On Design And Application Of Mold Level Control System For Continuous Caster

Mold level control has been successfully used in the slab continuous casting machine that cross sectional area is above 150 mm×150 mm, but effect is not good for the billet caster (the cross sectional area is 130 mm×130 mm.). Although Shougang is a large enterprises in output aspect of the continuous casting in domestic production, but automatic control technology of Shougang lagges far behind the developed countries. It is difficult to improve the product quality with artificial casting and liquid level control. On the basis of the digestion and absorption of ideas of continuous caster mold level control of other steel plants it had designed a mold level control system in suitable for billet caster, for further improving of the quality of billet and for builting on experiences of automation of others continuous casters.At first in this paper, it had established mathematical model of each constituent part according to the mechanism of mold level control system. Then it had analyzed the characteristics of the fuzzy and PID control and then combined them organically. A Fuzzy and PID Hybrid controller is designed in this paper. This controller synthesizes the advantages of both fuzzy and PID controlling modes, thus making the controller possess not only the simplicity and efficiency of the fuzzy in controlling over the non-linear system but also the accuracy of PID controlling. Based upon the system modeling and the design of controller it had carried on the simulation experiment for PID and Fuzzy-PID Hybrid algorithm by using the Matlab software. The simulation results show that this system has a better stability and a higher precision than conventional PID system. This method has the advantages of simple structure, stronger anti-jamming ability and quick response, and according to both dynamic and static characteristics of system.Based on theoretical research, in this control system it had used the Siemens S7-300 PLC, programmed and debugged software with STEP7 and WinCC 4.0 configuration software for software and hardware of host computer and lower computer. Compound fuzzy-PID control of mold level was realized. The method of detection of level is method of radio isotopic detection (Cs137); the implementing agencies for stopper on the use of high-precision digital electric cylinder, which simplifies the mold level control structure from cascade control structure to one order closed-loop control and shortens to the response time of the implementing agencies. In the production process, error of the mold level in±5mm, which meets the requirements basically. Application shows that the controller has good dynamic and static characteristics and a certain robustness. Control is simple and easy to achieve. In this way, product quality is improved effectively.