# Sequential-Fault Diagnosis Strategy for High-Speed Train Traction Systems Based on Unreliable Tests
## 5 Conclusions  
This paper puts forward a construction method for a traction system fault diagnosis strategy using unreliable tests. Firstly, the traction system is introduced, the possible uncertain factors and the results caused by various factors in the test process are analyzed, and the concept of test reliability is put forward. Secondly, the quantitative evaluation index of test reliability is constructed, the quantitative evaluation method of test reliability based on a cloud model is proposed, the basic elements and optimization objectives of fault diagnosis strategy are analyzed, and fault reasoning method based on a reliability dependency matrix is proposed. Then, a quantitative evaluation of the test reliability of a traction system is realized using a cloud model, and the fault-test dependency matrix of the traction system based on test reliability is constructed. Finally, under the condition of unreliable test, considering the reliability of test results and test cost, a single-fault diagnosis strategy construction method based on a reliability dependency matrix is established. The differences between single-fault diagnosis strategies in traction systems under the conditions of reliable tests and unreliable tests are compared and analyzed. From the results of the diagnosis strategy, the reliability of the test has a certain impact on the fault detection, isolation, and location sequence of the traction system. It also shows that the construction method of a diagnosis strategy considering unreliable testing plays a certain role in guiding practical engineering applications.  
However, the construction method of fault diagnosis strategy under unreliable tests studied in this paper only considers the construction method of a fault diagnosis tree under a single fault. However, in practical engineering applications, there are many concurrent faults. Therefore, the following consideration is to build a multi-fault diagnosis strategy for concurrent faults.  
The following supporting information can be downloaded at: [[https://www.mdpi.com/article/10.3390/app13148226/s1](https://www.mdpi.com/article/10.3390/app13148226/s1)]([https://www.mdpi.com/article/10.3390/app13148226/s1](https://www.mdpi.com/article/10.3390/app13148226/s1)), Figure S1: Fault diagnosis tree of traction system under reliable test; Figure S2: Fault diagnosis tree of traction system under unreliable test; Table S1: The FMECA of Traction system; Table S2: Complete test set failure-test dependency matrix; Table S3: Expert cloud matrix; Table S4: Comprehensive Cloud Evaluation Matrix; Table S5: Reliability failure--test dependency matrix.  
**Author Contributions:** Conceptualization, M.L. and Y.Z.; methodology, M.L.; validation, Y.Q. and Z.W.; investigation, Y.Z.; writing--original draft, L.J. All authors have read and agreed to the published version of the manuscript.  
**Funding:** This research is supported by the Fundamental Research Funds for the Central Universities (Science and technology leading talent team project, Grant No. 2022 JBQY007), the National Key R&D Program of China (No. 2022 YB84300601) and the National Natural Science Foundation of China (Grant 61833002).  
**Institutional Review Board Statement:** Not applicable.  
**Informed Consent Statement:** Not applicable.  
**Data Availability Statement:** No new data were created or analyzed in this study. Data sharing was not applicable to this article.  
**Conflicts of Interest:** The authors declare no conflict of interest.