Research And Implementation Of Job Shop Scheduling Based On Digital Twin

In the manufacturing process of discrete enterprises,workshop production is the basic unit and job shop scheduling is the decisive factor affecting the manufacturing efficiency.With the emergence of intelligent manufacturing and the integration of various information technologies,the traditional job shop scheduling is not enough to meet the requirements of real-time,robustness and accuracy.And it is also impossible to dynamically adjust abnormal events in the process of workshop manufacturing.At the same time,due to the characteristics of virtual-real interaction,real-time mapping and co-evolution,digital twin has attracted wide attention.Therefore,the application of digital twin to job shop scheduling is an important way to improve manufacturing productivity.In this study,real-time mapping and interaction of digital twins are achieved based on data perception and abnormal events monitoring in production workshop.Considering the double resource multi-objective flexible job shop scheduling problem with machine and labor resources,an improved multi-objective optimization algorithm is proposed.Through real-time monitoring of abnormal conditions in production,the dynamic adjustment and optimization of scheduling plan are accomplished.The main research contents are as follows:(1)Research on workshop-oriented data perception and virtual-real interaction.Since that the workshop data have many types,wide sources and diverse structures,a total-elements workshop information analysis method is proposed.According to the characteristics of workshop data,a perception framework for workshop-oriented totalelements workshop information is proposed.The monitoring of abnormal production events based on workshop perception data is studied.The monitoring of abnormal production events based on RFID and the state recognition based on equipment operation data are proposed,which provide the basis for dynamic scheduling adjustment of workshop.The mapping framework between virtual and physical space is established through the analysis of information difference between the two space in digital twin,and an information exchange method in digital twin based on event monitoring and triggering mechanism is proposed.(2)Research on evolutionary workshop scheduling method between virtual and physical space.Aiming at the shortcomings of traditional job shop scheduling methods in real-time response,a digital twin-based job shop scheduling mechanism is proposed and its operation principle is studied.Combined with the dynamic adjustment and interaction,the virtual and physical evolution of job shop scheduling is achieved.Taking completion time,processing cost,processing energy consumption,machine load and delivery delay as optimization objectives,a double resource flexible multiobjective job shop scheduling problem considering the flexibility of machine and operator is proposed.By introducing improved elitism and neighborhood search operator,an improved multi-objective genetic algorithm is proposed to solve the scheduling problem.Based on abnormal production events,stable dynamic rescheduling of workshop production is studied.Finally,the effectiveness of the proposed method is verified by simulation experiments and result analysis.(3)Design and implementation of job shop scheduling management system based on digital twin.On the basis of the overall design of the system and the idea of modular development,the job shop scheduling management system is designed to achieve information management module,information monitoring module and job shop scheduling module.The dynamic scheduling simulation is accomplished through the digital twin workshop model.Finally,each module is implemented and tested to verify the effectiveness of the system and achieve effective management of the job shop scheduling.