Study On Key Technologis For Design Quality Of Complex Mechanical And Electrical Products

Design quality is a key source of product quality, and this view has been shared now by more and more experts and manufacturing enterprises. Recently, more and more enterprises pay attention to the product design quality, set the best resource configuration and give the effective way to improve product quality. In view of the Quality Characteristics (QCs) of multi-scale, multi-field, multidisciplinary, evolvability and coupling, the theory of Key Design Quality Characteristics (KDQCs) is applied to the design process of computer numerical control (CNC) machine, then, the techniques and methods of extracting, mapping, optimizing and evaluating of KDQCs are proposed in this study. This paper is supported by"Complex mechanical and electrical products quality characteristic's multi-scale coupling and preventive control"(National Natural Science Foundation, No. 50835008), the National Major Scientific and Technological Special Project for"High-grade CNC and Basic Manufacturing Equipment"(No. 2009ZX04014-016), and supported by Open Research Foundation of State Key Lab. of Digital Manufacturing Equipment & Technology in Huazhong University of Science & Technology. By the theories on KDQCs are studied under the support of these grants, we put forward the solutions for improving the design quality of mechanical and electrical products. Topics covered in this dissertation are as follows:(1) Firstly, this paper introduced the basic theory of key design quality characteristics (QCs) of mechanical and electrical products. Secondly, the key concepts, development and technology of key QCs of mechanical and electrical products are analyzed based on the existing literature. Then, the source, the main works and frame of this treatise are illustrated here. Furthermore, the basic theory of key design QCs for mechanical and electrical products is studied.Finally, based on the research on theory about the formation and its effect on quality of key design QCs, the strategy of quality control of key design QCs are proposed.(2) This paper introduced the multi-scale DQCs of mechanical and electrical products in different subsystem, levels and function, and built the multi-scale QCs model of mechanical and electrical products. Aiming at the complexity of ranking multiple QCs of mechanical and electrical products, the mathematical method of Fuzzy Analytical Hierarchy Process (FAHP) and Information Entropy (IE) is presented, which can effectively solve the uncertain problems such as subjectivity and ambiguity existed in the computational process of some conventional methods. Fuzzy theory and FAHP are introduced to establish the ordering model of multiple QCs. Then, the subjective weights are determined by the method of fuzzy comparison which is expressed by the triangular fuzzy number, while the objective weights of the QCs are obtained by Information Entropy. In addition, the importance of multiple QCs is sequenced by Fuzzy Borda method combining with FAHP and Information Entropy, and finally determined according to the value of fuzzy Borda. The importance sequencing problem is effectively solved by this method based on considering the subjective and the objective together. Finally, a practical example is illustrated to show the rationality and feasibility of the integrated method.(3) Based on the particularity and complexity in the design process of mechanical and electrical products, integrated with the multi-source and multi-stage process of Quality Function Deployment (QFD), this paper increased mapping machining process to identify the elements of machining quality. Then, the user needs and quality requirements (QRs) are mapped into the QCs of mechanical and electrical products, and the product design, manufacturing and using stages are applied to form a closed loop system, so that product quality information is timely, roundly and accurately reflected in the product stages, so as to improve design quality and customer satisfaction. In order to improve the machining accuracy, the accuracy design QCs for mechanical and electrical products should be analyzed and evaluated. This paper studies the transfer relationships between QRs and accuracy design QCs, and proposes a reverse mapping model combines rough set (RS) with house of quality (HoQ) in QFD. RS theory is first applied to simplify and extract the QRs of the machining quality requirements. Then, a novel concept known as approximate accuracy rough number is proposed to determine the final importance weights of the QRs. Furthermore, a reverse mapping model is designed to translate the main QRs into accuracy design QCs, which would help product designers achieve the design goals in product development. The applicability of the proposed reverse mapping model is demonstrated by an illustrative example of CNC machine.(4) By analyzing the specific requirements of multiple DQCs of design scheme for mechanical and electrical products, the design optimization program decision-making process are proposed to ensure the design quality based on multi-attribute index system. In this paper, we propose a novel method combined the improved Technique for Order Preference by Similarity to Ideal Solution (TOPSIS) with Elimination and Choice Translating Reality (ELECTRE) I for reliability design scheme decision of mechanical and electrical products. Based on the improved TOPSIS method and ELECTRE I, the decision model is built to select the optimal design scheme. The improved TOPSIS method is applied to determinate the weights of reliability design factors through the decision model. ELECTRE I method is then designed to rank reliability design scheme in order of decision maker's preference. To evaluate performance of the developed algorithm, an illustrative example of CNC machine is given. The computational results show that the proposed approach is reliable and performs well.(5) The paper analyzed the present application and proposed the evaluation index system model for multivariate QCs of mechanical and electrical products. A comprehensive evaluation method based on fuzzy matter element (FME) analysis is proposed to address problems of multiple performance quality evaluation for mechanical and electrical products. The FME theory is utilized to analyze multi-scale QCs and attributes. Then, the comprehensive quality evaluation model for mechanical and electrical products is founded by using FME analysis method. Analytical network process (ANP) and IE are applied to obtain the objective index weights. Furthermore, the combinational weight is calculated with the optimal mathematics model based on the least square method. Finally, the FME method is used to determine the assessment result. The case study indicated that the method had a certain rationality and feasibility.