*5.6. Analysis of center spring wear fault signalof fluid pressure based on FK*

In order to illustrate the validation and advantages of the Autogram, the signal is also analyzed by FK. Colormap presentation obtained based on FK is illustrated in Figure 19.

**Figure 19.** Colormap presentation of the center spring wear fault signal based on FK.

In Figure 19, the maximum kurtosis value is 1.6, and it corresponds to the node (1, 1), with a center frequency of 1230 Hz and a bandwidth of 2500 Hz. Thus, the node is used as a data source for further investigation. Its spectrum is shown in Figure 20.

**Figure 20.** Spectrums of the center spring wear fault data source node (1, 1) based on FK.

Figure 20 signifies that the fault feature information at fault feature frequency 24.5 Hz and most of harmonics are extracted. However, compared with standard Autogram based on no threshold processing in Figure 14a and the original center spring wear in Figure 12, the amplitude values are very small (Figure 20).

The conclusion can be drawn from above that standard Autogram based on no threshold processing can extract the fault feature information on center spring wear successfully, and it performs better than FK in fault feature extraction ability.
