## 1 Introduction
This part focuses on the evolution of the fault process and estimates the future behavior through the necessary models to realize the failure risk assessment and change of control strategy. The HP program generally consists of HI construction, HS division, and RUL prediction. Finally, MD is done according to the results of HCM, FD, and HP. An MD describes the O&M vision of how to maintain the health and safety of assets in a whole life cycle. This paper aims to systematically review the methods, strategies, and application of MSAE in prognostics and health management. We set three keywords for searching the relevant kinds of literature, such as ship, marine, and mechanical systems. A systematic search is undertaken for the specific words combined with the methods and strategies in the four processes of HCM, FD, HP, and MD in the article title, abstract, and keywords. The search period is mainly from 2010 to 2020, and the search source is Web of Science. We excluded the papers of biology, navigation, chemistry, and port navigation in the marine fields. Some related articles with similar characteristics to MSAE are also included in the scope of discussion. A total of more than 300 articles have been retained through the processes. There are also some excellent review papers related to PHM of ship mechanical system. For example, [PERSON] et al. (2019) provided a review on the online condition monitoring and self-repairing techniques for in-service marine diesel engine. [PERSON] et al. (2019) reviewed different blade fault types and current blade fault detection methods. [PERSON] et al. (2019) mainly focused on data-driven models and gave a review on the problem of performing Condition-Based Maintenance for naval propulsion systems. However, these papers just reviewed the technical processes and lacks a systematic review covering the whole program of the PHM about its advancements in recent years. A review still leaves a blank space to cover the PHM framework comprehensively in the maritime domain systematically. In order to overcome the shortcomings above, this article systematically reviews the research status and future development trend of PHM in the marine field. Compared with the existing review papers, the contributions of this review are detailed below. \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Technical Processes** & \multicolumn{2}{c}{**Constitution**} & **Description** \\ \hline \multirow{4}{*}{HCM} & \(\bullet\) & Data acquisition & \multirow{2}{*}{HCM is to use various monitoring data, information, and} \\  & \(\bullet\) & Data processing & knowledge to realize the monitoring and assessment of MSAE \\  & \(\bullet\) & Condition monitoring & \\ \hline \multirow{4}{*}{FD} & \(\bullet\) & Fault feature selection & \multirow{2}{*}{FD exhibits an important role in demonstrating the relationship between the HCM information to the health condition.} \\  & \(\bullet\) & Fault description & \\ \hline \multirow{4}{*}{HP} & \(\bullet\) & HI construction & \multirow{2}{*}{HP aims to predict the RUL of machinery based on the historical and ongoing degradation trends observed from HCM information.} \\  & \(\bullet\) & HS division & \\ \cline{1-1}  & \(\bullet\) & RUL method & \\ \hline \multirow{4}{*}{MD} & \(\bullet\) & Corrective maintenance & \multirow{2}{*}{MD is to consider the coordination of health and safety of assets} \\  & \(\bullet\) & Preventive maintenance & \\ \cline{1-1}  & \(\bullet\) & Predictive maintenance & \\ \cline{1-1}  & \(\bullet\) & Proactive maintenance & \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Technical list of each process.