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

Abstract

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