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Handbook of Reliability, Availability, Maintainability and Safety in Engineering Design - Part 14

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Handbook of Reliability, Availability, Maintainability and Safety in Engineering Design - Part 14 studies the combination of various methods of designing for reliability, availability, maintainability and safety, as well as the latest techniques in probability and possibility modelling, mathematical algorithmic modelling, evolutionary algorithmic modelling, symbolic logic modelling, artificial intelligence modelling, and object-oriented computer modelling, in a logically structured approach to determining the integrity of engineering design. . | 3.3 Analytic Development of Reliability and Performance in Engineering Design 113 Determination of an optimum conceptual design is carried out as follows a A performance parameter profile index PPI is calculated for each performance parameter xi. This constitutes an analysis of the rows of the matrix in which PPI n -1 n X 1 Cij I J 1 3.80 where n is the number of design alternatives. b Similarly a design alternative performance index API is calculated for each design alternative yj. This constitutes an analysis of the columns of the matrix in which -1 m API m 1 cij I v 1 3.81 where m is the number of performance parameters. c An overall performance index OPI is then calculated as 100 OPI ---- mn t PPI API i 1J 1 3.82 where m is the number of performance parameters n is the number of design alternatives and OPI lies in the range 0-100 and can thus be indicated as a percentage value. d Optimisation is then carried out iteratively to maximise the overall performance index. 3.3.1.5 Labelled Interval Calculus Interval calculus is a method for constraint propagation whereby instead of designating single values information about sets of values is propagated. Constraint propagation of intervals is comprehensively dealt with by Moore 1979 and Davis 1987 . However this standard notion of interval constraint propagation is not sufficient for even simple design problems which require expanding the interval constraint propagation concept into a new formalism termed labelled interval calculus Boettner et al. 1992 . Descriptions of conceptual as well as preliminary design represent sets of systems or assemblies interacting under sets of operating conditions. Descriptions of detail designs represent sets of components functioning under sets of operating conditions. The labelled interval calculus LIC formalises a system for reasoning about sets. LIC defines a number of operatives on intervals and equations some of which can be thought of as inverses to the usual notion of interval