Model Based FMEA Method And Application To Aircraft Systems

Safety is the most basic characteristic of civil aircraft and is very important for aircraft manufacturers.In order to comply with safety requirements,aircraft requires safety analysis during design phase.Failure Mode and Effect Analysis(FMEA)is an important method for safety analysis.It can identify potential failure modes and reduce failures through design improvements.At the same time,FMEA can also provide support for system safety assessment process and fault tree analysis method.Traditional FMEA method has many problems,such as relying on experience overly and difficulty in determining the impact.Improving the FMEA method and solving the shortcomings are of great significance for aircraft system safety analysis.To solve these problems,this paper proposes a model based FMEA method for aircraft systems.Based on the system model,fault extension and injection analysis were carried out.As a result,fault propagation paths,state transitions,and output changes were obtained which can help safety analysts complete FMEA.Through design improvement,the safety and reliability of the system can be strengthened.The main work is as follows:(1)Based on the system dynamic model,the system failure mode model was proposed.Firstly,by using the state mechanism and regarding failure mode as a extend state,the single component failure mode model was built.Then,based on the static hierarchical model of the system,the hierarchical failure mode modeling method was proposed,which made the failure mode modeling method with good expansibility(2)Based on fault propagation theory,a fault propagation variable was defined.Then combining fault propagation variables with state machine modeling,a system fault propagation model was constructed.(3)Based on the system failure model,the fault was injected to obtain the fault propagation path,state transition and output change results for analysis the impact of local faults.Then based on the hierarchical structure of the system,a hierarchical fault impact analysis method was proposed to clarify the final impact of local faults.Finally,this paper applied the model based FMEA method to the highlift system.Based on Simulink/Stateflow the system model was built,through fault identification,modeling and injection,the local and hierarchical impact analysis was carried out and the results provided input for FMEA.Compared with the traditional method,model based FMEA method can clarify the relationship between failure modes and effects,reduce the dependence of experience and be integrated into the design iteration process,providing bases for safety design.