Research Of Fault Diagnostic Method For Spacecraft Propulsion System Based On Directed Graph

The qualitative and semi-qualitative fault diagnostic methods were studied in order to apply them to bipropellant-united propulsion systems of spacecrafts in this thesis. The research works focus on some main techniques of fault isolation and localization including the fault mode analysis, the modeling and analysis based on signed directed graph (SDG), the strategy of qualitative reasoning, and the integration of qualitative and quantitative information.Firstly, fault modes in the process of orbit maneuvering and attitude controlling for bipropellant-united propulsion systems were summarized. 12 main fault modes are obtained as a result.Secondly, the modeling and analytical method based on SDG was investigated along with SDG-based diagnostic strategy. Then, the SDG models of a certain bipropellant-united propulsion system and "Shenzhou" propulsion module subsystem were set up. Some diagnostic results based on these models show that SDG-based qualitative diagnosis methods are effective. They are able to comprise almost all the fault candidates.Finally, to improve the resolution of qualitative diagnosis, the SDG-based methods were modified by two means to integrate quantitative information. One was to develop temporal SDG (TSDG) method. Another was to combine analytical results of the governing equations with the branches of SDG. Diagnostic results were verified by the "Shenzhou" propulsion module subsystem, and show that the methods proposed can improve the resolution of diagnosis effectively.The methods proposed and developed can not only provide a good basis for the design and realization of on-board fault diagnosis and isolation system for bipropellant-united propulsion system of spacecrafts, but also can be available for reference in the development of autonomous control systems of spacecrafts.