This thesis looks into ways of developing a new approach for fault tree automation.
Initially an extensive literature survey was undertaken to try and identify if any
methods contained useful features that might warrant further development. The two
methods that were chosen were the decision table method and the digraph method.
The new hybrid method is based on the flexibility of the decision table method but
incorporates a way of detecting, classifying and analysing control loops, similar to the
use of operators in the digraph approach. As well as using operators to deal with
control loops new operators are introduced that deal with current and no current in
electrical circuits. These new operators have been developed to be able to handle
components that are common to multiple circuits. The advantages of applying
operators during fault tree construction is to reduce the number of repeated and
inconsistent events that may occur in the tree, and to significantly reduced the size of
the constructed fault tree. Thus producing a tree logic that can easily be followed by
an analyst and is in an appropriate format for direct input to an fault tree analysis code.
The new method has been automated and successfully applied to three railway safety
systems obtained from London Underground Ltd. To test the ability of the Automatic
Fault Tree Construction Code (AFTCC) the complexity of each of the three systems
increased. The first system, the Train Stop system, did not contain any circuits; the
second, the Train Detection system, contained simple circuits and lastly the Train
Braking system, contained multiple nested circuits.
A Doctoral Thesis. Submitted in partial fulfillment of the requirements for the award of Doctor of Philosophy of Loughborough University.