# A Review on Vibration-Based Condition Monitoring of Rotating Machinery
## 1 Introduction
\begin{table}
\begin{tabular}{c c c c c c c} \hline \hline
**Ref.** & **First Author** & **Year** & **General** & **Focused** & **Vibrations** & **Phase** & **Main Topic** \\ \hline
[25] & [PERSON] & 2021 & x & & Diagnostics &
\begin{tabular}{c} Wind turbine gearboxes \\ operating under non-stationary \\ conditions \\ \end{tabular} \\ \hline
[26] & [PERSON] & 2020 & x & & All & Wind turbine bearings \\ \hline
[3] & [PERSON] & 2019 & x & x & All & Rolling bearings \\ \hline
[2] & [PERSON] & 2019 & x & x & Diagnostics & Non-linear systems \\ \hline
[27] & [PERSON] & 2019 & x & & Diagnostics &
\begin{tabular}{c} Wind turbine condition \\ monitoring \\ \end{tabular} \\ \hline
[28] & [PERSON] & 2019 & x & x & All & Wind turbine planetary gearbox \\ \hline
[29] & [PERSON] & 2017 & x & & Feature extraction & Low-speed slew bearings \\ \hline
[30] & [PERSON] & 2017 & x & & x & Feature extraction \\ \hline
[31] & [PERSON] & 2015 & x & & & Diagnostics \\ \hline
[5] & [PERSON] & 2015 & x & x &
\begin{tabular}{c} Features extraction \\ and selection \\ \end{tabular} & Journal bearings \\ \hline
[32] & [PERSON] & 2014 & x & & All & \\ \hline
[33] & [PERSON] & 2004 & x & x & All & Helicopter transmission \\ \hline
[34] & [PERSON] & 1999 & x & x & All & Rolling bearings \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Main review publication closer to the condition monitoring in a rotating machinery theme. Besides these considerations, the preliminary analysis of the current literature reveals the lack of review works on condition monitoring based on vibration analysis, in rotating machines, not focused, and not referring to a specific phase. These--not even the paper \"Vibration Analysis & Condition Monitoring for Rotating Machines: A Review\" by [PERSON] et al. [30], which, by title, would appear to be the best candidate--mainly focus on feature extraction methods. According to the results of this analysis, the proposed review aims to fill the highlighted research gap, outlining the current state-of-the-art on the subject of condition monitoring of rotating machines, based on vibrations, in a comprehensive way. In more detail, the proposed literature review presents two different analysis levels:  
1. A prospective review, or an observational study of the distribution of published documents over time, by phase, and by intervention level;
2. An analytical review, consisting of an in-depth study of the most used and most recently introduced methodologies, for the main phases of the condition monitoring process. The current work, in addition to providing an up-to-date review, also aims to support the researcher, as it is suitable for application in everyday practice. For this reason, the paper analyzes the literature with a systematic approach and presents the results in a schematic layout. The paper is organized as follows: Section 2 describes the research method in terms of a data selection protocol, prospective, and analytical review. Section 3 reports the results of the prospective review; Section 4 presents the results of the analytical review, declined for phases. Section 5 (conclusion) summarizes the review work and future ideas.