The relevance of safety applications within the automotive industry is increasing continuously, for example due to vehicle automation and decreasing performance of mechanical backups. To cope with these trends, the power supply of safety-related electrical and/or electronic systems needs to be ensured. This leads to increasing functional safety requirements. Compliance with ISO 26262 will be more in focus in the future. Currently, the compliance with ISO 26262 may be used to argue the state of the art focusing on product liabilityhowever, it will become mandatory for homologation in the future. Thereby, the power supply system is a crucial point since faults of the power supply system are currently the major contributor for vehicle breakdowns with increasing tendency. So far, there is no standard approach within the automotive industry how to ensure functional safety for power supply systems. To fill this gap, this technical elaboration evaluates functional safety with focus on power supply system development. Hence, guidelines on how to apply the ISO 26262 are provided based on discussions within the automotive industry and research institutes. The focus is on the concept phase, i.e. item definition, hazard analysis and risk assessment, and the functional safety concept. The functional safety concept is based on a structured hierarchical breakdown to systematically derive safety requirements from the item level down to the power supply system level. The essential requirementbeside the safe power feed and safe power distributionis to assure the freedom from interference between the safety and non-safety relevant components.
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.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.