Study Of Automatic Gauge Control System For Hot Strip Mill

The thickness accuracy is one of the important quality indexes in hot rolled strips.It directly affects the production efficiency and product quality of the downstream manufacturing industry.With the development of science and technology,the requirement of the strip thickness accuracy from users is getting higher and higher.The main function of the automatic gauge control(AGC)system is to control the strip thickness within the range of setting target deviation.Its performance directly affects the precision of strip thickness.Therefore,a comprehensive and in-depth research was carried out on AGC system for hot strip mill in this dissertation.The main research contents are as follows:(1)The new monitor AGC and its improvements were researched.To shorten adjustment cycle of monitor AGC for improving its correction speed of thickness deviation,the intensive study on a new type of monitor AGC system was conducted and its existing problems were analyzed.In order to keep constant distribution ratio of the rolling force on each stand in favor of the stability of rolling process and the control of shape quality,an improved algorithm of thickness-deviation distribution coefficients for the new monitor AGC was proposed,and then the problem of reasonable calculation of thickness-deviation distribution coefficients was well solved.For the sake of obtaining the best comprehensive thickness control effect,the control structure of the new monitor AGC was improved,and the problem of mutual interference between the new monitor AGC and gauge meter AGC(GM-AGC)was solved efficiently.(2)Compensation methods of roll eccentricity were investigated.In order to avoid the misoperation of GM-AGC caused by roll eccentricity,the research on dynamic-deadband filter method of roll eccentricity was done.Then,the problem that the fixed deadband width could not accommodate the variation of roll eccentricity was solved preferably.The dynamic-deadband filter method could prevent the deterioration of thickness accuracy causing by roll eccentricity through suppressing the malfunction of GM-AGC,but it could not eliminate the harmful effect of roll eccentricity on strip thickness.To further improve the accuracy of the strip thickness,a method of roll eccentricity compensation based on swarm intelligence identification was proposed and the active roll eccentricity compensation method was enriched.The swarm intelligence algorithm based on the fusion of ant colony optimization algorithm and particle swarm optimization(PSO)algorithm was designed to preferably solve the problem that PSO algorithm with linear decreasing inertia weight was easy to fall into local optimum due to the rapid loss of population diversity.(3)The multi-objective optimization methods of load distribution for hot continuous rolling were studied.To solve the multi-objective optimization problem in load distribution of hot continuous rolling,multi-objective optimization method for load distribution based on improved ant-colony system(IACS)algorithm was designed.This method improved the solving speed and accuracy of load distribution optimization.To avoid the problem of the difficulty in determining grid number of solution space affecting the optimization performance of IACS algorithm,a multi-objective balance iteration algorithm for solving the problem of the multi-objective optimization of load distribution was proposed.Its optimization solution speed and accuracy were both better than that of IACS algorithm.Moreover,the multi-objective balance iteration algorithm had the features,such as low requirement for initial value,uncomplicated principle and simple parameter setting and so on,and it also had the good prospect for online application.(4)The AGC system was designed.The AGC system for the 650mm hot strip mill in a steel plant was designed and its control algorithms for practical use were given.To improve the control precision of GM-AGC in the last stand,the measurement method of mill stiffness based on rolling data was designed,and the accuracy of mill stiffness measurement was improved.According to the field experimental data,the effects of experimental on the determination of the reference zero of mill roll gap,the measurement of the mill stiffness,multi-objective optimization of load distribution,the control of actual strip thickness and the roll eccentricity compensation based on swarm intelligence identification were analyzed and evaluated.The research results of this dissertation have a positive effect on the improvement of thickness control level for hot strip mill in China.