Sequential Logic for State/Event Fault Trees: A Methodology to Support the Failure Modeling of Cyber Physical Systems

摘要

The society is nowadays increasingly controlled through embedded systems. The certification process of such systems is often supported by tree based approaches like fault trees. Nevertheless, these methodologies have some crucial drawbacks when it comes to dynamic systems. In the standard fault tree analysis it is not possible to model dependent events as well as timing behavior. To deal with these disadvantages state/event fault trees (SEFTs) were developed. However, this method is mainly restricted to academic problems due to its poor analysis procedures. To overcome this problem, this paper introduces a new qualitative analysis technique for SEFTs based on event sequences that can be identified out of their reachability graphs. To analyze these sequences an event sequence minimization schema similar to minimal cut sets of normal fault trees is proposed. Afterwards, a sequence algebra is used to further minimize these temporal expressions and transform them as far as possible into static ones.