Multi-State Reliability Analysis For Electromechanical System Based On Dynamic Bayesian Network Theory And Software Development

As an important performance indicator of electromechanical products, reliability is closely related to customer satisfaction and enterprise's economic efficiency. In traditional theory of reliability, components or systems follow binary logic. Since the functions and structures of products are becoming more and more complicated, traditional reliability theory cannot describe the practical states of components and lack sufficient ability to assess the reliability of complicated electromechanical systems.In this thesis, Dynamic Bayesian Network (DBN) theory is used to assess the multi-state reliability for electromechanical systems, by combining the Failure Mode and Effect Analysis (FMEA) and Structure Analysis and Design Technique (SADT), on the basis of probability theory. Case studies are conducted to illustrate the applicability of proposed models. On the basis of mathematical modeling and case studies, a multi-state reliability assessment software package is developed by employing DBN theory. Moreover, the software package is used to analyze practical cases for validation. The major work is as follows:(1) DBN theory is used to analyze the reliability of complicated systems and identify their reliability bottlenecks. Based on FMEA and SADT, the leveling system is divided into several modules, and the possible failure modes, failure causes and their effects of its components are analyzed. Besides, SADT analysis diagram of the leveling system is developed. On this basis, the DBN model is established. Then, the system reliability is assessed thanks to the DBN's ability of forward reasoning, and the reliability bottleneck is identified by using the backward reasoning ability of DBN.(2) Choosing electromechanical servo systems as the main object, the basic reliability databases are developed after data collection. The procedures of reliability analysis based on DBN are modification and simplified. Microsoft Foundation Classes (MFC) are used as development tools to develop software package for multi-state reliability assessment of electromechanical systems. In addition, the development ideas, and the design and realization of software interface are introduced Furthermore, a case is calculated and analyzed by the software, and the effectiveness of the software is demonstrated.(3) The electromechanical system of pedestal is considered as object of the study. Based on analyzing the structure and functions of the system, FMEA and SADT analysis are performed, and the SADT analysis diagram is built. The DBN model of this system is established in the developed software, and the reliability analysis is conducted. Finally, by comparing with the actual situation, the applicability of the software is therefore validated.In this paper, multi-state electromechanical systems are chosen as main objects, investigation on the multi-state reliability assessment based on DBN theory is carried out, and the corresponding cases studies are conducted. In addition, a multi-state reliability assessment software package is developed for engineering application on the basis of simplification and modification of the approach. The software simplifies the procedure of multi-state reliability assessment for complex systems. Reliability analyses of this kind of electromechanical systems are facilitated by the developed software.