| With the advent of small-lot,customized production models,production systems have become increasingly complex,making it difficult for mathematical modeling to accurately model complex problems,and also inevitably resulting in reduced performance of scheduling results.With the development of computer simulation,simulation modeling has more advantages than mathematical modeling in terms of both authenticity and flexibility.At present,the simulation scheduling methods for permutation flowshop scheduling problems still have the following shortcomings:lack of consideration of more practical constraints,lack of systematic flexible modeling methods,and lack of efficient optimization algorithms.Therefore,in order to reduce the modeling difficulty and improve the scheduling performance,this paper proposes the idea of using simulation models instead of mathematical models for scheduling optimization,and proposes suitable improved algorithms to interact with and optimize the simulation models.From the practical problem,the simulation scheduling method of permutation flowshop is proposed and the practical problem is solved with better results,which illustrate the superiority of the method proposed in this paper.The main research contents of this paper include:(1)Research on simulation scheduling method combining discrete-event simulation and NEH algorithm.The constraints are divided into dynamic constraints and static constraints,and the two types of constraints are added to the simulation model using static and dynamic methods respectively,thereby proposing a flexible modeling method for the simulation model of the permutation flowshop.At the same time,the simulation environment is built based on the flexible modeling method,and four functional areas are established in the simulation environment according to the functional requirements.Then designed the optimization framework of the simulation environment and NEH heuristic algorithm,and proposed the specific simulation optimization ideas.Based on the discrete-event simulation platform Plant simulation,the simulation environment is implemented to interact with the NEH algorithms to optimize the process,and the feasibility and correctness of the method is verified by comparing it with the solution process of an arithmetic example in the literature.(2)Research on the improvement and testing of NEH algorithm.In order to further improve the solution quality of the proposed scheduling method,analyze and compare several better improved NEH algorithms in the literature to derive an improved idea about the initial ordering rules firstly.Based on this idea,kurtosis is introduced into the initial ordering rules,and an improved NEH algorithm is proposed.On 37 scale examples of the VRF test set,the solution quality,computational efficiency and comprehensive performance of a total of 9 NEH-baesd algorithms are compared to prove that the proposed improving NEH algorithm is better than the existing improved NEH algorithm.(3)Research on permutation flowshop scheduling problem with sequence-dependent recovery time.In order to further improve the proposed simulation scheduling method as well as to better solve the practical problems,three models of recovery time and their concepts are introduced firstly.Based on this,this paper proposed four permutation flowshop scheduling problems with sequence-dependent recovery time.On the basis of the proposed simulation scheduling method,the recovery time constraint belonging to the static constraint is introduced to obtain the permutation flowshop simulation model with the sequence-dependent recovery time.By designing and solving calculation examples,the effectiveness of the proposed simulation optimization method in solving this problem and the importance of recovery time are verified.(4)Comparison of simulation scheduling method and traditional mathematical scheduling method when solving complex practical problems.When solving practical problems,the traditional mathematical scheduling method will have two deviations,while the simulation scheduling method will only have one deviation.The simulation scheduling method and the traditional mathematical scheduling method are used to solve a practical problem respectively to prove the superiority of the simulation scheduling method proposed in this paper in solving the actual problem. |
