Currently, the prevailing maintenance strategy for high-speed rail rolling stock in China is predicated on Time-Based Maintenance (TBM), with the gradual implementation of Condition-Based Maintenance (CBM), component replacement, and centralized repair of major components [1]. China's high-speed rail maintenance model is transitioning from traditional "Time-Based Maintenance" to "Condition-Based Maintenance."

As PHM is an advanced development of condition-based maintenance, it can enhance the safety of high-speed trains, accelerate the optimization of maintenance strategies, alleviate heavy maintenance workloads, and reduce maintenance costs. Therefore, utilizing PHM for analyzing the health status of high-speed trains is a meaningful and important research endeavor.

With the integration and intelligentization of high-speed rail equipment and the development of train control networks, the continuous improvement of state monitoring and data transmission functions for critical components of high-speed electric multiple units (EMUs), and the gradual application of Prognostics and Health Management (PHM) systems [41,43,60], it has become possible to establish a theoretical system for fault prediction and health management for high-speed rail equipment. Currently, a complete theoretical system for PHM of high-speed rail equipment has not yet been formed domestically. This paper exploratively proposes a reference theoretical system for PHM of high-speed rail equipment. The PHM theoretical system for high-speed rail equipment consists of five major systems: the High-Speed Rail Equipment PHM Theoretical System, the High-Speed Rail Equipment PHM Business System, High-Speed Rail Equipment PHM Technical Methods, the High-Speed Rail Equipment PHM Management System, and the High-Speed Rail Equipment PHM Application System, as shown in Figure 2.1. (1) The High-Speed Rail Equipment PHM Theoretical System is the prerequisite and foundation for establishing PHM for high-speed rail equipment. It is composed of several interacting and interrelated elements, and its functions are determined by the system's structure. The High-Speed Rail Equipment PHM Theoretical System is the core part of the PHM theoretical framework for high-speed rail equipment, playing a guiding and dominant role for all other systems. (2) The High-Speed Rail Equipment PHM Business System utilizes a large amount of data provided by various information systems and related instruments, and provides the logic and requirements for specific business operations. The business system plays a fundamental role in supporting other PHM systems.

(3) The High-Speed Rail Equipment PHM Technical System is the means by which PHM value is realized. (4) The High-Speed Rail Equipment PHM Management System is a system designed to standardize human factors. It plays an important role in the entire PHM theoretical framework for high-speed rail equipment, and rigorous management contributes to the realization of PHM value. (5) The High-Speed Rail Equipment PHM Application System is the ultimate embodiment of PHM value.