Research On Modeling And Analysis Of State/Event Faults Trees

With the development and improvement of technology, more and more mechanical and electrical components are replaced by software control system(also called embedded system) in safety-critical domains such as avionics, automobile, railway and industrial automation. When traditional method of reliability modeling analysis(like fault tree analysis) is applied on software control system, it is insufficient to deal with duration, temporal order of events and state dependencies.To make up for the defects of traditional modeling method, Bernhard Kaiser et al. propose a new model which combines elements from FTA and from state-based modeling techniques, called state/event fault trees. However, state/event fault trees has not been widely applied because research based on state/event fault trees(including the qualitative and quantitative analysis of it) is still under developing. Therefore, this paper is mainly about modeling and analysis of state/event fault trees.First of all, we start from the modeling ability of state/event fault trees, take avionics network as an example, establish the corresponding state/event fault trees model of Avionics Full Duple X Switched Ethernet's data integrity reliability according to its characters and working mechanism, show the advantages of state/event fault trees model on the description ability of states dependencies and extensibility of system components.Secondly, we start from the simplification method of state/event fault trees, expand the Guarded Interface Automata combining with the semantic specification of state/event fault trees model according to the feature that Guarded Interface Automata can be simplified. We design the transform rule from state/event fault trees model to Guarded Interface Automata and improve the merge algorithm of Guarded Interface Automata. We provide the simplification procedure of equivalent calculation model of state/event fault trees, prove the validity of the simplification method through examples and show the effect of simplification.Furthermore, this paper has done some further study of quantitative calculation of Minimal Cut Sequence based on the generation method of Minimal Cut Sequence of state/event fault trees. This paper also design the semantic transform rule from state/event fault trees to Colored Petri Net based on the feature that tokens in Colored Petri Net can pass attribute. According to this rule, the pass and transfer of original fault can be reflected in Colored Petri Net. We can present the radical reason of system fault through the attributes of tokens in system failure place corresponding to Colored Petri Net. And we can also calculate the probability of fault states corresponding to different token's attributes so we can get the probability of system fault generated by each piece of Minimal Cut Sequence. At last, we calculate the degree of effect generated by each piece of Minimal Cut Sequence through experiment in fire protection system and optimize the design of the system according to the results.