Research On Safety Analysis Approach Of FADEC System Based On Bayesian Network

Safety analysis is the main method to improve the system safety level in the progress of civil aircraft system development,is also the important airworthiness compliance verification method.Full Authority Digital Engine Control systems installed on modern aircaraft engines,take all aspects of control by using electronic computer.The failures of FADEC system show dynamic and multi-state characteristics due to the high integration and complex interaction between the components.The classical analysis methods like reliability block diagram and fault tree are not applied to do the safety analysis of dynamic and multi-state systems.In this paper,a safety analysis method of FADEC system is proposed based on system functional logic Bayesian networks.The specific research contents are as follows:1.The functional principle and typical fault characteristics of FADEC system are analyzed the failure mode are devided into output error,lack of output,non-output according to show the multi-states and dynamic characteristics in FADEC system.2.The Bayesian network based on system functional logic is built,the Bayesian network nodes represent system components,and the edges between the nodes represent the logical relationships among the components;and The model is discretized in time domain,the Bayesian network security evaluation model of FADEC system is established;and the algorithm of top event probability is proposed by Bayesian reasoning.3.The minimum cut set method based on Bayesian network is proposed,DAL allocation principle as the constraint,aircraft development costs as the minimum objective function,the DAL value of each device or function as the decision variable,the DAL allocation optimization model is bulit,a DAL allocation optimal algorithm based on hybrid genetic algorithm and tabu search is proposed;And the effectiveness of the model and algorithm is proved by an example.The research results of this paper can be used for civil aircraft development and airworthiness,and is of great significance to improve the safety of civil aircraft.