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
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.
A Doctoral Thesis. Submitted in partial fulfilment of the requirements for the award of Doctor of Philosophy of Loughborough University.