Abstract: The ever-increasing functionalities and escalating complexity of existing Advanced Driver Assistance Systems inevitably cause the problem of Safety of The Intended Functionality. The identification and generation of trigger conditions play a critical role in SOTIF activities. Most existing trigger condition identification approachesare mainly based on the System-Theoretic Process Analysis method, which however neglect the issues within the system's functional state transitions. This paper adopts a knowledge-driven approach to construct a trigger condition identification mechanism by integrating STPA and Finite State Machine theories to establish an expanded system control structure. Safety analysis is conducted concerning the expanded control architecture and functional state transitions. By considering system limitations and human misuse, trigger conditions are identified, generated, described, classified, and labeled. Finally, the proposed trigger condition generation mechanism is applied to an Integrated Cruise Assistance system, obtaining trigger conditions and their classifications. The generated mechanism is compared with existing trigger condition generation methods, demonstrating its practicality, feasibility, and effectiveness.

Key words: safety of the intended functionality (SOTIF), system theoretic process analysis (STPA), finite state machine (FSM), trigger condition, advanced driver assistance systems (ADAS)