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321.
Arc fault detection is desperately required in Solid State Power Controllers (SSPC) in addition to their fundamental functions because arcs will provoke growing harm and threat to aircraft safety. Experimental study has been done to obtain the faulted current data. In order to improve the detection speed and accuracy, two fast arc fault detection methods have been proposed in this paper with the analysis of only half cycle data. Both Fast Fourier Transform (FFT) and Wavelet Packets Decomposition (WPD) have been adopted to distinguish arc fault currents from normal operation currents. Analysis results show that Alternating Current (AC) arcs can be effectively and accurately detected with the proposed half cycle data based methods. Moreover, experimental verification results have also been provided. 相似文献
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综合考虑软件和硬件对空管自动化系统可靠性的影响,建立空管自动化系统故障树模型,并进行定性和定量分析,确定影响系统可靠性的关键因素。结果表明,该方法有利于保证和提高系统的可靠性。 相似文献
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Houria Yagoub Ahmed Hafid BelbachirNoureddine Benabadji 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2014
Satellite data, taken from the National Oceanic and Atmospheric Administration (NOAA) have been proposed and used for the detection and the cartography of vegetation cover in North Africa. The data used were acquired at the Analysis and Application of Radiation Laboratory (LAAR) from the Advanced Very High Resolution Radiometer (AVHRR) sensor of 1 km spatial resolution. The Spectral Angle Mapper Algorithm (SAM) is used for the classification of many studies using high resolution satellite data. In the present paper, we propose to apply the SAM algorithm to the moderate resolution of the NOAA AVHRR sensor data for classifying the vegetation cover. This study allows also exploiting other classification methods for the low resolution. First, the normalized difference vegetation index (NDVI) is extracted from two channels 1 and 2 of the AVHRR sensor. In order to obtain an initial density representation of vegetal formation distribution, a methodology, based on the combination between the threshold method and the decision tree, is used. This combination is carried out due to the lack of accurate data related to the thresholds that delimit each class. In a second time, and based on spectral behavior, a vegetation cover map is developed using SAM algorithm. Finally, with the use of low resolution satellite images (NOAA AVHRR) and with only two channels, it is possible to identify the most dominant species in North Africa such as: forests of the Liege oaks, other forests, cereal’s cultivation, steppes and bar soil. 相似文献
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通过分析自动速度刹车系统有关部件的受力情况,从力矩传递的角度分析速度刹车手柄自动伸出慢或伸出不完全的原因,以便快速准确地排除故障。 相似文献
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针对某型涡桨发动机减速器负拉力试验不合格故障,分析了负拉力传感器的结构特点和影响因素,建立了故障树开展故障排查,明确了故障原因,提出了改进措施。 相似文献
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基于定性模型的诊断方法,由于无需系统定量模型,尤其适用于航天器等复杂系统的故障诊断.该方法推理过程包括冲突集的确定及诊断集的生成.基于BHS-树的方法,是一种由冲突集生成诊断集的有效途径,但存在诊断结果冗余及反向递归过程复杂的问题.采取异常/正常特征量相结合的措施,有效地解决了诊断结果冗余的问题,能够准确确定诊断集;同时在系统单故障的假设前提下,对反向递归过程进行适当简化,降低了推理的复杂程度,并通过实例对上述改进进行了验证. 相似文献