Reliability-based parameter design for FlexRay network in vehicles

Abstract

FlexRay has been extensively applied to safety-critical systems, such as powertrain, chassis, and X-by-wire system in vehicles. Its transmission reliability considerably influences vehicle safety. In this study, frame coding and media access control in the FlexRay protocol are analyzed, and calculation equations are deduced for the length of time slot and coded frame of FlexRay. Redundant transmission of FlexRay static frame is introduced to solve the transmission failure caused by the bit error in the physical layer, and the transmission reliability of a static segment is defined for the mechanism. Considering the demands on transmission reliability and network schedulability, the configuration of FlexRay parameters, including communication cycle, time slot allocation, and segment length, is formulated as a generalized optimization problem with constraints on predefined transmission reliability and response time of messages. A Reliability-Based Parameter Optimization algorithm and its sub-algorithms, Response Time of Dynamic Segment and Slot Allocation for the Predefined Reliability, are presented to approximately solve the optimization model. Experiment results validate the proposed method, which can efficiently improve the transmission reliability and guarantee the real-time performance of the FlexRay network.