Method and apparatus for controlling snake motion in rolling mills

Claim 2

In a method for controlling a rolling mill including a step of obtaining a first value corresponding to an amount of a snake motion of a material being rolled so as to control the snake motion of the material; the improvement further comprising counteracting instability which occurs regardless of system gain in trying to control said snake motion by obtaining a second value corresponding to a differentiated value of said first value, obtaining a first sum of said first and second values, multiplying the first sum by a variable control factor given by α/Kl where α is a control factor larger than "1" and Kl is the parallel rigidity of the rolling mill, and applying a control operation to the material being rolled to control the snake motion on the basis of the result of said multiplication of said first sum by said variable control factor to prevent a divergent control characteristic for the snake motion control which develops due to instability regardless of the system gain if only the first value is used for controlling the snake motion.

Claim 3

A method according to claim 1, wherein said first value obtaining step includes a step for detecting a difference in rolling load between values at an operating and a driving side of roll means of said rolling mill, said rolling load difference being used as said first value.

Claim 4

A method according to claim 1, wherein said first value obtaining step includes steps of detecting a difference in rolling load between values at an operating and a driving side of roll means of said rolling mill, detecting a difference in roll gap between values at said operating and driving sides of said roll means corresponding to values thereof under no-load condition, and obtaining a second sum of said difference in rolling load and said difference in roll gap, said second sum being used as said first value.

Claim 6

A method according to claim 1, 2 or 3, wherein said second value is obtained by directly differentiating said first value.

Claim 7

A method according to claim 1, 2, or 3, wherein said second value is obtained by detecting the snake motion independently of said first value.

Claim 8

In an apparatus for controlling a rolling mill including first means for obtaining a first value corresponding to an amount of a snake motion of a material being rolled, to thereby control the snake motion on the basis of the output of said first means, the improvement further comprising second means for counteracting instability which occurs regardless of system gain in trying to control said snake motion by obtaining a second value corresponding to a differentiated value of said first value, third means responsive to said first and second means for obtaining a sum of said first and second values, means for multiplying said sum by a variable control factor given by α/Kl where α is a control factor larger than "1" and Kl is the parallel rigidity of the rolling mill, and fourth means for applying a control operation to the material being rolled to control the snake motion on the basis of an output of said multiplying means to prevent a divergent control characteristic for the snake motion control which develops due to instability regardless of the system gain if only the first value is used for controlling the snake motion.

Claim 9

In an apparatus for controlling a rolling mill including first means for obtaining a first value corresponding to an amount of a snake motion of a material being rolled, to thereby control the snake motion on the basis of the output of said first means, the improvement further comprising second means for counteracting instability which occurs regardless of system gain in trying to control said snake motion by obtaining a second value corresponding to a differentiated value of said first value, third means responsive to said first and second means for obtaining a sum of said first and second values, means for multiplying said sum by a variable control factor given by α/Kl where α is a control factor larger than "1" and Kl is the parallel rigidity of the rolling mill, and fourth means for applying a control operation to the material being rolled to control the snake motion on the basis of an output of said multiplying means to prevent a divergent control characteristic for the snake motion control which develops due to instability regardless of the system gain if only the first value is used for controlling the snake motion.

Claim 10

An apparatus according to claim 7, wherein said first means includes means provided on said rolling mill for detecting a position of the material being rolled.

Claim 11

An apparatus according to claim 7, wherein said first means includes means provided on the rolling mill for monitoring conditions of the material being rolled.

Claim 12

An apparatus according to claim 7, wherein said first means includes first and second rolling load detectors respectively provided on an operating side and a driving side of said rolling mill.

Claim 14

An apparatus according to claim 7, 8, 9 or 10, wherein said second means includes at least one of means for detecting a speed of displacement of the material being rolled and means for detecting an incident angle of the material at an input side thereof.

Claim 15

A system according to claim 10, wherein said first means includes arithmetic means responsive to said first and second rolling load detectors for obtaining a difference in rolling load between values at said operating and driving sides of the roll means.

Claim 16

An apparatus according to claim 7, 10 or 13, further comprising, a first and a second detector provided on an operating a driving side of said rolling mill respectively for detecting respective roll gaps thereat corresponding to values thereof under no-load condition, a first arithmetic element responsive to said first and second roll gap detectors for obtaining a difference in roll gap corresponding to a value thereof under no-load condition, and a second arithmetic element for obtaining a difference between the respective outputs of said multiplying means and said first arithmetic element, said control operation being effected on the basis of the output of said second arithmetic element.

Claim 17

A rolling mill control apparatus comprising: a first roll gap detector provided at an operating side of said rolling mill for detecting a roll gap corresponding to a value thereof under no-load condition; a first rolling load detector provided at said operating side; a second roll gap detector provided at a driving side of said rolling mill, for detecting a roll gap corresponding to a value thereof under no-load condition; a second rolling load detector provided at said driving side; a first operational amplifier for comparing the respective outputs of said first and second roll gap detectors with each other; a second operational amplifier for comparing the respective outputs of said first and second rolling load detectors with each other; means for multiplying the output of the second operational amplifier by a variable control factor given by α/Kl where α is a control factor larger than "1" and Kl is the parallel rigidity of the rolling mill; a third operational amplifier for comparing the output of said first operational amplifier with the output of said multiplying means; and control means for controlling respective reduction means at said operating and driving sides in response to the output of said third operational amplifier, wherein said system further comprises means for differentiating an amount of a first control signal which corrresponds to a snake motion of a material being rolled at one predetermined point in a control loop including said first and second rolling load detectors and said control means and means for counteracting instability which occurs regardless of system gain in trying to control said snake motion by adding the result of said differentiation to said amount of said first control signal to produce a combined control signal as a controlling output from said control means to control the snake motion on the basis of the combined control signal to prevent a divergent control characteristic for the snake motion control which develops due to instability regardless of the system gain if only the first control signal is used for controlling the snake motion.

Claim 18

A rolling mill control apparatus comprising: a first roll gap detector provided at an operating side of said rolling mill for detecting a roll gap corresponding to a value thereof under no-load condition; a first rolling load detector provided at said operating side; a second roll gap detector provided at a driving side of said rolling mill, for detecting a roll gap corresponding to a value thereof under no-load condition; a second rolling load detector provided at said driving side; a first operational amplifier for comparing the respective outputs of said first and second roll gap detectors with each other; a second operational amplifier for comparing the respective outputs of said first and second rolling load detectors with each other; means for multiplying the output of the second operational amplifier by a variable control factor given by α/Kl where α is a control factor larger than "1" and Kl is the parallel rigidity of the rolling mill; a third operational amplifier for comparing the output of said first operational amplifier with the output of said multiplying means; and control means for controlling respective reduction means at said operating and driving sides in response to the output of said third operational amplifier, wherein said system further comprises means for differentiating an amount of a first control signal which corrresponds to a snake motion of a material being rolled at one predetermined point in a control loop including said first and second rolling load detectors and said control means and means for counteracting instability which occurs regardless of system gain in trying to control said snake motion by adding the result of said differentiation to said amount of said first control signal to produce a combined control signal as a controlling output from said control means to control the snake motion on the basis of the combined control signal to prevent a divergent control characteristic for the snake motion control which develops due to instability regardless of the system gain if only the first control signal is used for controlling the snake motion.

Claim 19

An apparatus according to claim 15, wherein said differentiation-adding means differentiates each of the outputs of said first and second rolling load detectors and adds the values obtained by the differentiation to the outputs of said first and second rolling load detectors respectively, the respective resulting sums being applied to said second operational amplifier.

Claim 20

An apparatus according to claim 15, wherein said differentiation-adding means differentiates the output of said second operational amplifier and adds the value obtained by the differentiation to the output of said second operational amplifier, the resulting sum being applied to said third operational amplifier.

Claim 21

An apparatus according to claim 15, wherein said differentiation-adding means differentiates the output of said third operational amplifier and adds the value obtained by the differentiation to the output of said third operational amplifier, the resulting sum being applied to said control means so that said control means controls said respective reduction means in response to said sum.