Architecture of By-Wire Systems Design Elements and Comparative Methodology 2003-01-1291

By-wire systems have the potential of augmenting the normal capabilities of human drivers as well as serving as enablers for emerging safety technologies. To achieve these features, these systems must be carefully designed, analyzed, and verified for safety because they are new, complex, and potentially exhibit new and different failure modes and effects. Duplication may be required to ensure that safety margins are met in the presence of faults. Full duplication of every system may not lead to a cost effective implementation, especially if multiple independent by-wire systems are placed on a single vehicle. Other architectural approaches for the integration of by-wire systems need to be considered and analyzed. These architectures should meet if not exceed the safety requirements while providing a more cost effective implementation than a fully duplicated architecture. We focus on architectures based on software redundancy and dynamic reconfiguration of tasks over different but existing processors. We identify essential elements that govern the design of such architectures and present key comparison elements that may differentiate amongst the candidate architectures. We also present a methodology to evaluate a variety of architecture designs. The methodology integrates commercially off the shelf software tools to generate a figure of merit that compares different architecture designs.