Research On Continuous Casting-Hot Rolling Scheduling Problem With Flexible Periodical Preventive Maintenance Of Equipment

Continuous casting and hot rolling are essential parts of the steel production process.Due to the inconsistent production rhythm between the continuous casting and hot rolling processes,a large number of slabs produced in the continuous casting process cannot be rolled directly and need to be heated to a predetermined temperature in the heating furnace before they can be rolled,resulting in energy consumption and heat loss.Optimizing production scheduling of continuous casting and hot rolling is one of the effective ways to reduce energy consumption.In addition,machines involved in steel production will degrade over time,which may lead to machine failures.Preventive maintenance activities can improve the reliability of the machine and keep the machine in good operation.Therefore,this thesis considers the preventive maintenance of continuous casting machine and hot rolling mill,and adds preventive maintenance activities as machine unavailability constraints to the production scheduling of continuous casting-hot rolling.The continuous casting-hot rolling scheduling problem with flexible periodical preventive maintenances of equipment is studied to reduce the energy consumption,improve the reliability of the machine and ensure the smooth implementation of the production scheduling scheme.Specific research contents are as following.(1)Taking the production scheduling of continuous casting-hot rolling as the research object,and considering the preventive maintenance activities of equipment with flexible period and flexible maintenance time during the scheduling plan period,the mathematical model of joint production scheduling and equipment preventive maintenance plan is established,and the optimization objectives are to minimize the maximum completion time and the number of slabs processed by cold charging.(2)For the multi-objective optimization problem proposed in this thesis,the non-dominated Sorting Genetic Algorithm-II(NSGA-Ⅱ)is designed,and the mutation operator of NSGA-Ⅱ is improved to increase the diversity of solutions;the adaptive mutation probability is designed to maintain the optimality of the population in the late evolution of the algorithm.The improved NSGA-Ⅱ is combined with the Simulated Annealing(SA)algorithm to improve the local search ability of the algorithm.(3)The algorithm program is written in C++ language.Based on the actual production data of an iron and steel enterprise,different size test cases are generated.The improved NSGA-Ⅱ combined with SA optimization algorithm and the original NSGA-Ⅱ are utilized to simulate the test cases.The simulation results demonstrate that the performance of the improved NSGA-Ⅱ combined with SA is better than that of the original NSGA-Ⅱ,and the improved NSGA-Ⅱ combined with SA algorithm is more suitable for solving the problems proposed in this thesis,with better optimization performance.(4)Based on the idea of combining theory with practice,a results query system for continuous casting-hot rolling scheduling is designed and implemented.The results obtained by the algorithm are stored in this system,which is convenient for the on-site scheduling personnel of iron and steel enterprise to consult and plays a good auxiliary role in the production decision of enterprise.The system functions mainly include user registration and login,adding,deleting,updating and querying information of equipment,production planning,maintenance planning and scheduling results.