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

• Analytical model of a multistate system with aging.
• Limits of analytical techniques for Dynamic Probabilistic Risk Assessment.
• General definition of Hybrid Basic Events for Dynamic Reliability.
• Conception of a Stochastic Hybrid Automaton model based on Simulink.
• Dynamic reliability as a design tool for the dimensioning of industrial systems.

Dynamic reliability aims to relax the rigid hypotheses of traditional reliability enabling the possibility to model multi-state systems and consider changes of the nominal design condition of a system. The solution of such type of models is a complex task that cannot be tackled with analytical techniques and must involve other types of formalisms based on simulation. One of the most promising simulation approach is Stochastic Hybrid Automaton (SHA), able to breakdown a system into a physical and a stochastic 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 regard to a case of study; it has allowed to compute the reliability of a multi-state aging system under dynamic environmental and operational conditions. The same model has permitted to understand the system behaviour resulting a useful tool for its design. Such type of highlights could not be inferred using traditional 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 the conception and the delivering of a user-friendly tool for the DPRA.