Integrated knowledge-based Petri net intelligent flexible assembly planning

Automatic assembly planning is recognized as an important tool for reducing manufacturing costs in concurrent product and process development. A novel knowledge-based Petri net (KBPN) is defined, based on the incorporation of expert systems into the usual Petri nets, and used for a unified assembly knowledge representation scheme. A KBPN-approach integrated with a sequence generation algorithm is proposed for the modeling, planning, simulation, analysis and evaluation of the flexible assembly system (FAS). The developed KBPN-based assembly planning system (KAPS) can automatically adjust the deviations between the theoretical planning parameters and the process parameters of real assembly operations to guarantee the best strategies and plans (sequences) for flexible assembly. The research findings are exemplified with a simple assembly to show the effectiveness of the method.     

A Petri net based approach for multi-robot path planning

This paper presents a procedure for creating a probabilistic finite-state model for mobile robots and for finding a sequence of controllers ensuring the highest probability for reaching some desired regions. The approach starts by using results for controlling affine systems in simpliceal partitions, and then it creates a finite-state representation with history-based probabilities on transitions. This representation is embedded into a Petri Net model with probabilistic costs on transitions, and a highest probability path to reach a set of target regions is found. An online supervising procedure updates the paths whenever a robot deviates from the intended trajectory. The proposed probabilistic framework may prove suitable for controlling mobile robots based on more complex specifications.     

Knowledge intensive Petri net framework for concurrent intelligent design of automatic assembly systems

The integration of design and planning of flexible assembly system has been recognized as a tool for achieving efficient assembly in a production environment that demands assembly with a high degree of flexibility. This paper proposes a concurrent intelligent approach and framework for the design of robotic flexible assembly systems. The principle of the proposed approach is based on the knowledge Petri net formalisms, incorporating Petri nets with more general problem-solving strategies in AI using knowledge-based system techniques. The complex assembly systems are modeled and analyzed by adopting a formal representation of the system dynamic behaviors through knowledge Petri net modeling from the specifications and the analysis of those models. A template is first defined for a knowledge Petri net model, and then the models for assembly system individuals are established in the form of instances of the template. The design of assembly systems is implemented through a knowledge Petri net-based function–behavior–structure model. The research results show that the proposed knowledge Petri net approach is applicable for design, simulation, analysis and evaluation, and even layout optimization of the flexible assembly system in an integrated intelligent environment. The integration of assembly design and planning process can help reduce the development time of assembly systems.     

基于面向对象Petri网的Web服务合成

主要讨论了基于面向对象Petri网的Web服务合成技术。利用此技术,不仅可以精确描述Web服务与合成运算的形式化语义,还可以建立合成Web服务的控制流模型。研究了Web服务组件与OOPN(面向对象Petri网)元素之间的映射关系,讨论了基于OOPN的Web服务合成的各种运算,并给出了建模步骤。最后结合应用实例进一步验证了本文的工作。     

基于面向对象Petri网的动态合同网协议通用模型

传统的合同网协议模型通过管理Agent和承包商Agent之间招投标进行交互和协商以共同完成目标任务。但传统合同网协议模型也存在一些如协作过程中通信量大、通用性不强等问题。为此，采用面向对象Petri网，引入对象Agent，对动态合同网协议进行建模,并采用Petri网的数学分析方法对模型进行了分析，表明模型具有通用性、并发性、活性的特点且通信量减少。     

基于面向对象Petri网的煤矿CPS建模

针对煤矿CPS的特点,利用面向对象Petri网对其进行建模.从多Agent系统的角度,建立煤矿CPS的体系架构;建立该体系中各对象内部的子网模型;通过对煤矿CPS的业务流程分析,建立系统对象间的整体模型,描述各对象内部的静态、动态特性以及对象间的交互过程;对所建模型进行系统可靠性分析,分析结果表明,所建立的煤矿CPS模...     

基于面向对象Petri网的无人机协同追踪系统建模*

从离散事件系统角度出发,基于动态角色配置的思想,提出了协同追踪过程中无人机在搜索、协助者、领导者和空闲四个角色之间切换,动态构建团队追踪地面移动目标的协同追踪策略,采用面向对象Petri网对无人机、移动目标以及协同追踪策略组成的协同追踪系统进行建模研究。利用改进的人工势场法作为无人机的追踪算法,设计了一种协同追踪的情景对协同追踪系统进行了仿真,仿真结果表明了系统建模的可行性。     

一种基于知识约简的Petri网模型简化方法

提出一种基于知识约简的Petri网模型简化方法,利用知识约简中的属性约简方法,去除Petri网对应的产生式规则的冗余规则和冗余条件,简化产生式规则得出关键规则。经过知识约简后的规则库转化为Petri网模型,此时的Petri网模型的结点数目减少,因此在一定程度上降低了网系统的复杂程度。简化后的模型保持原有的信息量,而所含的库所、变迁得到了减少,在其基础上进行的知识推理,更加简单和高效。最后通过一个病例实例说明,此方法简单实用,可以有效减少时间和空间复杂度,提高知识搜索和推理效率。     

应用带标识的模糊Petri网的知识表示方法

提出一种在某些库所中带有标识的模糊Petri网模型来进行知识表示。为了获得更多的加权模糊产生式规则的信息,在知识表示的过程中考虑了权值,确定性因子,阈值等参数。这种模糊Petri网充分利用了Petri网的并行处理能力。随着带标识的模糊Petri网的运行,网中标识的变化可以标记加权模糊推理的运行。通过文中给出的基于相似性测度的计算方法可以更加高效地计算出多层加权模糊推理的推理结果。     

An interactive approach of assembly planning

An interactive approach to assembly planning is presented. It provides a virtual reality interface for production engineers to program the virtual representation of robotic manipulators in a three-dimensional (3D) operation space. The direct human involvement creates a user-defined assembly sequence, which contains the human knowledge of mechanical assembly. By extracting the precedence relationship of machinery parts, for the first time it becomes possible to generate alternative assembly sequences automatically from a single sequence for robot reprogramming. This interactive approach introduces human expertise into assembly planning, thus breaking down the computational complexity of autonomous systems. Experiments and analysis provide strong evidence to support the incontestable advantages of "manufacturing in the computer".     

基于智能Petri网的物流配送路径优化算法

基于智能Petri网构建了物流配送路径的优化模型。通过定义智能Petri网的运行规则,得到了基于智能Petri网的物流配送路径优化算法与计算流程,分析了车辆在交叉口的实际延误阻抗对配送分析的影响。该算法具有求解不需要对物流网络图作任何修改和容易实现配送过程的动态模拟的特点,利用该算法可以获取配送车辆从出发点到城市中任何一个节点的最优路径。将算例与改进的Dijkstra算法进行了对比分析,结果表明了该算法的可行性和有效性。     

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.     

FCRP网：机器人规划的赋时有色网实现*

针对流演算无法表示动作执行时间和进行动态规划的问题,提出了一种基于流演算的表示机器人规划的赋时有色网实现方法——BFRP网(A representation based on Fluent Calculus for robot plan),BFRP网采用双向搜索策略来生成动作序列,并提出了一种BFRP网系统的构造方法,此BFRP网系统不仅能形式化地描述动作、状态以及动作和状态之间的关系,而且能动态地规划出实现目标的动作序列并计算执行动作序列所需时间。最后,对办公室环境规划实例进行了建模和仿真,结果证明了BFRP网系统作为一种机器人规划系统的可行性。     

Preliminary design and manufacturing planning integration using web-based intelligent agents

Software agents have been increasingly used in the product and process development in industry over the past years due to the rapid evolvement of the Internet technology. This paper describes agents for the integration of conceptual design and process planning. Agents provide mechanisms to interact with each other. This mechanism is important since both of those processes involve negotiations for optimization. A set of design and planning software agents has been developed. These agents are used in a computer-based collaborative environment, called a multi-agent platform. The main purpose of developing such a platform is to support product preliminary design, optimize product form and structure, and reduce the manufacturing cost in the early design stage. The agents on the platform have access to a knowledge base that contains design and planning rules. These rules are derived from an analysis of design factors that influence process and resource planning, such as product material, form, shape complexity, features, dimension, tolerance, surface condition, production volume, and production rate. These rules are used by process planning agents to provide process planners with information regarding selecting preliminary manufacturing processes, determining manufacturing resources, and constructing feedback information to product designers. Additionally, the agents communicate with WEB servers, and they are accessible by users through Internet browsers. During performing design and planning tasks, agents access the data pertinent to design and manufacturing processes by the programming interfaces of existing computer-aided design (CAD) and manufacturing system. The agents are supported by a developed prototype agent platform. The agents and the platform enable the information exchange among agents, based on a previously developed integrated design and manufacturing process object model.     

An approach to system design based on P/T net simulation

This work presents a technique of early simulation in the design phase of concurrent and distributed systems. A P/T net is used to model the system whose behavior is simulated by the net execution; the truly concurrent semantics of P/T nets establishes a partial order among the system events. The designer can interact with the simulator asking for measures about the system behavior that concern all executions respecting the same partial order. Some measures, such as the degree of parallelism exploited, are not easily obtainable from an interleaving semantics. Moreover, the designer can force the system behavior to reflect resource-constrained environments.     

基于信息熵Petri网模型的知识发现研究

为描述命题和规则的可信度,定义了命题和规则的可信度信息熵。从熵的角度研究产生式规则中的不确定性推理,应用Petri网和可信度信息熵,建立了一类新的Information Entropy Petri网模型(IEPN),介绍了不确定性知识表示和推理步骤。同时分析IEPN推理对知识发现(KDD)的指导意义,并给出了IEPN推理过程及知识发现(KDK)方法。     

An algebraic approach to the design of compilers for object-oriented languages

In this paper we describe an algebraic approach to construct provably correct compilers for object-oriented languages; this is illustrated for programs written in a language similar to a sequential subset of Java. It includes recursive classes, inheritance, dynamic binding, recursion, type casts and test, assignment, and class-based visibility, but a copy semantics. In our approach, we tackle the problem of compiler correctness by reducing the task of compilation to that of program refinement. Compilation is identified with the reduction of a source program to a normal form that models the execution of object code. The normal form is generated by a series of correctness-preserving transformations that are proved sound from the basic laws of the language; therefore it is correct by construction. The main advantages of our approach are the characterisation of compilation within a uniform framework, where comparisons and translations between semantics are avoided, and the modularity and extensibility of the resulting compiler.     

An object-oriented approach to computer-aided design of a plastic injection mould

This paper describes a knowledge-based and object-oriented approach for the design of the feed system for plastic injection moulds. The gating system of a plastic injection mould plays a significant role in producing a quality part. Designing of this gating system entails a great amount of effort from an experienced designer and it is time-consuming. CADFEED (Computer-Aided Design of the FEED system of the plastic injection mould) is developed to accurately and efficiently design the type, location and size of a gating system of a plastic injection mould. This system provides an accurate and fast means of obtaining solutions based on the users' requirements, which are easily handled by the rating algorithm in the system. CADFEED generates acceptable solutions at a lower cost than most traditionally and commercially available analysis packages. This system can be used to verify designs proposed by the design engineers. It can also help novice engineers in the understanding of mould design. Another important feature of CADFEED is that it is a low cost system, which uses AutoCAD and an expert system shell on a personal computer. This feature makes CADFEED easily affordable by small-scale industries.     

An object-oriented approach for mechanical components design and visualization

In this paper, development of shape modeling tools for engineering design, analysis, simulation, and visualization is presented. The approach based on the idea of function-based shape modeling is combined with the power and versatility of the object-oriented programming (OOP). An OOP code, initially developed as a teaching and learning tool for educational use in an undergraduate Modeling and Simulation course, to generate mechanism components is presented. Different parametric, explicit, and implicit functions or their combination are used to generate mechanical components shapes. Using a blending process, sophisticated shapes have been generated on the graphical interface. However, the ideas and concept of the OOP mechanical components design presented in this paper can be applied to other application areas.     

基于模块PTR8000的无线数据通信

针对无线通信在测控领域的优越性,基于无线射频收发模块PTR8000,采用分层结构.利用特殊的通信协议实现了一种传输可靠、扩展方便、使用灵活的无线数据通信系统.介绍了无线射频模块PTR8000的结构、工作模式、射频收发流程以及片内SPI接口的配置,在此基础上分析了系统的硬件设计和软件设计.基于PTR8000的无线通信系统具有功耗低.多频道多频段的特点,可以很方便地实现点对点及点对多点的无线通信.可应用于遥感、遥控、无线抄表、工业数据采集及家庭自动化等领域.