The Study On The Safety Of Avonics System Based On Multifailure-condition-space Analysis

For these years,avionics system is developing to the direction of openness,synthesis and modularity.With the more and more complexity of the electronic system,the safety of avionics system faces more challenges.In order to avoid multiple failures and relevant failures,avionics system generally adopts the technology of dynamic reconfiguration,namely based on system functional redundancy and using system configuration changes to realize the real-time and active fault tolerant control,which leads to the fact that the analytical method of single failure-condition-space has not completely fit to the safety analysis of the new generation of avionics system.This thesis deeply studies the basical safety theories and technologies,and then makes research on the automated generation method of fault-analysis sheet,the getting method of probability data needed by safety-analysis,and the analysis and evaluation method of the quality of reconfiguration strategies for solving the safety problem of anvionics system under the multifailure-condition-space brought by dynamic reconfiguration characteristics.The main work is as follows:1.An abstract method of system block graph is given for a kind of modular dynamic reconfigurable anvionics system.It can authentically and directly describe the system's component modules,fault-tolerant actions,and the relationship between modules leading by fault-tolerant actions.Then the information contained in the system block graph is abstracted as mathematic form,namely,defining a failure-connection matrix called Modularshift,which transforms the system block graph into mathematic expression.Furthermore,based on the Modularshift,an automated generation method of failure-connection-analysis sheet basing on Modularshift is proposed.It can achieve automated generation of the multifailure-condition-space analysis sheet,increase the efficiency of failure analysis,and can effectively avoid faults caused by factitious factors,and it can offer supports and data for the next safety analysis.2.For solving the problem of state-space explosion brought by using Markov analysis to get probability data,a method of getting data based on Stateflow,namely finite state machine plus flow chart,is given.It can avoid generating state-space explosion,because it can put the link of calculating system-state probabilities aside to get directly probabilities requested when doing the analysis and evaluation of the quality of reconfiguration strategies.At the same time,it achieves removing coupling,not requiring the supports from data-results in the sheet anymore,so it can avoid error propagation caused by data-errors in the sheet.3.On the basis of the method of analysis and evaluation based on failure ratio,a method of analysis and evaluation based on safety probability is given.It takes into consideration not only the effect of failure ratio,but also the safety probability relating to reconfiguration strategy in the whole lifetime.Therefore,it can more efficiently and comprehensively evaluate the contribution of reconfiguration strategies on system safety.4.Based on the above studies,a kind of automated multifailure-condition-space safety-analysis plan is designed.The testing result shows that this plan has high efficiency and practicability,and can offer references for further increase in the level of system safety.