Research On Reliability Of Uncertain Multi-statesystem Based On Dynamic Bayesian Network

With the rapid development of modern science and technology,in order to meet the higher needs of Engineering research,the structure of various systems and equipment is becoming more and more complex.The complexity of system composition and operation state will lead to the complexity of reliability analysis,evaluation and optimization.The state of this kind of system breaks through the "two-state hypothesis" of normal and fault.Traditional reliability design and analysis methods can hardly meet the requirements of describing the performance state and fault law of this kind of system.Therefore,it is very important and urgent to study the reliability of complex polymorphic system.In this context,this thesis takes uncertain polymorphic systems with complex basic characteristics at the system structure,operation status,working environment and fault mode as the research object,and evaluates the polymorphic reliability of such systems based on dynamic Bayesian network theory.Finally,the example analysis is completed.What's more,considering the fuzziness of component failure state and failure rate,the fuzzy dynamic Bayesian method is used to complete the system's fuzzy dynamic reliability analysis.The main content of this thesis is as follows:(1)Focusing on the reliability analysis of complex polymorphic system,the characteristics and limitations of the traditional modeling method for the dynamic reliability are first reviewed and summarized,and the reliability modelling for the stochastic polymorphic system is then adopted based on dynamic Bayesian network in order to meet the demand of reliability evaluation and identification of weak link in the system.The quantitative analysis of DBN can be carried out along two lines,that is,forward(or predictive)analysis and reverse(or diagnostic)analysis.Therefore,the method proposed can not only implement the reliability pre-measurement accurately,but also carry on the fault diagnosis.(2)Based on the reliability analysis method of multi-state system proposed above,taking the deployment mechanism of satellite antenna as the object,the structure and working principle of the system are analyzed,and the reliability functional block diagram of the system is drawn.According to the analysis results,the reliability model of the system is constructed by combining structured analysis and design technologies(SADT)and failure modes and effects analysis(FMEA)methods.The state transition process of each component of the system is represented by Markov process,and the DBN qualitative modeling of the system is completed.Then the parameters of the system model,such as prior,posteriori and conditional probability table(CPT),are determined.Finally,through programming and simulation,the reliability change process of the system is obtained,and the weak links in the system are identified.According to the analysis results,some modification suggestions are put forward to provide theoretical reference for the design stage of the system.(3)The reliability research method of fuzzy polymorphic system based on fuzzy dynamic Bayesian network(FDBN)is adopted.Fuzzy set theory and DBN are combined to model and analyze the system's fuzzy reliability.Firstly,the SADT model of the system is established and the FMEA analysis is carried out,then the DBN model of the system is constructed;after the fault state and failure rate of the node are represented by fuzzy number and fuzzy subset respectively by introducing the fuzzy set theory,the FDBN model for the system is completed.Moreover,aiming at the radar lifting system,the fuzzy dynamic reliability of the system is evaluated and the fault diagnosis is carried out,which verify the validity of the method proposed.With this method,the situation that the component failure rate is difficult to express due to the lack of historical data and the change of the system storage environment can be addressed.