Research On Soft-measuring Of Strip's Grain Size And Composite Magnetic Field Intelligent Control In Aluminum Electromagnetic Roll-casting

The technology of aluminum electromagnetic roll-casting which was developed by China in recent years is a new kind of technology of metallic materials processing. It is an exploratory research subject that integrates multidisciplinary and new technologies. During its production process, whether high-performance aluminum can be gotten depend on whether fine and uniform grains can be obtained. The key to achieve optimal control of roll-casting process is that the grain size of aluminum melt can be detected online. However, the aluminum strip's grain size can not be detected online and real-time with current detection methods, and it is detected through offline metallographic analysis by manual sampling. Therefore, there is great delay which affects aluminum products quality of the electromagnetic roll-casting seriously.It is difficult to establish accurate mathematical models for the process of aluminum electromagnetic roll-casting due to its charac-teristics of complicacy, time-varying, large delay and so on. Based on the analysis of mechanism of aluminum electromagnetic roll-casting and the affecting factors of aluminum strip's grain size, the soft-measuring of aluminum strip's grain size and intelligent control technology of composite magnetic field were researched in this paper. The intelligent integrated soft-measuring model of aluminum strip's grain size based on FCM clustering and fuzzy active disturbance rejection control strategy for composite magnetic field were proposed. Based on soft-measuring model of aluminum strip's grain size, a double closed loop control system of composite magnetic field was designed. The online measuring of aluminum strip's grain size and the intelligent control of composite magnetic field are realized effectively. With these methods, the closed loop control of aluminum strip's grain size was realized, which is the key to improve product quality and production efficiency. The main work and contributions in the paper are as follows:(1) The process mechanism of the aluminum electromagnetic roll-casting technology and the forming principle of composite magnetic field are discussed. The characteristics of the traveling electromagnetic force and the pulsating electromagnetic force in the molten aluminum are analyzed. In addition, the composite magnetic field of roll-casting area is analyzed by the numerical simulation method. Then, the roll-casting factors and electromagnetic factors of the influencing factors of grain size are described. Therefore, the foundation of the auxiliary variables in the grain size soft-measuring is established.(2) For the disadvantages of the standard FCM clustering algorithm, as the sensitivity to initial value and the existence of local extremum, such an improved FCM clustering algorithm is proposed based on the sample point density index. An artificial data set and the classic IRIS data sets are simulated and analyzed by using the algorithm. The results show that the improved algorithm has many advantages, including reduction of the iteration number, improvement of the clustering efficiency, and so on.(3) Based on the BPNN of using the L-M algorithm, the soft-measuring model of grain size is established and the simulation is researched. For the problem of BPNN's stability and generalization, the parameters of weight and threshold of BPNN are optimized by the particle swarm optimization algorithm. For some disadvantages of BPNN, theε-SVR-based soft-measuring model of grain size is researched and the parameters are optimized by the particle swarm optimization algorithm. The simulation results show that the generalization of the model is enhanced highly.(4) To improve the precision of soft-measuring model, the intelligent integrated model is established based on BPNN, s-SVR and FCM clustering algorithm. Firstly, the data samples are clustered by the improved FCM clustering algorithm. Then, the different model for each cluster is selected in accordance with the number of its samples. Finally, using the fuzzy membership weighted strategy, the output of integrated model is calculated. The simulation results show that the training accuracy and the prediction accuracy are improved in the model.(5) For the key technology of electromagnetic roll-casting, the problem of intelligent control of composite magnetic field, a new style and practical controller based on fuzzy ADRC is proposed. The basic principles of fuzzy ADRC and the design methods of fuzzy ADRC for composite magnetic field were discussed in details in this paper. And the simulation results show that fuzzy ADRC for the composite magnetic field is feasible and correct.(6) Based on the soft-measuring model of grain size, the double closed loop control system of composite magnetic field is developed. A composite magnetic intelligent controller using the fuzzy ADRC and a software system of grain size soft-measuring are developed. Though the experimental debugging, the strip's grain is refined and the grain size reaches the first-class level.The strip's grain size's online measuring and the control of composite magnetic field are the issues in the aluminum industry. These achievements have important research significance and good prospects in the industrial applications.