1、PDF外文：http:/ 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
2、 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 specifical
3、ly 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 fr
4、ames 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-
5、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 method
6、s. 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 contr
7、ol 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.
8、 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 m
9、etal 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 produ
10、ction 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
11、 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
12、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、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 genera
14、ted 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 a
15、nd 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,
16、 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 re
17、quisite 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 o
18、perations 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 o
19、n 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 co
20、nstruction 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 matu
21、re 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 syste
22、m (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
23、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 integ
24、rated 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 eithe
25、r 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 applicat
26、ion 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 statemen
27、ts, 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 ty
28、pical 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 suspe
29、nsion, 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 companys KBE group devised a system th
30、at 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 numer
31、ical 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
32、, 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
33、 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 C
34、APP 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
35、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
