| Flexible manufacturing as a kind of multi-batch small variety of production methods,can adapt to the requirements of today's manufacturing development,and can provide a wide range of products to the market quickly.However,there are some problems in the process of flexible manufacturing system,such as large investment,risk and unpredictability.In particular,the control process has the characteristics of discrete dynamic characteristics such as asynchronous and complicated,and it is difficult to analyze and control.Therefore,the control system in flexible manufacturing system Modeling and simulation has always been the subject of academic attention and research.The primary task of analyzing flexible manufacturing systems is to model them.The Petri net used in this paper is a kind of structured and visual description language,which can simulate the events in the system,highlight the logical relationship among the system elements,and capture the sequence of events.However,the ability of the basic Petri net is not enough to describe the system,and with the increase of the complexity of the system,such as the problem of node explosion.In order to solve the above problems,this paper proposes an object oriented timed colored Petri net,which is used to solve the problem such as node explosion,difficulty in analysis,poor repeatability and so on.In this paper,timed Petri nets are used to describe system events that related to the time property,such as processing,transportation and so on;The colored Petri nets are used to assign the color attributes to the states or transitions,which are used to distinguish the different elements of the same type of system elements in order to achieve the purpose of reducing the network size;From the view of object oriented,according to the attribute,behavior or state of the control system is divided into several modules and encapsulated the operation mechanism of package,while the system is running the object only through the interface information to communicate,make the model more hierarchical and concise.The exchange of information between objects is controlled by the “gate”,and the system coordinates the activities and sequences of different objects through the excitation of control gate change to solve the conflicts and deadlocks in the system by controlling the ignition of the gate transitions.The Petri nets have static structure and logical description of the system.In order to analyze it's dynamically,we maps the logic control relation and message transfer mechanism in Petri nets to the simulation software,and uses the Flexsim object-oriented technology to driven the Petri nets and then to validate the dynamic characteristics of Petri nets by simulation.Then analyzes the operation status and results of each object in the model,the system found that the existence of emergencies in the system such as machine failure and urgent order.In this paper,an embedded heuristic algorithm is used to control and schedule the uncertainties such as machine fault,emergency order and so on to reduce the occurrence of problems such as equipment conflict and resource waste in production system,thus improving the production efficiency of the flexible manufacturing system.By comparing the simulation results of the control system before and after the improvement,it is proved that the Object-Oriented Timed Petri Net proposed in this paper is effective and practical in the static description and the dynamic analysis and the flexible manufacturing control system. |
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