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

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.