Fault tree analysis in an early design stage using the Dempster-Shafer theory of evidence

The Dempster-Shafer Theory of Evidence (DST) has been considered as an alternative to probabilistic modelling if both a large amount of uncertainty and a conservative treatment of this uncertainty are necessary. Both requirements are normally met in early design stages. Expert estimates replace field data and hardly any accurate test results are available. Therefore, a conservative uncertainty treatment is beneficial to assure a reliable and safe design. The paper investigates the applicability of DST which merges interval-based and probabilistic uncertainty modelling on a fault tree analysis from the automotive area. The system under investigation, an automatic transmission from the ZF AS Tronic series is still in the development stage. We investigate the aggregation of expert estimates and the propagation of the resulting mass function through the system model. An exploratory sensitivity based on a nonspecifity measure indicates which components contribute to the overall model uncertainty. The results are used to predict if the system complies with a given target failure measure.