Research On BIT False Alarm Reducing And Fault Prediction Technologies Based On Time Stress Analysis

The high False Alarm Rate (FAR) in Built-in Test (BIT) and low fault prognostics ability of equipments are two common key problems in the fault diagnosis field. They directly prevent BIT and fault prognostics system from more extensive application. In recent years, with some new conceptions such as Prognostics and Health Management (PHM) appearing, how to reduce FAR of BIT and improve the fault prognostics ability become more and more important.The time stress include all kinds of environment and operating stress such as shock, vibration, temperature and so on that the equipment suffered in the manufacture, transport and operating process. On the one hand, the real-time time stress is the main factor that disables system temporarily and incurs the BIT false alarms. On the other hand, the time stress directly induce degradation or deviation of the components from an expected normal condition. Therefore, analyzing the time stress can reduce false alarms of the BIT and improve fault prognostics ability effectively.This paper is aiming to solve the two problems of BIT's high FAR and equipment's low fault prognostics ability in fault diagnosis field. The mechanisms of the faults and BIT false alarms induced by time stress are analyzed systematically. Then, the BIT false alarm reducing and fault prognostics technologies based on time stress analysis are studied.The main contents of the dissertation are as follows.1. The mechanisms of how the time stress induces faults and BIT false alarms are analyzed systematically and some relative models are built.Firstly, the mechanisms of the faults and BIT false alarms induced by time stress are analyzed in detail. In order to analyze the relationship between time stress and BIT fault alarm, a relevance analysis model based on Support Vector Machine (SVM) is built. The model can acquire the main time stress region that induces the BIT false alarms. Secondly, a dynamic description damage model is researched based on Generalized Stochastic Petri Nets (GSPN). This model can analyze the evolution relationship between time stress and component's damage. Finally, a probability fault evolution model based on Hidden Markov Model (HMM) is studied. This model can analyze the evolution process of component's fault.2. The BIT false alarm reducing technology based on time stress analysis is studied.(1) Two relevance analysis methods between time stress and BIT false alarm based on Failure Mode, Effect and Stress Analysis (FMESA) and logistic regression are studied. These two methods can analyze the main stress factor that induce BIT false alarm from qualitative and quantitative aspects. In order to acquire the optimization threshold values of the relevance analysis model between time stress and BIT false alarm, the threshold values optimization selection method is discussed in detail.(2) A false alarm recognition method based on SVM and time stress analysis is studied, and it can recognise the false alarms in the time stress relevance region. But this method can not recognise the real faults in the time stress relevance region and the false alarms out of the time stress relevance region effectively. In order to solve the first problem, a false alarm recognition method based on SVM-HMM and time stress analysis is proposed. In order to solve the second problem, a false alarm recognition method based on Kernel based Principal Component Clustering Analysis (KPCCA) and HMM is studied. Finally, a synthetical false alarm recognition method based on SVM-KPCCA-HMM and time stress analysis is proposed. And it can recognise the false alarms and real faults in the whole time stress region.3. The fault prognostics technology based on time stress analysis is studied.(1) An accumulative damage assessment method based on component's failure models and Multi-component Life Consumption Monitoring (MLCM) is studied. Then, the accumulative damage assessment methods of joint and separate components are studied in detail. It can transform the time stress suffered in the life time into equipment's damage.(2) Considering the history current of damage and the abrupt change affection of time stress, a fault prognostics method based on dynamic optimization auto-regression (AR) model and multipoint damages is studied. Because there are some uncertainties in the damage assessment process, a fault prognostics method based on optimization AR model and HMM is proposed. This method can improve the accuracy. The experimental results show that this method has a higher degree of confidence.4. The BIT false alarm reducing and fault prognostics technologies based on time stress are applied and validated.In order to evaluate the efficiency of the BIT false alarm reducing and fault prognostics technologies, a PHM system for heading attitude system of the helicopter is built and implemented. Then, some time stress experimental studies on the heading attitude system are executed. The results show that BIT false alarm reducing technology in this paper can reduce false alarms of BIT effectively, and the fault prognostics technology has a good fault prognostics effect.