Development And Application Of High Accuracy Gauge Control For Plate Mill

With the development of modern industry, the demand for plate thickness accuracy is becoming critical. The high-accuracy gauge control technologies are hot issues in rolling automation research. Under the background of automatic control system development project for 3000mm plate mill in a steel company, the study was carried out on preset system of process control, rapid and high-accuracy gap control, piecewise thickness control, compensation methods for improving thickness accuracy and so on. The research results were applied on site successfully, and the precision of thickness were satisfied. The main progress is as follows:(1) The rolling schedule preset models and process data tracking method were analyzed, including rolling strategy selection, rolling schedule computation by load distribution methods, load distribution mathematical models and their self-learning methods. The rolling schedule automatic setting technology was developed for the full automatic rolling control purpose, based on mill pacing control.(2) Comparing the position control characteristic curves with variable and constant accelerated velocity, the merits and drawbacks were pointed out. Rapid and high accuracy EGC technology was developed by on-line parameters adaptive method, based on the characteristic curve with constant accelerated velocity. EGC keeps rapid and high-accuracy characters by real-time adjusting and optimizing the curve's parameters.(3) A dynamic compensation method for servo valve's zero drift was developed which improves the positioning accuracy of HGC system without decreasing its dynamic response rate. Applications on site showed that HGC system kept high-accuracy with positioning error in±2μm.(4) Piecewise thickness control technology was put forward based on high-accuracy gaugemeter model. Work piece is divided into thin pieces along the longitudinal direction. The thickness and plastic stiffness of every piece are computed by high-accuracy gaugemeter model with measured gap and rolling force respectively. This technology tracks the thickness and plastic stiffness fluctuation of every piece and controls its thickness. Applications showed that the thickness deviations of same plate were eliminated greatly. The automatic judgement methods for the starting point of thickening and thinning wedge in variable-thickness rolling were developed, adopting piecewise thickness control technology and the coupling characteristic of the position and rolling force closed loop in HGC system.(5) In accordance with the features on site, adopting piecewise thickness control technology, a gap zero point self-learning method was developed by using the measurement signal from gauge meter.(6) In order to eliminate the oversize thickness at the plate head and tail, a new gauge control method for plate head was developed, which has good performance on site. The crop of cutting head was reduced greatly, by adjusting the parameters. It is benefit to finishing yield.The results of the study are practical for high-accuracy thickness control of plate mill. The automatic control system has been applied successfully in many plate mill lines which has achieved great economic results.