毕业设计(论文)英文翻译

学生姓名： 张志明 学 号： 2513060140 所在学院： 南京工业大学 专 业： 机械工程及自动化 设计(论文)题目： NJ6597SFF5车架设计及有限元分析 指导教师： 王 东 方

20xx年4月1日

车架

整个车辆的基础被称之为车架，车架的作用是增加车身的强度和刚度，以承受弯曲和扭曲载荷。在车辆与地面碰撞的情况下, 车架是受压迫且吸收大部分能量冲击的。它必需托住汽车发动机, 汽车车身，汽车轮子, 和汽车其他元件。车架是由槽钢或U形截面槽钢组成, 利用焊接或用铆钉固定在一起。交叉支柱使他们坚固并足以能够抵抗震动,冲击, 扭转和它们在运行中所碰到的振动。

车架有两个冲压成型的钢制直梁, 五个横梁, 前轮轴, 后轮轴和四个车轮组成。两根钢制直梁的前部比后部靠的更近些。这样做的目的是考虑到前面的那个轮子更好的引导驾驶。后轮轴的功能不只是承载负荷而且也是传送扭转力到后面轮子的。后车桥穿过一个差速器传递一个相等量扭矩给两者车桥。当必要时，差速器是让每个车轮以它自己的速度旋转的一个重要的总成。例如：轿车在转弯行驶时，外侧车轮要比内侧车轮转的快，内侧车轮起到枢轴的作用。

为了要吸收与大地表面的陡震，前车桥和后车桥被板片弹簧连接到车架。现在，前车桥正在被独立的前悬挂系统组件所取代。发动机、车轮，电力系统、制动器和转向系统是装在车架上，然后总成称作为底盘。底盘作为支架，所有的部件都牢牢的固定在上面。在大部份的情形下，发动机被三或四个车架上的位置所托住。支座上的排列包括被放置在发动机支承凸缘和车架托架之间的橡皮衬垫或垫圈。橡皮衬垫或垫圈能够避免金属与金属间的碰撞。他们以此方式吸收发动机的振动和噪音。可阻止发动机的振动和噪音直接传到车架上，进而传给车身和乘客。在这些项目被装在车架上之后，在车身操作完成期间应紧密的装配在一起。

汽车车体总成性质上模拟制度的构架

摘录：车体总成程序设计 （BAPD）制度现在在上海交通大学的汽车车体制造技术中心实验室发展之下。要确保总成议题已经适当地在概念上的设计阶段中

被考虑，不同的方法、程序和工具应该要开放式的概念。这报告提供 BAPD 系统的系统建筑学的简短思想方式，而且报告将会呈现一个构架携带性质上的模拟 proce－dure 而且引导阶层的性质上的模拟已有限制的参数和模糊知识分析并且预测总成变动流量；系统引导总成特征的车身参数的性质上获得数据，而且根据总成程序的定性分析法获得主要因素产生相关变动。一个分析案例被讨论说明定性分析的功能。

1.介绍：

发展一个新车辆模型或现代车辆变型设计，设计者将会需要加发展程序的新技术、新材料和设计方法。随着人工智能技术的迅速发展，它提供一个良好的机会给设计者和制造业者不断地改良产品品质，实行并发设计并且减少销售时间。车辆车体在竞争成本面对现在逐渐增加环境竞争下一定要建造一个完整的空间。自动化制造者应该生产在指定的公差里面的设计组件│产品，所以设计者将细致谨慎地选择适当的装配运作和他们的应用造形一个可行的装配过程顺序。程序逐渐地改变设计的组件│产品的总成误差，主要尺寸需求和最后一个成形工艺。概念上的设计将会大大的影响产品成本的基础结构。在自动车体概念上的设计中，设计者需要决定数以百计的零件│组件之间的复杂的连接和结构。现在，汽车制造商通常由设计者决定联合的结构和长时间测试总成经验的装配顺序。针对设计者的知识和判断能力的限制，对所有的设计观念作出合理、正确选择和决定尤为困难，问题的问题根源缺少概念上的设计尺寸和设计工具。不同的方法和程序应该被发展来确保总成议题已经适当地在概念上的设计阶段中被考虑。整个的总成程序逐渐地改变装配的类型和总成阶段研发最能实行的装配顺序和准许总成合量主要尺寸需求之内的误差和会最后一个成形或被设计的组件的其他功能的需求。在每个装配运作中，这个装配或制造公差将保证按部就班的装配组件，控制设计公差符合要求。每个设计公差被一些装配制造强制加诸于装配运作的公差极限的和│或者保证一直生产组件和副装配。Prisco 和 Giorleo ［1] 审视了表现的模型的现在状态，操纵和分析了尺寸偏差数据主要通过计算机的数据－现在商用的辅助公差系统。在工程学中， VisVSA 商业的软件熟悉快速的变动分析模拟和促进以蒙地卡罗模拟为基础的零件和总成的空间变化的统计分析的图解式

的模拟。Shen ［2] 就目前简短的评论商业的计算机辅助的公差分析系统 VisVSA。Schlatter ［3] 利用 VisVSA 在磁盘驱动器中进行尺寸管理和分析。3DCS 也是一个非常成功的数量变动计算商业软件。然后，公差分析在VisVSA 和 3DCS 被运行，包括一总成顺序和一组公差设定的固定的总成和现有的变动积累。此外，这些工具不能够主动地选择能实行、最佳的总成顺序，变通地变更连接接合器的类型或者主动地调整公差极限实现最佳总成变动合量积累。因此，准备好的设计制度无法具有如此的变动分析方法和工具处理大概念上设计不确定的设计方案和这一个大范围探测。从远景来看，一个模拟模型的建立联合的结构整合，部分结构类型，和装配顺序统在初步设计阶段概念上是非常必要的。通常，一部车辆有大约 4000个组件和超过在他们之中的 100个主要零件。由于这非决定论概念上设计和特性完全了解而且在概念上总成期间做模型变动和机构设计期间，当部分电脑辅助设计模型和总成程序是以设计好或者未知，传统的数字计算不能够被传达尺寸变动的数量模拟。传统的设计技术如 VisVSA 和 3DCS 不完全支持初步设计阶段。因此，新技术，像是专家系统和性质上的模拟，被介绍帮助引导变动模拟配合装配观念。性质上的模拟技术已经进入创作家的调查计划之内。当在概念上的设计期间的不确定性之下对多目的车体总成强延长设计，在这报告中的目标是调查这一个模拟构架的适用性。计划使用类似运算法则抬起箱底座的最能实行的案例之一同样地设计起点和当做参考设计，然后介绍整合的随机程序最佳化方法，启发式地在参考设计期间中生产总成替代选择。质量上模拟以概念上的设计期间的性质形状上各种不同总成变数的处理提供适应性。概要地，报告以公差误差的极限设定在自动车体总成程序设计中，为性质上的推论设计一个新奇的模型，和在不同的总成顺序下的联合的模糊结构。报告依下列各项被排列。第 1 节是简短的介绍。报告评论装配公差设计和报告。第2节是性质上的理论发展的状态。车体总成设计制度的基本系统车架在第 3 节呈现。性质上的模拟概念构架在第 4 节被介绍, 而且在最后一部分中，作者得到一个结论并且介绍较进一步的研究和工作。2相关的研究和问题陈述在辅助的计算机中存在过度、成功的发展和研究，在不变的机械总成设计和各种不同的公差设计方法公差相对一点已经把概念上的设计期间的车辆个放进车体的公差设计里。这报告的目的将描述车辆广泛的架构车体，概念上的装配公差已经在上海交通大学的汽车车

体制造技术中心的实验室在发展设计的。报告将会把重心集中在车辆的系统建筑学装配程序概念上的设计，附带一些简单的分析讨论。

2．车体装配和公差设计

一个典型的汽车车体是由白色的不同类型的复杂的连接方式下超过400张仪表板组成的。自动化制造者希望实现新观念的和探测达成副装配│零件的联合结构方法的最佳结合的连续品质进步，总成顺序和公差配置。

2.1装配设计和公差设计

为装配 （DFA） [4,5] 方法的设计在早期产品中被考虑，装配议题设计可能研究在装配运作期间感应的问题。在过去数十年内，重要的工作［6-10] 已经发展到对装配顺序计划的解决办法。Shi 和他的同事［11-13] 首先介绍空间模型描述产品变动横跨车站，他们发展仿制公差的程序排气管－向上而且利用空间模型研究多变化车站机制程序而且研究造形的一个程序诊断方法控制尺寸品质。蔡司［14] 做了很多和公差设计中的深入研究而且发展仿制分析机械的装配的变化的矢量，以装配模型为基础的一个方法。这些模型建构有共同工程元件：矢量链条、运动学的接合器，总成材料、空间、几何学的特征公差和装配公差极限。方法与工程一同设计实践而且很好地为商业的电脑辅助设计系统整合。Gao ［15] 比较了直接的线性化方法 （DLM）、和蒙地卡罗模拟。线性化使装配限制和矩阵代数的 DLM 预测装配的变化或者运动学的变数，从而预测不良品。一个被修正的蒙地卡罗模拟为闭环装配使用了一个反复的技术，比较的结果表示 DLM 是正确的，如果公差与组件的公称尺寸相较相对小，装配功能不是高非线性的。显示的试样尺寸对蒙地卡罗模拟的精确度有很大的影响力。从装配的不同观点，匈牙利［16] 为合并非理想零件的装配程序呈现了一个数字的模拟方法。由于装配用工具的变动，焊接畸变、和弹返效果，这一方法在复杂的零件之间认为有交互作用和相互干涉的。经过泰勒的优化，使线性化的方法能很快地运行一个公差分析和配置，因此为概念上的设计重复产生能实行的设计方案是适当的。在自动车体构成概念上的设计期间，部分电脑辅助设计模型和装配程序是在一定的或者模糊之下的，传统的数字方法如 VSA 和 3DCS 用不完全的数据无法善于如

此的变动模拟，因此进一步的研究要在概念上的设计之中寻求先进的本质上的方法。

2.2性质上的模拟研究

传统的数字方法要求完全数据运行分析和评估复杂的产品，当数据是不完全和比较不确定的时候在概念上的设计方案中，通常，设计方案时常将会在较后的设计中被修正或改变。除此之外，许多程序不能很好的够描述数量方程。性质上的模拟技术适用于它本身去解决非常麻烦的一种情形，而且性质上的模拟是将收集关于特定的事件或活动的必要资讯的去尽可能实现自然的研究方法。性质上的模拟作为一种新技术已经取得很大的成功，定性分析的本质将性质地识别系统的一个重要的变数，并且只能使用有限数据预测系统，所以性质上的模拟在早期设计方案中在决策方面，尤其突出。现在，性质上的理论越来越多应用于工程学。在性质上模拟的发展中Kuipers 和 Forbus ［20,21] 对这个领域作出了非常大的贡献，就像是 QSIM 运算法则和性质上的理论程序一样。进而的研究主要地在各种的工程学专注的先进的模拟运算法则和实际的应用中。

3车辆装配设计和建模

在这里在副装配中存在复杂的三个链条,联合的链条，尺寸│公差链条，和装配程序链条，这些三个链条互相影响彼此。误差沿着尺寸链条而增加，装配程序和接合处结构影响尺寸链条的选择。装配顺序链条决定尺寸链条的构成，不同的装配顺序会造成一个不同的变动积聚，而且程序会以相似的方式影响接合形状。接合形状和参数也同样影响装配变动增值。虽然这三个链条持有非常复杂相互的关系，因为这些问题是相关的，但是装配程序的操作应该考虑三个链条，为了要这些三个链条合作而且作装配程序的最佳结合，接合器结构、和公差分布。在正确的安置中，滑动接合器能吸收而且补偿装配变动，因为来自部分的运动学的限制丘状焊痕在各特征接合器间断开。

4.发展展望

未来，计划队将会扩张而且加深更高深的研究调查车辆车体装配的范围。同时, 其他重要的设计目的包括时间和成本因素将会被增加去研究将来概念上的装配方法。最后，作者将会变宽实际应用的数量、性质上的模拟程序，完美实现车辆车体数字并发设计的应用。

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Frame

The basis of the entire vehicle is called the frame, the frame's role is to increase the body's strength and rigidity to withstand bending and twisting loads. Vehicle collision with the ground situation, the frame is the most oppressed and absorb impact energy. It must try to jack up car engines, auto body, car wheels, and other car components. Frame is a channel or U-shaped cross section channel, which uses the welded or riveted together. Cross-pillar make them strong enough to resist shock and, shock, reverse, and they encountered in the operation of the vibration.

There are two pressing molding frame steel straight beams, five beams, front axle, rear axle and four wheel composition. Two steel beams of the front straight back come closer than some. The aim is to take into account that in front of the wheels to better guide motorists. Rear axle load bearing function of not only power but also sent to the rear wheels turn. After passing a bridge through a differential equal to the amount of torque to both axles. When necessary, the differential is to allow each wheel to the speed of rotation of its own as an important assembly. For example: car driving in the corner, the outside than the inside wheels turn the wheel fast, play a pivotal role in the inside of the wheel.

In order to absorb the shock with the earth's surface and steep, and after the bridge before the bridge plate springs are connected to the frame. Now, before the bridge is to be an independent front suspension system components replaced. Engine, wheels, power systems, brakes and steering system is mounted on the frame, then known as the chassis assembly. Chassis as a stand, all the parts are firmly fixed in it. In most cases, the engine was three or four trailers on the location of the lift up. Bearing arrangement including being placed on the supporting flange and the frame in the engine bay rubber gasket or washer between. Rubber gasket or washer to avoid collisions between metal and metal. In this way they absorb the vibration and noise.

To prevent engine vibration and noise transmitted directly to the frame, and then passed to the body and passengers.

These items are mounted on the frame after the operation to be completed in the body the assembly should be close together.

A framework of auto body assembly qualitative

simulation system

Abstract

The body assembly process design(BAPD)system is currently under development at the laboratory of Auto Body Manufacture Technology Center of Shanghai Jiao Tong University. To ensure that assembly issues have been properly considered in the conceptual design phase, different methods, procedures and tools should be developed. The paper gives a brief view of the system architecture of the BAPD system, and the paper will present a framework to carry qualitative simulation procedure and conduct hierarchical qualitative simulation to analyze and predict assembly variation flow with limited parameters and fuzzy knowledge; the system conducts qualitative information acquisition of physical parameters of assembly features, and obtains cardinal factors influence the variation results by qualitative analysis in the assembly process. An analytical case is discussed to explain the function of qualitative analysis.

1 Indroduction

While developing a new vehicle model or performing vehicle variant design, designers will need to apply new technology, new materials and design methods in the

development process. With the rapid development of AI technology, it provides designers and manufacturers with a great chance to continuously improve product quality, to carry out concurrent design and to reduce the time to market. Vehicle bodies must be built to have high dimensional integrity at competitive costs in the face of the current environment of increasing competitions. Auto- makers should produce the designed components/products within the specified tolerances, so that designers shall delicately select appropriate assembling operations and their application sequence to form a feasible assembling process. The process gradually alters the assembly errors into the key dimensions’ requirements and the final shape of the designed component/product. The conceptual design will greatly impact the basal structure of product cost. In the auto-body conceptual design, designers need to determine complex connection and structures between hundreds of parts/components. Currently, automakers usually determine joint configuration and assembly sequence by virtue of designers’ long-tested empirical experience. Subject to the limitation of designer knowledge formation and judgment ability, it is too difficult to make reasonable and right validation and decision to all the design concepts, the root cause of the problem is short of dimension design tools corresponding with the conceptual design stage. Different methods and procedures should be developed to ensure that assembly issues have been properly considered in the conceptual design phase. The whole assembly process gradually alters joint types and assembly steps to produce the most feasible assembling process and enable assembly resultant errors into the key dimensions’ requirements and meets the final shape or other functional requirements of the designed component. At each assembling operation, he assembling or manufacturing tolerance is to be specified to assure that the step-by-step assembled component satisfies the design control tolerance. Each design tolerance is warranted by a number of assembling and/or manufacturing tolerance limits imposed on the assembling operations used to produce the component and subassembly. Prisco and Giorleo[1]surveyed the current status of the models for representing, manipulating and analyzing dimensioning and tolerancing data behind the major computer-aided to lerancing systems, now commercially available. In engineering fields, VisVSA

commercial software is familiar with quick variation analysis simulation and friendly graphic presentation, which facilitates statistical analysis of dimensional variations in parts and assemblies, based on Monte Carlo simulation. Shen[2]presented a brief review of the leading commercial computer-aided tolerance analysis system VisVSA. Schlatter[3]made use of VisVSA to perform dimension management and analysis in disk drives.3DCS also is a successful quantitative variation calculation commercial software. While, tolerance analysis in VisVSA and 3DCS is passively performed the existing variation accumulation in the settled assembly solution including one assembly sequence and one set of tolerance settings. Furthermore, these tools cannot actively select the feasible and optimal assembly sequences, flexibly change the types of connection joint or actively adjust the value of tolerance limits to fulfill the optimal assembly variation resultant accumulation. Therefore, ready design systems could not possess such variation analysis methods and tools to deal with big uncertain space of conceptual design and large scope of solution exploration in this stage. From this perspective, construction of a simulation model integrated with joint configuration, part structure types, and assembly sequences concurrently in the conceptual phase is greatly needed.

Generally, a car has about 4000 components and more than 100 key parts among them. Due to the non-deterministic characteristics of conceptual design and the inability to fully understand and model the mechanisms of variation propagation and behavior during the conceptual assembly design phase and when part CAD model and assembly process are underdetermined or unknown, conventional numerical calculation cannot be carried to perform quantitative simulation of dimension variation. Such conventional design techniques as VisVSA and 3DCS are inadequate to support the conceptual phase. Therefore, new technologies such as expert system and qualitative simulation are introduced to help conduct variation simulation catering to assembly concept. Qualitative simulation technology has been investigated into the project by authors. It is the goal in this paper to investigate the applicability of this simulation framework when extended to multi-objective body assembly robust design

under uncertainty during the conceptual design stage. The project employs similarity algorithm to pick up one of the most feasible cases from the case base as design beginning point and as reference design, and then introduce integrated stochastic optimization methods to heuristically produce assembly alternatives in term of reference design solution.

Qualitative simulation provides the flexibility in the manipulation of various assembly variables in qualitative form during the conceptual design stage. Summarily, the paper proposes a novel model for qualitative reasoning in auto-body assembly process design with inaccuracy handling in tolerance limits setting and vague joint configuration at the different assembly sequence.

The paper is organized as follows. Section 1 is a brief introduction. The paper reviews the state of art of assembly tolerance design and qualitative theories development in the second section of the paper. The basic system frame of body assembly design system is presented in Section 3.The qualitative simulation conceptual framework is introduced in Section 4,and in the last section, the authors come to a conclusion and introduce further research and work.

2 Related research and problem statement

There exists excessive and fruitful development and research in computer aided tolerancing in rigid mechanical assembly design and various tolerance design methods, however, relatively little attention has been paid to tolerance design of vehicle sheet body during the conceptual design stage. The objective of this paper is to describe a comprehensive framework for vehicle body conceptual assembly tolerance design that has been under development at the laboratory of Auto Body Manufacture Technology Center of Shanghai Jiao Tong University. The paper will focus on the system architecture of the vehicle body assembly process design in the conceptual design stage, with some simple analytical discussion.

2.1 Body assembly and tolerance design

A typical automotive body-in-white is composed of more than 400 sheet panels, which are joined together through different kinds of complex connection methods. Auto-makers hope to fulfill the quick generation and exploration of new concepts to achieve continuous quality improvement by optimal combination of joint configuration methods of subassembly/parts, assembly sequence and tolerance allocation.

2.1.1 Assembly design and tolerance design

Design for assembly(DFA)[4,5]methods consider the assembly issues at the early product design stage to foresee problems that may be induced during the assembly operations. In the past decades, significant work[6–10] has been done to develop solutions to assembly sequence planning. Shi and his colleagues[11–13]first introduced the state space model to describe the product variation propagation across multi-station assembly, they have developed procedure of modeling tolerance stack-up and utilized the state space model to study the stream of variation in multi-station machining process and formed a process level diagnostic methodology to control dimension quality. Chase[14]has made much and deep research in tolerance design and has developed a method based on vector assembly models for modeling and analyzing variations in mechanical assemblies. These models are constructed of common engineering elements: vector chains, kinematic joints, assembly datum, dimensional and geometric feature tolerances, and assembly tolerance limits. The method is consistent with engineering design practice and is well suited for integration with commercial CAD systems. Gao[15]compared the direct linearization method(DLM),and Monte Carlo simulation. The DLM uses linearized assembly constraints and matrix algebra to estimate the variations of the assembly or kinematic

variables, and to predict assembly rejects. A modified Monte Carlo simulation employs an iterative technique for closed loop assemblies, the results of the comparison show that the DLM is accurate if the tolerances are relatively small compared to the nominal dimensions of the components, and the assembly functions are not highly nonlinear. Sample size is shown to have great influence on the accuracy of Monte Carlo simulation. From different perspectives of assembly, Hu[16]presented a numerical simulation method for the assembly process incorporating compliant non-ideal parts. This method considers the interaction and interference between compliant parts due to part variation, assembly tooling variation, welding distortion, and spring back effects. Through Taylor’s series, the linearized methods can perform a tolerance analysis and allocation quickly, so it is suitable to generate feasible solutions for conceptual design iteration. During the auto-body structure conceptual design, part CAD models and assembly process is underdetermined or fuzzy, conventional numerical methods such as VSA and 3DCS could not be adept at such variation simulation with incomplete information, therefore further research into conceptual design calls for advanced qualitative methods.

2.1.2 Joint configuration in body assembly design

Joint configuration plays an important role in the optimization of complex part assembly process. Liu and Hu[17]found that different joint type configuration and combination would result in different dimensional assembly quality in sheet metal assembly. Variation of these flexible products is less than traditional products which have the same part structure and same tolerance limit setting because slip joint can absorb variations in its mating surface. Nikolaidis and Long, et al.[18]described a method to develop tools that relate response parameters that describe the performance of a component to the physical design variables that specify its geometry. Neural networks and response surface polynomials were used to rapidly predict the performance characteristics of the components given the component dimensions. The method was applied in design of an automotive joint. Lee and Saitou[19]used genetic

algorithm to generate candidate assemblies based on a joint library specific for an application domain. Each candidate assembly is evaluated by an internal optimization routine that computes the subassembly partitioning for optimal in-process adjust- ability, by solving an equivalent minimum cut problem on weighted graphs. In conclusion, joint design is a dynamical and non-quantified process based on designers empirical knowledge joint design so far has not had a method to quantitatively determine design rules and design experience.

2.2 Qualitative simulation research

Conventional numerical methods require complete information to perform analysis and evaluation for complex product, while the information is incomplete and under-determined in the conceptual design phase, generally, design schemes will often be modified or changed in the later design stages. Besides that, many processes cannot be well described by quantitative equations. Qualitative simulation technology applies itself to solve such a troublesome situation, and qualitative simulations are such research methods whose purpose is to gather essential information about certain events or activities in a state as natural as possible.

Qualitative simulation as a new technology has achieved some great success, the essence of qualitative analysis is to qualitatively identify the significant variables in a system, and only use limited information to predict the system’s behavior, so that qualitative simulation does well in intelligent decision-making especially in the early phase.

Nowadays, qualitative theory is applied in more and more engineering fields. In the development of qualitative simulation, Kuipers and Forbus[20,21]have made a great contribution to this domain, such as QSIM algorithm and qualitative process theory. Ongoing research mainly concentrate on advanced simulation algorithm and practical application in all kinds of engineering fields.

2.2.1 Qualitative information presentation

Acquirement and presentation of such limited and critical information in the conceptual design stage is a key element of effective and successful qualitative decision-making. Coiera[22]summarized the representation of physical systems using qualitative formalisms in detail. Qualitative data can come from multiform sources, such as design experience, expert knowledge, and case learning. Qualitative data are mostly described as written/spoken words or observations; sometimes, qualitative data do not have a direct numerical interpretation. Exploration is the most often motive for using qualitative methods. Given these conditions and functions, it is really natural to make good use of qualitative simulation methods, which aim to provide understanding and explanations by studying selected issues based on information of a qualitative nature. The authors will have an attempt to construct a conceptual framework for the systemic treatment of vagueness and uncertainty both qualitatively and quantitatively via fuzzy sets and qualitative methods, which allow for a set of concrete steps to be taken for assembly productivity and quality improvement, based on a tangible understanding of the relevant assembly process issues in a particular scheme.

2.2.2 Qualitative evaluation and application

The essential sources of many problems and errors which happen in the production, customer use, and maintenance phases are concealed early in the conceptual design stage, so that designers should determine these latent key factors the first time. Qualitative techniques can deal well with underdetermined and/or incomplete information to form qualitative description of physical system states in rigorous logic. Though at the absence of complete information, designers still could utilize qualitative reasoning technology to compare and improve design alternatives to form optimal design solutions. Characteristics of body conceptual assembly design model are: that model parameters are uncertain and difficult to numerical analysis and

the other that assembly process is hierarchical process, in this situation, assembly design should conduct assembly variation predictive simulation analysis with the help of qualitative methods.

There exist much development and research in qualitative evaluation and application. Adam[23,24]has developed a qualitative modeling toolbox called QMTOOL which was constructed using AI and object oriented software to design and develop application independent control architecture’s for automated workcells. He applied the QMTOOL to deal with discrete-time description of electromechanical systems and processes. Bohanec and Rajkovic[25,26]have developed the DEX, an expert system shell for qualitative multi-attribute decision modeling and support with the integration of qualitative knowledge and multi-attribute decision, and have applied it in many fields with relatively great successes. Qualitative assembly research is a method of research that yields nonnumeric information generated by conceptual design. Because assembly sequence and joint configuration are not easily translated into numbers and/or not quantifiable, qualitative data is utilized to perform multi-attributes qualitative evaluation to evaluate the joint configuration in the early assembly design scheme. Qualitative decision system constructs qualitative description function of inputs parameters(tolerance allocation, joint configuration, and assembly sequence)and output parameters(body assembly resultant variation),and builds corresponding reasoning methods and reasoning mechanism with the support of database and knowledgebase systems.

3 Vehicle assembly design and modeling

There exist three chains in a complex subassembly or product in Fig.1,joint chain, dimension/tolerance chain, and assembly sequence chain, these three chains interact and affect each other. Errors propagate along the dimension chain, the selection of dimension chain is effected by assembly sequence and joint configuration.

Assembly sequence chain determines the composition of dimension chain, a different assembly sequence would result in a different variation accumulation, and the sequence would affect joint connection type in like manner. Joint types and parameters also affect assembly variation propagation.

Though the three chains possess a really complex mutual relationship because these issues are interrelated, the task of assembly process should take into consideration three chains together in order to cooperate these three chains and make optimal combination of assembly sequence, joint configuration, and tolerance distribution. In the right arrangement, slip joint can absorb and compensate assembly variation, because kinematic constraints pass from part to part across the feature joints.

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