Integrating FMEAs, FMEDAs, and Fault Trees for Functional Safety
Chad Kymal, Omnex Gregory Gruska · 2021
The functional safety FMEA (Failure Mode Effects Analysis) will be shown to include both single and multi-point faults and incorporate safety mechanisms as preventive controls. Furthermore, by constructing this FMEA using requirements flow down from the System, Hardware and Software development, the FMEA can link with the FMEDA (Failure Mode Effects and Diagnostic Analysis) and the FTA (Fault Tree Analysis) and together they provide Single-Point and Latent Fault metrics (SPFM and LFM) including the "Probabilistic Metric for random Hardware Failures" (PMHF) metrics in a consistent manner.FMEAs traditionally have only incorporated single-point faults. In this ground breaking presentation of this approach, the functional safety FMEA will be shown to include both single and multi-point faults and incorporate safety mechanisms as preventive controls. As the FMEA is filled out, the FMEDA will be populated, providing consistency between the FMEDA and FMEA techniques. The FMEA of the hardware is developed at the different levels, while the FMEDA is at the component level and the failure modes of the FMEDA are component failure modes. If the FMEA is completed using the AIAG-VDA FMEA handbook approach, where the higher level, focus level, and lower levels relationships are used and there is a cause and effect relationship between the failure modes at the different levels, then the FTA can also be developed from the FMEA. In this way, the FMEA, FMEDA and FTA are linked documents and the FMEDA and FTA provide the single-point fault, multi-point fault, and the "Probabilistic Metric for random Hardware Failures" (PMHF) metrics in a consistent manner.