基于改进谐波小波包的柔性薄壁轴承背景周期性冲击分离

柔性薄壁轴承是一种特殊的轴承,其内外圈是椭圆,在旋转时椭圆的长、短轴会对轴承产生一种周期性冲击,这种周期性冲击和轴承元件的故障周期性冲击混合在一起,对故障周期性冲击是一种极大的干扰。为消除这种干扰,通过分析椭圆长短轴引起的周期性冲击的特点,结合谐波小波的盒形频率特性,提出一种改进的谐波小波包来消除这种周期性冲击。普通谐波小波包的子带频率范围是根据分解层数确定的,而改进的谐波小波包的各个子带频率范围则针对椭圆长短轴引起的周期性冲击的频率分布特点而设计,可以有效地提取到这种冲击的每一个谐波分量,从而可准确地分离出整个周期性冲击。对实际柔性薄壁轴承振动信号的处理结果表明,改进的谐波小波包从混合的复杂周期性冲击中准确地分离出了椭圆长短轴引起的周期性冲击,而故障周期性冲击却被完好保留,从而消除背景周期性冲击的影响,实现对柔性薄壁轴承损伤的正确识别。

Separation of Background Periodic Impact of Flexible Thin-wall Bearing Based on Improved Harmonic Wavelet Packet

Flexible thin-wall bearing(FTB) is a special bearing, the inner and outer rings of which are ellipses. During the rotation process, the long and short axes of ellipse will cause the periodic impact on the bearing, and this kind of impact is mixed with the fault periodic impact caused by the injured elements of FTB and is a great interference to the fault periodic impact. In order to eliminate this impact interference, the characteristics of this periodic impact are analyzed, and based on the box frequency characteristic of harmonic wavelet, an improved harmonic wavelet packet is proposed to separate this periodic impact. For the ordinary harmonic wavelet packet, the frequency range of each sub-band is determined by the number of decomposition layers, while for the improved harmonic wavelet packet, the frequency range of each sub-band is designed based on the frequency distribution characteristic of the periodic impact caused by the long and short axes of ellipse, and each harmonic component of this impact can be effectively extracted,so that the whole background periodic impact can be accurately separated. The processing results of vibration signals of the actual FTBs show that the improved harmonic wavelet packet accurately removes the background periodic impact from the complexly mixed periodic impact, while the fault periodic impact is well retained, thus the interference of background periodic impact is eliminated, and the damage of the FTBs is correctly identified.