Job Shop Scheduling Optimization With Uncertain Factors

In the production environment of many varieties and small batches,the processing time of workpiece and the periodical maintenance of equipment are important influencing factors of job shop scheduling.The traditional job shop scheduling is considered under the condition of the workpiece processing time and equipment maintenance time.In the production process of the actual workshop,the processing time and the maintenance cycle of the equipment are often uncertain,in the face of this situation,a job shop scheduling scheme with uncertain factors is urgently needed.Based on the above considerations,this paper focuses on the work-shop scheduling optimization problem Considering the uncertain factors of processing time and periodical maintenance.First,a job-shop scheduling model with uncertain processing time is proposed,and a genetic algorithm based on multilayer coding is introduced to solve the above model.Considering the actual situation of job shop scheduling,the model assumes that the processing time of workpiece is the random processing time of normal distribution,and the preventive maintenance period of the equipment is determined,because of the randomness of machine processing time,the model takes the expected minimum of the maximum completion time as the objective function.Secondly,based on the above research,a job shop scheduling model is proposed,which is the double uncertainty of maintenance period and processing time.This model takes into account the reality of the job shop,in order to reduce the idle time of the machine,making the research more realistic,the fixed maintenance period of the model is changed to assume that each machine has fixed one or more "time windows" in the dispatching process,all machines should be maintained in the "Time Window".Make the model more practical.Finally,the simulation and comparison of two models are realized through an example.The simulation of the job shop scheduling model with uncertain processing time and the double uncertainty of the maintenance period and processing time of the job shop scheduling model verifies the rationality of the two models and the effectiveness of the algorithm.The simulation results of the job shop scheduling model with the double uncertainty of maintenance cycle and processing time are proved to be more effective,and have more practical significance in actual production,which can provide the decision basis for enterprise dispatching optimization.