Insights into the Sensitivity of the BRAIN (Braided Ring Availability Integrity Network)--On Platform Robustness in Extended Operation

Low-cost fault-tolerant systems design presents a continual trade-off between improving fault-tolerant properties and accommodating cost constraints. With limited hardware options and to justify the system design rationale, it is necessary to formulate a fault hypothesis to bound failure assumptions. The system must be built on a foundation of real-world relevance and the assumption of coverage of the fault hypothesis. This paper discusses a study that examines the sensitivity of a BRAIN (braided ring availability integrity network) design to different fault types and failure rates in a safety-relevant application. It presents a Markov-based model (using ASSIST, SURE, and STEM analysis tools) and a series of experiments that were run to analyze the overall dependability of the BRAIN approach. The study evaluates the mission reliability and safety in the context of a hypothetical automotive integrated x-by-wire architecture on top of the BRAIN. Drawing from experience in the aerospace domain, the authors investigate the possibility of continued operation for a limited period after a detected critical electronic failure. Continued operation would allow a driver to reach repair facilities rather than stopping the vehicle to call for roadside assistance or "limping home."