Reliability and Safety Analysis on Multi-state System of EMUs with Degraded Components

Aiming at the restrictions of the conventional reliability analysis based on binary logic on the systems with degraded components, a multi-state reliability analysis modeling method is proposed. The components and systems are classified into different states in this model according to different failure levels. Then a multi-state logic relation is established among units and systems as per the systematic block diagram, and the reliability analysis model for multi-state system is constructed, in which multi-level system reliability is realized and the major hazards resulted from neglecting potential faults in the binary system are avoided. Meanwhile, in line with the temporal distribution of system reaching ultimate limit state in safety, a system risk function is formulated. Therefore, the safety analysis model for a multi-state system is constructed. The examples of reliability analysis on EMU traction system indicate the effectiveness and advantages in evaluating reliability and safety of a complex system with multi-state reliability and safety analysis model.