Three methods(correlation coefficient method

KL divergence method

energy conservation combined with frequency divergence method)for extracting valid intrinsic mode function(IMF)from empirical mode decomposition(EMD)were presented.Moreover

decomposition test was performed on typical rubbing(between dynamic and static parts)and oil film oscillation signal of a steam turbine

by using the above three methods.The results show that

the selection method which combing the energy conservation method for low frequency component with the frequency divergence method for high frequency component was superior to the correlation coefficient method in discrimination

and to the KL divergence method in adaptability

and to both of them in overall stability of judgements.