CONTROLLING METHOD FOR SHEET THICKNESS IN STEEL SHEET ROLLING

PURPOSE:To control the sheet thickness with high accuracy, by effectively applying both of the 1st sheet thick controlling system such as a predictive sheet thickness controlling system and the 2nd sheet thickness controlling system such as a sheet thickness controlling system using a gauge meter system. CONSTITUTION:The 1st and 2nd sheet thickness controllers 3 and 4, connected parallelly to a CPU 5, are connected to a rolling mill 2 of a cold steel-sheet rolling line 1. An information signal of temp. irregularity in the longitudinal direction of a material 6 to be rolled obtained at the time immediately after hot rolling of the preceding stage or before feeding to the cold rolling line 1, is inputted to the CPU 5 to set gains G1 and G2 of the controllers 3 and 4. The controllers 3 controls the mill 2 so as to obtain DELTAH=0 by a detected signal of a thickness gauge 7 placed at the inlet side of the mill 2. The mill 2 is equipped with a hydraulic cylinder 9 having a servovalve 8 to control the hydraulic pressure, and the controllers 3 and 4 are connected to the valve 8, and further, a rolling-down force of the mill 2 is detected by a load cell 10 to be fed back to the controller 4. The sheet thickness is controlled in a feed-forward manner by making a gain G1 lower and a gain G2 higher when the temp. irregularity of the material 6 is large, and making the G1 higher and the G2 lower when the irregularity is small.