Research On Theory And Key Technologies Of Conceptual Design Based On Product Gene

Conceptual design is the important phase that determines product quality, cost and creativity in the lifecycle of mechanical products. Firstly, the research state-of-the-art and progress of computer aided conceptual design (CACD), product genetic theory and growth design were systematically discussed in this paper. In order to solve the problems existed in the process of conceptual design for mechanical products, the modeling method of conceptual design and the transformation pattern of design knowledge were investigated, the theory and the key technologies for conceptual design automation were studied in full use of genetic engineering thinking and the power of product gene in the field of design knowledge expression and product evolution. So it can be helpful to develop the CACD platform. The research content and contribution are as follows.The decomposition and reconstitution principle and the generalized position principle were investigated, the conceptual modeling technology, conceptual design automation technology and reverse acquisition technology for product gene were analyzed, and the knowledge transformation model and the theoretic framework for conceptual design were proposed. As the smallest unit which has definite functional concept, functional surface is the functional and structural information carrier. It can be taken as the media to formalize the product gene. In order to support the function description and form expression for conceptual products, the concept of functional unit was proposed on the base of describing functional surface and functional pattern with mathematical method. The transformational model of design knowledge was created, according to the characteristics and the informational requirement of product conceptual design. The model includes knowledge representation, knowledge transformation and knowledge acquisition, it can be divided into design information transformation and design process transformation. The system architecture for conceptual design was built and the system framework for CACD was proposed after taking the decomposition & reconstitution principle and generalized position principle as the theoretical basis, the modeling technology, design automation and reverse acquisiton for product gene as the key technologies, the design knowledge base and the CAD platform as supporting environment.The product functional model, product information model and product mapping model for conceptual design were proposed. The product conceptual design model is the descriptive and expressive computer abstraction for design objects and processes, and is the foundation to realize CACD. The product functional model was proposed. The product information model, including functional surface model, part model and product model, was built using object-oriented technology. The model was organized in multilevel to make design information easily understood and processed. The product model (function-functional surface-form) for conceptual design of mechanical products was described with mathematical method and taking functional surface as the medium, then the steady mapping relationship from function to form was realized. The three level process model of conceptual design was proposed, so the designer can think many kinds of schemes and capture design intent at the same time during the processes of function decomposition, functional surface expression and physical implementation. The problems existed in the function to form mapping process were solved well using the proposed models.The design automation technology is the key technology for the implementation of CACD. To express the complex and heterogeneous design knowledge concerned in the conceptual design process, the concept of product gene was proposed and the product gene model was created and the by using the thinking of genetic engineering and referring to the biological gene. The object-oriented definition of product gene was given and the coding scheme with varied length for product gene was describe. The formalization method and evolutionary policy for product gene were proposed using functional surface as the medium to transfer information from function to form in deeper level. The process model and system framework for conceptual design based on product gene was built. The problems exited for knowledge representation and transformation were solved and it was helpful to develop CACD tool.The modeling methods for reverse acquisition and database management of product gene were proposed. The prerequisite and basis to generate new product through gene evolution were to acquire product gene with excellent information composition and establish product gene database. The system function information model for product gene database was described with IDEF method, and the reverse acquisition for product gene was proposed. The main functions of reverse acquisition for product gene include STEP information transformation, ACIS based product modeling, conceptual structure generation, design process reconstitution and product gene expression. The object-oriented technology is good at data operation and process, the relational database is good at data storage and management, in order to have the full use of their advantages, the object-oriented hierarchical model for product data management was proposed based on relational database. The realization method for product gene database and its management tool was created. The problems exited for knowledge acquisition and management were solved well, the establishment of product gene database would support for the design knowledge reuse and product creative design greatly.The product gene based DARFAD (Decomposition and Reconstitution for Automation Design) system was developed on the basis of the proposed design theory and key technologies. The system was developed using object-oriented method and based on ACIS geometrical modeling platform. The main system functions include reverse acquisition of product gene, evolution of product gene, design scheme generation, product gene management and system management. The function decomposition method and product evolution process ware described by taking the mechanical system of numerical controlled milling machine as the example. The proposed theory and key technologies were verified by the development of PGBDARFAD system and design example.