Thickness control system for a rolling mill

Claim 2

In 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 system so as to compensate for the variation of the outgoing thickness of the strip due to the roll eccentricity.

Claim 3

A method for controlling strip thickness according to claim 1, in which the rolling pressure is continuously detected as a parameter relating to the outgoing strip thickness.

Claim 4

A method for controlling strip thickness according to claim 1, 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.

Claim 5

A method for controlling strip thickness according to claim 1, further comprising inserting a narrow band filter in said feedback loop of said thickness control system for passing only those components close to the roll eccentricity frequency in synchronism with said roll eccentricity frequency and the output of said filter is rendered proportional to the ratio of power spectra of the predetermined part of the region to power spectra of the whole region.

Claim 6

A method for controlling strip thickness according to claim 1, further comprising determining the gain and phase angle of the roll eccentricity component in synchronism with the rotation of said rolls by detecting at least one of the strip thickness on the output side and the rolling pressure, and applying a roll eccentricity compensating command based on said gain and said phase angle to said automatic thickness control system.

Claim 7

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.

Claim 8

A method for controlling strip thickness according to claim 2, further comprising inserting a narrow band filter in said feedback loop of said thickness control system for passing only those components close to the roll eccentricity frequency in synchronism with said roll eccentricity frequency and the output of said filter is rendered proportional to the ratio of power spectra of the predetermined part of the region to power spectra of the whole region.

Claim 9

A method for controlling strip thickness according to claim 2, further comprising determining the gain and phase angle of the roll eccentricity component in synchronism with the rotation of said rolls by detecting at least one of the strip thickness on the output side and the rolling pressure, and applying a roll eccentricity compensating command based on said gain and said phase angle to said automatic thickness control system.

Claim 10

A method for controlling strip thickness according to claim 1, in which the outgoing thickness of the rolled strip is continuously detected as a parameter relating to the outgoing strip thickness.

Claim 11

In 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 determining a roll eccentricity power signal from the ratio between the power spectra for the predetermined part of the region and the power spectra for the whole region, and means for applying the roll eccentricity power signal to the strip thickness control system.

Claim 12

In 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 determining a roll eccentricity power signal from the ratio between the power spectra for the predetermined part of the region and the power spectra for the whole region, and means for applying the roll eccentricity power signal to the strip thickness control system.

Claim 13

A strip thIckness control system according to claim 10, 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.

Claim 14

A strip thickness control system according to claim 10, 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.