基于EMD和Lempel-Ziv指标的滚动轴承损伤程度识别研究

Fault severity assessment for rolling element bearings based on EMD and Lempel-Ziv index

针对不同损伤程度的滚动轴承内、外圈故障,提出一种基于经验模式分解(EMD)和Lempel-Ziv指标的评估方法。EMD用于高效地分解信号,并结合能量与峭度条件找出蕴含故障本质特征的最优IMF分量,在此基础上分别计算最优IMF及其包络的Lempel-Ziv归一化值,再加权求和得到最终的Lempel-Ziv综合指标。由于EMD消除了噪声干扰,有利于准确揭示轴承恶化情况,并且指标本身受实验条件影响不明显,同时介于0和1的取值方便快速使用。轴承内、外圈故障实验证实:内圈损伤的Lempel-Ziv综合指标随故障加重递减,而外圈损伤相反,随故障加剧递增。同时还分别给出了内、外圈损伤情况下不同故障程度评估的Lempel-Ziv取值区间,能有效用于轴承故障程度的识别。

To evaluate the fault severity of rolling element bearings with inner and outer race defects,a measure based on EMD and Lempel-Ziv index was proposed.EMD was used to decompose the signal into meaningful components,from which the best IMF could be found according to the energy and kurtosis conditions.On the base of the best IMF,the normalized Lempel-Ziv values were calculated for both the envelope and the high-frequency carrier signal.Then the two values were summed up with given weights to form a final measure named the integrated Lempel-Ziv index.The method is suitable for uncovering the real inside of bearing deterioration in light of EMD,the index itself is robust and the normalized value is convenient to be used as the value is between 0 and 1.The inner and outer race fault experiments show that the integrated Lempel-Ziv value is increased as the outer race fault grows,and an opposite trend will be achieved in other fault cases.The new index can be used as a fault severity measure for rolling element bearings effectively according to the Lempel-Ziv ranges indicating the degree of faults.