The Integrated Theory And Method Of The Principle And Structural Conceptual Design For Mechanical System

The key of product competition consists in the innovative product design,whose key also rests with the conceptual design,so the researches of theory and methods on computer aided conceptual design have become the inevitable trend in today's design techniques.However,the difficulties encountered in the conceptual design- a key link in product design,which consists with principle conceptual design and structural conceptual design, and being incapable of seamless integration between the result of conceptual design and the downstream of design-the detailed design, hinder the realization of computer integrated technology. Taking the mechanical system as the objective of study,a series of going deep into researches are made on the integration of principle motion and structural conceptual design of products in this paper,which is supported by National Natural Science Foundation of China(No.50075012 and 50275016),and the Office of Education Foundation of Liao Ning(No.20060719).Some new ideas,theory,models and methods are developed.The main points are as following:(1)A uniform model used to represent the design requirements of all life cycle is proposed.The generalized basic mechanical unit is defined from the point of view of motion transformation.The state equation, which is used to depict the relations among the input eigenvector , output eigenvector,and the state matrices on the basic mechanical unit,is established.The knowledge base of the basic mechanical units do likewise.The solution method for the principle motion concept is deduced by applying above theories.Because it is difficult to convey unabridged design knowledge to the structural conceptual design and obtain computer solution of the structural concept through the semantic results of the principle motion concept ,the notation of the basic mechanical units ,and the sign algorithm between the basic mechanical units are also put forward. These methods have some merits,such as predigesting the expression of the principle motion concept,avoiding the oversight of the sign concept,establishing the base for the succedent design stage, and acquiring the feasible solutions of the principle motion sign satisfying the actural engineering needs.(2)Analyzing the requirements of computer aided structural conceptual design of mechanical system(CASCD-MS) for the product information model,the concept of element of strongly connected aggregate (ESCA),which is an abstract objects integrating the functions and structure, is proposed,which is taken as a basic unit of a product model in the stage of the structural concept.Based on the ESCA,we can match the top-down and trial-and-true designing idea and solving model of product.(3)The method of the structural conceptual design using the structure of the kinematic pair to describing the framework of mechanical system has been firstly provided after analyzing detailedly the compositive configuration of the principle motion concept.In this method,all kinds of the kinematic pairs are visually expressed as the shafting,whose structural equation has also been established.Thus,the universal methmatic expression of the kinematic pair's structure is come true.(4)The theories and methods about the packing problem and layout design of the shafting on the kinematic pair are put forward.Aimed at the characteristics of the shafting on the kinematic pair,the abstract symbols about the ESCA,which are used to express the function-structure of the shafting on the kinematic pair,are defined,the laying algorithms about these symbols are also established.In order to visualizing the structural concept of the shafting on the kinematic pair,the concept of the strongly connected element aggregate(SCEG),which is the corresponding assembly unit of the ESCA, is brought forward. The concept of the set of strongly connected elements,which is used to represent the assembly structure of ESCA,and the algorithms of the assembly structure about the shafting on the kinematic pair are also defined.Based on above methods,the structure conceptual design about various shafting on the kinematic pair is realized.(5)The knowledge base of structure conceptual design,and the structure state equation on the structural conceptual design are suggested.Using it,the mathematic representation about the structural conceptual design is obtained.The corresponding algorithms of the structural concept are set down.The process of the structural conceptual design containing the abstract and assembly symbles of the mechanical system is completed by changing the values of the transfer function in the structure state equation. A kind of data structures for a structure concept——two-dimensional doubly linked lists,which is used in the layout information transfer,are also proposed.Thus,the layout multi structural concept of the constant and various speed mechanical system are obtained easily.(6)Appling object-oriented technique in representing ESCA and SCEG of product,the object of information intercommunication and step by step perfect at the whole stage of product design is achieved.A new approach is suggested for solving CAx's data acnode. These methods have both theoretical and engineering significance to solve the bottleneck problem on data incompatibility between conceptual design and detailed design.(7)On the basis of the above researches, a conceptual design program on the mechanical transmission system in the state space has been developed based on VC-H-6.0.Some practical examples, which are used in production, are given to show the feasible and effective of the approach in the stage of conceptual design of the mechanical transmission system.