Research On Conceptual Design Method And The Similarity Of Variable Function Mechanical System

General mechanical systems are usually only has one or some fixed function, but in some certain circumstances, this kind of system can’t meet the need of application, such as the situation like limited of resource and area, and asked to make the upgrade of system is convenient. In this paper, a mechanical system of variable function was put forward by changing the structure of connection or the way different parts combine to get a new function. The variable of the system is based on the invariant of certain firmware, which means the new system by change the local component and the former system must have a certain similarity. In view of this, the similarity of variable function mechanical system was researched in this paper. The communication in time and space of function, behavior and structure of the mechanical system, the expression form of similarity and similarity measurement model was studied, and the related influence factors for similarity was analyzed, the problems in the conceptual design of interface were discussed as well.On based of the thesis of “functional-behavior-structure(FBS)”model, this paper firstly discussed the function decomposition process by using function tree model, clear the function relationship and the logical relationship, temporal relationship in the behavior process, etc., carry on the design solution according to the mapping of function, behavior, structure and reasoning knowledge.Then the system concept design model was built based on the parallel FBS model framework, and combined with the similarity theory, this paper defined the function sequence structure and the behavior sequence structure, then analyzed their composition relationship, expounded the concrete steps of the similar expression model’s construction. With examples illustrated that the model building comply with the design cognitive process and the description for similarity were reliable. Realized the similarity measure for each design layer, and the feasibility of the method was validated.Then, on the basis of the above work, further application of the theory of domain ontology on concept similarity computation was studied. The method for calculating the attribute similarity and relation similarity were analyzed, and combining with the attributes and relations similarity calculate the concept similarity.Finally, the influence factors of system similarity were analyzed. The system coupling factor and connection of sharing component have impact on system similarity and variable function design. Summarized the connection of shared artifacts, and put forward the necessity of expression aimed at function connection. In order to study the interface of the mechanical system in the composition and expression form of it, the concept of interface function meta-model was put forward. Nine categories including connection, separation, conversion, amplification, reduction, axis movement conversion, movement way conversion, etc. were illustrated. Several situations of function transformation were analyzed to establish an interface model of the mechanical system. On the basis of the design process framework, a case study of an automatic cleaning device was conducted by developing the interface function meta-model to demonstrate the practicability and feasibility of the proposed methodologies.