Reliability analysis of safety critical systems: a truncated Markov modelling approach with state-space reduction

Dependability analysis, such as reliability, safety, etc., is a key factor for the evaluation of safety critical systems. in this article, we propose a hybrid reliability assessment framework, which is an amalgamation of two risk analysis methods namely: fault tree analysis (FTA) and truncated Markov modelling (TMM) for reliability evaluation. The proposed hybrid framework is a two-step process. First, it analyzes the system using FTA by discovering the basic events responsible for its failure. second, it uses TMM to evaluate the reliability analysis of the system. The two major contributions towards this framework are mapping an FTA to TMM, and reducing states in TMM to avoid the state-space explosion problem by proposing an algorithm named as FTA2TMM. The proposed framework is illustrated by considering the drone communication system as a case study, under the assumptions of non-repairable components, independent failures, and constant failure rates from the NPRD-2016 dataset following an exponential distribution. Reliability and unreliability measures obtained from the proposed method are evaluated mathematically and through simulation, and are compared with results from state-of-the-art methods. The results indicate that the TMM yields reliability results consistent with those obtained state-of-the-art risk analysis methods, while requiring a substantially reduced number of states.