A safety-critical study of FlexRay-based electronic control system design

This paper investigates the safety-critical design issues for the FlexRay-based electronic control of a brakeby- wire system. Electronically controlled safety-critical functions have recently become more important in the vehicle design. In the recent years, the IEC-61508 is considered as a state-of-The-Art standard for the development of safetycritical systems. The IEC-61508 has defined four safety integrity levels for providing a guide in safety critical design. Those integrity levels are determined by the acceptance probability of a dangerous failure per hour for the respective system. In this paper, associated safety metrics such as diagnostic coverage (DC), safe failure fraction (SFF), probability of failure on demand (PFD) and probability of failure per hour (PFH) are discussed. The standard IEC-61508 is applied to the safety-critical design of a brake-by-wire system. Calculation results show that CAN bus used as a single channel structure design only meets SIL-2 requirement. Instead, the design by using dual channel type of ECU such as FlexRay module is verified to satisfy the SIL-3 requirements of the IEC-61508 standard.