circuit
  • the rolling mill used is the same as that shown in FIG. 1.
  • the rolling pressure is detected by a rolling pressure gage 8, and the detection signal P(t) is produced in the form of P(t 1') through a delay circuit 12.
  • P(t) is multiplied by P(t 1') at a multiplier circuit 13, the output of which is applied to an averaging circuit 14 whereby the autocorrelation function of the rolling pressure R,D is obtained.
  • This autocorrelation function R is divided into two. One of the results of the division is applied to a phase shifter 15 having the range T,, 7' 5 T the output of which is multiplied by e 11 r in the multiplier circuit 16 and averaged by the averaging circuit 17 thereby to obtain a power spectrum corresponding to the roll eccentricity.
  • the other output of the correlation function R is multipled by e 11' r in the multiplier circuit 18 for the range 0 7 7' 1 without any special process, and the result of the multiplication is integrated by the averaging circuit 19, thereby producing the total power 4),. of the rolling pressure at the eccentricity frequency fe. Also, p and are applied to the divider circuit 20 thereby to obtain B (p 4 Reference is made to FIG. 4 showing a block diagram for calculating the gain
  • the output of the circuit 22 is applied to a filter 23 synchronized with the roll eccentricity frequencyfe and having such a weight as to pass the roll eccentricity component alone, whereby the output of the circuit 22 is compared with the output signal from a reference signal generator 21.
  • the result of comparison as well as the relation between the rolling pressure and roll eccentricity is used to calculate the gain
  • of the roll eccentricity compensating command e and the phase angle e are obtained by the circuit 25.
  • FIG. 5 shows an example of the construction of the automatic thickness control system of gagemeter type making use of the power spectrum ratio B and the roll eccentricity compensating command e' derived from the foregoing calculation processes.
  • the symbol hd shows a roll gap command
  • an electrical signal representing the roll gap command hd is amplified by the amplifier 30, so that the output current of the amplifier is used to energize the servo-valve 4, thereby determining the roll gap S at the time of no-load through the block of the pipe 32.
  • the symbol 2 shows the amount of roll eccentricity, h the thickness on the output side, and h the thickness on input side.
  • the difference between h and h causes a rolling pressure as shown in the block 33, and the roll gap is increased by the amount obtained by dividing the difference by the mill constant Km.
  • Reference numeral 9 shows a block representing the reciprocal of the mill constant.
  • a rolling pressure feedback loop 38 is formed for the purpose of dampening the variation in roll gap due to such a rolling load.
  • the block shows a section for regulating the mill constant a, which is unity at infinite rigidity (in thecase of ordinary BISRA-AGC) and zero at natural state, its normal value employed being close to 1.
  • the output of the block 35 is separated into a couple of loops including the lines 39 and 40.
  • the signal on the line 40 is applied through a narrow band filter 36, which has no loss nor phase delay only at the roll-eccentricity frequency, through the eccentricity regulating section 37 with the coefficient of ,B, and then combined with the signal from the line39 so that the output 41 of the regulator section 37 is subtracted from the line 39 and the result of subtraction is fed back to the input terminal 42.
  • a narrow band filter 36 which has no loss nor phase delay only at the roll-eccentricity frequency
  • phase relation of pure roll eccentricity e since the phase relation of pure roll eccentricity e is given from FIG. 4, the application to the input terminal 42 the phase relation e for offsetting it permits the roll eccentricity to be completely eliminated, thus making it possible to regulate the thickness on the output side exactly at a fixed level.
  • the roll eccentricity 2 obtained from the block diagram of FIG. 4 is obtained through the calculation processes by measuring the strip thickness on the output side as shown in FIG. 6.
  • the thickness of the strip rolled on the output side is continuously detected by the X-ray thickness gages 26 and 27 and produced from a thickness measuring circuit 22.
  • This signal is compared with the signal 21 synchronous with roll rotation at the filter 23, and the result of comparison is applied to the eccentricity calculation circuit 24 thereby to obtain the gain [2 of roll eccentricity and the phase angle e.
  • the phase relation of roll eccentricity is applied to an input calculation circuit 25 whereby the offset signal 2' is obtained.
  • a roll eccentricity compensation command enables a rolling operation while at the same time compensating for any roll eccentricity.
  • a strip thickness control system of the gagemeter type comprising a plurality of rolls, a hydraulic jack for giving rolling power to said rolls, a flow rate control valve for adjusting the roll gap by controlling the amount of oil in said hydraulic jack.
  • a valve control device means for giving a command associated with a desired thickness to said control device and a position detector for detecting the roll gap, the output of said position detector being fed back to said valve control device;
  • a method of controlling the strip thickness for the rolling mill comprising steps of continuously detecting a value of at least one parameter relating to the outgoing thickness of a strip rolled by said rolls, producing an autocorrelation function R of the detected value of said parameter, producing a power spectra for the whole region and a power spectra for a predetermined part of the region covered by said autocorrelation function, determining a roll eccentricity power from the ratio between said power spectra for the predetermined part of the region and said power spectra for the whole region, and applying said roll eccentricity power to the strip thickness control
  • a method for controlling strip thickness according to claim 2 in which the power spectra over the whole region of the entire frequency variation corresponding to roll eccentricity is calculated by the use of the whole positive region of a delay time, whereas the power spectra for the predetermined part of the region is calculated by the use of regions excepting those regions close to the delay time of zero.
  • a strip thickness control system of the gagemeter type comprising a plurality of rolls, a hydraulic jack for giving rolling power to said rolls, a flow rate control valve for adjusting the roll gap by controlling the amount of fluid in said hydraulic jack, a valve control device, means for giving a command associated with a desired thickness to said control device and a position detector for detecting the roll gap, the output of said position detector being fed back to said valve control device, the improvement comprising means for generating a roll eccentricity signal and for applying said roll eccentricity signal to the strip thickness control system so as to compensate for the variation of the outgoing thickness of the strip due to the roll eccentricity, said roll eccentricity signal generating means including means for continuously detecting a value of at least one parameter relating to the outgoing thickness of a strip rolled by said rolls, means for producing an autocorrelation function R of the detected value of said parameter, means for producing a power spectra for the whole region and a power spectra for a predetermined part of the region covered by said autocorrelation function, means for
  • a strip thickness control system wherein said means for continuously detecting a value of at least one parameter relating to the outgoing strip thickness includes means for continuously detecting the rolling pressure and providing an output signal indicative thereof, and further comprising means for providing an output signal indicative of the rotation of said rolls and determining means responsive to the roll pressure signal and the rotation signal for determining the gain and phase angle of the roll eccentricity component in synchronism with the rotation of the rolls.
  • a strip thickness control system wherein the means for continuously detecting a value of at least one parameter relating to the outgoing strip thickness includes means for continuously detecting the outgoing strip thickness and providing an output signal indicative thereof, and further comprising means for providing a signal indicative of the rotation of said rolls, and determining means responsive to the outgoing strip thickness signal and the roll rotation signal for determining the gain and phase angle of the roll eccentricity component in synchronism with the rotation of the rolls.

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  • Mechanical Engineering (AREA)
  • Control Of Metal Rolling (AREA)
US515030A 1973-10-17 1974-10-15 Thickness control system for a rolling mill Expired - Lifetime US3928994A (en)

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Cited By (17)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4036041A (en) * 1975-02-12 1977-07-19 Hitachi, Ltd. Gage control system for rolling mill
DE2748033A1 (de) * 1976-12-17 1978-06-22 Secim Courbevoie Fa Universalwalzgeruest fuer eine i-traegerwalzstrasse und duowalzgeruest fuer eine profilstahlwalzstrasse
FR2392737A1 (fr) * 1977-06-03 1978-12-29 Westinghouse Electric Corp Procede et installation pour corriger l'excentricite d'un laminoir
US4194383A (en) * 1978-06-22 1980-03-25 Gulf & Western Manufacturing Company Modular transducer assembly for rolling mill roll adjustment mechanism
US4222254A (en) * 1979-03-12 1980-09-16 Aluminum Company Of America Gauge control using estimate of roll eccentricity
EP0015866A1 (en) * 1979-02-28 1980-09-17 Mitsubishi Jukogyo Kabushiki Kaisha Method of controlling roll eccentricity of rolling mill and apparatus for performing the same method
US4521859A (en) * 1982-10-27 1985-06-04 General Electric Company Method of improved gage control in metal rolling mills
US4580224A (en) * 1983-08-10 1986-04-01 E. W. Bliss Company, Inc. Method and system for generating an eccentricity compensation signal for gauge control of position control of a rolling mill
US4648257A (en) * 1985-08-30 1987-03-10 Aluminum Company Of America Rolling mill eccentricity compensation using actual measurement of exit sheet thickness
US4685063A (en) * 1984-07-05 1987-08-04 Siemens Aktiengesellschaft Process and device for compensation of the effect of roll eccentricities
US4910985A (en) * 1986-07-09 1990-03-27 Alcan International Limited Method and apparatus for the detection and correction of roll eccentricity in rolling mills
US4946523A (en) * 1988-12-22 1990-08-07 Ford Motor Company Method and apparatus for use in manufacturing safety glass laminates
US5203188A (en) * 1991-09-16 1993-04-20 Morgan Construction Company System and method for monitoring a rolling mill
DE4411313A1 (de) * 1993-05-08 1994-11-10 Daimler Benz Ag Verfahren zur Ausfilterung des Exzentrizitätseinflusses beim Walzen
US5647238A (en) * 1994-03-29 1997-07-15 Siemens Aktiengesellschaft Method for suppressing the influence of roll eccentricities on a control for a rolling-stock thickness in a roll stand
WO2000005450A1 (en) * 1998-07-24 2000-02-03 Valmet Corporation Method and device for changing the natural frequency of a nip roll construction in a paper or board machine
DE10226499A1 (de) * 2002-06-14 2003-12-24 Abb Patent Gmbh Verfahren und Vorrichtung zum Erfassen und Auswerten von Messsignalen

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3100410A (en) * 1959-06-27 1963-08-13 Westinghouse Canada Ltd Control systems
US3543549A (en) * 1967-11-21 1970-12-01 Davy & United Eng Co Ltd Rolling mill control for compensating for the eccentricity of the rolls
US3580022A (en) * 1968-11-12 1971-05-25 Youngstown Sheet And Tube Co Rolling mill including gauge control
US3709009A (en) * 1970-03-20 1973-01-09 Ishikawajima Harima Heavy Ind Method for detecting eccentricity and phase angle of working or backing roll in rolling mill
US3793860A (en) * 1972-12-04 1974-02-26 Westinghouse Electric Corp System to compensate for roll eccentricity effects and/or to simulate a mill with variable stretch characteristics

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3100410A (en) * 1959-06-27 1963-08-13 Westinghouse Canada Ltd Control systems
US3543549A (en) * 1967-11-21 1970-12-01 Davy & United Eng Co Ltd Rolling mill control for compensating for the eccentricity of the rolls
US3580022A (en) * 1968-11-12 1971-05-25 Youngstown Sheet And Tube Co Rolling mill including gauge control
US3709009A (en) * 1970-03-20 1973-01-09 Ishikawajima Harima Heavy Ind Method for detecting eccentricity and phase angle of working or backing roll in rolling mill
US3793860A (en) * 1972-12-04 1974-02-26 Westinghouse Electric Corp System to compensate for roll eccentricity effects and/or to simulate a mill with variable stretch characteristics

Cited By (21)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4036041A (en) * 1975-02-12 1977-07-19 Hitachi, Ltd. Gage control system for rolling mill
DE2748033A1 (de) * 1976-12-17 1978-06-22 Secim Courbevoie Fa Universalwalzgeruest fuer eine i-traegerwalzstrasse und duowalzgeruest fuer eine profilstahlwalzstrasse
FR2392737A1 (fr) * 1977-06-03 1978-12-29 Westinghouse Electric Corp Procede et installation pour corriger l'excentricite d'un laminoir
US4194383A (en) * 1978-06-22 1980-03-25 Gulf & Western Manufacturing Company Modular transducer assembly for rolling mill roll adjustment mechanism
EP0015866A1 (en) * 1979-02-28 1980-09-17 Mitsubishi Jukogyo Kabushiki Kaisha Method of controlling roll eccentricity of rolling mill and apparatus for performing the same method
US4222254A (en) * 1979-03-12 1980-09-16 Aluminum Company Of America Gauge control using estimate of roll eccentricity
US4521859A (en) * 1982-10-27 1985-06-04 General Electric Company Method of improved gage control in metal rolling mills
US4580224A (en) * 1983-08-10 1986-04-01 E. W. Bliss Company, Inc. Method and system for generating an eccentricity compensation signal for gauge control of position control of a rolling mill
US4685063A (en) * 1984-07-05 1987-08-04 Siemens Aktiengesellschaft Process and device for compensation of the effect of roll eccentricities
US4648257A (en) * 1985-08-30 1987-03-10 Aluminum Company Of America Rolling mill eccentricity compensation using actual measurement of exit sheet thickness
US4910985A (en) * 1986-07-09 1990-03-27 Alcan International Limited Method and apparatus for the detection and correction of roll eccentricity in rolling mills
US4946523A (en) * 1988-12-22 1990-08-07 Ford Motor Company Method and apparatus for use in manufacturing safety glass laminates
US5203188A (en) * 1991-09-16 1993-04-20 Morgan Construction Company System and method for monitoring a rolling mill
DE4411313A1 (de) * 1993-05-08 1994-11-10 Daimler Benz Ag Verfahren zur Ausfilterung des Exzentrizitätseinflusses beim Walzen
DE4411313C2 (de) * 1993-05-08 1998-01-15 Daimler Benz Ag Verfahren zur Ausfilterung des Exzentrizitätseinflusses beim Walzen
US5647238A (en) * 1994-03-29 1997-07-15 Siemens Aktiengesellschaft Method for suppressing the influence of roll eccentricities on a control for a rolling-stock thickness in a roll stand
WO2000005450A1 (en) * 1998-07-24 2000-02-03 Valmet Corporation Method and device for changing the natural frequency of a nip roll construction in a paper or board machine
US6521090B1 (en) 1998-07-24 2003-02-18 Metso Paper, Inc. Method and device for changing the natural frequency of a nip roll construction in a paper or board machine
DE19983424B4 (de) * 1998-07-24 2008-10-02 Metso Paper, Inc. Verfahren und Vorrichtung zum Verändern der Eigenfrequenz eines Spaltwalzenaufbaus bei einer Papier- oder Pappmaschine
DE10226499A1 (de) * 2002-06-14 2003-12-24 Abb Patent Gmbh Verfahren und Vorrichtung zum Erfassen und Auswerten von Messsignalen
DE10226499B4 (de) * 2002-06-14 2011-12-15 Abb Ag Verfahren und Vorrichtung zum Erfassen und Auswerten von Messsignalen

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JPS5075956A (enrdf_load_stackoverflow) 1975-06-21

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