Stochastic hybrid automaton model of a multi-state system with aging: Reliability assessment and design consequences

Dynamic reliability aims to relax the rigid hypotheses of traditional reliability enabling the possibility tomodel multi-state systems and consider changes of the nominal design condition of a system. Thesolution of such type of models is a complex task that cannot be tackled with analytical techniques andmust involve other types of formalisms based on simulation. One of the most promising simulationapproach is Stochastic Hybrid Automaton (SHA), able to breakdown a system into a physical and astochastic model that are coupled together with shared variables and synchronising mechanisms.In order to foster this latter research path, a simulation model, based on SHA, was codified as regardto a case of study; it has allowed to compute the reliability of a multi-state aging system under dynamicenvironmental and operational conditions. The same model has permitted to understand the systembehaviour resulting a useful tool for its design. Such type of highlights could not be inferred using tra-ditional reliability modelling, as shown in the comparison with a dynamic fault tree.The SHA model was codified in Simulink environment and represents a small step ahead for theconception and the delivering of a user-friendly tool for the DPRA.