Study On Modeling And Simulation Of Cyber-Physical Systems Based On Extended Time Petri Nets

Cyber-Physical Systems(CPS)are a class of distributed and real-time feedback systems that integrate the information processing process with the real physical environment process and include three functions: computation,communication,and control.They can not only perceive the physical environment in real time,but also realize the dynamic control of physical entities through computation systems and communication systems.CPS have the advantage that traditional systems can hardly achieve and are the core factor for intelligent manufacturing in “industry 4.0”.CPS are complex and powerful,which brings not only advantages but also difficulties and challenges to its research.CPS are composed of a large number of distributed heterogeneous subsystems with different forms and different functions,and there are a lot of interaction and collaboration among the subsystems.In addition,realtime control of physical entities is required.These requirements have greatly increased the complexity of the systems.Therefore,to effectively describe the properties and functions of CPS,a sound modeling theory and a feasible verification method are necessary.Petri nets have the ability to intuitively express the structure of the system and describe asynchronous concurrent events,and time Petri nets add time factor to Petri nets and are often used to model distributed real-time systems.However,time Petri nets are difficult to express the spatial factors effectively,so a single time Petri net is not perfect for CPS modeling.Aiming at the shortcomings of time Petri net,descriptions of the spatial information are added to it,so that it has the ability to describe the location transitions of physical entities,and an extended time Petri net model called SpatialTemporal Petri net(STPN)is constructed in this paper and is applied to the modeling research of CPS.First,by the studies of the properties and characteristics of physical entities in CPS,the physical modules of CPS are classified,and their formal definitions are given,also,models of physical entities are established.And by analyzing the properties and requirements of CPS,the space factor is added and the classical time Petri net is extended,so that the constructed STPN can not only describe the performance of the system from time lever,but also describe the physical entity's transition at the spatial level,which satisfying the modeling requirements of CPS.Then,taking a cyberphysical production system(CPPS)as the research background,the corresponding STPN model is established and its feasibility.Finally,through the studies and analyses on the BNF grammar and model verification method,the model verification tool UPPAAL is described.And the STPN model constructed in this paper is transformed into the time automaton model which can be used by UPPAAL through the UML sequence diagram.The key properties of the model are described and verified through CTL formulas,which illustrate the reliability and effectiveness of the model.