Liquid Rocket Engines Qualitative Model-based Fault Diagnosis Method

In this thesis, the qualitative-model-based fault diagnosis methods for a liquid-propellant rocket engine (LRE) are studied in order to provide ones with novel approaches to build the fault diagnosis system, which possesses good robustness, real-time operating ability and practicability. The qualitative-model-based fault diagnosis methods hopefully substitute for quantitative-model-based methods for their limitations of computational complexity, robustness and practicability, and for the traditional rule-based method for its limitations of the acquisition of knowledge and flexibility.First of all, The classification, characteristics, actualities and trends of qualitative-model-based diagnosis are discussed and summaried in this thesis. Then, The fault diagnosis methods including component-model-based approach, the qualitative bond-graph-based method and the causal-temporal-graph-based method are studied respectively. The thesis focuses on the basic principles of fault diagnosis, qualitative modeling of LRE, qualitative reasoning techniques and diagnosis mechanism for LRE.In the thesis, the theoretical foundation of diagnosis based on component is expounded. On the basis of above works, a relation-based diagnosis method is proposed by considering the practical diagnosis problems for LRE, and a diagnosis example is demonstrated. A qualitative-bond-graph-based fault diagnosis approach for LRE is developed based on its advantage on modeling. In the thesis, the bond graph of LRE is constructed, and the mechanism of fault diagnosis based on bond-graph-models is formulated. Then, the fault diagnosis method based on bond-graph-models is studied furtherly. To overcome the disadvantages of diagnosis methods based on static models, a new diagnosis method for LRE based on temporal causal graph (TCG) is developed. The TCG model of LRE is set up, and based on this model the qualitative simulation and diagnosis analysis under abnormal conditions for LRE are carried out. The results show that the theory and methods proposed and discussed provide a theoretical basis for the design and realization of practical LRE fault diagnosis from qualitative point of view.