Functional Safety Analysis and Proposal of Fail-Operational Steer-by-Wire System

In the pursuit of enhancing vehicle safety and reliability, this paper offers an in-depth analysis and improvement of steer-by-wire (SbW) systems. Steer-by-wire technology, which removes the mechanical link between the steering wheel and the wheels, depends heavily on electronic and electromechanical components to control vehicle lateral movement. This study follows the guidelines of ISO 26262, which outlines a framework for functional safety in automotive systems. The paper starts by outlining the SbW system and its key components. Continues with, the introducing of the reference system that derived from NHTSA's publication and mechanical backup excluded to focus on the full SbW system and its primary functions. After the reference system is defined for analysis, Hazard Analysis and Risk Assessment (HARA) applied to the reference system to obtain the vehicle level hazards and safety goals. Following, Fault Tree Analysis (FTA) utilized the discover root causes of failures that can violate the safety goals. After that, a methodology presented to discover potential dependent failure scenarios by combining the coupling factor classes and obtained failure modes with the system components. As a result of the analysis, the system level requirements developed to ensure the SbW system can transition to safe states during variety of failure scenarios. In the next step, proposed system architecture that meets with developed requirements presented. The proposed architecture ensures that even in the case of failures, the vehicle can maintain essential steering capabilities.