Research On Computer-Aided Method And Technology For Generalized Execution Mechanisms In Conceptual Design

Conceptual design is at the early stage of design, and also the most important and the most innovative stage. Statistics show that only about 5% conceptual design cost determines 85% product cost, 70% product quality. On the other hand, with the development of modern machinery, mechanisms are integrated kinematic chain between the rigid body and non-rigid body. Due to generalized execution mechanism(GEM) is the key part of electromechanical product, it's significant to put much effort on the study of its conceptual design theory and method.Design activity at any stage should be carried out on the theme of product function. In the view of computer-aided analysis, descriptive conceptual design process model is proposed in this dissertation. Related computer-aided analysis method and technology is studied, providing with computer technology support for conceptual design realization of generalized execution mechanisms. For the above ideas, this paper covers the following areas:1. The study of process modeling of computer-aided GEM conceptual design is carried out. For the conceptual design process should be specific rather than universal, process model of GEM conceptual design is built with the use of hierarchical refinement by describing design tasks in different stages, as well as the realization of computer-assisted technical support. The characteristics of the process model and related research methods, as well as technology support are given in detail, providng with theory guidance for the study of GEM conceptual design.2. A novel approach is put forward to analyze and forecast importance of product function requirements based on subjective & objective synthetic method and combination forecasting model. Customer requirements on product function are classified into basic function, principal function and surprise function in the view of analyzing representation forms of product function in customer requirements from function design standpoint; importance weights of requirement characteristics are determined by AHP, information entropy and mean square; importance weight variation of requirements is predicated by modeling regression analysis, grey theory and BP neural network combination forecasting model. 3. Function representation method based on XML&RDF is studied. Design information is divided into functional data and functional semantics, functional data is expressed by using XML; functional semantics is expressed by using RDF; data structures of two parts are defined. Function basis is introduced for describing function semantincs. In order to extend utility of functional data and functional semantics, functional information schema and functional semantics resource based on XML Schema and RDF Schema are defined respectively for ensuring its syntax validity and structure precision.4. Knowledge base modeling method of GEM is studied. Objects of GEM are represented by classification and coded based on GEM function solving framework. Knowledge base of function unit, function mapping and mechanism is built by applying relational database. Complicated data is decomposed by simple tables and their relations. Forward and backward combined reasoning is designed and discussed.5. Model base of generalized execution mechanisms is built based on Simulink and SimMechanics. By dividing GEM into executive mechanism and drive component, executive mechanisms library and drive components library are constructed respectively. Model interface of executive mechanism is encapsulated by using mask technology and defining basic parameters as variables. GEM simulation model is easy to be created rapidly by the two following approaches: searching and applying models for scheme directly; decomposing and combining similar models mannually.Finally, knowledge base indexing technology, mapping technology from user domain to function domain, hierarchal knowledge representation technique are studied based on analysis of existing design software. Scheme generation scope is determined with the discussion of applicability selection of various software tools. Software platform FDPGEM is built by introducing key integrated technology. A case study of ship-borne mobile executive body is analyzed by simulation.