## 1 Introduction  
With the development of modern technology, the level of ship automation and intelligence is gradually improving, and then the O&M technology for MSAE is facing new problems. The ship alarm monitoring system (AMS) relying on human experience and knowledge can no longer meet the condition assessment requirements by maintenance engineers. The traditional ship maintenance modes characterized by corrective maintenance (CM) and planned maintenance (PM) have gradually highlighted the disadvantages of \"over repair\" and \"missing repair\" lead to the increasing of ships' operation costs. With the advancement of comprehensive equipment monitoring, assessment, diagnostics, and prognostics technology, the PHM of MSAE based on a more proactive maintenance strategy has gradually become a new trend of intelligent O&M. Currently, based on the perfect situ monitoring and advanced analysis methods, PHM technologies, approaches, and applications are developing rapidly. Its application objects gradually expand to military, aerospace, ships, and so forth. There are some representative PHM systems in these fields, such as PHM system for F-35 aircraft, AHM system for helicopter, IVHM system for spacecraft, and ICAS and PEDS system for ships [1], and so forth. At present, PHM technology has been widely studied and popularized in FD and HP of marine diesel engines and rotating machinery. The PHM of the marine diesel engine was established, and the performance prediction was realized [2]. Various applicable data and suitable technologies were integrated for engine PHM [3]. [PERSON] et al. presented a comprehensive review of the PHM design for rotary machinery systems, followed by introducing a systematic design methodology and converting multivariate data to abstract prognostics information [4]. Modern MSAE is a complex system composed of mechanical, electrical, and hydraulic systems, consisting of interrelated subsystems, equipment, and components. Exception of any component may result in changes in health conditions. A viable PHM system framework provides condition monitoring, early fault detection, and isolation of any node in the system. The outcome of an effective PHM model provides a tool to monitor the health condition and help make O&M decisions. It is more urgent for intelligent and unmanned ships to realize the PHM to improve the integrated management of HCM, health assessment, FD, performance prediction, and maintenance implementation. The PHM solutions of MSAE mainly cover a complete process (Figure 1), from capturing the data, information, and knowledge (DlaK) up to utilizing the results for decision-making (in maintenance, operation management, life cycle optimize control, system design, etc.). A technical list of each process is shown in Table 1. At first, HCM process is to obtain ship condition parameters, realize real-time online monitoring of the mechanical system, and complete condition assessment and anomaly detection. The HCM consists of three basic processes, data acquisition, data processing, and condition monitoring. With intelligent technology and modern sensing technology, vast amounts of ship data are being collected. The data collected on-board involve navigation, MSAE condition perception, and environmental data. Data processing should first ensure the data's accuracy and integrity, and then extract and deduce valuable and meaningful data for health management from a large number of possibly disordered and complex to understand data. Condition monitoring realizes early warning, alarm and anomaly detection according to online data. Then, based on the abnormal problems of HCM, FD focuses on the failure modes and their causes and demonstrates the relationship between the monitoring data and the fault  
Figure 1: Relationship diagram of four parts of PHM. condition. After that, the realization of HP is to obtain the failure data of mechanical system through HCM and FD, and then establish the degradation model to complete the life prediction.