Research On Conceptual Design Modeling And Solving Strategies Of Mechanical Products

Conceptual design is increasingly and extensively considered as a key activity during the product design process. The traditional modeling techniques are mainly focused on physical modeling and geometric representation, so it makes the conceptual design of products not obtain effective technique support. The conceptual design scheme generation model and solving strategies, description model of conceptual design product, qualitative space configuration design are deeply researched from some key problems of conceptual design such as process modeling and product description. The purpose of this paper is to achieve the design schemes and provide effective design information for subsequent design process. The main research works and conclusions include: (1) To the main object——function dealt with during the product conceptual design, standard functional basis(SFB) for product functional modeling is expatiated, and a comment on the applied mapping strategies for shceme generation is made. Qualitative space configuration design is taken into consideration in the conceptual design process, then the product conceptual design framework is built up from the aspects of conceptual design process model, conceptual design product(CDP) description model and the system of computer-aided conceptual design, and the research contents of these models included in the conceptual design are bounded. Conceptual design process model is composed of design specification mapping model, conceptual design scheme generation model, conceptual design scheme evaluation model and spatial configuration generation model. CDP description model includes product requirement model, function structure model, behavior structure model, structure scheme model and configuration scheme model. The proposed conceptual design framework lays the foundation for scheme(structure scheme, configuration scheme) generation and subsequent design process. (2) SFB-based conceptual design scheme generation model of mechanical product is built up. The function layer is composed of meta-function layer and function object layer, and the structre layer is composed of structure component layer and structure relation layer in this model. The flexible and manifold mapping strategies are proposed to complete mapping from function to structure according to actual circumstance. The definition and the content of motion function transforming and transferring unit (FTU) is given. The knowledge base of FTU for solving motion scheme is set up adopting coding technique to give the FTU's code of the behavioral feature, input/output behavior relation and structure relation. The hybrid reasoning approach based on redefinition of design specification and problem solution is proposed to solve the motion sub-function of mechanical system. The controlling strategy is adopted to prevent scheme explosion in the process of scheme generation. After discussion about the problem of the design features clustering and establishment of the design features coding system, the design features are clustered applying FCM clustering arithmetic to improve the computer search efficiency in the scheme generation. (3) In the CDP model, the primitive components represented by certain symbol are connected each other to complete a certain of function, so the design features used to constitute CDP are classified into two categories: primitive component and primitive joint. The definition of entity joint and non-entity joint in the primitive joints is given and the primitive joints are classified. The hierarchical structure P/T model based on primitive component-primitive joint and P/T model including energy flowing are set up. In order to ensure function realize, the P/T model including energy flowing is used to simulate the operating status of CDP. Conceptual design product modeling should be not only describe the function, behavior and structure of conceptual design sheme, but also represent the design knowledge, relation included in the scheme, so the design information representation relation network of CDP is constructed. Therefore the mathematic description of CDP is constructed in order to represent in computers. This representation is convenient to store and manage the product design information. (4) Spatial configuration is a very important attribute during the mechanical product design. The qualitative spatial configuration design is brought into the category of conceptual design. The methodology of combining qualitative vectors with screw representation is proposed to solve the configuration design of complicated mechanical system in 3-D space. Every unit is represented by abstract graph during configuration design stage. The representation of the qualitative input and output screw and characteristics of spatial configuration about each FTU are given. The configuration solution space, satisfying given requires, is acquired through reasoning and computation. An efficient methodology is proposed to deal with the configuration design of mechanical systems. (5) In order to realize and validate the thought and methodology proposed in this paper, the primitive system of mechanical system conceptual design——MSConDesigner is developed, and the practice application is discussed.