外文翻譯--基于知識(shí)工程的汽車覆蓋件沖壓路線分析[中文8000字]【中英文文獻(xiàn)譯文】,中文8000字,中英文文獻(xiàn)譯文,外文,翻譯,基于,知識(shí)工程,汽車,覆蓋,籠蓋,沖壓,路線,線路,分析,中文,中英文,文獻(xiàn),譯文 KBE-based stamping process paths generated for automobile panels Jinqiao Zheng . Yilin Wang . Zhigang Li Abstract: As automobile body panels are one kind of sheet metal part with groups of free form surfaces, the process planning is more complicated than common sheet metal stamping to implode effectively and practically. Based on KBE, new frameworks have been presented as intelligent master model at the system level and as procedure model at the activity level. In accordance with these frameworks, an intelligent CAPP system has been specifically developed. Based on feature technology, features have been extracted and represented by the object-oriented method. Stamping features and their parameters have been defined and extracted based on feature technology and stamping process rules. The whole product knowledge has been represented by frames which directly map to objects (or features) in the object-oriented sense. Relevant appropriate operations features have been assigned to stamping features of a product based on feature-operation criteria, parameters of the stamping feature and their correlativity. This assignment is a decision-making activity using a set of rules with a decision-making tree and model-based reasoning methods. With knowledge between operations, such as operations order constraint (do-after) and operations combination constraint, process paths have been improved based on relevant intelligent reasoning methods. Based on the relationships (preferred-to) between processes and machines/dies, the structure of die and machine for each process can be identified, since the process route has been determined. In this stamping process planning, the procedure and information have been controlled by a process control structure that is associative and integrated. 1 Introduction Recently, research on the computer-aided process planning (CAPP) system for sheet metal has been widely reported. Park et al. [1] constructed an automated process planning system for ax symmetric deep drawing products. Tessa [2] and Kang and Park [3] presented a group technology and modularity to construct a CAPP system for process sequence design in an expert system for non-ax symmetric deep drawing products with elliptical shape. Gao et al. [4] developed an advanced software toolset used for the automation of sheet metal fabrication planning for aircraft components. Zussman and Horsch [5] proposed a motion planning approach for robot-assisted multiple-bent parts based on C-space and a potential field. Wang and Bourne [6] proposed an automatic process planning system with the features well investigated and the production plans researched with near-minimum manufacturing costs. De Vin et al. [7 , 8] developed a sheet-metal CAPP system called PART-S, which integrates cutting, nesting, bending and welding processes for bending sequences. Streppel et al. [9] showed the ambiguity of conventional tolerances and presented a method which replaces conventional tolerances with geometrical tolerances for process planning in small batch sheet metal part manufacturing. Amoral et al. [10] proposed a method which generated feasible bending sequences of a sheet metal part handled by a robot, and discussed the determination of the best grasping positions and repositions. Aomura and Koguchi [11] pro- posed a method to generate bending sequences of a sheet metal part handled by a robot. Liao and Wang [12] proposed an evolutionary path-planning approach for robot-assisted handling of sheet metal parts in bending. Lutters et al. [13] developed a generic architecture for computer aided process planning based on information management for sheet metal manufacturing in a small batch part environment. Kumar and Rajotia [14] had proposed a method of scheduling and its integration with CAPP, so that on-line process plans can be generated taking into account the availability of machines and alternative routes. The contents above are mainly for process parameter calculating, path-planning and some sketch map of work-pieces for specific types of sheet metal, such as axis-metric and non-ax symmetric deep drawings, complex bandings and sheerings, and so on. The automobile body panel is one kind of sheet metal part, which is complicated in shape, with groups of free form surfaces, a large figure in size and is always manufactured by stamping processes. Automobile panels can be considered as a combination of some common stamping, such as irregular drawing, flanging/bending, trimming and piercing, etc. The process planning of these panels is more complicated than common sheet metal stamping, which is generally dependent on engineers experience to complete. It is believed that the process path plan for automobile panels is requisite and acquirable. In essence, the stamping process path for automobile panels is to determine the necessary forming processes and their sequences in order to produce a particular part economically and competitively. Process paths generation is a decision-making process. Decisions on stamping operations for a particular feature have to be formed on various independent conditions such as which operation should be performed with which die and tools and under what forming parameters. A CAPP system for these should be an integrated environment to deal with knowledge to reduce the dependence on engineers or experts, and realize the process planning with scientism. Thus, knowledge based engineering (KBE) is applied to advance the stamping CAPP system for automobile panels, and even to improve the competitiveness for the automobile industry. This paper is particularly concerned with the construction involved with developing a CAPP system based on KBE. 2 KBE in CAPP system for stamping 2.1 KBE Knowledge based engineering (KBE) is one innovative method of artificial intelligence for engineering design developed in the 1980s. So far, there is no generally accepted and mature definition for KBE. However, it is recognized that KBE is an intelligent method to resolve engineering problems, which can realize inheritance, integration, innovation and management of domain expert knowledge through the drive, multiplication and application of knowledge. A knowledge-based system (KBS) is one that captures the expertise of individuals within a particular field (the “domain”), and incorporates it and makes it available within a computerized application [15]. The level of complexity of the tasks performed by such a system can vary greatly. However, it can generally be said that while a domain expert would find them routine, they would be outside the capabilities of a person unfamiliar with the domain [16]. KBE provides an open architecture and reuse ability of experience and knowledge, which can deal with multi- domain and multi-expression of knowledge, and can form an integrated environment. A KBE application is further specialized, and typically has the following components of geometry, configuration, and engineering knowledge: – Geometry – there is very often a substantial element of computer-aided design (CAD). Most of the software used to create KBE applications either has CAD capabilities built in, or is able to integrate closely with a CAD package. – Configuration – this refers to the matching of valid combinations of components. – Engineering knowledge – this enables manufacturing and other considerations to be built into the product design. When a candidate application area requires a high degree of integration of the above elements, KBE is likely to be the best method for its integration. KBE is sometimes termed rule-based engineering, as within the discipline, knowledge is often represented by rules. These may be mathematical formulae or conditional statements, and although simple in concept, they may then be combined to form complex and powerful expressions. KBE systems, on the other hand, are usually provided with specialized geometrical capabilities, with the ability to embed engineering knowledge within a product model. The following examples of typical KBE applications demonstrate some of the considerable benefits to be gained from its use. 1) Lotus engineering. This used the integrated car engineer (ICE) system in the design of the Lotus Elise. ICE consists of a vehicle layout system, and modules to support the design of suspension, engines, power-train, wheel envelope and wipers [ 17]. 2) The Boeing Commercial Airplane Group. This uses KBE as a tool to capture airplane knowledge to reduce the resources required for producing a design [18]. 3) Jaguar cars. The company’s KBE group devised a system that reduced the time taken to design an inner bonnet from 8 weeks to 20 min [19]. 2.2 Problem to solve in a CAPP system based on KBE A stamping CAPP system should deal with all knowledge including geometry, non-geometry, engineers experience, rules and criteria, results of tests and numerical simulation, or even successful cases, because of the complexity of automobile body panels. The knowledge is involved in diverse fields, such as metal forming technology, metal forming mechanics, modern design methodology, numerical simulation technology, and artificial intelligence. Accordingly, the CAPP system has to solve the problems with expression and application of all knowledge, and integration of all multidisciplinary design. A CAPP system is essentially a set of instructions and guidelines on how to perform a complex procedure. It details the individual sub-tasks, how they should be carried out, in what order, and how the work should be documented. Furthermore, as system requirements change, new solutions tend to evolve from existing ones, so computer applications and their descendants can outlive the personnel involved in their initial development. All in all, a stamping CAPP system for automobile panels based on KBE should readily solve the following problems: (1) Representations for all knowledge. (2) Reasoning based on all this knowledge. (3) Appropriate operation features acquired from stamping features and process rules incorporated with form- ability analysis. (4) Process routes based on process sequencing and process combination knowledge. (5) The control or management of process procedures for rapid response to all changes. 3 Framework of a CAPP system 3.1 The integrated master model for a CAPP system To solve all corresponding problems mentioned above, the integrated ma ster mode l is advanced at the system level t o control and frame t he CAPP system for automobile panels. I t is a common concept and framework to generalize and specialize the function, course control , process planning circumstance, and act iv it ies involved in t he development o f an integrated and intelligent system into abstract groups, and to make t he m carry out all contents and processes. This mode issue table for knowledge expression and application, process controlling, information integration, change response , etc .The intelligent master model (IMM) of stamping process planning for automobile panels is composed of a knowledge base, process control structure (PCS), process planning optimization (PPO), process information model (PIM), and linkable environment (LE), which are integrated and combined based on KBE. The structure of the IMM is shown in Fig. 1. The IMM of process planning is not only the foundation of intelligent CAPP for automobile panels, but also the integration of knowledge and methods, which combines the KBE system with the process planning. With this model, KBE acts as a knowledge source to drive PCS, PIM, and LE, which makes process planning integrated and associative. The PIM is a dynamic expanded information model, in which the information can be added and updated along with process planning. Using knowledge multi-expression format, the integrated information model of process planning is built based on a feature model. For the hierarchy and framework of the features, semantic net and object- oriented methods are adopted to express knowledge and establish an information model in which process knowledge, e.g. database, parameter, rules, and experience, act as rules and attributes of the objects, and where whole product knowledge acts as a framework for relationships of objects. With a process information model, the process planning can be completed through knowledge-reasoning and decision-making based on knowledge encapsulated in the objects. The PCS is a key point to ensure process planning is integrated and consistent; it manages the process information model, process planning to generate stamping process plans and detail design, and controls the changes of the planning. In IMM, the PCS comes into being dynamically along with the process planning. If one part of PCS is created, it will monitor and control relevant planning and information subsequently. When results of process planning are deleted, the corresponding PCS part will fade away accordingly. The LE provides several methods to deal with the links among process planning procedures, the geometry between product and detail design of work pieces. To achieve intelligent process planning for large complicated stampings, there are problems to solve, i.e. linking of process planning procedures, the geometry link between product and detail design of work pieces. The LE provides several methods to deal with these links, e.g. parameters variable link, data structures link, and geometrical link. The PPO is a methodology of design optimum for complex engineering, which can deal with the complicated optimization problem of process planning in an economic view. 3.2 The framework of CAPP system based KBE The stamping CAPP system for automobile panels based on the intelligent master model above consists of several stages such as stamping features extraction from product data, operation features reasoning from stamping features to form a process information model, process planning to get the sequence of operations and relevant tools, detail design for work pieces, simulation for detail design, and finally the process plans and 3D die-face model generation which is shown in Fig.2. It is a tangible activity level to control and frame a CAPP system for automobile panels. In the CAPP system, stamping process planning of automobile panels needs to first establish a process information model based on a 3D model product and feature technology. Stamping features are extracted, and operation features are attained subsequently. The features all carry knowledge about themselves, the process and constraints. Then the PIM and PCS are established. There-after, the sequence planning is setup based on PIM and knowledge such as operation sequence rules, operation combination guides and reasoning methods, and then the dies and machinery are options. Along with the process of the planning, PCS, PPO and LE of IMM are built by knowledge driving. PCS consists of an integrated collection of tasks that can initiate, control, manage, evaluate and update all the planning information and results timely. PPO optimizes process paths and enterprises resource environments, and PCS and PPO carry out the optimization and find the optimal solution. PCS and LE make process planning associated and linkable. 4 Key points of process path generation Unigraphics has several features that provide a subset of the capabilities of a KBE language —UG/KFL, which provides a way to specify knowledge rules that can cover all Unigraphics applications. The stamping CAPP system for automobile panels has been developed based on the frameworks advanced above, which choose C and UG/KF language as t he implementation language, a nd ACCESS as its database o n t he UG/CA D development environment. UG/Open and UG/Open++ allow custom i zation and extension of Unigraphics using a standard procedural language (C and C++). UG/KFL provides a way to specify knowledge rules that can cover all Unigraphics applications. Rules of UG/KFL are easily written by the developer, easy to read, understandable, and reusable by the user. Furthermore, UG/Open can be integrated with KBE by accessing C programs from the KBE language described under External Function. For access to named attributes from C, there will be a utility program that takes a design definition in the language and produces C bindings to access the attributes of an object instance of that design. The access consists of functions and methods for getting and setting the value of the named attributes of object instances. Additionally, there are UDF and UDO in UG/ CAD and UG/KF, which can be dealt with by UG/Open and UG/KF. What is more, Unigraphics is integrated with many other knowledge tools and sources, such as spread sheets, other ICAD KBE language systems, finite element analysis, CAM, etc. 4.1 Stamping feature To generate appropriate process plans, the product data requires the original inputs, which includes the geometry, topology, tolerance, material and quantity of product. Based on the feature technology and stamping technology, a stamping feature is the portion of a part which can be formed by means of certain stamping operations. For ex- ample, a drawn feature or bend feature is defined as the main feature, which is to describe the near net shape of a component, while flange, hole, emboss, bead, notch and flange-hole are defined as the auxiliary ones, which are required to describe the local part of the final shape. Using feature technology and the geometry extraction method, the stamping design features, such as the main forming feature (e.g. drawing, bend), flange, hole, emboss, bead, notch, and so on, can be extracted from a 3D solid model, which are first defined as UG/UDO. For example, Fig. 3 shows the stamping features of one automobile panel. The stamping feature model should then be defined to represent product knowledge integrated and unambiguous. The stamping feature is represented as object-oriented class or object and instance using UG/KF language (UG/KFL);it not only represents feature parameters, tolerance, material, etc. as attributes of class or instance, but also represents geometrical objects by importing UG/UDO and UG/UDF referenced solid geometry as an instance attribute or child. And this realizes the connectivity and integration between the symbol of a feature and its geometrical object. It can also get an attribute value from a function, rule, expression and database. 4.2 Operation feature Accordingly, stamping operation features are categorized into initial and subsequent, such as drawing, bending, flanging, trimming, hemming, re-striking, and piercing and so on. The relevant appropriate operations are assigned to form stamping features of products based on feature- operation criterion, parameters of the stamping feature and their correlativity. This assignment is a decision-making activity using a set of rules with decision-making tree and model-based reasoning methods. For example, drawing→ trimming is reasoning from the main draw feature, flanging is reasoning from the flange feature, and piercing is reasoning from the hole. Fig. 5 show the typical illustration of flanging operation features reasoning from its stamping feature, and the sequence rules of these operation features are attached to the operation features. Customarily, relationships between features, especially the hierarchy, should be an important factor, while the operation feature is the reasoning. In Fig.4, the features flange3, flange1 and bead1 should be in the form of a set together to deduce relevant appropriate operations. In this way of reasoning, the operation features can get fundamental knowledge for subsequent planning. In this paper, the operations features reasoned from stamping features are represented as object-oriented entities and UG/UDO, and the relationships are expressed as network based on t