组合导航系统（integrated navigation system, INS）广泛用于航空航天、海洋探索等领域，因其工作环境、系统构成的复杂性等因素，系统从正常工作到完全失效会经历各种退化状态，进而增加系统可靠性分析难度。将有限退化结构（finite degradation structures, FDS）方法应用于多态组合导航系统可靠性分析。首先，参考故障模式与影响分析（failure mode and effect analysis, FMEA）方法将组件的故障模式转化为状态空间；其次，利用抽象运算得到组件状态和系统状态的关联关系，建立组合导航系统的FDS模型；然后，进行系统临界场景分析和可靠性指标计算，得出系统状态的发生概率、组件状态的敏感性，找到系统的薄弱环节、系统完全失效前的退化边界；最后，根据结果指导制定系统维护策略、预防系统风险发生方案等可靠性决策。

The integrated navigation system (INS), vital in aerospace and ocean exploration, faces challenges in reliability analysis due to its complex operational environment. Addressing this, the finite degradation structures (FDS) method was employed for a thorough examination of the multi-state integrated navigation system. Initial steps involve transforming component fault modes into a state space using the failure mode and effect analysis (FMEA) method. Subsequently, an abstraction operation establishes the relationship between component states and system states, forming the required FDS model. This model serves as the basis for critical scenario analysis and calculation of reliability indicators. Through this systematic approach, the occurrence probability of various system states can be computed and the sensitivity of individual component states can be assessed. The identifications of the weak points and the degradation boundaries of the system are well demonstrated with illustrative case studies. These results can be seen as insights to guide reliability decisions, including the development of system maintenance strategies and risk prevention schemes.