机械本科毕业设计（论文）外文翻译-基于原型液压系统特征的机构模型.doc

中国矿业大学 2007 届本科生毕业设计 第 1 页 英文原文 FEATURE-BASED COMPONENT MODELS FOR VIRTUAL PROTOTYPING OF HYDRAULIC SYSTERM Abstract: This paper proposes a feature-based approach for the virtual prototyping of hydraulic systems. It presents a framework which allows the designer to develop a virtual hydraulic system prototype in a more intuitive manner, i.e. through assembly of virtual components with engineering data. The approach is based on identifying the data required for the development of the virtual prototypes, and separating the information into behaviour, structural, and product attributes. Suitable representations of these attributes are presented, and the framework for the feature-based virtual prototyping approach is established,based on the hierarchical structure of components in a hydraulic system. The proposed framework not only provides a precise model of the hydraulic prototype but also offers the possibility of designing variation classes of prototypes whose members are derived by changing certain virtual components with different features. Key words: Computer-aided engineering; Fluid power systems;Virtual prototyping 1.Introduction Hydraulic system design can be viewed as a function-to-form transformation process that maps an explicit set of requirements into a physical realisable fluid power system. The process involves three main stages: the functional specification stage,the configuration design stage, and the prototyping stage.The format for the description of the design in each stage is different. The functional specification stage constitutes the initial design work. The objective is to map the design requirements. To achieve this, the design problems are specified Correspondence and offprint requests to: Dr S. C. Fok, Schoool of Mechanical and Production Engineering, Nanyang Technological University, Nanyang Avenue, Singapore 639798. The designer must identify the performance attributes, which can include pressure, force, speed, and flowrate, with the required properties such as size, cost, safety and operating sequence. performance requirements for each attribute. In this stage, the design is abstracted in terms of the performance attributes with associated values. The objective of the configuration design stage is to synthesise a hydraulic circuit that performs the required functions conforming to the performance standards within defined constraints. A typical hydraulic system is made up of many subsystems. The smallest building block in a subsystem is the standard hydraulic component (such as valves, cylinders,pumps, etc.). Each type of 中国矿业大学 2007 届本科生毕业设计 第 2 页 standard component serves a specific elemental function. The design effort in the configuration design stage is fundamentally a search for a set of optimal arrangements of standard components (i.e. hydraulic circuit) to fulfil the functional requirements of the system. Based on this framework, the designers would normally decompose the overall system functions in terms of subfunctions. This will partition the search space and confine the search for smaller hydraulic subcircuits to perform the subfunctions. Computers are often used to support the configuration design process. For example, Kota and Lee devised a graph-based strategy to automate the configuration of hydraulic circuits. After the development of the hydraulic circuits, digital simulation tools are often used to study and evaluate these configurations. With these tools, designers can compare the behaviour of different circuits and also analyse the effects when subcircuits are combined. In the configuration design stage, the design is traditionally represented as a circuit drawing using standard icons to symbolise the type of standard component. This is a form of directed graph S(C,E) where the circuit S contains components C in the form of nodes with relations between components denoted by edges E. The prototyping stage is the verification phase of the system design process where the proposed hydraulic circuit from the configuration design stage is developed and evaluated. Physical prototyping aims to build a physical prototype of the hydraulic system 666 S. C. Fok et al. using industrial available components. The process of physical prototyping involves the following: Search for appropriate standard components from different manufacturers. Pre-evaluation and selection of components based on individual component cost, size, and specification, and compatibility factors between components. Procurement and assembly of the selected components.Test and evaluate the physical prototype based on the overall system requirements. Use other components or redesign the circuit (or subcircuits) if necessary.Besides dynamics, the development of the physical prototype must take into consideration other factors including structure,cost, and weight. The dynamics data are used to confirm the fluid power system behaviour whereas the geometric information is used to examine the assembly properties. The development of the physical prototype will provide the actual performance,structure, and cost of the design. The main disadvantage of physical prototyping is that it is very tedious and time consuming to look for a set of suitable combinations of standard components from among so many manufacturers. Although the basic functions of the same types of standard component from different manufacturers do not differ, their dynamics, structural and cost characteristics may not be similar, because of design variation. Hence, for a given hydraulic circuit, different combinations of 中国矿业大学 2007 届本科生毕业设计 第 3 页 parts from different manufacturers can have implications on the resulting system,in terms of dynamics, structure, and cost. Value engineering can be used at this stage to improve the system design by improving the attributes at the component level. This includes maximizing the performance-to-cost ratio and minimising the size-to-performance ratio. Virtual prototyping can be viewed as a computer-aided design process, which employs modelling and simulating tools to address the broad issues of physical layout, operationalconcept, functional specifications, and dynamics analysis under various operating environments. The main advantage of virtual prototyping is that a hydraulic system prototype can be assembled, analysed, and modified using digital computers without the need for physical components, thus saving lead time and cost. The main requirement of a virtual hydraulic system prototype is to provide the same information as a physical prototype for the designer to make decisions.To achieve this, the virtual prototype must provide suitable and comprehensive representations of different data. Furthermore, transformation from one representation to another should proceed formally. Xiang et al. have reviewed the past and current computer-aided design and prototyping tools for fluid power systems. The work revealed that the current tools could not provide a complete representation of the design abstractions at the prototyping stage for design judgement. Most of the tools concentrate on the dynamics behaviour. Vital geometrical and product information that relates to the system prototype consideration and evaluation is frequently missing.To advance the development of computer-aided virtual prototyping tools for fluid power systems, there is a need to address the formal representations of different abstractions of behaviour,structural, and product data along with their integration. This paper focuses on these issues and proposes the formalism of a unified component model and the taxonomy based on the feature-based approach. In Section 2, we discuss the feature- based approach focusing on the key information and their representations required for hydraulic system prototyping. Section 3 presents a formalism of the feature-based model and structure for the development of virtual hydraulic system prototypes.The structure is illustrated with an example. Future work and conclusions are given in Section 4. 2. Feature-Based Approach Features can be defined as information sets that refer to aspects of attributes that can be used in reasoning about the design, engineering or manufacturing processes. The concept of using features to integrate CAD/CAPP/CAM is not new and there are many papers on the application of this approach in CIM. In all these applications, the feature model is regarded as the basis whereas design by features is the key for the integration. To develop a feature model, the relevant 中国矿业大学 2007 届本科生毕业设计 第 4 页 information concerning the design must be identified and grouped into sets based on the nature of the information. The relevant information should contain sufficient knowledge for activities such as design, analysis, test, documentation, inspection, and assembly, as well as support various administrative and logistic functions. Design by features is the process of building a model of the design using features as primitive entities. The feature model provides the standardisation of relevant data. Through the design by features approach, vital knowledge of the design will be generated and stored. Together, the feature model and the design by features approach will provide the essential information, which can be used, not only for the simultaneous consideration of many different concerns with the design, but also to interface the many activities in the design realisation process, including the life cycle support operations. The main drawback of the feature-based design approach is that the feature model should be properly defined . This can be difficult, as features are sets of knowledge that are application dependent. The organisation of the features can also be application specific. Non-trivial data-management problems could arise if the feature model is not properly defined. To avoid these problems, the type,representation and structure of the features should be resolved prior to using the feature-based design methodology. The main concern when developing a feature model is that it is application-specific. In the domain of virtual prototyping of hydraulic systems, the details of the constituent standard components must be able to be used to describe the overall system. The component features are bearers of knowledge about that part. To create a suitable feature model for hydraulic system design based on the assembly of standard components, the relevant information associated with various standard components must be identified and classified. This definition Feature-Based Component Models 667 of the component feature set can then be extended to encompass the subsystem feature set based on the hierarchical structure between the components in the subsystem. In the same manner, a hierarchical structure for the hydraulic system feature representation would evolve by considering the system as a hierarchy of subsystems. The necessary information required for a proper description of the virtual prototype must be no less than that derived by the designer from a physical prototype for decision making. These data should generally include the shape, weight, performance properties, cost, dimensions, functionality data, etc. Comparison with the physical prototyping process, the information required for each standard component could be separated into three distinct groups: behaviour attributes, structural attributes, and product attributes. 2.1 Behaviour Attributes The behaviour of a hydraulic component can be defined in terms of the dynamics 中国矿业大学 2007 届本科生毕业设计 第 5 页 characteristics used to satisfy the functional requirements. Consider a hydraulic cylinder connected to a load. Its function is to transmit a force from the stroke of the piston to the load. The maximum force it can transmit can be used to define the functionality and the behaviour requirements can be specified in terms of the desired load acceleration characteristics. Hence for a hydraulic component, behaviour attributes express functionality and can be reflected in the dynamics characteristics. The designer is responsible for the proper definition of the overall system behaviour characteristics in terms of the desired dynamics. A standard component will have its own behaviour and provide a specific function.Complex functions that cannot be achieved by a single standard component are derived using a combination of components. Hence, the behaviour of the standard component will play an important role as the individual behaviours of components together with their arrangement can alter the overall system function . The behaviour of a standard component can be nonlinear and can be dependent on the operating conditions. When two components are combined, it is possible that their behaviours can interact and produce undesired or unintended characteristics. These unwanted behaviours are assumed to have been resolved during the configuration design stage. The hydraulic circuit used in the prototyping stage is assumed to be realisable and without any undesirable interacting behaviours. This means that the output behaviour of a component will provide the input to the subsequent component. The representation of behaviours for hydraulic systems has been widely investigated. These representations include transfer functions, state-space and bond graphs. Transfer functions (for single-inputsingle-output systems) and state-space equations (for multiple-inputmultiple-output systems) are based on the approximation of the dynamics about a nominal operating condition. The power bond graph model is based on the causal effects that describe the energy transformations in the hydraulic system. This approach is appealing for hydraulic system analysis. The main disadvantage is that the derivation of the dynamics equation in a bond graph of a complicated fluid power system can become very tedious. As a result, recent work has concentrated on the used of artificial intelligence to represent the nonlinear mapping between the input and output data, which can be obtained via experimental work. These nonlinear mappings can be accomplished using artificial neural networks . It is quite natural for a hydraulic system designer to use inputoutput data to describe the behaviour of a hydraulic component. The configuration design of a hydraulic system is often achieved through steps of function decomposition. To design a hydraulic system, the designer often tries to decompose the functions and their requirements down to the component level. 中国矿业大学 2007 届本科生毕业设计 第 6 页 中文译文 基于原型液压系统特征的机构模型 摘要摘要：本文为原型液压系统的设计提出了一种基于特征的方法。它提出 了一个框架,允许设计师以更加直觉的方式开发一个真实液压机构原型，例 如， 通过真实的工程学数据进行设计。这种方法是在真正原型数据的基础 上发展起来的， 它可以分离信息入行为，结构，和产品属性。这些属性被 用适当的表示法提出， 并且框架为基于特点的真正原型 的方法建立，根 据组分等级结构在一种液压机构。它所提出的框架不只是真实的液压系统 的一个精确模型，而且为设计成员提供了当由于某些零件的一些特性改变 导致系统改变而获得一个新的液压系统精确模型的可能性。 关键词关键词: 计算机辅助工程; 液压动力系统;真实样机 1. 介绍介绍 液压机构设计可能被看作是一个为映射明确套要求入物理可实现的液 压能力系统的作用对形式变革过程。这个过程涉及三个主要阶段: 功能规 划阶段，结构设计阶段， 和样机制造阶段。描述各个设计阶段的所用的格 式是不同的。 功能的规划是所有设计中最初的工作。为了达到这个要求， 设计问题 是以指定的书信和印成单行本发给新加坡南阳大道南阳技术大学机械和制 造工程的Dr S. C. Fok。明确地根据作用和表现。设计师必须确定产品的 性能和属性， 其中包括压力， 强度， 速度和流体速度， 以及一些所必 需的东西如尺寸大小，成本, 安全要求和操作顺序。其次， 设计师必须叙 述出各个特征的精确性能要求。在这个阶段，设计以摘要的形式写出产品 的相关性能要求。 结构设计阶段的目标是完成一个液压系统回路。这个回路能完成系统 设计参数规定的各个功能。一种典型的液压机构由许多子系统组成。组成 子系统的最小模块是标准液压系统元件(譬如阀门， 气缸，液压泵等。). 每种液压标准元件都有各自的特殊作用。结构设计阶段的任务就是从根本 上找到一个基本液压元件（例如液压回路）的布置图。这个基本的液压回 路能达到系统的各个功能要求。根据这个结构， 设计师通常把整个系统功 能模块分成一个个最基本的子函数。这样就能隔开搜索空间，通过搜索较 小一级的液压系统基本回路去实现各个子函数的功能要求。 在外观设计过程中计算机往往会发挥很大的作用。例如， Kota 和Lee 想出了一个基于图表的液压系统回路结构的自动设计方法。在液压回路被 中国矿业大学 2007 届本科生毕业设计 第 7 页 发展以后，人们经常被使用数字模拟实验工具来学习和评估这些结构。通 过这些工具， 设计师能比较不同的电路块的功能，并且能够分析出这些功 能块结合后的效果。在结构设计阶段，传统上设计往往用一张回路图来代 表标准元件。这里是被(C ，E)包含结构C 的回路S以结的形式联系组分之 间由边E 表示的地方图表的形式。 样机设计阶段是结构设计过程中提出的液压回路的证明阶段。通过这 个阶段能证明结构设计中对回路的提出与评估是否正确。实际样机的目的 是建立液压机构666 S 的一个物理原型。使用工业可利用的零件。 涉及真 实样机的过程以下: 从不同的制造商手中寻找适当的标准零件。零件的选 择和评估是建立在零件之间的成本，尺寸大小，规格和互换性等因素之上 的。选择的零件取得和装配。根据整个系统要求测试和评估物理原型。使 用其它零件或重新设计电路(或支电路) 如果需要。除动力学以外， 物理 原型的发展必须考虑到其它因素包括结构，成本与重量。动力学数据用来 确认液压动力系统的性能，但是几何学信息用来系统的安装性能。 物理样 机的研制将提供设计产品的真实性能，结构和设计成本。 物理样机的主要缺点是, 它必须非常繁琐和费时地从在许多制造商手 中寻找一套标准零件的适当组合。由于设计的变化，从不同的制造商购买 的同样类型的标准零件的作用都不相同， 他们的动力学， 结构和费用特 征也不可能相似。因此， 为同样的一个液压回路，选择不同的制造商的标 准零件去组装，所完成的系统，最后在力学、结构和产品的成本等方面也 会不同。在这一过程中可以使用评估工程，通过在零件标准特性上的改变 来改进在这个情况下的系统设计。其中就包括最优化的性价比率和对零件 大小进行最合理的设计。真正样机设计过程可能被观看作为一个计算机辅 助设计过程， 它可以使用模拟制造和模拟仿真工具来验证样机的物理布局， 操作，功能规格，以及在在各种各样的操作环境下的力学分析。虚拟样机 的主要好处是, 不需要实际零件，通过使用数字计算机就可以对一个液压 机构原型进行装配和分解，因而大大的节省了时间和费用。 一个真正虚拟液压机构样机的主要要求是，它必须能像真实的产品一 样，为设计者提供信息和帮助他们做出决定。为了达到这个要求， 虚拟样 机必须提供另外不同数据的适当和全面表示法。 此外，从一个表示方法到 另一个表示方法的改进应该进行下去。 Xiang 等。回顾了过去和当前的液 压动力系统的计算机辅助设计和样机制造工