Hot Strip Mill Looper Direct Digital Control System

Abstract

A high level of accuracy and quick response are required in the looper control to keep up with the changes in the operational conditions in modern hot strip mills, such as operation at higher speed and rapid acceleration on the finishing mill and bigger skid marks, and to achieve improvements in the dimensional accuracy of the products (thickness (gauge) and width) and in the yield rate.The old looper control system at the hot strip mill in Kakogawa Works has consisted of analog circuits until now. Despite their constant height and tension-control capabilities, there were some instances where they failed to cope with such changes in the operational conditions as mentioned above owing to their rather unreliable control performance.Recently, since the looper analog control system has been replaced with a DDC (direct digital control) system which consists of μ-computer, a high level of accuracy control has been achieved through the precise calculations of the control parameters, which are based on the data on rolling conditions such as the rolling mills, the screwdowns and the looper drives, and on the information obtained from the main process computer.Appreciable improvements in both the quality of products and the yield rate have been accomplished through the use of this new system and the details of the control performance are discussed.