供应链环境下的性能评价系统研究

在竞争全球化的趋势下，供应链管理越来越受到企业重视，供应链性能评价系统(supply Chain Performance Mea-surement System,SCPMS)是供应链管理的关键组成部分，然而企业却不愿意或没有能力建立有效的性能评价系统。总结了供应链性能评价的定义、发展过程及难点，在此基础上提供了一套供应链性能评价的方法，为企业快速建立集成供应链性能评价系统提供借鉴。     

液体循环热回收系统研究进展及应用

液体循环热回收系统是空调排风热回收系统的一种形式，可以从排风中回收能量从而减小新风能耗，广泛应用于高档酒店、医院建筑和洁净生产车间。本文介绍了液体循环热回收系统的工作原理，对系统性能评价指标和计算方法进行讨论，针对该系统在设计和运行过程中存在的问题进行了探讨，并提出解决方法，还分析了该系统的应用前景。提出可以从静态参数优化与动态计算结合、空调工况分区焓湿图与系统能效比结合、大数据分析等方面研究该系统的高效运行方法和精准控制策略。     

城市轨道交通受电弓参数敏度分析及优化设计

为研究城市轨道交通受电弓单参数优化和双参数优化对弓网系统耦合性能的影响,首先建立受电弓-刚性接触网系统动力学模型,根据线路实测数据验证模型的准确性,然后采用接触力随机统计特征作为参数优化的目标函数,对CED125D型受电弓的9 个等效参数进行敏度分析,得到弓头等效质量的敏度评级最高,上框架等效质量及等效刚度次之,下框架等效刚度最低,并给出单参数优化建议。最后分析受电弓弓头3 个等效参数联合变化时的接触力统计特征,结果表明双参数优化能实现比单参数优化更好的弓网耦合性能,该研究可为城市轨道交通弓网系统设计、选型和评价提供参考。     

分布式TMD对双密频结构的减振研究

针对密集频率结构的减振问题,以典型的2自由度对称结构为例,研究基于H2性能的梯度优化法对密集模态振动减振的分布式TMD(tuned mass dampers)的参数优化和减振效果。建立适合闭环静力反馈控制的组合系统模型,将基于H2性能的梯度优化法扩展至分布式TMD的参数优化;定义针对密集模态振动的控制输出和无量纲评价指标,分析了控制输出的模态控制权重对优化参数和评价指标的影响,指出能使评价指标峰值相等的模态控制最优权重,进一步给出优化参数和评价指标随模态密集度的变化规律;与经典方法对TMD的设计相对比,分析和验证了基于H2性能优化的分布式TMD的良好减振效果,并确认在TMD个数增多时基于H2性能的梯度优化法将具有更佳的优化效果。     

基于Petri网的包装物流系统建模仿真与优化

采用离散事件动态系统理论和Petri网建模技术,研究包装物流系统建模、仿真与优化,描述和分析系统要素及逻辑序列.以纸箱包装物流系统为例进行建模、仿真,优化分析,获得了该系统的优化模型.结果表明,这种研究方法可行有效.     

协议分布式测试系统的性能模型

协议测试领域专家们已经达成共识：新一代的协议测试系统应该是分布式架构的。本文用广义随机Petri网(GSPN)对目前提出的几种协议分布式测试框架构造了性能模型，进行了性能比较和分析。为了解决状态空间爆炸的问题，提出了一种同步变迁实施速率等价法(STER)，这种方法能够对具有同步变迁的随机Petri网模型分解求解。     

多层隔振系统的参数优化研究

多层隔振系统的结构参数选择对于提高隔振效率具有重要意义，本文从频率优化的角度，以隔振器刚度参数为例探讨多层隔振系统的参数选择方案，提出可容变差多面体方法和摄动方法，在文末，给出应用实例加以说明。     

热泵型溶液除湿新风系统性能分析与优化

本文建立了热泵型溶液除湿(HPLD)新风系统数学模型,研究了新风温度、湿度对系统运行性能的影响。结果表明:新风温度升高1℃,系统COP平均下降率为0.9%;新风含湿量增加1 g/(kg干空气),系统COP平均下降率为3.6%,新风湿度增加导致HPLD系统COP大幅下降,系统新风湿度变化的适应性差。为扩大HPLD系统适应范围,提出了冷却除湿与HPLD组合式除湿系统,以组合式除湿系统COP为评价指标,得到组合系统级间新风参数最优状态:温度为21℃,含湿量为14.1 g/(kg干空气)。夏季典型工况下,组合式除湿系统COP为5.40,比单一HPLD系统COP提高87.5%。最后,根据HPLD系统设计参数制作了实验样机,并对模拟结果进行了验证。     

路面结构性能评价与材料参数的动态反算

近二十年来，路面的无损检测与评价技术在国内外得到了迅速的发展，由无损检测数值反演路面结构层模量也逐步引起人们的关注。本文根据FWD无损检测结果，采用系统识别方法对路面结构层模量进行动态反演分析，以达到对路面结构性能进行动态评价的目的。     

电动燃油泵性能检测系统开发研究

针对当前电动燃油泵性能检测方法的弊端,开发了一种基于单片机的新型燃油泵性能检测系统,实现了燃油泵参数的自动采样、存储、动态显示功能,并能够依据检测结果自动评价燃油泵的性能。实际测试结果表明。该系统可有效提高电动燃油泵的检测精度和检测效率。     

Modelling and simulation of automated manufacturing systems for evaluation of complex schedules

Automated manufacturing systems have been studied widely in terms of scheduling. As technology evolves, the behaviour of tools in automated manufacturing systems has become complicated. Therefore, mathematical approaches to the analysis of complex schedules no longer reflect reality. In this paper, we propose a systematic way of conducting simulation experiments to evaluate the complex operating schedules of automated manufacturing systems. A simulation model is based on a timed Petri net to take advantage of its mathematical strength. Since a Petri net cannot itself have token firing rules, we introduce additional states called operational states. Operational states are not directly related to a Petri net, and are only used for decision making. In addition, a decision function that is responsible for the conflict resolution of a Petri net model and an operational state transition function are introduced. The parallel simulation concept is also suggested by dividing a Petri net into several independent decision sub-nets. A multi-cluster tool system for semiconductor manufacturing is analysed as an application.     

Petri-net based applications for supply chain management: an overview

Supply networks are discrete event dynamic systems consisting of suppliers, manufacturers, distributors, and customers. It is a difficult and challenging task to model such a complex system. Recently, characterised as being capable of model parallelism and synchronisation, Petri nets (PNs) have attracted great attention for modelling and studying a supply network. Since each type of Petri net has its unique properties to model specific applications, this paper reviews and classifies Petri net applications for supply chain management (SCM). According to the decision problems facing SCM, we have the Petri net applications classified into three areas: competitive strategy, firm focused tactics, and operational efficiency. Categorising the Petri net applications will provide a guideline to industry practitioners and research academics to choose the appropriate Petri net for the problem. In addition, the paper attempts to offer future directions in applying the Petri net to SCM including: (1) modelling with uncertainty elements; (2) addressing the scalability issue of Petri nets; (3) integrating Petri nets with other tools; and (4) extending Petri nets to emerging applications.     

System Failure Analysis Through Counters of Petri Net Models

Petri nets are a powerful technique widely used in the modeling and analysis of complex manufacturing systems and processes. Due to their capability in modeling the dynamics of the systems, Petri nets have been combined with fault tree analysis techniques to determine the average rate of occurrence of system failures. Current methods in combining Petri nets with fault trees for system failure analysis compute the average rate of occurrence of system failures by tracking the markings of the Petri net models. The limitations of these methods are that tracking the markings of a Petri net represented by a reachability tree can be very complicated as the size of the system grows. Therefore, these methods offer less flexibility in analyzing sequential failures in the system. To overcome the limitations of the current methods in applying Petri nets for system failure assessment, this paper expands and extends the concept of counters used in Petri net simulation to perform the failure and reliability analysis of complex systems. The presented method allows the system failures to be modeled using general Petri nets with inhibitor arcs and loops, which employs fewer variables than existing marking‐based methods and substantially accelerates the computations. It can be applied to real system failure analysis where basic events can have different failure rates. Copyright © 2003 John Wiley & Sons, Ltd.     

Decomposition in automatic generation of Petri nets for manufacturing system control and scheduling

Despite the efforts in developing Petri net models for manufacturing control and scheduling, the generation of Petri net models cannot be automated for agile manufacturing control and scheduling without difficulties. The problems lie in the complexity of Petri net models. First of all, it is difficult to visualize the basic manufacturing process flow in a complex Petri net model even for a Petri net modelling expert. The second problem is related to the complexity of using Petri net models for manufacturing system scheduling. In this paper, a decomposition methodology in automatic generation of Petri nets for manufacturing system control and scheduling is developed. The decomposition methodology includes representing a manufacturing process with the Integrated Definition 3 (IDEF3) methodology, decomposing the manufacturing process based on the similarity of resources, transforming the IDEF3 model into a Petri net control model, and aggregating sub Petri net models. Specifically, a sequential cluster identification algorithm is developed to decompose a manufacturing system represented as an IDEF3 model. The methodology is illustrated with a flexible disassembly cell example. The computational experience shows that the methodology developed in this paper reduces the computational time complexity of the scheduling problem without significantly affecting the solution quality obtained by a simulated annealing scheduling algorithm. The advantages of the methodology developed in this paper include the combined benefits of simplicity of the IDEF3 representation of manufacturing processes and analytical and control properties of Petri net models. The IDEF3 representation of a manufacturing process enhances the manmachine interface.     

Petri net based scheduling

Timed Petri nets can be used to model and analyse scheduling problems. To support the modelling of scheduling problems, we provide a method to map tasks, resources and constraints onto a timed Petri net. By mapping scheduling problems onto Petri nets, we are able to use standard Petri net theory. In this paper we will show that we can use Petri net based tools and techniques to find conflicting and redundant precedences, upper- and lower-bounds for the makespan, etc. This is illustrated by a Petri net based analysis of the notorious 10×10 problem due to Fisher & Thompson (1963)     

A Petri-net-based state-transition model for an optimal operator cyclic walking pattern development in GT cells

An approach for developing the optimal operator scheduling solution for a group technology (GT) production problem is studied. A state-transition model is developed to analyse and gain insight into the operator-machine interaction of the problem. Operator cyclic walking patterns are then denned. A Petri net model has succeeded in determining the optimal cyclic walking pattern. The computational efforts needed for the Petri net model are compared with those for an integer programming model. The results show large savings in computational effort by using the Petri net model. In addition, the extendability of the Petri net model for various system aspects is addressed     

Modelling and planning of the disassembly processes using an enhanced expert Petri net

A sound disassembly Petri net model for the effective planning of disassembly processes and tasks is outlined. Owing to the unmanageable complexity associated with modelling of the disassembly processes and tasks, it becomes essential to have a more powerful Petri net model developed by incorporating the concepts of expert system, knowledge representation techniques, etc. Disassembly task planning at high and low levels can easily be represented by proposed high- and low-level expert Petri net. An algorithmic approach is also suggested for evaluating the end-of-life values of a product. These values are used to determine an optimal disassembly sequence and it is incorporated in the expert disassembly Petri net. A proposed expert enhanced high-level coloured disassembly Petri net is empowered to express such details vividly. The application of the proposed expert enhanced high-level coloured disassembly Petri net model is demonstrated through the sample disassembly of a flashlight.     

Assembly/disassembly task planning and simulation using expert Petri nets

Automatic assembly/disassembly planning is recognized as an important tool for reducing the manufacturing costs in concurrent product and process development. This paper developed a knowledge-based expert Petri net model by incorporating expert system techniques in artificial intelligence into ordinary Petri nets for an analytical framework of understanding, representing and reasoning the assembly/disassembly tasks. Substantial extensions have been made to ordinary Petri nets by adding control places, time constraints, and place and transition knowledge annotations. The proposed expert Petri net model can be considered as the hybrid of expert systems and ordinary Petri nets. Through these extensions, the capacities of modelling and representation of ordinary Petri net models are largely enhanced, and thus the expert Petri net models are more powerful than ordinary Petri nets. Such intelligent Petri net models can combine the abilities of modelling, planning, and performance evaluation for assembly/disassembly tasks in an integrated and intuitive way, and can therefore be applied to either linear/non-linear, static/dynamic, or on-line/off-line assembly/disassembly tasks at both high and low levels. The developed assembly/disassembly planning system can generate the best strategies and plans for assembly/disassembly. The research findings are exemplified with a real assembly to show the effectiveness of the method.