Research On Evolutionary Creative Design Based On Population Of Product Cases

Product creative design, especially the computer aided creative design is just in the ascendant now. After analyzing the history, present and future of product design, especially that of the product creative design, aiming at some main existent problems in this research area, through contrasting the way of heredity and evolution of living creatures, the genetic engineering technique, and combining case-based reasoning technique and evolutionary computing technique, the rapid intelligent evolutionary creative design theories and method based on population of product cases is proposed in this thesis, and a thorough research is made on computer aided product scheme creative design specially. The main research results and contributions are as follows:1. The product scheme design is the most creative phase in the whole product design process, but it is still a bottleneck because of having difficulty in obtaining knowledge by using traditional design method. Through contrasting the heredity and evolution of living creatures, the concept of population of product cases is proposed. The characteristics, division and establishment of population of product cases are researched and the relationship between population of product cases and product family is analyzed. These works prepare good preconditions for the management and modeling of population of product cases, the product gene extracting and the product evolutionary design.2. Product information modeling and reasoning technologies are the key technologies for computer-aided creative design. Multi-dimensional creative design view map product model based on population of product cases is proposed, which support product design in whole product life cycle. This product model can represent product information in multiple aspects and views, and support all applications of each related stages in the whole life cycle of product, overlaid from product design, process planning design, manufacturing, maintenance, discarding to recycle etc. This kind of model lays a solid theoretic foundation for the product multi-dimensional creative design.3. The three dimensional view map product model based on population of product cases is founded further, which support product scheme creative design. A complete research is carried on the function, principle and structure view. The hierarchical-decomposition representing method of product cases and populations is presented and the representing information of the knowledge in product cases is analyzed in detail, and the product case tree is set up using object-oriented method. This provides an effective method for completely expressing the hierarchy, decomposition, heredity and dynamic change of a complicated product design. It makes a physical foundation for extracting the product gene and realizing the product scheme evolutionary creative design further. 4. The emergence of evolutionary design method based on evolutionary algorithms makes automatic case-based design available. The representation and acquisition of product gene is the kernel of product evolutionary design. A new methodology of product gene representation and acquisition from population of product cases is proposed. Product gene is the basic information unit that decides product characteristics and forms. It is composed of the function base, principle base, structure base, and material base, which are formulated by scheme design knowledge extracted from product cases in populations. It decides the principle solution of product. And the product gene tree is established by using object-oriented method. The product gene can be distinguished into four types of gene: energy, movement, material and signal. This kind of method addresses the difficulty of acquiring design solution in the phase of scheme design process in traditional product design process. This provides an effective means of acquiring the product gene quickly. This design method will be helpful in the processing of knowledge formulation, heredity, accumulation, and reuse. Then combining this with the evolutionary reasoning technology, an automatic and intelligent evolutionary product scheme design based on population of product cases can be realized.5. The design of evolutionary operator and fitness function is the key point for automatic evolutionary design. New improved evolutionary operators such as selection, crossover and mutation operators are presented for the evolutionary individuals that have the product gene tree structure form. New insert, delete and comparison operators are designed for the individuals of tree structure form. And special fitness function is designed aiming at the product evolutionary design, which is a multi-targets optimization problem. The evaluation criteria and the evaluation method of the product scheme design are given out and the process model of product scheme evolutionary creative design based on population of product cases is built up, which can constitute various evolutionary mode satisfying different design requirements. By optimizing the design scheme in multiple levels and aspects of product function, principle, and structure etc., the level of creativity in the scheme design can be improved.6. A rapid intelligent evolutionary creative design prototype system based on population of product cases is developed. The feasibility and validity of the theory and method are proved through design examples. The prototype system is composed of seven modules: product customization system, population of cases system, evolutionary design system, knowledge management system, system control center, CAD system and product data center. The customization management system based on WEB can let customers to customize products remotely through internet, and communicate with designers online at real time. The population of product cases management system is responsible for an establishment and management of product cases and populations. Evolutionary design system is responsible for extracting product genes and establishing product gene tree, managing evolutionary algorithms and evolutionary operation, and realizing product design mission in the end. The knowledge management system is used to establish the product knowledge base including the general used design knowledge and product case related knowledge. The CAD system is used to build the 3D models of product cases. The system control center is responsible for responding to various events of the system through message transmission mechanism and active responding mechanism with ECA rules to control the system running and evolving progress. The product data center can manage various databases, providing the data support for each system, realizing unified data environment integration.