Scientific paper ID 1272 : 2016/1

One of two principles which build critical safety systems (Safety Critical Systems) is fault tolerance (Fault-tolerance). In the article are modeled and tested k˅n systems, in particular the majority 2˅3 (Triple modular redundancy) and 3˅5, which are typical of the Fault-tolerance principle. The aim of the study is to derive mathematical models by which to quantify the impact of the structure contained in the surplus on the mean time between failures of the system and to propose an algorithm and perform calculations to verify the effectiveness of the redundancy.

A comparative value ξ is introduced, which assesses the change in the time indicator, depending on the verge of majority and reliability of the elements of which it is built. New formulas are derived and relationships are determined between the times sought and their influencing values - the parameters of the structural rdundancy k and n and the coefficient of availability of the building elements Kг. It is found that when the level of readiness of the structural element that builds the system is lower than an established threshold, the excess effect is lost. It is concluded that the costs of structural redundancy are beneficial, but only at sufficiently high initial reliability of the building units that make up the system.