Research On Integrated Diagnosis Expert System For Wear Faults Of Aircraft Hydraulic System

Aircraft hydraulic system is the important composing part, and it mainly offers controlling power for airplane control system, landing gear system and thrust reverser etc. The faults of the aircraft hydraulic system will affect the normal operation of the aircraft, and it even lead to the disastrous aviation accidents. Therefore, it is very important to integratedly monitor the operation condition of the aircraft hydraulic system in time, give maintaining decision-making so as to prevent future faults and timely repair and maintain the hydraulic system. But because the oil sample analysis methods have the characteristics, such as indeterminacy, inconsistency, randomicity and redundancy, it is difficult to determine the faults of aircraft hydraulic system by using single method. So, in this paper, an aircraft hydraulic system integrated monitoring expert system is studied.(1)The working principles of the typical aircraft hydraulic systems which include energy sources subsystem, flag control system, drag plate, cargo cabin door and elastic door etc are expounded; Further, the main oil sample analysis methods of Particle Counting Analysis, Ferrograph Analysis, Spectrometric Analysis and physicochemical Analysis etc and their application in hydraulic system contamination monitoring are introduced.(2)A case-based reasoning method of hydraulic system is developed. Firstly, the expert system searches and obtains the sub- comparability in every sub-case database; afterward, it integrates all sub- comparabilities to compute and obtain the total comparability; finally, according to the total comparability obtained, it sorts the correlative cases so that the maintaining personnel make decision-making easily.(3)A Multi-agent collaborative diagnosis method for monitoring the conditions of aircraft hydraulic system is put forward. This method can synthetically use the redundancy and complementary of every oil sample analysis methods, achieve integrated diagnosis of many oil sample analysis methods and effectively use the characteristics and advantages of every oil sample analysis methods to improve diagnosis precision. The expert system is composed of contamination analysis agent, physicochemical analysis agent, ferrograph analysis agent, spectrometric analysis agent and integrated diagnostic agen which is charge of controlling and managing other agents for collaborative diagnosis. In this paper, according to the actual situation of aircraft hydraulic system diagnosis, every agent diagnosis rules are given, and the test results of specific data of the oil samples show the effectiveness of the multi-agent collaborative diagnosis.(4)Because the trend of wear increases with time lapsing, the grey system theories can accurately forecast the growing trend of the wear. This paper uses the model of GM(1,1) to forecast and analyze the wear trend of aircraft hydraulic system, and enumerates computing examples to validate the analysis results.(5)In this paper, an Aircraft Hydraulic System Integrated Monitoring Expert System is developed by using the development tools of Microsoft Visual C++6.0 language and Microsoft ACCESS 2000database. The whole structure of the system is constructed, and the functions of multi-agent collaborative diagnosis, case integrated diagnosis and grey forecasting etc are realized. Finally, the validation and analysis are carried out and the results show the validity of the diagnosis of the expert system.