Reliability Analyses of Combined Voting and Standby Redundancies

There is a trend towards more elaborate architecture of redundancy for ultrareliable systems. When used with discretion, mathematical analyses do provide some useful yardsticks for the system engineer at the conceptual stage of a design. This paper provides a statement of conventional mathematical assumptions and the consequent limitations of the formulae which result from them. More importantly, the paper provides simple formulae for reliability prediction which assist rapid manual appraisals of a large number of possible configurations of majority voters and voter-switches (voter-switches combine voting with standby redundancy). In short order, the decision maker can appraise the potential benefit on system reliability of sophisticated redundancy.