基于网络的实时虚拟装配系统的研究

基于网络的虚拟装配为虚拟制造领域提出了一个崭新的思路和方法.提出了虚拟装配过程中约束的实时控制与虚拟装配仿真磁心定位的概念,从产品的装配分析角度出发,实现了网络环境下虚拟装配系统的智能化动态仿真、装配信息实时反馈以及虚拟环境下数据库的快速查询,并研究了仿真动画和交互的关键技术.     

胶印机虚拟结构功能认知系统的研究与开发

目的满足用户对胶印机结构功能的认知,为产品操作手册提供虚拟化结构展示平台,方便用户快速了解胶印机相关信息。方法选用PZ1740E单张纸胶印机为实机模型建立三维模型,将.fbx格式的胶印机模型导入unity中进行场景环境的搭建、交互功能的开发、脚本代码的编写,实现系统软件的制作开发与优化。结果操作手册实现了图文内容的多维信息展示,用户可利用该系统控制自动装配过程、显示隐藏部件结构及其信息,全方位地观察了解印刷机内外结构。针对结构相关信息内容,用户点击具体部件结构后可以显示其名称、作用、此部位有可能出现的故障及其引起的印刷故障问题;针对故障问题,用户可以调节控制条观察背面蹭脏痕迹的变化。结论利用三维建模技术实现了胶印机的虚拟展示功能,虚拟现实技术实现了人机交互功能;胶印机的结构展示与功能信息介绍,补充了图文内容的立体化展示,为后续的胶印机虚拟仿真系统以及故障仿真系统提供了前期的印刷理论知识基础与结构展示学习基础。     

Computer simulation for quality and reliability engineering

Computer simulation has been used widely in many industries for many applications. A simulation model mimics a real world system, enabling an investigation of its operation. More recently simulation models have incorporated a visual display and interactive features to aid understanding and enhance the investigation. Computer simulation has many potential uses in quality and reliability engineering, for instance, modelling equipment failures, quality control strategies, maintenance requirements and operational logistics. A case study shows how simulation has been used to study the throughput, flexibility and robustness of a manufacturing plant design. Alternative simulation software packages are briefly discussed.     

The propagation of faults in process plants: 10, fault tree synthesis-2

An interactive, computer-based facility has been developed for the investigation of fault propagation in process plants, including fault tree synthesis, which is embodied in the FAULTFINDER code. The general development and status of the work and the modelling are described in an overview paper and work on dividers and headers, on trip systems and on fault tree synthesis in further companion papers. This paper describes the treatment of control systems in the methodology. Control loops are integral to the whole pattern of operation of the plant. They tend to be a central feature of, and to dictate the form of, manually constructed fault trees. It is desirable that this feature be reflected in automatically synthesised trees also. Further, it is found in practice that it is necessary to treat control loops as a special feature in order to obtain correct trees. Characteristic features of the methodology developed include systematic decomposition of the control system; special features of the modelling of the control loop units; use of control loop templates; and additional rules for handling hierarchial and other complex control systems.     

An interactive tool for designing manufacturing cells for an assembly job-shop

Cellular manufacturing is often implemented to reduce work in progress, materials handling, set-ups and storage space, as well as to improve quality and worker satisfaction. Wemmerlov and Johnson (1997) have pointed out that cellular configurations do not automatically deliver these advantages. An interactive tool is presented to design manufacturing cells for an assembly shop. The method is based on an analysis of operation sequences and durations and it allows the design of hybrid layouts. We show that a cellular configuration is not always desirable and discuss the conditions where this is so.     

Improving the Reliability in the Next Generation of US Army Platforms through Physics of Failure Analysis

Published studies and audits have documented that a significant number of U.S. Army systems are failing to demonstrate established reliability requirements. In order to address this issue, the Army developed a new reliability policy in December 2007 which encourages use of cost-effective reliability best practices. The intent of this policy is to improve reliability of Army systems and material, which in turn will have a significant positive impact on mission effectiveness, logistics effectiveness and life-cycle costs. Under this policy, the Army strongly encourages the use of Physics of Failure (PoF) analysis on mechanical and electronics systems. At the US Army Materiel Systems Analysis Activity, PoF analyses are conducted to support contractors, program managers and engineers on systems in all stages of acquisition from design, to test and evaluation (T&E) and fielded systems. This article discusses using the PoF approach to improve reliability of military products. PoF is a science-based approach to reliability that uses modeling and simulation to eliminate failures early in the design process by addressing root-cause failure mechanisms in a computer-aided engineering environment. The PoF approach involves modeling the root causes of failure such as fatigue, fracture, wear, and corrosion. Computer-aided design tools have been developed to address various loads, stresses, failure mechanisms, and failure sites. This paper focuses on understanding the cause and effect of physical processes and mechanisms that cause degradation and failure of materials and components. A reliability assessment case study of circuit cards consisting of dense circuitry is discussed. System level dynamics models, component finite element models and fatigue-life models were used to reveal the underlying physics of the hardware in its mission environment. Outputs of these analyses included forces acting on the system, displacements of components, accelerations, stress levels, weak points in the design and probable component life. This information may be used during the design process to make design changes early in the acquisition process when changes are easier to make and are much more cost effective. Design decisions and corrective actions made early in the acquisition phase leads to improved efficiency and effectiveness of the T&E process. The intent is to make fixes prior to T&E which will reduce test time and cost, allow more information to be obtained from test and improve test focus. PoF analyses may be conducted for failures occurring during test to better understand the underlying physics of the problem and identify the root cause of failures which may lead to better fixes for problems discovered, reduced test-fix-test iterations and reduced decision risk. The same analyses and benefits mentioned above may be applied to systems which are exhibiting failures in the field.     

Implementation of an object-oriented tool for the simulation of manufacturing systems and its application to study the effects of flexibility

Although there is a reasonable number of currently available modelling tools for the analysis and evaluation of flexible manufacturing systems, these models, in general, neglect flexibility. They do not consider that in a flexible manufacturing system there is the possibility of different operation sequences. As a consequence, while flexibility in manufacturing is much 'in vogue', the development of models that are able to improve the understanding and consequences of having flexibility is still incipient in the literature. This paper presents work to develop a tool to support the analysis of flexible automation. The tool described is an objectoriented discrete-event simulator, called OOSimFlex, capable of modelling different alternative systems design and analysing a manufacturing system using multiple performance measures under different manufacturing flexibility levels. The paper describes the major theoretical concepts employed for the development of a highly flexible and interactive simulation model environment.     

叉车振动仿真及发动机总成悬置优化

利用ADAMS软件建立某型叉车整车在怠速工况下的振动仿真模型,并进行实验验证,实验表明通过采用对连接螺栓的柔性化方法可以有效提高叉车仿真模型的准确性。在此基础上利用ADAMS试验设计方法,对整车动力总成悬置刚度阻尼匹配进行优化,结果表明通过刚度阻尼的合理匹配能在一定程度上改善整车车架上的振动情况。     

Modelling of material handling systems for facility design in manufacturing environments with job-specific routing

Traditionally, flow times distance is used as a surrogate for cost in facility design. However, this performance measure does not fully capture the impact of facility design decisions on operational performance measures such as cycle time and work-in-progress in the system, which are often more meaningful for managers, especially in a manufacturing environment. To better measure operational performance, modelling of material handling systems using a queueing network must be integrated in the facility design process. A number of approaches are discussed in the facility design literature for modelling material flow using queueing networks. In these approaches, Poisson arrival or Markovian job routing assumptions have been used. However, for many manufacturing environments, these assumptions lead to an inaccurate estimation of the material handling system's performance and thus lead to poor facility designs. Incorporating more general queueing results for non-Markovian systems is difficult, however, because the facility design process must investigate a large number of potential solutions and thus the results from the queueing models for the material handling system must be quickly obtained. In this paper, the need for more general queueing models of material handling systems in facility design is confirmed. Then, an approach based on multi-class queueing models is adapted to capture the change in variability of the system performance caused by both different arrangements of workstations in the facility and different arrival processes to the workstations due to the job routing in a computationally efficient manner. The proposed modelling approach is shown to provide more accurate results than previous methods used in facility design based on numerical comparisons with results from discrete-event simulation.     

3D mathematical modelling for robotic pick up of textile composites

An area of interest in the automated manufacture of composite components is the prediction in real-time of the deformed shape of a textile reinforcement in 3D space during robotic handling operations. The deformed shape can be used to guide robotic end-effectors to ensure accurate fabric placement and avoid collisions. In this paper, a nonlinear mathematical model using large deflection plate and shell theories is presented. The model is able to predict the 3D deformed shape of limp sheet materials being picked-up by multi robotic grippers for three boundary conditions. The main factors affecting the deformation behaviour of the sheet during the operation are identified and analysed, and the contributions of different energies during deformation are presented in detail. Good agreement is obtained when comparing the solutions of the model with FE simulation results. This study demonstrates the possibility of developing a modelling capability for material on-line response in automatic flexible material handling.     

Optimizing the configuration of a keyboard assembly cell

This paper describes how the configuration of a three station serial keyboard assembly cell can be optimized using a combination of discrete event simulation modelling and experimental design techniques. The investigation is based on a discrete event simulation model written in ARENATM. Optimum buffer sizes and number of pallets are initially determined by factorial design to identify the most significant factors affecting the throughput of the cell. Response surface methodology is then used to determine the optimal settings. The paper illustrates the methodology of using a combination of discrete event simulation modelling and experimental design techniques to design the optimal configuration of serial assembly cells and similar configurations in the manufacturing environment.     

Quantifying Gains Using the Capabilities‐Based Test and Evaluation Method

Today's military operating environments are more operationally diverse and technically challenging. Fielding relevant weapons systems to meet the demands of this environment is increasingly difficult, prompting policy shifts that mandate a focus on systems capable of combating a wide threat range. The capabilities‐based test and evaluation construct is the Department of the Navy's effort to concentrate on integrated system design with the objective of satisfying a particular operational response (capability) under a robust range of operating conditions. One aspect of capabilities‐based test and evaluation is the increased employment of advanced mathematical and statistical techniques in the test and evaluation (T&E) process. This case study illustrates advantages of incorporating these invaluable techniques, like design of experiments and modeling and simulation, within the T&E process. We found through statistical analysis that the application of design of experiment concepts to the System Under Test throughout three primary phases of T&E quantifiably improved the accomplishment of the selected response variable of interest. Copyright © 2012 John Wiley & Sons, Ltd.     

Least squares methods for the mechanics of nonhomogeneous granular assemblies

Summary Using least squares methods consistent averages for stress and strain of a nonhomogeneous granular assembly are derived. The expression for the average of the strain increment serves as a constraint in a functional approach to solving the displacements and spins of particles of a granular assembly in a statistical manner. The method shows directly what microscopic angular distributions are needed to describe the internal state of an assembly. They are the distribution of contacts, the distribution of both the averages and the variations in the interactive properties of the grains. The method is then applied to an assembly with normal-interacting circular grains in two dimensions. The incremental stiffness and the average displacement of the contacts as a function of the angle are obtained for the case of non-rotating strains. The results show clearly that for this case the sliding mode of motion is the most relevant one for deviatoric loading.     

Flexible modelling of correlated operation times with application in product-reuse facilities

For each job (product instance) to be serviced in a product-reuse production system, multiple operations are often scheduled. Typically, there is high variability in the same operation times required by different jobs; and for each individual job, there is often significant probabilistic dependence (correlation) between many of the job's required operation times. Well-conditioned jobs require fewer operations with shorter durations. Poorly conditioned jobs require more operations with longer durations. Accurate and rapid methods for representing the uncertainty of operation necessity and duration are required to use simulation effectively as a schedule evaluation tool. This paper develops such methods using an alternative to the conventional multivariate extension of the Johnson system of univariate probability distributions. The alternative methods match the first three, and often four, marginal moments of the random vector of operation times for a given job as well as all pairwise correlations between those operation times. A logistic regression model is used to estimate the distribution of the binary random variable indicating the necessity of an operation conditioned on the indicators for the job's preceding operations. The proposed overall mixed-distribution modelling technique is computationally efficient, useful in product-reuse system practice, and easily integrated into existing simulation software platforms.     

Point-based approach to enhance the quality of geometric data for CAE applications

Commercial CAD surface modelling software is based almost exclusively on Bézier, B-spline and NURBS representations. These methods offer simple interactive shape modification and computationally efficient interrogations, but have some serious practical limitations. The root cause of all these problems is that the parametric polynomial methods are not geometry-based, and the trouble is compounded by the master geometry philosophy which treats the CAD model as if it were absolutely correct. An alternative purely geometric approach to surface modelling has been established, where the surface shape is characterised by a grid of points lying on the surface, but it is recognised that this approach would require major changes in existing CAE systems. This application paper explains the rationale to develop algorithms, which would plug into existing CAE software systems, so that the user could benefit from the point-based construction without disturbing the established mode of operation. The new point-based approach has achieved significant success in ensuring that form tools produce panels within a specified tolerance.     

Research of Dynamic Material Handling in an Automobile General Assembly Line Based on Real-time Information

The status of material delivery of an automobile general assembly line is analyzed,and the technique to achieve the real-time tracking of assembly statas information is proposed based on RFID( Radio Frequency Identification) . Thus the consumption of line-side buffer is obtained dynamically,then the type and quantity of needed material are fed back to the subsystem of material handling; the algorithm for determining the best time departure time of delivery driver based on minimizing of total time penalty function is proposed. This approach makes the ma- terial amount of a single delivery trip maximized and improves the efficiency of delivery drivers significantly in the case of does not affect the assembly line normal throughput. Additionally,although this dynamic material handling method is developed for the automobile assembly plant,it should be pointed out that this method is also applicable to other mixed model assembly plants such as electronics,semiconductor and aerospace industry.     

基于行为体验的交互式酒包装设计研究

目的 将行为体验理论应用于酒包装设计实践,以降低用户对交互式包装的理解和学习成本,探索理论用于实际的有效方法,寻求生产装配与设计之间的潜在联系。方法 从行为体验中行动的几个阶段框架出发,提炼出用户行为阶段中的无意识阶段、交互的执行和评估鸿沟。将理论与设计实践结合,着重对无意识阶段、执行鸿沟、评估鸿沟进行设计,将理论融入产品的设计全流程。结果 得到了一款基本满足用户要求的交互式酒包装,用户行为的无意识阶段能够减少用户的操作步骤,降低学习使用的成本。结论 行为体验理论的基本框架可以有效提炼出用户的无意识阶段、执行鸿沟、评估鸿沟,对产品交互设计能够起到较好的设计指导,探索出交互式包装设计的新方法,不仅为同行在包装设计上提供了理论研究参考,也对行为体验的理论应用研究有一定扩展。     

Visual interactive simulation and artificial intelligence in design of flexible manufacturing systems

The design of flexible manufacturing systems is a complex decision-making process that typically involves the evaluation of a number of different design alternatives. The evaluation is often performed using modelling and simulation techniques. The role of visual interactive modelling and simulation in design of flexible manufacturing systems is discussed. The application of artificial intelligence techniques to implement a set of knowledge sources, used for accomplishment of various design activities, is described. An object-orientated implementation is used to illustrate the underlying concepts.     

基于LMS自适应滤波的汽车主动悬架研究

针对简化的车辆模型，确定汽车簧上质量的加速度、车轮与地面问的动载荷以及车身的动挠度为悬架系统性能评价指标。将LMS自适应滤波算法与广义自适应控制相对比，仿真计算表明，LMS自适应控制策略不仅计算简单，而且性能指标明显优于广义自适应控制方法。     

含有柔性电缆的复杂系统装配仿真

将装配单元划分为“刚性组件”和“柔性电缆”,从装配对象建模、装配工艺规划和装配过程模拟三个方面对复杂系统的装配仿真方法进行系统的研究。首先,根据刚性组件和柔性电缆的不同特点,给出相应的建模方法,即针对刚性组件的CAD三维建模方法和针对柔性电缆的虚拟布线方法;然后,将装配过程视为拆卸过程的逆过程,提出含有柔性电缆的复杂系统的装配工艺规划方法,其中考虑了电缆形变过程及相应的模拟方法;最后,以装配工艺为基础对仿真对象进行装配仿真。实例表明,所提出的方法可以用于含有柔性电缆的复杂系统装配仿真。