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1.
时间约束工作流模型的简化分析与可调度性验证   总被引:4,自引:0,他引:4  
为解决复杂工作流的时间建模与可调度性验证问题,提出了将简化规则应用到Petri网工作流模型中的方法.首先,给出了时问约束Petri网的相关定义和基于此的工作流建模方法,实现了工作流模型及其时间信息建模.然后,为了对工作流网的可调度性进行验证和分析,给出了时间约束Petri网时间可调度的概念,并根据时间约束等价变换原则,提出了基于时间约束Petri网的四种基本工作流组件模型的简化规则和压缩推理方法.该方法可以对复杂的工作流模型进行简化,计算模型节点的时间参数,从而完成含有时间信息工作流结构或流程的时间建模和可调度性分析.最后,以保险索赔为例验证了所提方法的可行性.  相似文献   

2.
实时嵌入式系统的重时间特性决定了在系统设计时需对系统作确定性验证。本文分析了不同的验证方法后认为形式化验证中基于时间自动机的模型检验方法最适用于实时嵌入式系统的分析和验证。在此基础上本文给出了时间自动机的定义和验证性工具UPPAAL的介绍,并对行人优先可控交通灯控制系统实例做了详细的建模、验证分析,结果表明该系统满足预定的各种特性要求。  相似文献   

3.
资源约束下多过程的不确定时间建模与分析   总被引:1,自引:0,他引:1  
由于测量不精确、信息不完备以及信息包含噪声等原因,工作流的时间信息会具有不确定性。针对不确定性情况下工作流时间建模和分析的实际需求,基于可能性理论,给出扩展模糊时间工作流网(Extended fuzzy timing work flownets,EFTWFN)定义,实现对不确定性时间信息的全面描述。在考虑资源约束情况下,提出一种工作流多过程EFTWFN模型的推理分析方法,将EFTWFN与线性逻辑结合,定义多种变迁间的化简规则,再基于规则逐步化简EFTWFN模型,从而实现对不确定性时间问题的解决。所提出的方法实用性较强,能够有效处理资源约束情况下工作流多过程的定量和定性两方面问题;而且效率较高,可在线性时间复杂度内完成对问题的求解。在某制造企业中的实例应用与仿真验证表明,该方法具有很好的效果。  相似文献   

4.
针对复杂制造环境下RFID应用可靠性问题,给出了一种RFID系统应用可靠性的评价指标,在此基础上建立了改善RFID系统应用可靠性的分层数据处理模型。在该模型中,简单事件处理层接收阅读器网络产生的原始阅读事件,通过不重复约束规则清洗重读产生的冗余事件,聚合成精简的逻辑阅读事件;复杂事件处理层建立应用完整性约束规则,分析逻辑阅读事件,侦测并纠正多读、漏读现象,并以物理对象路径约束为例,描述了多读、漏读判定方法。应用案例验证了该模型的可用性。  相似文献   

5.
闫崇京 《中国机械工程》2015,(2):184-187,222
针对广义BOM建模中的时间模糊性和约束多样性问题,提出了BOM时间的多色图描述方法。采用模糊数表达BOM时间,通过图的"着色"实现多种时间约束的表达;建立了BOM时间到时间约束网络的映射规则,给出了BOM时间一致性的判定和求解方法;最后通过实例对BOM时间模型及其求解方法进行了验证。  相似文献   

6.
提出了一种基于数字化的生产模型,使用控制图、故障树分析和专家知识,能够进行制造过程实时监控的诊断,该模型提高了故障诊断系统的可靠性,并提供了可实际操作的可视化建模工具.所开发的在线统计过程控制系统能够根据生产事件的监测,动态响应制造过程变化.该系统运用可视化建模工具,根据专家经验进行故障树建模,通过故障树自动生成专家系统诊断规则库,实现诊断知识的自动获取.将该系统应用于汽车变速箱装配过程的检测与故障诊断,验证了方法的有效性.  相似文献   

7.
为建立涵盖两种重组方式的系统模型,避免现有方法中模型相互转化造成的信息丢失以及动态特性的不完整,在分析了可重组制造系统重组实现方式的基础上,提出了基于统一建模语言与面向对象Petri网的建模与性能分析方法。采用模块化方法对制造资源进行划分,利用统一建模语言建立系统逻辑模型,利用面向对象Pe-tri网建立系统物理模型,分析了各自活动机理,给出了模型关联映射的触发规则。为实现模型的性能分析,对面向对象Petri网引入时间参数,提出基于随机过程理论的性能分析方法。通过实例验证了建模与分析方法的有效性。  相似文献   

8.
多体系统仿真分析平台参数化建模技术研究   总被引:1,自引:0,他引:1  
针对复杂多体系统建模效率低、建模过程修改频繁等问题,研究了多体系统仿真分析平台的参数化建模技术,提出了一种工程约束推理求解和模型元素更新机制相结合的参数化方法.该方法采用点参数、设计变量参数和元素属性参数构建多体系统参数化模型.通过规则约束和表达式约束,描述了元素属性参数间的工程约束关系.针对工程约束的过程无关性,使用有向图作为参数化求解的内部表达,根据参数间的偏序关系获得工程约束求解序列.结合多体系统模型元素关联关系的特点,提出了一种事件驱动的模型参数化更新机制.最后通过轿车参数化建模实例,验证了该方法的有效性和可靠性.  相似文献   

9.
工作流多过程动态时序一致性的实时模型检测   总被引:1,自引:0,他引:1  
现实企业中通常存在多个并行的工作过程,并且它们之间可能存在资源冲突。在运行阶段,动态验证资源约束下多个过程的时序一致性具有重要意义。基于实时模型检测技术,提出一种工作流多过程时序一致性动态验证方法。采用时间自动机(Time automata,TA)对多个并发过程建模,并将所需验证的时序约束转化为对TA模型的性质查询。当运行到检测点,依据已知的时间信息更新TA模型,再进行相关性质查询,从而完成时序约束的验证。该方法实用性较强,能够有效处理现实业务环境中资源约束情况下多个业务过程的动态时序验证问题。具有较好的柔性和扩展性,当时序约束发生变化时,仅需改变相应TA模型。本方法有多种实时模型检测工具或软件的支持。  相似文献   

10.
基于工作流模式的BPMN过程模型验证方法   总被引:1,自引:0,他引:1  
针对业务流程建模符号过程模型语义验证问题,提出了一种新方法.该方法基于正确的业务流程建模符号过程模型是工作流模式的合理组合的理念,通过扩展和改进业务流程建模符号及其执行语义,设计了工作流模式的形式化编码规则;借鉴Petri网化简方法,设计了工作流模式组合化简规则;基于工作流模式编码及组合化简规则,给出了业务流程建模符号过程模型验证方法.应用示例表明了该方法的有效性.  相似文献   

11.
为了克服自适应光学系统中倾斜镜的迟滞响应,提高响应的线性度,改善倾斜镜的控制精度,研究了倾斜镜的迟滞非线性效应。提出了一个基于频率相关的Mutified-Prandtl-Ishlinskii(MPI)模型的补偿方法来在线自适应逆补偿倾斜镜的迟滞非线性。结合反馈PID控制构成了自适应逆前馈复合控制方案,其中自适应逆前馈克服了由于频率等因素引起的迟滞曲线变化,反馈PID则改善了整体的控制性能。建立了倾斜镜二阶系统模型来估计倾斜镜系统的输出,解决了MPI模型参考信号的问题,避免了增加额外前馈传感器,保证了光能量的利用率。实验结果表明,倾斜镜系统15 Hz非线性迟滞率由原来的24.28%降为1.17%,线性度提高了约95%,控制精度较传统PID方法提高了约60%。该方法能够有效补偿倾斜镜的迟滞非线性,提高了自适应光学系统中倾斜镜的校正精度。  相似文献   

12.
This paper proposes a systematic approach for the design of a supervisory controller for discrete event systems (DES) and their ladder logic diagrams (LLD). The method is based on Petri nets, which is used for modeling the systems. It involves, defining the control policy and simplifying it by using Espresso software to form the compiled controller by adding inhibiting and enabling arcs to the original model and then the method is used to drive structured ladder logic code. A design example is presented to clarify the full procedure.  相似文献   

13.
Aiming at the problem of abstract and polytype information modeling in product conceptual design, a method of conceptual modeling based on logical expression and evolvement is presented. Based on the logic expressions of the product conceptual design information, a function/logic/structure mapping model is set up. First, the function semantics is transformed into logical expressions through function/logic mapping. Second, the methods of logical evolvement are utilized to describe the function analysis, function/structure mapping and structure combination. Last, the logical structure scheme is transformed into geometrical sketch through logic/structure mapping. The conceptual design information and modeling process are described uniformly with logical methods in the model, and an effective method for computer aided conceptual design based on the model is implemented.  相似文献   

14.
The conventional computerized numerical controller (CNC) of machine tools has been increasingly replaced by a PC-based open architecture CNC (OAC) that is independent of a CNC vendor. The OAC and machine tools with an OAC have led to a convenient environment in which user-defined applications can be efficiently implemented within a CNC. This paper proposes a method of diagnosing the cause of operational faults. The method is based on the status of a programmable logic controller in machine tools with an OAC. An operational fault is defined as a disability that occurs during the normal operation of machine tools. Operational faults constitute more than 70 percent of all faults and are also unpredictable because most of them occur without any warning. To quickly and correctly diagnose the cause of an operational fault, two diagnostic models are proposed: the switching function and the step switching function. The cause of the fault is logically diagnosed through a fault diagnosis system using diagnostic models. A suitable interface environment between a CNC and developed application modules is constructed to implement the diagnostic functions in the CNC domain. The results of the diagnosis were displayed on a CNC monitor for machine operators and transmitted to a remote site through a Web browser. The proposed diagnostic method and its results were useful to unskilled machine operators and reduced the machine downtime.  相似文献   

15.
为了提高液晶自适应光学系统的波前探测精度,研究了该系统中倾斜镜的校正方法。分析了液晶自适应光学系统中各环节的物理特性,利用拉格朗日方程给出了倾斜镜系统模型的基本结构;采用子空间辨识方法确定了模型参数,同时利用非线性最小二乘算法对子空间模型的频域特性进行了修正。修正后模型幅频特性均方根误差为0.024 5dB,相频特性均方根误差为1.9008°。引入Smith控制策略来解决倾斜镜校正波前整体倾斜过程中的时滞问题;利用子空间辨识出的模型分别进行Smith和PID的仿真和实验验证,得到的结果与仿真计算相吻合,即在相同稳定裕度的情况下,采用Smith补偿PID算法的误差抑制带宽比传统PID算法提高了23.97%。最后,用提出的方法对一组湍流整体倾斜信号进行了校正。结果显示:采用Smith补偿PID算法的控制精度比传统PID算法提高了21.03%,证实提出的方法优化了倾斜镜的校正精度,保证了开环液晶自适应光学系统的波前探测精度。  相似文献   

16.
Real options analysis is being increasingly used for assessing investments under uncertainty; however, traditional real options methods have some characteristics that restrict their use, such as modeling the value of the underlying asset using geometric Brownian motion and assuming a fixed cost in exercising the options. In this paper, another real options method is expounded that mitigates some of the difficulties posed by traditional methods. Another important aspect that we analyzed in this paper is considering the fuzzy aspects of real options theory. In this section, we are trying to use fuzzy logic concepts integrated with system dynamics to assessing real options in investment projects and we examine dynamic versions of fuzzy logic systems. System dynamics (SD) is an effective method for studying dynamic conditions and changes in complex systems. In this paper, a new dynamic model of real-world systems is designed based on the concepts of system dynamic and fuzzy logic approach. The method is explained with an example from aviation. The analysis offers obvious proof that the integrated fuzzy–SD model could help investors to decide how they should choose an investment program, that managers can use the same results to restructure the program to improve the financial feasibility of the project, and that both investors and managers can define minimum needs to ensure program success.  相似文献   

17.
杨培林  刘青  樊娟妮  侯翌 《中国机械工程》2020,31(14):1639-1646
直接利用模型检测工具提供的形式化语言对系统进行形式化建模直观性较差、建模难度大,因此利用概率行为树对机电系统进行形式化建模,并通过概率模型检测对机电系统进行可靠性评价。对机电系统功能执行过程中功能载体的状态及其变迁进行了研究。基于概率行为树的语义和句法,提出了机电系统状态变迁过程的概率行为树建模方法,开发了建模支持工具。利用该建模工具可实现机电系统的概率行为树建模并能将其转换为基于PRISM语言的形式化模型。基于机电系统的潜在故障,用连续随机逻辑对机电系统可靠性评价指标进行形式化规约。基于概率行为树模型和可靠性评价指标的形式化规约,利用模型检测工具PRISM实现了对机电系统的可靠性评价。该方法比直接使用形式化语言建模更直观、易于理解和掌握。  相似文献   

18.
Computer-Integrated Manufacturing (CIM) systems may be classified as real-time systems. Hence, the applicability of methodologies that are developed for specifying, designing, implementing, testing, and evolving real-time software is investigated in this article.The paper highlights the activities of the software development process. Among these activities, a great emphasis is placed on automating the software requirements specification activity, and a set of formal models and languages for specifying these requirements is presented. Moreover, a synopsis of the real-time software methodologies that have been implemented by the academic and industrial communities is presented together with a critique of the strengths and weaknesses of these methodologies.The possible use of the real-time methodologies in developing the control software of efficient and dependable manufacturing systems is explored. In these systems, efficiency is achieved by increasing the level of concurrency of the operations of a plan, and by scheduling the execution of these operations with the intent of maximizing the utilization of the devices of their systems. On the other hand, dependability requires monitoring the operations of these systems. This monitoring activity facilitates the detection of faults that may occur when executing the scheduled operations of a plan, recovering from these faults, and, whenever feasible, resuming the original schedule of the system.The paper concludes that the set of surveyed methodologies may be used to develop the real-time control software of efficient and dependable manufacturing systems. However, an integrated approach to planning, scheduling, and monitoring the operations of these systems will significantly enhance their utility, and no such approach is supported by any of these methodologies.  相似文献   

19.
为提高现代企业仓储物流的设计质量和效率,提出了一种基于资源颜色时序信号的扩展Petri网建模及控制系统设计方法.该方法首先采用资源颜色时序信号的扩展Petri网建立了仓储系统的动态模型,清晰地描述了各种物流活动的顺序、并发,冲突等关系,并结合关联矩阵,阐述了判断死锁和陷阱的方法.该方法建立的模型可根据Petri网运算规则进行保性化简,便于仿真分析和验证,且可直接用于系统可编程逻辑控制器的控制程序设计.最后,以仓储物流控制系统为例,阐述了系统建模及控制设计过程.  相似文献   

20.
A new Petri-net-based design technique, called the inhibitor are method, for the synthesis of compiled supervisors for discrete event systems is used to solve a forbidden state problem in an experimental manufacturing system. The technique used offers the following advantages: 1. The closed-loop (i.e. controlled) behaviours of the systems are non-blocking and do not contradict the forbidden state specifications. 2. The closed-loop behaviours of the systems are maximally permissive within the specifications. The supervisors to be synthesised consist of a controlled automation Petri net (APN) model of the syetem. Automation Petri nets include the following extensions to the ordinary Petri-net framework; sensor readings as firing conditions at transitions and actions assigned to places. Ladder logic diagram (LLD) code is used to implement the superviosors on programmable logic controllers (PLC). It is important to note that the supervisors obtained are correct by construction, therefore there is no need for verification. This paper particularly shows the applicability of previous results [1] to low-level real-time control where the role of the supervisor is to arrange low-level interaction between the control devices, such as motors, actuators, etc. This is done by considering an experimental manufacturing system.  相似文献   

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