Abstract
The integrated determination of the charge batching and casting start time (CBCST) is a combinatorial optimization problem extracted from the production and operations management of steel plants. A hierarchical optimization method based on variable neighborhood search (VNS) is proposed in this paper for integrated determination of CBCST. The number of casts on each continuous caster and the number of charges in each cast are determined in the encoding. The decoding process is decomposed into solving two sub-problems. A mixed integer programming (MIP) model is built for the first sub-problem by considering it as a prize collecting multiple traveling salesmen problem, and a VNS algorithm is proposed for solving the model. In addition, another MIP model is developed for the second sub-problem, and the model is solved by CPLEX directly. Experimental results on practical production data demonstrate that the proposed algorithm is effective for determining the charge batching and the casting start time simultaneously.
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