Modeling And Solution For Production Order Scheduling Problem In Cold Rolling Supply Chain

Cold rolling process is the last stage of the production processes in the steel enterprise, which contain multiple production lines including acid rolling line, continuous annealing line, hot galvanized line, hot galvanized line etc. Reasonable production plan has direct influence on improving the production efficiency and reducing the production costs. This thesis derives the order selecting and scheduling problem from cold rolling supply chain, focusing on how to decide the order selection and scheduling of the selected orders, under the restrictions of the time delay of the supplements between two consecutive production stages and the equilibrium of the burden of the involved production lines. We aim at improving the productivity, keeping the logistics remaining smooth, as well as improving the production efficiency and the economic benefits.The main work of this thesis includes:(1) For the order selecting and scheduling problem in cold rolling supply chain, considering the production restrictions, order requirements and time delay between the production stages, a mixed integer linear model is formulated with the objective of minimizing the total production costs. Then the model is solved by CPLEX to achieve the optimal solution for the small-scale instances.(2) An improved differential evolution (DE) algorithm is developed to solve the focused problem. In the algorithm, a integrate coding and decoding strategy is proposed to solve the difficulties that the classical DE faced in solving problems with discrete variables. Meanwhile, a new mutation strategy and mutation factor is developed, which can obviously improve the convergence rate of DE, and avoid the algorithm from falling into a local optimum or precocity. The efficiency of the proposed DE is verified by comparing with the results obtained by CPLEX and the heuristic based on artificial experience. The efficiency of the proposed improvement strategies are illustrated by tests based on the standard test functions.(3) According to the requirements achieved by investigation, the thesis develops the contract analysis system including small order cost analysis function etc.