Research On Fault Diagnosis And Localization Method Of Aircraft Wire

With the development of Chinese civil aviation transport service, the modern aircraftequipment has gradually improved to be large-scale and complicated. The wire is animportant device of the aircraft electrical system, which connects the various electricalequipments together and transfers the electrical signals. That its performance is good orbad directly influences the stability of the electrical equipment and the security of theaircraft flight. The short circuit fault, the open circuit fault and the wear fault are thetypical faults of the aircraft wire and will cause that the signal transmission to beabnormal, the indicating instrument to be instable, the mechanical control to be inactiveand the aircraft to be ignitable. Therefore, in order to ensure the safety and continuousairworthiness of the aircraft, the wire fault diagnosis and localization is an importantcontent to improve the quality and efficiency of the civil aviation maintenance repair. Thefunction of this research task is to track the research topics of the international civilaviation and improve the scientific research level of Chinese civil aviation administration.In this paper, in the first place, the material and electrical properties of the wire arestudied based on the thorough research of the reflection technique of the fault diagnosisand localization of the aircraft wire. The rule of the signal in the wire influenced by thevariation of the material structure is put forward. And the relationships between thefrequency of the signal, the structure characteristics of the wire, the material properties ofthe wire, the circumstance temperature and the propagation velocity of the signal arestudied separately. The propagation velocity of the signal is determined.In the second place, in order to improve the accuracy received by the short circuitfault and the open circuit fault diagnosis and localization of the aircraft wire based on thetime domain reflection measurement principle, a control method is proposed. The waveletpacket transform algorithm is used to denoise the reflected signal in order to suppress theelectromagnetic interference of the measuring environment. By making use of themethods of the partial least-squares regression analysis algorithm and thecross-correlation algorithm respectively, the time interval of the incident signal and the reflected signal is identified and the accurate position of the wire hard fault is obtained.In the third place, due to the reflected signal of the wear fault of the aircraft wire istoo weak to detect using the time domain reflection measurement principle, so thetime-frequency combined domain reflection measurement method is proposed todiagnose and locate the wear fault. By emitting an incident signal in the time-frequencycombined domain which is composed of a linear frequency modulation signal and agaussian envelope, the reflected signal of the wear fault is obtained. The fractionalwavelet packet transform algorithm is used to denoise the reflected signal. Then thecross-correlation function of the incident signal and the reflected signal is designed tolocate the soft fault of the aircraft wire.In the last place, the wire fault diagnosis and localization system is designed, ofwhich the industrial control computer is the control core and the LabVIEW is the driversoftware. The whole process of transmitting the incident signal, searching the wire data,denoising the reflected signal, diagnosing and locating the fault is accomplishautomatically. The experiment results show that the proposed methods to diagnose andlocate the hard fault and the soft fault of the aircraft wire are effective and accurate.