Hybrid task and message scheduling in hard real time distributed systems over FlexRay bus

Abstract

FlexRay is a vehicular communication protocol designed by the FlexRay Consortium since 2000 to meet growing requirements in hard real time automotive systems and to support Time Triggered as well as Event Triggered paradigms. FlexRay is designed to be faster and more reliable than the Controller Area Network (CAN) and The Time Triggered Protocol (TTP) in order to provide communication infrastructure for future generation high-speed control and safety critical applications, such as advanced powertrain, chassis and by-wire systems. Thus, there has been a lot of recent interest in timing analysis techniques in order to provide bounds for the message communication times on FlexRay. In this paper, we present an approach to check the schedulability and to compute the Worst Case Response Time (WCRT) for periodic and sporadic tasks, within a FlexRay node, responsible for sending messages on the Static Segment (SS) and Dynamic Segment (DS). On the other hand, we propose a scheduling table for messages transmitted over the FlexRay Static Segment. An interesting innovation would be the use of a scheduling algorithm performed on a FlexRay node to guarantee the arrival of the right data on the right time and to ensure that every task meets its deadline. In this paper, we will use as application an extended SAE (Society of Automotive Engineers) benchmark for the FlexRay network to identify the static and dynamic tasks, and calculate the response time, based on a hybrid scheduling model to further prove that the deadline of the SAE benchmark applications is insured.