The Optimal Control Of LF Alloying Component Based On Fuzzy Programming

Ladle furnace has become one of the key equipments in secondary refining process, it plays an important part in the control of components of molten steel. However the model we use in fact cannot satisfy the requirement, it may cause fluctuation of the component in molten steel and fail to keep the component in a narrow range. Therefore, this thesis has studied the model of alloying component controlling to make it consistent.In order to make the component fluctuate narrowly, this thesis has added the fuzzy theory into the model which is widely used, and use a triangular fuzzy number to replace the target component. The model used in factory take the cost of alloy as the target and the final range of composition as the bounds. As the answer of the Linear Program has always been the bound of the feasible region, this characteristic may cause the component widely fluctuate and have a bad influence on the following operation. So a Fuzzy Program has been constructed to solve this problem. And then use the symmetry theory of Werner to take the sum of the degree of membership as the target to solve this program. Based on this Fuzzy Program, alloying cost minimize has been put into the program as an extra target, and then solve this multi-objective problem with the NSGA-Ⅱ. The answers of this program are Pareto non-dominated solutions. This may help the operator make a suitable choice based on the fact of factory.Element yield has a big relationship with the model’s precision, predicting element yield accurately is the premise of calculating the amount of alloy, however it is difficult to measure directly. In order to obtain the accurate element yield, we have studied the factors which influence the element yield, and a predication model of element yield has been established with SVM. Then the GA algorithm has been used to determine the parameters of SVM in order to make the answer more precise.With the real LF furnace data for testing, the answer shows that this model cannot only reduce the alloying cost but can also satisfy the requirement of the precision and the deviation of elements among furnaces has also been mostly avoided.