JPS6471513A - Device for controlling sheet thickness in rolling mill - Google Patents

Abstract

PURPOSE:To remarkably reduce sheet thickness deviation at the time of rolling start by setting up a proportional arithmetic circuit working in parallel with a PI controller and setting up a changeover circuit which changingly uses both the controller and the arithmetic circuit in the rolling start and a constant rolling time. CONSTITUTION:A sheet thickness controller is provided with a PI controller 4 and a proportional arithmetic circuit 7 working in parallel with the controller and a changeover circuit 10. At the time of rolling start, a low-pass filter 6 cuts off high frequency components of a sheet thickness deviation by an outlet side thickness gage 2 and then the arithmetic circuit 7 multiplies the deviation by a prescribed proportional constant to operate a gap correction amount having an increased proportional gain; a roll gap is controlled based on the correction amount through a switch 10a. In constant rolling time, a gap correction amount found by proportioning and integrating by the controller 4 is outputted from a switch 10b. Hence, a sheet thickness deviation is remarkably reduced by increasing a gain at the time of rolling start.