IMPROVEMENT OF MOLD-LEVEL CONTROL USING FUZZY-LOGIC

This paper reports on a feasibility study on art improvement of conven tional mold-level control using fuzzy logic. Nowadays, for economic st eer production, continuous casting is used. Of special interest for co ntinuous casting is the mold, because in this part of the process the liquid steel will be fed to the mold. From the metallurgical point of view it is necessary to keep the mold-level constant, as large variati ons of the mold-level cause non-homogeneity in the product. Especially , an overflow of the mold (as well as an empty mold) has to be avoided , because the liquid steel overflows the working area ol the bottom pa rts of the mold respectively. Besides an interruption to the productio n, high maintenance costs will be caused. Using an example of a slab-e aster with varying mold geometry, this paper shows that in the case of disturbances an improvement on conventional control can be achieved b y the use of fuzzy logic. The basic idea is the use of a parallel cont rol structure with a complementary fuzzy logic controller. This provid es the advantage that under normal operating conditions the convention al controller, in this case a PI controller, is still in operation, wh ilst in the case of a disturbance the fuzzy controller supports the co nventional control. This leads to a much better disturbance control be haviour than without the fuzzy controller, with the result that, in co ntrast to conventional control, overflows can be avoided.