## 1 Introduction
Through the above literature review, it is clear that in the field of permanent magnet drive systems, particularly permanent magnet thrust bearings, numerous scholars have made significant progress in areas such as overall structure design, magnet arrangement, theoretical analysis, finite element simulation, and experimental validation. Moreover, related engineering applications are also being actively explored. However, it is important to note that the traditional structure of permanent magnet thrust bearings often exhibits a lack of diversity. Many existing bearings fail to demonstrate generalizability and scalability, limiting their adaptability across different systems and applications. This presents a clear and pressing need for innovative approaches to develop more versatile, modular, and scalable permanent magnet thrust bearings. In summary, the limitations of the existing permanent magnet thrust bearing design are as follows:  
(1) Permanent magnet thrust bearings typically adopt the method of embedding permanent magnet rings directly into the bearing structure [6]. This makes the assembly process more complex. Furthermore, if a single magnet is damaged, due to its direct embedding in the bearing mechanism, the damaged magnet could lead to secondary damage to the bearing structure and other magnets. (2) Existing permanent magnet thrust bearings are often designed for specific machines [20]. Their size, structure, and bearing capacity are tailored to meet the current design requirements, resulting in a lack of generalization and serialization capabilities. Additionally, their load-bearing capacity is often low, making them unsuitable for high-demand applications such as ship spindle propulsion. (3) The theoretical models for permanent magnet thrust bearings are usually limited to single-layer cross-nested structures [21]. There is a notable deficiency of well-defined theoretical models for multi-layer cross-nested structures. Moreover, the data on bearing capacity are commonly derived from theoretical calculations and simulations, often lacking rigorous experimental validation. To address these limitations, this paper proposes a novel modular multi-unit cell permanent magnet thrust bearing. The research framework is depicted in Figure 1, with the following contributions:  
(1) Drawing inspiration from bionics and the honeycomb structure, a modular approach is adopted that incorporates a unit cell consisting of four permanent magnets. The design replaces the traditional permanent magnet ring, which is directly embedded in the bearing structure, with multiple connected unit cells. This separation allows the magnets to be isolated from one another, improving both durability and performance. (2) By generalizing the unit cell structure and varying the number and arrangement of multiple unit cells, a flexible design with multiple nested and cross structures can be realized. This modular design enables the creation of a multi-unit cell permanent magnet thrust bearing adaptable to different configurations and requirements. (3) The theoretical model for multi-layer cross-nested permanent magnet thrust bearings is derived and calculated based on the principles of virtual displacement and virtual work. This extension broadens the applicability of traditional models, which were previously limited to single-layer cross-nested structures, allowing for multi-layer cross-nested configurations. Additionally, an experimental platform for the permanent magnet thrust bearing is designed with a focus on ship spindle propulsion, and experimental validation is carried out to confirm the theoretical findings. The main contents of this paper are organized as follows: Section 1 is the introduction; Section 2 outlines the structural design of a modular multi-unit cell permanent magnet  
Figure 1: The main architecture of this paper.