Feature Extraction Strategy with Improved Permutation Entropy and Its Application in Fault Diagnosis of Bearings

Figure 5

Comparative results of various features: (a) original features, (b)–(d) average features which are the means of three, five, and ten original features, respectively. The red solid lines are the mean values of these features plotted in the corresponding plots; std is the abbreviation of standard deviation.

(a)

(b)

(c)

(d)