System failure modelling using binary decision diagrams

The aim of th1s thesis is to develop the Binary Decision Diagram method for the analysis of coherent and non-coherent fault trees. At present the well-known ite technique for converting fault trees to BDDs is used Difficulties appear when the ordering scheme for basic events needs to be chosen, because it can have a crucial effect on the size of a BDD An alternative method for constructing BDDs from fault trees which addresses these difficulties has been proposed The Binary Decision Diagram method provides an accurate and efficient tool for analysing coherent and non-coherent fault trees. The method is used for the qualitative and quantitative analyses and it is a lot faster and more efficient than the conventional techniques of Fault Tree Analysis The Simplification techniques of fault trees prior to the BDD conversion have been applied and the method for the qualitative analysis of BDDs for coherent and non-coherent fault trees has been developed A new method for the qualitative analysis of non-coherent fault trees has been proposed An analysis of the efficiency has been carried out, comparing the proposed method with the other existing methods for calculating prime implicant sets. The main advantages and disadvantages of the methods have been identified. The combined method of fault tree Simplification and the BDD approach has been applied to Phased Missions This application contains coherent and non-coherent fault trees Methods to perform thmr simplification, conversion to BDDs, minimal cut sets/prime implicant sets calculation, and the mission unreliability evaluation have been produced.