借助Petri网进行流程审计

信息的使用者往往关注保存在介质上的信息而忽视处理信息的程序。由于保存在介质上的信息有多个操作入口,即使处理信息的程序真实地反映了组织的业务流程,也难保证信息使用者所获得的信息是正确的,也就是说对于访问数据的程序,存在外部干扰。引入数据库中的审计表功能,协助信息系统审计人员识别信息系统中数据的形成是否遵循了既定的业务流程。由于Petri网是描述流程的有力工具,对于复杂的业务流程,引入Petri网对流程进行审计是必要的。     

Neurovision-based logic control of an experimental manufacturing plant using neural net le-net5 and automation Petri nets

In this paper, Petri nets and neural networks are used together in the development of an intelligent logic controller for an experimental manufacturing plant to provide the flexibility and intelligence required from this type of dynamic systems. In the experimental setup, among deformed and good parts to be processed, there are four different part types to be recognised and selected. To distinguish the correct part types, a convolutional neural net le-net5 based on-line image recognition system is established. Then, the necessary information to be used within the logic control system is produced by this on-line image recognition system. Using the information about the correct part types and Automation Petri nets, a logic control system is designed. To convert the resulting Automation Petri net model of the controller into the related ladder logic diagram (LLD), the token passing logic (TPL) method is used. Finally, the implementation of the control logic as an LDD for the real time control of the manufacturing system is accomplished by using a commercial programmable logic controller (PLC).     

基于Perti网的工作流访问控制模型研究

提出了一种工作流访问控制模型WACM(Workflow Access Control Model),该模型支持基于角色的授权,通过工作流引擎中的访问控制矩阵进行同步授权,采用Perti网来描述工作流,对工作流参考模型进行了定义和描述,分析了工作流访问控制模型WACM的体系结构,并将该模型应用到电子商务工作流中,建立了基于安全电子商务协议(SET)的访问控制模型。     

Neuron type processor modeling using a timed Petri net

The basic operation of a digital neuron is reviewed, and the theory of time Petri nets used for modeling, representation, and analysis of the neuron-type processor (NTP) is reviewed. The timed Petri net is utilized to produce a model for the digital NTP. The neuron-type processor performs input temporal and spatial summation, as well as thresholding. The timed Petri net of the NTP operates asynchronously and sequentially takes on a series of distinct internal states, so that each of these states can concurrently realize a distinct set of steering switching functions depending on the pattern of steering inputs applied to it at the time. This model is structured using several subnets, called essential module units. Depending on the desired number of input dendrites required for the NTP, the essential module units (EMU) are interconnected to produce the required timed Petri net. The timed Petri net and representation facilitates a method of analysis of neural net works containing NTPs prior to hardware implementation.     

Petri net control of an automated manufacturing cell

This paper discusses the Petri Net approach to real time production control. Petri nets were developed to model concurrent and asynchronous systems. Having modeled a machining cell or a production system as a Petri net, one can analyze the effects of controller behavior on the system before implementing the controller.

Petri net principles are illustrated for a machining cell being implemented in the Manufacturing Automation Laboratory at Rutgers University. Observations are made concerning the difference between a Petri Net Controller and a Programmable Logic Controller for the same application.     

Synthesis a Petri net based control model for a FMS cell

Petri nets have been recognised as a high level formal and graphical specification language for modelling, analysis, and control of concurrent asynchronous distributed systems. This paper presents a PN model, synthesised by an extended version of the knitting synthesis technique. This method, as an incremental design approach, establishes the conditions under which the fundamental behavioural properties of the synthesised systems are fulfilled and preserved. That is, the synthesised models are live, bounded, and reversible (cyclic). A Petri net with the aforementioned properties is called a well-behaved Petri net system which is guaranteed to operate in a deadlock-free, stable, and cyclic fashion. Well-behaved Petri net models, synthesised using the proposed method can be compiled into control codes and implemented as real-time controllers for flexible manufacturing systems. The significance of this paper is due to the application of an extended version of knitting synthesis technique to a real life example of a flexible manufacturing system.     

Software modeling and analysis using a hierarchical object-oriented Petri net

Petri net is used widely to analyze and model various systems formally. Recently, many Petri nets mania devote their efforts to enhancing and extending the expressive power of Petri nets. One such effort is to extend Petri nets with object-oriented concepts. An object-oriented paradigm provides excellent concepts to model real-world problems. Object-oriented concepts allow us to build software systems easily, intuitively, and naturally. Although several high-level Petri nets with the concept of objects are suggested, these nets do not fully support the object-oriented concepts. In this paper, we propose a hierarchical object-oriented Petri net (HOONet). The formal syntax and semantics of HOONet are explained in detail. HOONet supports a wide range of object-oriented features including abstract, encapsulated and modularized objects, object interaction by message passing, inheritance, and ploymorphism. HOONet also supports a variety of modeling and analysis mechanisms such as incremental modeling of evolving systems, unfolding the HOONet to lower level Petri net, and incremental reachability analysis for HOONet models. We demonstrate the usefulness of HOONet by applying it to modeling and analysis with an example.     

A heuristic approach to automatic grasp planning for a 3-fingered hand

This paper presents the core of a software system able to determine a good grasp configuration on 3D objects for a three-fingered hand. The grasp planning problem has been studied considering both the constraints due to the stability and accessibility conditions, and the ones related to functionality. Physical, geometrical, spatial and task-related knowledge for solving the grasp planning problem have been properly modelled to support a heuristic-based reasoning process. A series of heuristic rules and geometric tests are used to scan the solution space, searching for a good grasp. In fact, when considering the three-dimensional case, a purely analytical and exhaustive approach appears too complex because of the dimension of the search space. This approach results in an incremental and modular model of grasp reasoning, that has been implemented using the Flex expert system shell. This work has been developed and demonstrated within the Esprit 2 project CIM-PLATO No. 2202.     

Detection of Ada static deadlocks using Petri net invariants

A method is presented for detecting deadlocks in Ada tasking programs using structural; and dynamic analysis of Petri nets. Algorithmic translation of the Ada programs into Petri nets which preserve control-flow and message-flow properties is described. Properties of these Petri nets are discussed, and algorithms are given to analyze the nets to obtain information about static deadlocks that can occur in the original programs. Petri net invariants are used by the algorithms to reduce the time and space complexities associated with dynamic Petri net analysis (i.e. reachability graph generation)     

Sequential failure analysis using counters of Petri net models

Assessment of reliability and safety of a complex system with sequential failures is an important issue in industries, since the reliability and safety of a complex system depends, not only upon all failed states of the system components, but also upon the sequence of occurrence of those failures. In this paper, we present an alternative methodology for assessing sequential failures in a complex system. In previous research, the probability of sequential failures is computed based on tracking the markings of Petri net models and it is assumed that the time to failure of basic events follows an exponential distribution. To overcome the limitations of the current methods in applying Petri nets for assessment of sequential failures, the method presented in this paper employs the concept of counters used in Petri net simulation to perform sequential failure analysis and is developed based on evolution equations that describe the dynamics of the system. It is demonstrated with a sequential failure analysis example of an automated machining and assembly system.     

Behavior modeling and control of 300 mm fab intrabays using distributed agent oriented Petri net

In a 300 mm integrated circuit (IC) foundry fab, the intrabay automation is more important than a 200 mm one. In general, the intrabay automation systems include the automated controls of the process tools, overhead hoist transports (OHTs), stockers, and rail shortcuts. These control systems are operated concurrently. They must cooperate seamlessly to increase the system performance and to avoid deadlocks. In the paper, the behaviors of the intrabay automation systems are modeled using the distributed agent oriented Petri net (DAOPN). The fab intrabay DAOPN models are categorized into the new-order generation, OHT vehicle dispatching, zone control, path decision, and tool processing agent models. Finally, the DAOPN is defined, and the modeling procedures of the intrabay behaviors are all illustrated. Consequently, an experimental intrabay OHT loop is discussed and evaluated using the proposed DAOPN models and the DAOPN simulator.     

Exploring airport traffic capability using Petri net based model

The first part of the paper introduces a novel tool for modeling and simulation of discrete event system. This tool called GPenSIM is a Petri net based simulator and offers significant benefits to model builders such as flexibility to include diverse libraries, ease of extending the models, and ease of programming. The second part of the paper presents a case study on modeling and optimization of airport traffic management; this study is to explore air traffic management capability of Evenes airport in Norway. The case study shows that with GPenSIM, modeling and simulation problems of large industrial discrete event systems can be done. Future research directions are discussed as well.     

EMG pattern classification using SOFMs for hand signal recognition

 We propose a method of pattern classification of electromyographic (EMG) signals using a set of self- organizing feature maps (SOFMs). The proposed method is simple to apply in that the EMG signals are directly input to the SOFMs without preprocessing. Experimental results are presented that show the effectiveness of the SOFM based classifier for the recognition of the hand signal version of the Korean alphabet from EMG signal patterns.     

Supervisory control of a multi-echelon supply chain: A modular Petri net approach for inter-organizational control

Petri nets (PNs) are frequently utilized to model system dynamics due to their ability to handle concurrencies and sequential dependence. In this paper, a portion of the supply chain operations reference (SCOR) model has been extracted and modeled using PNs for the purpose of exerting supervisory control upon a multi-echelon supply chain (SC). The activities of source, make and deliver, inherent in the SCOR model form the basis of the representation of the PN model for each echelon considered in the SC model. Two control nets are utilized: one above the base model of each echelon to exert local constraints and an enterprise level supply chain manager (SCM). The local constraints are at the tactical and operational levels while the SCM enforces additional constraints consisting of long term planning goals at the strategic level. Place invariants are used to create the supervisors. Performance measures of the total SC are formulated to determine the effectiveness of any partnership. An efficient method for finding the current state of the system is developed which is used to determine the performance measures of each echelon. This paper presents a modular approach to the overall structure and PN modeling for a SC system. It is intended to extend the use of supervisory control from a shop-floor level to an inter-organizational facility and enterprise level.     

Monitoring of flexible production systems using high-level Petri net specifications

The degree of reliability in the operation of flexible production systems depends not only on the operation of the individual components, but also on the structure and evolution of the embedded supervisory control system. Monitoring of operations and of the behaviour of the components and of the system as a whole is an essential function of such a supervisory control system. This paper focuses on the development and implementation of feature- and model-based monitoring methods using high-level Petri net specifications of flexible production systems and of the embedded discrete-event controllers. The combination of machine–human interface concepts with the developed monitoring methods leads to a user-friendly representation of monitoring information. An application at industrial level is shown by means of a case study, i.e., a sample flexible assembly cell, situated at the Institute for Manufacturing Automation and Production Systems, Germany.     

The implementation of a smartphone-based fall detection system using a high-level fuzzy Petri net

The falling down problem has become one of the very important issues of global public health in an aging society. The specific equipment was adopted as the detection device of falling-down in the early studies, but it is inconvenient for the elderly and difficult for future application. The smart phone more commonly used than the specific fall detection equipment is selected as a mobile device for human fall detection, and a fall detection algorithm is developed for this purpose. What the user has to do is to put the smart phone in his/her thigh pocket for falling down detection. The signals detected by the tri-axial G-sensor are converted into signal vector magnitudes as the basis of detecting a human body in a stalling condition. The Z-axis data sets are captured for identification of human body inclination and the occurrence frequencies at the peak of the area of use are used as the input parameters. A high-level fuzzy Petri net is used for the analysis and the development of identifying human actions, including normal action, exercising, and falling down. The results of this study can be used in the relevant equipments or in the field of home nursing.     

Decidability and closure properties of weak Petri net languages insupervisory control

We extend the class of control problems that can be modeled by Petri nets considering the notion of weak terminal behavior. Deterministic weak languages represent closed-loop terminal behaviors that may be enforced by nonblocking Petri net supervisors if controllable. The class of deterministic weak PN languages is not closed under the supremal controllable sublanguage operator     

基于Petri网的电子政务工作流模型研究

设计了一种基于Petri网扩展的、用于复杂工作流模型设计的建模方法及其相关规则。并且通过电子政务系统的网上审批子系统为例,详细阐述了用此方法及其相关规则构建Petri网工作流模型的过程。最后通过Petri网理论对模型进行了正确合理性分析,并对网上审批子系统的资源分配情况进行了定量分析。此建模方法简化了Petri网的建模过程,并保证了正确性和合理性资源分配的分析结果对合理的进行资源分配有指导作用。     

有色Petri网的扩展使用控制策略模型设计

为解决目前UCON模型和策略规范存在系统应用功能与安全策略集成性差、缺少事后义务和无并发性控制问题,通过定义行为、安全和并发规则,提出了一种扩展的使用控制策略,采用有色Petri网技术,达到形式化定义、分析的目的,为将来的研究工作提供基础。