共查询到20条相似文献,搜索用时 140 毫秒
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轴流压气机失速特征识别 总被引:1,自引:2,他引:1
为了能够准确识别压气机旋转失速过程中失速团的数目,将压气机旋转失速过程中脉动压力波动的相位和幅值特征绘制在极坐标中,然后根据其在极坐标图中表现出来的特征来确定失速团的数目.经过与传统方法对比说明该分析方法对于失速团数目的确定优于原有的方法,具有抗噪性和一定的精度.另外,使用该方法可以可视化周向失速分布区域,并能可视化压气机失速先兆的发生和发展. 相似文献
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基于模态波理论的压气机失速先兆识别方法 总被引:2,自引:2,他引:0
针对压气机气动失速预警存在无法兼顾对渐进型和突尖型失速先兆有效识别的不足,以及提取失速团幅值需要多路传感器信号的局限。分析了压气机失速发展过程中的信号特征;根据压气机失速信号的旋转特性,提出基于单路传感器信号重构周向多路失速先兆信号的方法,讨论了信号重构步长的取值;基于模态波理论,通过对重构信号进行空间傅里叶变换,得到失速扰动信号各阶模态幅值,根据低阶模态的幅值变化实现对渐进型与突尖型失速先兆的识别。以某压气机为例进行仿真,结果表明:当信号重构的步长小于突尖波时间尺度的一半时,重构的多路信号能够复现压气机周向位置失速发展过程,且步长越小,越有利于失速先兆的识别;由模态分解得到的1阶模态幅值的变化能够有效反映失速发展过程;通过合理设置模态幅值的阀值,可以在失速发展前期对失速先兆进行准确识别,从而,基于单路传感器失速信号即可实现对渐进型失速和突尖型失速均能进行预警。 相似文献
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采用时频-小波分析法对某型发动机的八级轴流压气机级间压力信号的失速先兆及发展信息进行了分析,检验了失速时刻信号的奇异值。结果表明,在失速前的阶段,不同的频率段表现出不同的失速先兆成分。 相似文献
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基于时频-小波分析的压气机失速过程研究 总被引:6,自引:0,他引:6
采用时频—小波分析的方法,针对某型发动机的八级轴流压气机级间压力信号,提取失速先兆及发展信息。结果表明,在失速前的阶段,不同的频率段表现出不同的失速先兆成分;并检验了失速时刻信号的奇异性,最后确定了最先失速级。 相似文献
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失速团动态演变特性试验 总被引:1,自引:1,他引:0
对一台单级低速轴流压气机进行了节流特性试验,通过周向布置动态压力传感器测得了节流过程的动态压力信号,结合时域、频域及极坐标可视化的分析方法,研究了节流过程的失速团动态演变特性.结果表明:失速先兆类型为模态波失速先兆,其传播频率约为40%转子转动频率;压气机进入失速初期349.5r时周向形成两个失速团,360r时两个失速团合并为单个失速团,压气机进入深度失速时单个失速团重新分裂并在410r时稳定为两个失速团;压气机退出失速的过程中,665r时两个失速团重新合并为单个失速团,674.5r时压气机退出失速. 相似文献
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基于小波分析的发动机惯性起动失速信号检测方法研究 总被引:1,自引:0,他引:1
针对某型涡扇发动机惯性起动失败,利用小波Mallat算法对采集到的风扇和压气机脉动压力信号进行快速高频滤波,通过对滤除高频噪声的信号进行傅里叶频谱分析,准确检测出发动机起动失败时的失速信号。研究结果表明,利用小波分析方法进行失速故障检测简单、直观,具有一定的工程实用价值。 相似文献
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Multiresolutional filtering using wavelet transform 总被引:1,自引:0,他引:1
An algorithm for optimal and dynamic multiresolutional distributed filtering is derived. The wavelet transform is utilized as a bridge linking signals at different resolution levels. The algorithm can be employed for dynamic multisensor/data fusion 相似文献
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Hough transform for long chirp detection 总被引:1,自引:0,他引:1
The online detection of a very long and weak chirp signal is studied. The signal has an extremely slowly decreasing frequency, and is corrupted by white Gaussian noise and possibly also by powerful tones. By exploring and comparing candidate methods, it is found that the Hough transform (HT) detector appears to be most suitable given constraints on computational load and detectability. The analytical and the simulational performance of the HT detector are obtained and compared with the analytical performance of the generalized likelihood ratio test (GLRT), which is assumed to be optimal. Applying a suitable threshold for the HT can increase speed dramatically while preserving performance. We have found that both dithering (taking varied frequency shifts for fast Fourier transforms (FFTs)) and increasing the FFT length can reduce the minimum detectable frequency slope with nearly no additional computation 相似文献
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孙磊 《沈阳航空工业学院学报》2007,24(2):24-25
培养人们对三维几何形体及相关位置的空间逻辑思维能力和形象思维能力,是工程图学研究的主要任务之一。用投影变换来帮助学习者培养空间想象能力是学习中必用的手段和方法。讨论了工程图学研究过程中投影变换时如何合理、有效地利用有限空间来构建板图、如何恰当选择例图的方法等问题,同时提出了书中用图的不足及改进方法。 相似文献
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McGoey-Smith A.D. Vant M.R. 《IEEE transactions on aerospace and electronic systems》1992,28(3):666-674
When the basic step transform algorithm is used to compress synthetic-aperture radar (SAR) signals in azimuth, the linear FM rate and sampling rate must satisfy certain tight constraints. In practice, these constraints cannot be satisfied and errors are introduced into the compressed SAR image. A modification is described of the basic step transform which incorporates interpolation and resampling into the algorithm. These changes allow the removal of the constraints and make the step transform more useful for the compression of real data. An autofocusing capability is also included, without introducing much additional complexity 相似文献
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Canonical transform for tracking with kinematic models 总被引:1,自引:0,他引:1
A canonical transform is presented that converts a coupled or uncoupled kinematic model for target tracking into a decoupled dimensionless canonical form. The coupling is due to non-zero off-diagonal terms in the covariance matrices of the process noise and/or the measurement noise, which can be used to model the coupling of motion and/or measurement between coordinates. The decoupled dimensionless canonical form is obtained by simultaneously diagonalizing the noise covariance matrices, followed by a spatial-temporal normalization procedure. This canonical form is independent of the physical specifications of an actual system. Each subsystem corresponding to a canonical coordinate is characterized by its process noise standard deviation, called the maneuver index as a generalization of the tracking index for target tracking, which characterizes completely the performance of a steady-state Kalman filter. A number of applications of this canonical form are discussed. The usefulness of the canonical transform is illustrated via an example of performance analysis of maneuvering target tracking in an air traffic control (ATC) system. 相似文献
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Sanchez-Avila C. Sanchez-Reillo R. de Martin-Roche D. 《Aerospace and Electronic Systems Magazine, IEEE》2002,17(10):3-6
A biometric identification system, based on the processing of the human iris by the dyadic wavelet transform, has been introduced. The procedure to obtain an iris signature of 256 bits has been described, as well as the feature extraction block and the verification system. The results have shown that the system can achieve high rates of security. 相似文献
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Joint time-frequency transform for radar range-Doppler imaging 总被引:5,自引:0,他引:5
Conventional radar imaging uses the Fourier transform to retrieve Doppler information. However, due to the complex motion of a target, the Doppler frequency shifts are actually time-varying. By using the Fourier transform, the Doppler spectrum becomes smeared and the image is blurred. Without resorting to sophisticated motion compensation algorithms, the image blurring problem can be resolved with the joint time-frequency transform. High-resolution time-frequency transforms are investigated, and examples of applications to radar imaging of single and multiple targets with complex motion are given 相似文献
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Huang Shunji Wang Jianguo Qiu Hueizhong 《IEEE transactions on aerospace and electronic systems》1991,27(6):865-868
A fast algorithm is presented which computes the two-dimensional Hartley transform. This algorithm is referred to as the split vector radix algorithm. It uses the decimation in frequency decomposition and, due to its in-place property, it does not require midmemory devices or matrix transposition. Its computational structure is simpler than that of the algorithm of L.Z. Chen (1983), and it is easy to program. Compared with the vector radix algorithm of R. Kumaresan and P.K. Gupta (1986), the proposed algorithm saves about 35% of the multiplication and 10% of the additions for the discrete Fourier transform (DFT) of a 4096*4096 real valued input sequence.<> 相似文献
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小波分析已经成为目前雷达信号去噪的主要方法之一。通过对小波去噪问题的描述,揭示了小波去噪的滤波特性;分别阐述了目前雷达信号检测中常用的4类小波去噪方法并进行性能分析;对雷达信号的小波检测方法提出了展望。 相似文献