In order to ensure the safety of eVTOL,safety analysis of thermal runaway problem of lithium battery is needed.Due to insufficient failure data,a safety assessment method based on evidence theory and interval analysis is proposed.Firstly,a fault tree model for system is constructed.Secondly,for the imprecise failure rate of bottom events in fault tree analysis,the failure probability interval of bottom event is calculated by using the evidence theo-ry,and combining with the importance analysis to address the problem of inaccurate failure rate of bottom events in fault tree analysis.The evidence theory is used to calculate the probability interval of failure of bottom events and combine it with interval theory to calculate the top events of the fault tree.Finally,the importance analysis is used to find out the basic events that have the greatest impact on the top events.The proposed method is used to analyze the safety of the eVTOL's battery thermal runaway and calculate the importance of each bottom event,so as to pro-vide a basis for reducing the system failure probability and improving the system safety level.
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