An improved EWT method for fault diagnosis of rolling bearings
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摘要:
针对经验小波变换(EWT)在滚动轴承故障信号最优频带提取中存在的问题,提出一种基于提取能量包络趋势线以自适应划分频带的改进EWT方法,并应用于滚动轴承故障诊断。利用Teager能量算子将频谱转换成能量谱,通过反复希尔伯特变换得到能量包络线。提取极大值并平滑处理,获得能量包络趋势线,对其进行1阶差分,选取有效极值点以自适应划分频带。构造一种归一化故障特征频率显著性指标,作为故障诊断和最优共振频带选取的有效判据。通过滚动轴承故障仿真和试验数据对算法进行验证。结果表明:相比于原始EWT,该方法可有效识别滚动轴承早期故障并合理选取最优共振频带。针对外、内圈故障数据所提指标可平均提升48.0%和174.1%。
Abstract:Considering the problem of empirical wavelet transform (EWT) in extracting optimal frequency band of the rolling bearing fault signal, an improved EWT method based on extracting energy envelope trend line to adaptively divide frequency band was proposed and applied to rolling bearing fault diagnosis. The Teager energy operator was used to convert the spectrum into energy spectrum, and the energy envelope was obtained by repeated Hilbert transform. Local maximum values were extracted and smoothed to obtain the energy envelope trend line, and the first-order difference was performed to select effective extreme points to adaptively divide the frequency band. A normalized fault characteristic frequency saliency index was constructed as an effective criterion for fault diagnosis and optimal resonance frequency band selection. The algorithm was verified by rolling bearing fault simulation and experiment data. The results showed that compared with the original EWT, the proposed method can effectively identify the early faults of rolling bearings and reasonably select the optimal resonance frequency band. The proposed indexes for the outer and inner race fault data can be increased by 48.0% and 174.1% on average.
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表 1 反复希尔伯特变换Vs结果
Table 1. Vs results of repeated Hilbert transform
变换次数 第1次 第2次 第3次 第4次 第5次 Vs 1.123 1 1.092 4 1.061 7 1.013 4 0.946 6 表 2 仿真信号改进EWT分解得到各IMF的S0-1
Table 2. S0-1 of each IMF decomposed by improved EWT of simulation signal
IMF IMF1 IMF2 IMF3 IMF4 IMF5 $ {S_{0 {\text{-}} 1}} $ 0.017 5 0.180 8 0.216 9 0.927 4 0.028 3 表 3 HRB 6206深沟球轴承参数
Table 3. Parameters of HRB 6206 deep groove ball bearings
内径/
mm外径/
mm厚度/
mm滚珠直径/
mm节径/
mm滚珠数/
个接触角/
(°)30 62 16 9.5 46 9 0 表 4 外圈故障信号改进EWT分解得到各IMF的S0-1
Table 4. S0-1 of each IMF decomposed by improved EWT of outer race fault signal
IMF IMF1 IMF2 IMF3 IMF4 IMF5 S0-1 0.049 5 0.038 8 0.000 1 0.002 0 0.061 7 IMF IMF6 IMF7 IMF8 IMF9 IMF10 S0-1 0.008 7 0.014 8 0.912 1 0.999 8 0.853 6 表 5 外圈故障信号原始EWT分解得到各IMF的S0-1
Table 5. S0-1 of each IMF decomposed by original EWT of outer race fault signal
IMF IMF1 IMF2 IMF3 IMF4 IMF5 S0-1 0.003 6 0.088 7 0.013 0 0.015 7 0.000 1 IMF IMF6 IMF7 IMF8 IMF9 IMF10 S0-1 0.000 1 0.000 1 0.000 1 0.000 1 0.999 2 表 6 内圈故障信号改进EWT分解得到各IMF的S0-1
Table 6. S0-1 of each IMF decomposed by improved EWT of inner race fault signal
IMF IMF1 IMF2 IMF3 IMF4 $ {S_{0-1}} $ 0.000 6 0.000 7 0.648 5 0.002 7 表 7 内圈故障信号原始EWT分解得到各IMF的S0-1
Table 7. S0-1 of each IMF decomposed by original EWT of inner race fault signal
IMF IMF1 IMF2 IMF3 IMF4 $ {S_{0 {\text{-}} 1}} $ 0.001 2 0.004 8 0.000 1 0.064 5 表 8 不同转速下外圈故障信号S0-1及频带划分结果
Table 8. Outer race fault signal S0-1 and frequency band division result at different speeds
数据 转速/(r/min) S0-1 频带/Hz 原始EWT 改进EWT 原始EWT 改进EWT 1 1500 0.119 5 1.000 0 700~892 8 866~16 000 2 0.046 4 0.956 8 338~680 8 869~16 000 3 0.006 7 0.763 8 1 058~16 000 8 881~16 000 4 0.506 3 1.000 0 759~925 8 877~16 000 5 0.476 2 1.000 0 982~16 000 8 897~16 000 6 2500 1.000 0 1.000 0 442~977 435~975 7 1.000 0 1.000 0 442~977 452~975 8 1.000 0 1.000 0 442~977 427~918 9 0.141 2 1.000 0 368~809 438~913 10 0.990 4 1.000 0 442~883 434~970 11 3500 0.845 1 0.998 3 981~16 000 14 252~ 16000 12 0.989 8 0.999 7 981~15 192 8 796~15 192 13 0.976 6 0.999 4 981~16 000 8 778~15 268 14 0.978 2 0.999 5 1 829~16 000 10 002~14 399 15 0.834 2 0.947 7 914~16 000 14 369~15 265 S0-1平均值 0.660 7 0.977 7 大于0.8占比/% 60.0 93.3 表 9 不同转速下内圈故障信号S0-1及频带划分结果
Table 9. Inner race fault signal S0-1 and frequency band division result at different speeds
数据 转速/(r/min) S0-1 频带/Hz 原始EWT 改进EWT 原始EWT 改进EWT 1 1 500 0.376 7 1.000 0 353~773 351~897 2 1.000 0 1.000 0 353~883 345~875 3 0.409 4 1.000 0 705~ 1767 345~874 4 0.357 8 1.000 0 353~773 349~880 5 0.410 4 1.000 0 353~773 351~897 6 2 500 0.186 0 0.659 2 1060 ~16 000941~2 371 7 0.125 2 0.691 1 1211 ~16 0001 777~3 279 8 0.275 0 0.646 3 1211 ~16 0001 175~2 372 9 0.696 0 0.815 5 881~16 000 862~8 968 10 0.040 4 0.547 3 1101 ~16 0001 174~2 550 11 3 500 0.166 5 0.633 5 87~401 1 442~2 314 12 0.021 1 0.570 5 882~16 000 1 102~1 741 13 0.033 6 0.642 8 784~16 000 792~4 256 14 0.029 7 0.735 6 882~16 000 807~1 520 15 0.055 4 0.526 2 784~16 000 807~4 508 S0-1平均值 0.278 9 0.764 5 大于0.5占比/% 13.3 100.0 -
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