Sheet Continuous Casting Mold Level Control System Design And Optimization

The metallurgical casting process is an important industrial procedure of an iron and steel company. It features multi-variable, nonlinearity and uncertainties. The stability of the mould level in casting process is very meaningful to improve the quality of iron and steel, reduce accidents, and ensure production quantity. Therefore, how to stabilize the mould level under the influence of uncertain factors during the casting process is one of the most critical problems to be solved.Based on the technology analysis of the casting process of compact strip product (CSP) thin slab caster in Lianyuan Steel, the various uncertain factors influencing the mould level are qualitatively analyzed, such as characteristics of the stopper rod, changes of ferrostatic width and thickness, materials of stopper rod and nozzle, cast speed, tunish liquid steel weight, nozzle clogging/unclogging, and the submerged nozzle cracks. The hardware configuration and control strategies of the mold level control system in Lianyuan Steel's CSP plant are discussed in detail. Furthermore, the limitations of currently adopted PTD control strategy with feedforward compensation are analyzed and pointed out.Due to the existed problems of the mould level control, this dissertation presents a compound control method by combining the feedforward compensation and fuzzy PID control for the mould level of the casting process, based on modeling of the mould level. Intelligent control of the mould level is realized by adjusting the position of the stopper rod. Based on the existing control system platform of a making-rolling plant in Lianyuan Steel, a fuzzy PID control module for mould level is developed, the interface for setting control parameters is designed using HMI software, and a fuzzy PID control system with feedforward compensation control for mould level is established, which was successfully applied to a CSP caster in Lianyuan Steel.The results of actual runs show that the system is robust, and effectively suppresses overshoot with fast dynamic response. The fluctuation of mould level is reduced by 18.5% under non-steady-state, and the steady precision is improved to some extent. The designed system yields satisfactory industrial application results.