SUBTITLE Advanced Techniques in Reliability Model Representation

The current tendency of ight control system designs is towards increased integration of applications and increased distribution of computational elements. The reliability analysis of such systems is di cult because subsystem interactions are increasingly interdependent. Researchers at NASA Langley Research Center have been working for several years to extend the capability of Markov modelling techniques to address these problems. This e ort has been focused in the areas of increased model abstraction and increased computational capability. The reliability model generator (RMG) is a software tool that uses as input a graphical objectoriented block diagram of the system. RMG uses a failure modes-e ects algorithm to produce the reliability model from the graphical description. The ASSURE software tool is a parallel processing program that uses the semi-Markov unreliability range evaluator (SURE) solution technique and the abstract semi-Markov speci cation interface to the SURE tool (ASSIST) modelling language. A failure modes-e ects simulation is used by ASSURE. These tools were used to analyze a signi cant portion of a complex ight control system. The successful combination of the power of graphical representation, automated model generation, and parallel computation leads to the conclusion that distributed fault-tolerant system architectures can now be analyzed.