With an increasing degree of automation, automated vehicle systems become more complex in terms of functional components as well as interconnected hardware and software components. Thus, holistic systems engineering becomes a severe challenge. Emergent properties like system safety are not solely arguable in singular viewpoints such as structural representations of software or electrical wiring (e.g. fault tolerant). This states the need to get several viewpoints on a system and describe correspondences between these views in order to enable traceability of emergent system properties. Today, the most abstract view found in architecture frameworks is a logical description of system functions which structures the system in terms of information flow and functional components. In this article we extend established system viewpoints towards a capability-based assessment of an automated vehicle and conduct an exemplary safety analysis to derive behavioral safety requirements. These requirements can afterwards be attributed to different viewpoints in an architecture frameworks and thus be integrated into a development process for automated vehicles.
Regarding safety goals and the resulting requirements, functionalities provided by a system have to be defined. @cite_18 discuss requirements for maintaining a safe state of a vehicle at any time. For that reason, the system needs to detect an occurring fault and, afterwards, transfer the vehicle into a predefined safe state. The duration of this process depends on a variety of parameters, e.g. the type of automated function and the driving conditions. As a prerequisite for a fall back mode, the vehicle has to be equipped with redundancies in case of degraded functionality. This applies to every component implementing a specific function (e.g. the communication network) and depends on the degree of relevance for meeting the safety goals. However, the relevant components are not visible in a singular architecture.
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Driver assistance systems have been successfully deployed to the market in the last fifteen years resulting in an increase of driving comfort and driving safety. In the future, these systems will be able to analyze ever more complex traffic situations and to support the driver or even act independently. Upcoming functionality will lead to partially automated driving, highly automated functions will follow soon after. With the increase of automation the role of the driver is going to change gradually from an active driver to a passenger at least for some duration of the drive. We discuss the implications of this evolution on the requirements for future vehicle architectures. In particular, we discuss the electric on-board power supply of critical driving components for longitudinal and lateral vehicle guidance and derive system safety and architectural requirements.