Steel-sheet meandering amount measurement device, steel-sheet meandering amount measurement method, hot-rolling equipment for hot-rolled steel strip, and hot-rolling method of hot-rolled steel strip

A steel-sheet meandering amount measurement device measuring a meandering amount of a steel sheet during rolling by a rolling mill having a plurality of rolling stands, the device comprising:

• an imaging device installed between rolling stands adjacent to each other and configured to periodically image a surface of the steel sheet traveling during rolling;
• and
• a meandering amount arithmetically operating device configured to calculate the meandering amount of the steel sheet based on a plurality of captured images captured by the imaging device;
• wherein the meandering amount arithmetically operating device includes:
• an uncorrected edge detection unit configured to calculate a luminance difference between pixels adjacent to each other in a width direction of each of the plurality of captured images periodically captured by the imaging device, detect a plurality of sites where an absolute value of the luminance difference is maximum on a drive side in the width direction of the steel sheet as a drive side edge site zds of the steel sheet, and detect a plurality of sites where the absolute value of the luminance difference is maximum on a work side in the width direction of the steel sheet as a work side edge site zws of the steel sheet;
• a measurement reliability determination unit configured to determine that the drive side edge site zds(N) and the work side edge site zws(N) at a current time have low reliability when each of sums αds, αws of change amount absolute values is equal to or larger than a predetermined threshold, and determine that the drive side edge site zds(N) and the work side edge site zws(N) at the current time have high reliability when each of the sums αds, αws is less than the predetermined threshold, the sums αds, αws being represented by Equations (1), (2) of the drive side edge sites (zds (i), i=1, 2, . . . , N) and the work side edge sites (zws (i), i=1, 2, . . . , N) detected by N times in a past including the current time extracted from the plurality of drive side edge sites zds and work side edge sites zws, respectively, detected by the uncorrected edge detection unit;
• a sheet width updating unit configured to calculate a number of pixels W′ corresponding to a sheet width calculated from both the drive side edge site zds(N) and the work side edge site zws(N) at the current time and update a number of pixels W corresponding to the sheet width to the calculated W′ when the measurement reliability determination unit determines that both the drive side edge site zds(N) and the work side edge site zws(N) at the current time have high reliability, and leave the number of pixels W corresponding to the sheet width as the number of pixels W when the measurement reliability determination unit determines that at least one of the drive side edge site zds(N) and the work side edge site zws(N) at the current time has low reliability;
• and
• a meandering amount calculation unit configured to calculate the meandering amount of the steel sheet using the drive side edge site zds(N) and the work side edge site zws(N) at the current time when the measurement reliability determination unit determines that both the drive side edge site zds(N) and the work side edge site zws(N) at the current time have high reliability, calculate by interpolation another side edge site using the number of pixels W from the sheet width updating unit with the drive side edge site zds(N) or the work side edge site zws(N) at the current time having high reliability as a reference and calculate the meandering amount of the steel sheet using the drive side edge site zds(N) or the work side edge site zws(N) at the current time having high reliability and the another side edge site subjected to the calculation by interpolation when the measurement reliability determination unit determines that only one of the drive side edge site zds(N) and the work side edge site zws(N) at the current time has high reliability, and not calculate the meandering amount of the steel sheet when the measurement reliability determination unit determines that both the drive side edge site zds(N) and the work side edge site zws(N) at the current time have low reliability,
• and wherein the sheet width updating unit, optionally, is configured to update the number of pixels W corresponding to the sheet width to the calculated W′ when the calculated W′ is within a preset upper and lower limit range in calculating the number of pixels W′ corresponding to the sheet width calculated from both the drive side edge site zds(N) and the work side edge site zws(N) at the current time, and leave the number of pixels W corresponding to the sheet width as the number of pixels W when the calculated W′ is out of the preset upper and lower limit range,
• the meandering amount arithmetically operating device, optionally, includes an uncorrected edge holding unit configured to hold the plurality of drive side edge sites zds and work side edge sites zws of the steel sheet detected by the uncorrected edge detection unit, wherein the measurement reliability determination unit is onfigured to acquire each of the plurality of drive side edge sites zds and work side edge sites zws of the steel sheet held by the uncorrected edge holding unit, and
• the meandering amount arithmetically operating device, optionally, includes an output unit configured to output the meandering amount of the steel sheet calculated by the meandering amount calculation unit to a meandering control device
• αds=Σi=2N|zdsi−zdsi−1 (1)
• αws=Σzwsi−zdwsi−1 (2).