FlexRay Protocol Research Articles

Message Scheduling for the FlexRay Protocol: The Static Segment

In recent years, <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">time-triggered</i> communication protocols have been developed to support time-critical applications for in-vehicle communication. In this respect, the FlexRay protocol is likely to become the <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">de</i> <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">facto</i> standard. In this paper, we investigate the scheduling problem of periodic signals in the <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">static</i> <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">segment</i> of FlexRay. We identify and solve two subproblems and introduce associated performance metrics: (1) The signals have to be packed into equal-size messages to obey the restrictions of the FlexRay protocol, while using as little bandwidth as possible. To this end, we formulate a nonlinear integer programming (NIP) problem to maximize bandwidth <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">utilization</i> . Furthermore, we employ the restrictions of the FlexRay protocol to decompose the NIP and compute the <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">optimal</i> <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">message</i> <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">set</i> efficiently. (2) A message schedule has to be determined such that the periodic messages are transmitted with minimum <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">jitter</i> . For this purpose, we propose an appropriate software architecture and derive an integer linear programming (ILP) problem that both minimizes the jitter and the <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">bandwidth</i> <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">allocation</i> . A case study based on a benchmark signal set illustrates our results.

An Automated Model Based Design Flow for the Design of Robust FlexRay™ Networks

The enormous increase of vehicle functions realized through electronic components significantly impacts the communication within the vehicle network. More functions are requesting higher bandwidth; safety applications require a deterministic communication scheme to ensure reliable system performance even under harsh real world conditions. The new FlexRay vehicle communication standard addresses these requirements, with production networks already on the road. The high transmission rate introduces new challenges for network developers dealing with the implementation of the electrical physical layer as the dynamic behavior of the system cannot be predicted using manual calculations. The FlexRay physical layer working group has therefore established a simulation task force dealing with issues related to FlexRay's physical layer implementation. This task force has developed a virtual prototype based methodology to give network developers early verification of FlexRay physical layer implementations. Topology variants that depend on equipment in the vehicle can be investigated quickly with regard to their robustness under nominal and even worst case conditions. This paper introduces an automated, simulation-based methodology based on the guidelines and criteria defined in the FlexRay physical layer specification. In addition, this paper shows how close OEMs, IC vendors, conformance testers and software tool vendors must work together to define and realize a robust design methodology that is based on a virtual prototype implementation of the FlexRay network. BASICS OF FLEXRAY COMMUNICATION SYSTEMS When developers are dealing with In-Vehicle network implementations they have to ensure that both the software part as well as the electrical physical implementations is robust. The design and verification of both parts is usually very time-consuming. Sufficient testing is not possible using vehicle hardware prototypes since these are usually not available in the very early design stage when network concepts need to be evaluated in terms of their robustness. This paper shows how to design and verify the physical layer implementation of FlexRay systems through an automated and robust simulation based engineering method. The focus of this paper is on the verification methodology. Details about the FlexRay protocol and how to model them are comprehensively described in [4]. The FlexRay protocol and its electrical physical layer are specified in the FlexRay protocol and the Electrical Physical Layer (EPL) specification. These activities are standardized through the FlexRay consortium which is a society of all major automotive OEMs and their suppliers. Unlike the most popular CAN communication protocol, FlexRay is a time triggered communication protocol with a maximum transmission rate of 10 MBit/s. This is 10x higher than the theoretical transmission rate of CAN which is 1 MBit/s (in practical applications the transmission rate of CAN is usually below 1 MBit/s to ensure enough robustness). FlexRay allows arbitrary topology types like linear, star, or even hybrid as shown in figure 1. Figure 2 shows a possible future vehicle Figure 1: FlexRay topology (source FlexRay EPL) 2008-01-1031 An Automated Model Based Design Flow for the Design of Robust FlexRayTM Networks

A Reliable Gateway for In-vehicle Networks

This paper presents a reliable gateway for communication between the LIN, CAN, FlexRay protocols. A gateway is indispensable device for constructing in-vehicle networks. Networks with different protocols have to include an additional gateway in order to exchange information among different networks. The main function of the gateway is translation. However, there is some latency when a message is transferred from one node (source) to another (destination); further, there is a high probability of error due to different protocol specifications such as baudrates, message frame formats, and so on. Therefore the implementation of a reliable gateway is a challenging task. In this paper, we propose a reliable gateway based on OSEK OS and OSEK NM for in-vehicle networks. We develop a gateway embedded system and implement a reliable gateway mechanism. We then examine the developed gateway system and present the results of experiments with several trials.

지능형 자동차의 분산형 시스템을 위한 FlexRay 네트워크 시스템의 구현

Safety critical systems such as x-by-wire systems require in-vehicle network systems that can interconnect various sensors, actuators, and controllers. These networks need to have high data rate, deterministic operation, and fault tolerance. Recently, FlexRay protocol that is a time-triggered protocol has been introduced, and many automotive companies have been focusing on this protocol. This paper presents a design method of FlexRay network system and implementation of FlexRay-based motor control system.

SAFETY AND SYSTEM INTEGRITY OF ISOBUS APPLICATIONS FOR AGRICULTURAL MACHINE CONTROL SYSTEM (AMCS)

This paper concerns the safety and system integrity analysis of a typical ISOBUS implementation for the communication network of a distributed mechatronics system for agricultural machines. Despite ISOBUS, described by the international standard communication network, is standardized under the norm ISO11783, we will make an analytical overview of a hybrid network for off-highway vehicles where ISOBUS and FlexRay protocols co-exist. A functional analysis has been conducted and a methodology for a quantitative evaluation of the overall system (in terms of performance and reliability) is carried out. The experiments described here (including the timeframe for future works) take the move from the framework depicted by the regional-funded project Pro-Tract: a lab has been set up to investigate these items related to off-highway vehicles.