Integration of Multiple Active Safety Systems using STPA 2015-01-0277

Automobiles are becoming ever more complex as advanced safety features are integrated into the vehicle platform. As the pace of integration and complexity of new features rises, it is becoming increasingly difficult for system engineers to assess the impact of new additions on vehicle safety and performance. In response to this challenge, a new approach for analyzing multiple control systems as an extension to the Systems Theoretic Process Analysis (STPA) framework has been developed. The new approach meets the growing need of system engineers to analyze integrated control systems, that may or may not have been developed in a coordinated manner, and assess them for safety and performance.

The new approach identifies unsafe combinations of control actions, from one or more control systems, that could lead to an accident. For example, independent controllers for Auto Hold, Engine Idle Stop, and Adaptive Cruise Control may interfere with each other in certain situations. This paper demonstrates a method to efficiently identify potential unsafe scenarios without requiring a complete enumeration or individual analysis of all possible scenarios. As a result, the approach is scalable to large systems with many controllers. In this paper, the method is demonstrated through a case study involving several driver assistance systems including advanced brake controls, advanced engine control, and advanced adaptive cruise control. Potential conflicts that would prohibit safe and successful operation are also efficiently identified, allowing engineers to develop suitable controls that prevent these conflicts.