US3889504A - Thickness control device for rolling mill - Google Patents

Thickness control device for rolling mill Download PDF

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Publication number
US3889504A
US3889504A US496209A US49620974A US3889504A US 3889504 A US3889504 A US 3889504A US 496209 A US496209 A US 496209A US 49620974 A US49620974 A US 49620974A US 3889504 A US3889504 A US 3889504A
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Prior art keywords
thickness
control device
roll
eccentricity
output
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Expired - Lifetime
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US496209A
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English (en)
Inventor
Ken Ichiryu
Masayuki Shigeta
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

  • the autocorrelation function and cross-correlation function are obtained according to the thickness both on the input and output sides to obtain a power spectra, after which coherence function is obtained from those spectra thereby determining a contribution factor of the input side thickness to the output side thickness.
  • the contribution factor is low, the roll eccentricity is considered to exert a great influence, so that the eccentricity obtained from the aforesaid coherence is fed as a command value in a gagemeter type thickness control system to compensate for the thickness of the strip.
  • This invention relates to a thickness control device for a rolling mill, and more particularly to a thickness control device of a gagemeter type capable of 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;
  • 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, assuming 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 despite a need to increase the roll gap, the aforesaid control system will function so as to decrease the roll gap. Accordingly, it is an important role 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 high 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.
  • the present invention incorporated a principle that input side thickness variation and output side thickness variation are continuously measured, and then the disturbance due to roll eccentricity is determined based on the statistical method according to the correlation function, after which the disturbance thus determined is removed from the thickness control system. More particularly, the autocorrelation functions R111, R112 and crosscorrelation function Rh 1 -h2 for the input side thickness hi and output side thickness k2 are determined and the level of roll eccentricity e is determined according to the coherence function as defined by y (2hlh2)/hl' (iv/22), wherein hl, h2 and hlh2 represent respective power spectra, whereby the value e is fed as a command input to the automatic thickness control system.
  • FIG. 1 is an outline of a gagemeter type automatic thickness control system of a general type, which is used in the present invention
  • FIG. 2 is a block diagram for obtaining roll eccentricity according to the gagemeter control method of the present invention
  • FIG. 3 is a plot showing coherence obtained in FIG.
  • FIG. 4 is a block diagram showing the automatic thickness control system ofa gagemeter type according to the present invention.
  • FIG. 5 is a block diagram used for obtaining the phase information of the roll based on the rotation pulse of a backup roll.
  • a rolling mill consists of a work roll 2 adapted directly to 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 displacements of the ram 6 is measured by means of a displacement meter 7, and then a measurement thus obtained is 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 added 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 case of the input side thickness of cyclic variation is lesser, and it is considered to be a statistical random signal in its nature.
  • the roll eccentricity is a cyclic variation.
  • the output side thickness variation is a function of the input side thickness variation and roll eccentricity variation, and thus it is a random signal. Since the measurable signals, i.e., the input side thickness hl and output side thickness h2 are random signals, respectively, it is necessary to process data as a statistical values in order to obtain roll eccentricity.
  • the autocorrelation function and the crosscorrelation function of the input side thickness hl and the output side thickness h2 are first obtained by using a correlator and then the correlation functions are Fourier-integrated to determine the respective power spectra, after which the coherence is calculated therefrom to separate the input side thickness hl and the roll eccentricity e.
  • the autocorrelation function is defined for the input side thickness hl (t) as follows:
  • the aforesaid correlation function primarily represents the statistic characteristic of a signal. However, this characteristic will be made further clearer by obtaining power spectrum.
  • This power spectrum corresponds to the square of the Fourier component, which is given as the Fourier transformation of correlation function. Accordingly, the auto power spectra d hl and (bill for the input side thickness hl (t) and output side thickness h2 (I) will be given as follows:
  • the coherence is a factor which represents the relationship of the each input to the output, in case there are multi-input in the control system. Accordingly, by measuring the coherence of input side thickness hl and the output side thickness h2, it can be numerically determined whether the cyclic variation in the output side thickness is stemming from the input side thickness hl or from the roll eccentricity e.
  • This coherence 'y is defined as follows:
  • the total power in roll eccentricity cycle fe and the power at the pure roll eccentric portion are first determined and then its ratio B l is obtained, after which a roll eccentricity component is fed as an output to the gagemeter type automatic thickness control system, thereby eliminating the influence thereof.
  • FIG. 2 shows a coherence calculating block serving as a basis for the present invention.
  • the input side thickness hl is measured by means of an X-ray thickness gages 13, 13' for an input side plate 11.
  • the X-ray thickness gage is positioned a distance I ahead of the roll center, so that the input side thickness hl may be obtained at the present time, by providing a delay circuit 14 which is adapted to delay the signal by I /v (v: speed of input side plate).
  • the rolling pressure is measured by means of a load cell 8.
  • those values hl and I12 are fed as an input to correlators 18, 19 and 20 to obtain autocorrelation functions Rhl and Rh2 and cross-correlation function Rhlh2, which are then Fourier-transformed by means of spectrum meters 21, 22 and 23 to obtain power spectra hl, h2, 41h 1h2.
  • those values are introduced to a coherence calculator 24 to obtain the coherence defined by 'y ((1)2111 h2)/hl"d h2), obtaining the roll eccentricity component e by means of an eccentricity calculator 25.
  • the coherence represents the relationship of the input side thickness hl to the output side thickness h2.
  • the factor affecting the variation in the output side thickness k2 is the input side thickness hl alone, 7 I will be maintained.
  • the factor affecting the output side thickness h2 includes other factors such as roll eccentricity component 6, then 7 1 at the frequency fe.
  • FIG. 3 shows one example.
  • the coherence function exhibits decrease at several points. This decrease at several points may be attributed to the mixing of the backup roll eccentricity with the work roll eccentricity. Assume that fbl and jb3 are the first and third frequencies of the backup roll, fwl and fw2 are the first and third frequencies of the work roll. The coherence will be lowered from 1, depending on the respective frequencies, suggesting the presence of eccentricity.
  • the correction of the roll eccentricity component may be determined independently commensurate to the thickness accuracy.
  • the extent, to which the roll eccentricity affects the output side thickness h2 has been determined as coherence y (f), so that the allowance 7 a of 'y Q) may be set commensurate to the thickness accuracy to be guaranteed. Accordingly, if 7 11 7%,) 1 is met, little influence due to the roll eccentricity will result, presenting sound roll system.
  • the third frequency fw3 of the work roll need not be corrected, whilejbl ,fwl and jb3 alone should be corrected.
  • FIG. 5 shows a block until this phase information is fed as an output to the thickness control system.
  • the phase information may be obtained by calculating by using a calculator 41 the correlation between the rolling load obtained from a pressure gage 8 and the rotation pulse obtained from a pulse generator 40. Then, the phase information thus obtained is fed as an output from a circuit 42 adapted for compensating the phase delay of the thickness control system.
  • FIG. 4 shows a block diagram of a typical embodiment of the gagemeter type thickness control system embodying the present invention.
  • G is a transfer function of a positioning servo for the thickness command hd, and the transfer function has a property free of delay and a gain of l in the low frequency zone.
  • the transfer function has a property free of delay and a gain of l in the low frequency zone.
  • or represents a coefficient of the mill modulus control, and in general, a l.
  • the roll eccentricity as disturbance affects the output side thickness hZ, but it is detected as a rolling pressure and is fed to the feedback path 26 through the aforesaid steps.
  • the feedback path 26 is divided into a feedback path 27 and a feedback path 28, whereby the signal through the feedback path 27 will be fed to a junction 32, while including the input side thickness component and roll eccentricity component.
  • the power of roll eccentricity component 2 may be obtained from the block shown in FIG. 2, and the phase may be obtained from the block shown in FIG. 5. Accordingly, if the reverse phase component of a signal (if the transfer function G, delays at frequency fe, some phase compensation is added to e) of this roll eccentricity is added to an summing point 35 from the command path 34, the influence of the roll eccentricity may be automatically offset, thereby constituting a gagemeter type automatic thickness control system.
  • the correlation between the rotation pulse of the work roll and the rolling pressure is obtained to determine the roll eccentricity component as has been described earlier, for feeding as an output to the thickness control system as same mentioned earlier.
  • the pure roll eccentricity component alone may be separated, and the roll eccentricity component alone may be completely removed from the gagemeter type automatic control system which is usually used, thereby effecting high accuracy thickness control.
  • a gagemeter type automatic thickness control system in a rolling mill consisting of rolls for rolling a strip, hydraulic jack for imparting a rolling pressure to said rolls, a flow rate control valve for adjusting a roll gap by adjusting the amount of oil in said hydraulic jack, a valve control device, a setting device for feeding a desired thickness command to said control device, and a position detector for detecting the roll gap and feeding back the detected value to said valve control device; a thickness control device, comprising means for detecting an input side thickness and an output side thickness of said strip;
  • a computing device for obtaining the respective power spectra hl, qShZ, d h3 from the autocorrelation functions Rhl and Rh2 and the crosscorrelation function Rh lh2 and then for obtaining from said power spectra the roll eccentricity based on the coherence defined by (cb hl h2)/h1-h2); and

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  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Control Of Metal Rolling (AREA)
US496209A 1973-08-22 1974-08-09 Thickness control device for rolling mill Expired - Lifetime US3889504A (en)

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JP9334273A JPS541657B2 (en, 2012) 1973-08-22 1973-08-22

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US (1) US3889504A (en, 2012)
JP (1) JPS541657B2 (en, 2012)
DE (1) DE2440166C2 (en, 2012)
GB (1) GB1479187A (en, 2012)

Cited By (8)

* 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
WO1985000998A1 (en) * 1983-09-08 1985-03-14 John Lysaght (Australia) Limited Rolling mill strip thickness controller
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
US5203188A (en) * 1991-09-16 1993-04-20 Morgan Construction Company System and method for monitoring a rolling mill
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
US20030210060A1 (en) * 2002-04-06 2003-11-13 Minebea Co., Ltd. Method and device for measuring the repeatable and non-repeatable runout of rotating components of a spindle motor
CN114130837A (zh) * 2021-11-16 2022-03-04 福建紫金铜业有限公司 一种冷轧设备轧辊公差自动判断方法和装置

Families Citing this family (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS5299957A (en) * 1976-02-18 1977-08-22 Tokyo Shibaura Electric Co Device for controlling rolling machine
JPS5992113A (ja) * 1982-11-15 1984-05-28 Nisshin Steel Co Ltd ロ−ル偏心制御装置
DE3844202A1 (de) * 1988-12-29 1990-07-05 Asea Brown Boveri Vorrichtung zur regelung der walzenexzentrizitaetskompensation an einem walzgeruest
JP2015230825A (ja) * 2014-06-05 2015-12-21 株式会社豊田自動織機 プレス装置

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
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

Family Cites Families (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB946820A (en) * 1959-03-24 1964-01-15 Davy & United Eng Co Ltd Improvements in or relating to the measurement and control of thickness in the production of sheet and strip material
DE1809636A1 (de) * 1968-11-19 1971-02-11 Hans Stolch Einrichtung zur beweglichen Anordnung von Pflanzenkulturen

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
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

Cited By (10)

* 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
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
WO1985000998A1 (en) * 1983-09-08 1985-03-14 John Lysaght (Australia) Limited Rolling mill strip thickness controller
US5203188A (en) * 1991-09-16 1993-04-20 Morgan Construction Company System and method for monitoring a rolling mill
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
US20030210060A1 (en) * 2002-04-06 2003-11-13 Minebea Co., Ltd. Method and device for measuring the repeatable and non-repeatable runout of rotating components of a spindle motor
US7256586B2 (en) * 2002-04-06 2007-08-14 Minebea Co. Ltd Method and device for measuring the repeatable and non-repeatable runout of rotating components of a spindle motor
CN114130837A (zh) * 2021-11-16 2022-03-04 福建紫金铜业有限公司 一种冷轧设备轧辊公差自动判断方法和装置
CN114130837B (zh) * 2021-11-16 2024-05-07 福建紫金铜业有限公司 一种冷轧设备轧辊公差自动判断方法和装置

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JPS541657B2 (en, 2012) 1979-01-27
DE2440166C2 (de) 1983-06-01
DE2440166A1 (de) 1975-03-13
GB1479187A (en) 1977-07-06
JPS5044149A (en, 2012) 1975-04-21

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