Digital-twin-oriented Modeling And Simulation Method For Discrete Manufacturing Workshop

Discrete manufacturing workshop,an important manufacturing system form,is widely used in the processing and assembly of complex equipment with its high flexibility.In the intelligent manufacturing era,information technology and manufacturing technology are integrated,information systems and manufacturing systems are interconnected,and information flow,material flow and control flow are intertwined.On this background,it becomes a challenging task to realize the efficient operation and closed-loop control of the discrete manufacturing workshop.Digital twin emphasizes on bidirectional data-exchanges between the physical entity and its virtual model,enabling optimizations and decisions making with the virtual system relying on the same data that is updated in real-time within the physical system,through synchronization enabled by sensors and controls.It is regarded as a key enabling technology to realize the new-generation intelligent manufacturing,and has received extensive attention and discussion in intelligent products,intelligent production,and intelligent services.This paper focuses on the research and application of digital twin in discrete manufacturing workshop.Although manufacturers and scholars have conducted extensive discussions and useful attempts on the connotation,modeling architecture,enabling technology,and application modes of digital twins,theories and methods of digital-twin-based intelligent production still need to be improved.How to construct a unified model of a heterogeneous discrete manufacturing workshop,and establish effective workshop-level virtual-real connections and interactions,then realize the closed-loop control of the digital twin model on the physical workshop remains to be solved.In response to the above questions,this paper explores a technology roadmap of digital twin shopfloor(DTS),studies the modeling,simulation and application methods for DTS,and develops a DTS modeling and simulation system,which aims to provide theoretical guidance and technical support for the promotion and application of digital twins in intelligent production.The main research contents are as follows:(1)To tackle the problem of unclear research ideas and technical roadmaps for DTS,the concept of DTS evolution model is proposed,which reveals the three evolution stages of DTS,i.e.,digital model shopfloor,digital shadow shopfloor,and DTS.Then,the operating mechanism of each evolution stage of DTS are discussed,which points out the direction for the research of DTS modeling,simulation and application.(2)For digital twin modeling of heterogeneous complex discrete workshops,a workshop digital twin modeling method based on virtual reconfiguration is proposed,including the identification and representation of workshop elements and relationships for configurable modeling,the workshop simulation modeling based on discrete event system(DES),and the workshop digital twin modeling towards cyber-physical system.(3)Aiming at the simulation mechanism and scheduling strategy of DTS,a digital twinbased production process simulation method is proposed.A digital twin-based simulation architecture is first designed.Then,a simulation scheduling strategy is explored and corresponding simulation algorithms were developed,including simulation initialization algorithms,simulation execution algorithms based on improved process interaction methods,and simulation data collection and analysis algorithms.Finally,with the above simulation strategy and algorithm enabled,three simulation execution modes are discussed,namely,evaluation mode,synchronization mode,and experimental mode,which meets the simulation needs of each stage of manufacturing execution.(4)Aiming at the problem of data perception and interaction in physical workshops,a workshop data acquisition,storage,mapping and interaction architecture towards digital twin is proposed.To achieve cyber-physical integration,three key technologies of this architecture are researched,namely,the workshop multi-source heterogeneous data acquisition and storage,virtual sensor-based data mapping and synchronization,virtual-real data connection and interaction in the workshop.(5)In order to realize the closed-loop control of DTS,a digital twin-driven intelligent manufacturing execution method is proposed.A digital twin-driven intelligent manufacturing execution application architecture is proposed.And four key enabling technologies of this architecture are implemented,namely,the virtual-real data interaction mechanism of the workshop manufacturing execution process,the solution evaluation and performance optimization based on the simulation evaluation mode,the process monitoring and disturbance detection based on the simulation synchronization mode,and the what-if analysis and dynamic scheduling based on the simulation experiment mode,which endow the manufacturing system self-organization,self-awareness,and self-decision-making intelligence.(6)Based on the theoretical and technical research results of DTS modeling,simulation,and application,an enabling system for DTS is developed.Firstly,the overall architecture of the system is constructed.Then,the main functional modules of the system have been designed and implemented,covering the simulation applications along the whole manufacturing execution.Finally,the system is verified by a large-scale complex aerospace structure workshop case study.This paper shows that the research of complex discrete workshop digital twin modeling and simulation method perfects the existing discrete manufacturing system modeling and simulation methods.The DTS modeling and simulation platform meets the application requirements,such as rapid virtual reconfiguration of the workshop,simulation of each stage of the manufacturing execution process,and optimization and control of the production process.It improves the digitization,transparency and intelligence of the workshop,and realizes the improvement of quality and efficiency.