Evidence of the Effectiveness of Cyclic Technical Safety Mechanisms

At the vehicle powernet level, technical safety mechanisms, e.g., smart switching modules, mainly operate in a discrete-time or cyclic manner. In accordance with the functional safety standard ISO 26262, safety-related E/E systems require a safety validation process. Therefore, evidence of the effectiveness of technical safety mechanisms shall be made available. Particularly for cyclic safety mechanisms (cyclic - regarding their fault handling performance), this is an open issue. In this regarding, a novel modeling approach for cyclic safety mechanisms is introduced to provide evidence of their effectiveness. Thus, cyclic diagnoses, e.g., vehicle start-up checks, or new dedicated measures could be utilized in the quantitative validation of residual faults. The novel approach enhances the current state of research in a way that makes the interpretation of a piecewise constant failure rate irrelevant. In addition, this approach is not solely based on the exponential distribution; therefore, it is universally adaptable, and it is demonstrated for the use case of alternating safety mechanisms. This degree of freedom is accompanied by more conservative quantitative results in comparison to those obtained in recent studies. Nevertheless, the current state-of-the-art method totally excludes the evaluation of cyclic safety mechanisms because of a lack of evidence of effectiveness. This elementary concept is based on the derivation, elaboration, and separation of time dependencies in a safety scenario while extracting and evaluating the partial system states with effective continuous behavior. The derived mathematical model and its approximation are based on fundamental statistics and are indicated as the final recommended cyclic approach.