Modeling And Solution Of Coil Scheduling Problem Considering Time Delayed Logistics In Acid Rolling

Cold rolling is important procedure of iron and steel deep processing stage, whose products have high-added-value. As the first procedure of cold rolling stage, acid rolling is the connection of hot rolling and cold rolling. Scheduling in acid rolling should satisfy the production technical restrictions consider the objective of minimizing the changeover and make the production continuously and steady; moreover, it is characterized by large number of jobs and complex restrictions.In addition, the coils supplied from acid rolling line are time-delayed, since the coils considered in the subsequent production lines of the acid rolling still resident in the preceding inventory of acid rolling and the capacity of acid rolling is limited. This restricts the processing and influences the inventory in the subsequent production lines, even causes shortage of materials.Considering all the characteristics above, this dissertation proposes the coil scheduling problem considering time delayed logistics in acid rolling to reduce the changeover loss and costs incurred by time-delayed phenomenon, a mathematical model is established, and the differential evolutionary algorithm with several improvement strategies is proposed. The main works of this dissertation are listed as follows:(1) With the background of large domestic steel enterprises, the characteristics of acid rolling production and the time delay property are analyzed, and the coil scheduling problem considering time delayed logistics in acid rolling is proposed. Based on the analysis, a mixed integer nonlinear programming model is established. After linearization processing, the model is solved by CPLEX.(2) According to the characteristics of the problem, the differential evolution algorithm is developed to solve the problem. In the algorithm, a heuristic is used to improve the quality of the initial population, and the mutation is implemented based on the deviation of the current solution from the current best solution. Moreover, with iterative changing crossover operator, a neighborhood search strategy is induced, and the selection strategy is implemented based on an enlarged population. Based on a large number of practical data, the proposed algorithm can solve the problem effectively and efficiently.(3) On the basis of practical investigation, this dissertation designs and develops the relative modules in the plant-wide adaptive planning system, including the parameter configuration and result display modules, and the system configuration part of the process performance evaluation system. Based on the proposed mathematical model and optimization algorithm, the function of making decision of scheduling in acid-rolling is realized in the plant-wide adaptive planning system. With the process performance evaluation system, the intelligent scheduling capacity of the whole process is improved synthetically.