Coil Scheduling Problem In Parallel Continuous Annealing Lines Based On Differential Evolution Algorithm

In iron and steel production,production schedule has a direct influence on the production costs,productivity,production continuity and product quality.Therefore,how to obtain a reasonable and effective production schedule is urgently needed by iron and steel enterprises.This thesis derives a production scheduling problem from the continuous annealing production line which includes parallel production lines,with consideration of equilibrium among production capacity utilization of the parallel production lines,production changeover costs,and on-time delivery of the products.The main contents are presented as follows.(1)Based on the practical production in continuous annealing production process,the production scheduling problem consisting of parallel continuous annealing lines is proposed,which is to assign the candidate coils to the production lines,and determine the coil sequence for each production line per day and the starting time of each coils,to in order to reduce the production changeover cost,improve the production capacity utilization,and keep on-time delivery.(2)For production scheduling problem consisting of parallel continuous annealing lines,a mixed linear integer programming model is formulated with the objective of maximizing the production capacity.The model is solved by CPLEX,and tested by the experiments based on practical production data and randomly generated data.(3)Since CPLEX cannot solve the large-scale instances in reasonable time,differential evolution(DE)algorithm is proposed to solve the problem.First,a manual experience based heuristic is developed to achieve the initial solution.Then the solution is improved by the proposed DE algorithm,which takes the initial solutions obtained by the above heuristic and the randomly generated solutions as a population,and designs a two-vector based mutation strategies.Finally,the efficiency of the proposed algorithm is tested by the computational experiments.(4)Based on the investigation in a large steel enterprise in China,a continuous annealing scheduling system is developed,which includes data management,parameter setting,and scheduling result display modules.