Research On System Level Fault Diagnosis And Testability Analysis Techniques For Civil Aircraft

System of civil aircraft is classified as complex systems with heavy sections, the failure of it hascomplex and dynamic characteristics. In order to improve diagnosis efficiency and lower maintenancecosts, it is important to point the fault sources quickly and accurately. This paper was based on thedata information of civil aircraft pneumatic system and studied the testability analysis and assessmenttechniques comprehensive and in-depth from the view of system level.The main work is as follows:1. The concept and scope of the system testability analysis had been elaborated and the researchbackround and the research purposes had been determined.This paper summarized the research statusof the testability modeling methods and test strategies optimization and pointed out the deficiencies ofthe existing methods.2. The multi-signal flow graph modeling method had been introduced in detail. The analysis forthe model’s elements of pneumatic system and the model building process was presented, laying thefoundation of pneumatic system’s testability analysis.3. The testability analysis based on failure-test the correlation matrix had been studied. The paperproposed the extended D matrix in order to improve the traditional D matrix. Baesing on pneumaticsystem’s test model, its extended D matrix was obtained. Then, the system’s testability analysis wasconducted. The result objectively reflected the degree of system testability and troubleshootingfeatures and the result also provided support for the improvement of the system’s testability.4. The diagnostic strategy optimization problem had been studied. In order to improve AO*algorithm’s defect in solving large-scale system with lot of nodes, AO*with discrete Particle swarmalgorithm (DPSO) had been coupled, because of DPSO’s global optimal characteristics. The paperredefined DPSO’s particles, speed and fitness and presented the DPSO-AO*algorithm‘s detailedsteps. Finally, the pneumatic system’s strategy optimization process was presented.5. Integrating theoretical method, a graphical modeling and analysis tool for testability analysiswas developed. The development process and pneumatic system’s modeling and analysis interfacewere presented.The tool was versatile, user-friendly and simple to operate.