Research On Steelmaking-continuous Casting Scheduling Considering Flexible Cycle Preventive Maintenance

With the continuous development of the steel production industry,the competition of the steel industry is becoming more fierce in the global.How to develop a scientific and reasonable production plan with limited resources and time has become one of the key concerns of steel production enterprises.In the practical production process,the production equipment will be worn out under long time and high intensity use,and the equipment failure rate will increase and the production reliability will decrease.The preventive maintenance activities for the production equipment can greatly reduce the downtime accidents caused by equipment wear and tear,but the equipment maintenance will take up certain production time and affect the maximum completion time of production.This thesis studies the steelmaking-continuous casting scheduling problem,in which an equipment preventive maintenance strategy is introduced,with maximum completion time and total maintenance cost together as optimization objectives.The main research contents are as following.(1)Combining with the actual steel production conditions,the thesis describes the current research status of steelmaking-continuous casting scheduling problem and preventive maintenance problem at home and abroad respectively.And it analyzes the practicality and importance of considering preventive maintenance in steelmaking-continuous casting scheduling,and according to the process requirements of steelmaking-continuous casting it selects the flexible cycle variable maintenance duration preventive maintenance strategy.(2)This thesis studies the steelmaking-continuous casting scheduling problem with flexible periodic variable maintenance duration preventive maintenance.A multi-objective mathematical model for the integrated optimization of steelmaking-continuous casting scheduling and preventive maintenance is developed,taking into account practical production constraints such as continuous casting.The model has the optimization objectives of minimizing the maximum completion time and minimizing the total maintenance cost.(3)For the steelmaking-continuous casting scheduling problem with flexible cycle preventive maintenance strategy,the thesis improves the fast Non-Dominated Sorted Genetic Algorithm-Ⅱ(NSGA-Ⅱ)with elite strategy and designs the NSGA-Ⅱ with variable neighborhood.To reduce the similarity between solutions,the Hemming distance constraint is introduced into the crossover and variational operators.The variational operator introduces the variable neighborhood search to expand the search range and thus improves the solution quality.The thesis chooses the scattering range and coverage as the algorithm evaluation index to measure the algorithm’s merit.(4)Combined with the actual production data,the before and after improvement algorithm and other optimization algorithms are compared with experimental experiments and experimental results analysis.In this thesis,variable-neighborhood NSGA-Ⅱ significantly improves the coverage index compares with the NSGA-Ⅱ on cases of different sizes.The variable-neighborhood NSGA-Ⅱ is verified the feasibility and superiority for solving the steelmaking-continuous casting scheduling problem considering flexible cycle prevention strategies.(5)According to the actual needs of users,this thesis designs the database tables and the scheduling management system,and the scheduling management system is combined with the database by calling the My SQL API.The thesis uses C#,C++ and Matlab joint programming to implement the user login,data management,algorithm running and result query,and drawing Gantt chart and Pareto distribution comparison chart modules,so that users can run the algorithm in real time to get a reasonable scheduling solution.