Evaluating System Architecture Safety in Early Phases of Development with MBSE and STPA

Abstract

Emerging segments such as autonomous driving require new by-wire system architectures for steering and braking. These system architectures are highly safety-critical and currently not commonly used in the automotive industry. This results in challenges for traditional development approaches. One issue is that a well-thought-out architecture selection is already required in early phases of development. Within this paper, a concept is proposed to help consideration of safety in this timely architecture selection, using a safety trade-off concept. An early consideration of system architecture safety is achieved by utilization of a formalized System-Theoretic Process Analysis on a Systems Modeling Language model. This underlying system model was developed with a Model-based System Engineering approach. Additionally, it is explained how classical safety considerations and safety principles can be integrated into this safety trade-off. Finally, the approach is demonstrated in an architecture comparison for a simplified Steer-by-Wire architecture. Results show that it is possible to find relevant safety requirements and use them to compare solution architecture candidates.