Study And Application Of Flatness Control System For Cold Rolled Strip

With the rapid development of industrial technology,the rising demands from such as auto industry,household electrical appliance industry and so on for the quality of cold rolled strip increasingly demands good strip flatness.The quality of flatness is becoming much more important and has been evaluated as one of the most important targets for cold rolled strip.In this paper,shape control system project of Angang 1250mm 6-H reversible UCM cold mill as a background.The studies mainly consists of flatness control method,flatness measurement,flatness preset system as well as flatness control system hardware configuration and software development.The main work is illuminated as follows:(1)The main factors affecting the flatness of cold-rolled strip and flatness control method have been analyzed and researched in-depth.(2)The characteristics,configuration and detection principle of the BFI piezoelectric shapemeter roll and the ABB magnetoelastic shapemeter roll which has been studied.Comparative analysis of the different characteristics of the two plate-shaped roller plate-shaped signal processing.(3)The priorities and the preset calculation process for different flatness actuators have been set.The flatness target curve has been developed.Dynamic compensation models such as coil shape,geometric error of shapemeter roll installation position,and temperature difference across strip,thickness drop in strip edge have been developed.(4)Based on efficiency factors of flatness actuators,the optimal multi-variable flatness control algorithm with the aid of constrained least square method has developed.Meanwhile,a self-learning model of actuator efficiency factors has been established to obtain accurate efficiency factors matrixes of flatness actuators.With the constrained least square method,the flatness control system calculates the adjustments of the actuators dependent on flatness deviation in the relay manner.Subsequently,the adjustments will be limited to their adjustable range and compensated by dynamic gains.In addition,the influence of measurement delay on control system has been analyzed to find a method to compensate this influence resulting from measurement delay.The Smith predictor has been introduced to the flatness control system for delay compensation.Based on the compensation method,the flatness system has been developed and simulated.(5)Based on the configured platform and developed software,models and schemes of flatness control have been tested offline.The flatness of both normal thickness gauge and ultra thin strips during rolling processes has been evaluated.Dynamic responses and adjustments during each control cycle of flatness actuators as well as the resulting flatness deviation change have been analyzed.The results of the study are practical for flatness control of cold rolling mill.Currently,flatness control system for cold rolling mill has been developed and applied to the revamp of Angang 1250mm 6-H reversible UCM cold mill,based on the strategies and models.Applications show that the study has certain significance to the flatness control system revamp of existing mill and the flatness control system development of upcoming new mill.