**7. References**

368 Advances in Wavelet Theory and Their Applications in Engineering, Physics and Technology

signal

TYPE 1 102.25 121.13 TYPE 2 58.61 72.87

Level *<sup>C</sup> j k*, Ratio of RMS F/N


Table 2. Comparison with coefficients of DWT: ratio of RMS value between the faulty (F)

the first decomposition level may be considered a reliable monitoring feature.

Table 2 shows the comparison between the RMS ratio of the DWT coefficients in faulty (F) and normal (N) conditions with the engine running at 120 rpm. The j = 1 level shows the highest difference between the faulty and normal vibration signals. Thus, the RMS ratio at

This chapter deals with WT applications for practical condition monitoring issues on flexible couplings and i.c. engine. In particular, CWT and DWT capability was assessed. The former was used for faulty event identification and impulse event characterization through the analysis of three-dimensional representations of CWT coefficients. The latter was applied for filtering and feature extraction purposes and for detecting impulsive events which were strongly masked by noise. Several CWT representation improvements were also evaluated. Comparing the results from both the CWT and DWT analyses, the ability of WTs in satisfying both condition monitoring and fault detection requirements for all tested cases was clearly demonstrated. In particular, traditional CWTs of the residual signal (i.e. the signal obtained by subtracting the time synchronous average from the raw signal) with the Morlet mother wavelet was revealed to be the most powerful tool in angularly localizing the

It can be concluded that the application of WTs not only enables changes in the state of the tested machine to be recognized but also the localisation of the source of the alteration.

This work was developed within the Advanced Mechanics Laboratory (MechLav) of Ferrara Technopole and brought into being with a contribution by the Emilia-Romagna Region – Assessorato Attivita' Produttive, Sviluppo Economico, Piano telematico - POR-FESR 2007-

Inverted piston

DWT of the transom right side signal

Coupling Original transom left side

Table 1. Mean value of the peaks of acceleration (m/s2).

and normal (N) conditions.

assembly fault within the engine kinematics.

**6. Acknowledgments** 

2013, Attività I.1.1.

**5. Conclusions** 


[18] Newland, E., 1994, Wavelet Analysis, Part II: Wavelet Maps, *Journal of Sound and Vibration* 116, 417-425.

**Part 4** 

**Image Processing** 

