Paul Milbredt

FlexRay schedule optimization of the static segment

The FlexRay bus is the prospective automotive standard communication system. For the sake of a high exibility, the protocol includes a static time-triggered and a dynamic event-triggered segment. This paper is dedicated to the scheduling of the static segment in compliance with the automotive-specific AUTOSAR standard. For the determination of an optimal schedule in terms of the number of used slots, a fast greedy heuristic as well as a complete approach based on Integer Linear Programming are presented. For this purpose, a scheme for the transformation of the scheduling problem into a bin packing problem is proposed. Moreover, a metric and optimization method for the extensibility of partially used slots is introduced. Finally, the provided experimental results give evidence of the benefits of the proposed methods. On a realistic case study, the proposed methods are capable of obtaining better results in a significantly smaller amount of time compared to a commercial tool. Additionally, the experimental results provide a case study on incremental scheduling, a scalability analysis, an exploration use case, and an additional test case to emphasis the robustness and exibility of the proposed methods.

Switched FlexRay: Increasing the effective bandwidth and safety of FlexRay networks

With the continued demand for more and innovative functions in series automobiles, significantly higher data-rates and more reliable communication are necessary than traditional automotive bus systems, e.g., the controller area network (CAN), provide. In this paper, we present a novel hardware device for FlexRay networks, which splits the bus into separate branches and operates as a selective central switch.

Automated Testing of FlexRay Clusters for System Inconsistencies in Automotive Networks

Most innovations in the automotive domain are nowadays enabled by networked embedded systems. In this context a new communication subsystem termed FlexRay was recently introduced. Relying on the time-triggered paradigm it promises to provide the bandwidth and reliability required for future applications. For building reliable systems with FlexRay, verification and testing are of utmost importance. In this paper a new system test approach that focuses on the communication subsystem is presented. With the help of a dedicated FPGA-based star-coupler we show that inconsistent system states (slightly-off- specification failures) can occur in real life systems, how they can be found using our solution and how one can avoid them.

FlexRay switch scheduling — A networking concept for electric vehicles

It is projected that the communication data volume in electric vehicles will significantly increase compared to state-of-the-art vehicles due to additional functionalities like x-by-wire and safety functions. This paper presents a networking concept for electric vehicles to cope with the high data volume in cases where a single FlexRay bus is not sufficient. We present a FlexRay switch concept that is capable of increasing the effective bandwidth and improving the safety of existing FlexRay buses. A prototype FPGA implementation shows the feasibility of our approach. Further, a scheduling approach for the FlexRay switch that obtains the optimal results based on Integer Linear Programming (ILP) is presented. Since the ILP approach becomes intractable for real-world problems, we present a heuristic three-step approach that determines the branches of the network, performs a local scheduling for each node, and finally assembles the local schedules into a global schedule. Test cases and an entire realistic in-vehicle network are used to emphasize the benefits of the proposed approach.

An investigation of the clique problem in FlexRay

Distributed, time-triggered communication based on FlexRay is likely to become an enabler for future safety related applications in the automotive domain. Prior to series deployment, however, confidence has to be established that all mechanisms work as expected. One particular issue in this regard is the clique problem. Cliques are groups of nodes connected to the same bus which are only able to communicate with the members of the same clique, but not with members from another one. In time-triggered systems cliques might be caused, for instance, by Byzantine faults leading to a different view of the global time. In constrast to other hard real-time systems, FlexRay lacks explicit protocol support for detecting and resolving cliques. Thus, in this paper we investigate the clique problem in a real FlexRay system. We explain the different types of cliques and give examples how they might emerge and look like. One focus is the experimental study of the behavior of a real FlexRay cluster with existing cliques. In particular, we investigate the integration behavior of nodes into a system with present cliques as well as the behavior of the system when it is in a clique state. After a presentation of the results, we conclude by giving some directions about some protocol features which might be used for implementing clique avoidance or clique detection mechanisms.

A Test Tool for FlexRay-based Embedded Systems

In this paper we present an architecture for a test and diagnosis toolset for FlexRay-based automotive distributed networks. Next to data monitoring and recording, this toolset provides facilities for fault injection and replay. Hence, the presented implementation is tailored for an embedded test and fault diagnosis and will enable an assessment of the reliability and dependability of future automotive solutions.

INDEXYS*, a logical step beyond GENESYS

Embedded computing systems have become a pervasive aspect in virtually all application domains, such as industrial, mobile communication, transportation and medical. Due to increasing computational capabilities of microcomputers and their decreasing cost, new functionality has been enabled (e.g., driver assistance systems) and cost savings have become possible, e.g., by the replacement of mechanical components by embedded computers. Conventionally, each application domain tends to develop customized solutions, often re-inventing concepts that are already applied in other domains. It is therefore expedient to invest into a generic embedded system architecture that supports the development of dependable embedded applications in many different application domains, using the same hardware devices and software modules. INDEXYS targets to pave the way from the European Commission Framework 7 GENESYS Project reference computing architecture approach towards pilot applications in the automotive-, railway- and aerospace industrial domains. INDEXYS will follow-up GENESYS project results and will implement selected industrial-grade services of GENESYS architectural concepts. The results of laying together GENESYS, INDEXYS and the new ARTEMIS project ACROSS, which will develop multi processor systems on a chip (MPSoC) using GENESYS reference architecture and services, will provide integral cross-domain architecture and platform, design- and verification- tools, middleware and flexible FPGA- or chip- based devices lowering OEM cost of development and production at faster time-to market.n of COOPERS.

Composability and compositionality in CAN-based automotive systems based on bus and star topologies

Controller Area Network (CAN) is the most widely used field bus protocol in the automotive domain. The development process of todays cars follows the well established automotive V-Model. Traditional bus-based CAN makes the development an ever increasing challenge. For example, the introduction of a single additional CAN message influences the timing of already existing messages and thereby increases testing and integration efforts. The lack of composability and compositionality of traditional CAN leads to an overhead in the whole development cycle. In this paper we propose a development process that is based on a time-triggered CAN router. We examine the influence of our proposed development approach on major phases of the automotive V-Model. Our evaluation is based on CAN traffic of a mass-produced car by a major car manufacturer and a Fiel Programmable Gate Array (FPGA) based prototype implementation of the CAN router. From the results we gathered during our evaluation we conclude that a CAN router based development approach has the potential to simplify the development efforts that have to be undertaken by car manufactures.

FlexRay Static Segment Scheduling

The FlexRay protocol was introduced by an international consortium including several car manufacturers to cope with growing real-time requirements of advanced driver assistance functions and safety functions in the automotive domain. The FlexRay protocol offers a static and dynamic segment with a high data rate of 10 Mbit/s. While the event-triggered dynamic segment is used mainly for diagnosis, maintenance, and calibration data, the time-triggered static segment might be used for critical data with strict real-time requirements. In addition to standard linear bus and star topologies, the FlexRay bus allows hybrid topologies including a dual channel mode to increase the reliability. However, in contrast to the prevailing CAN bus [4] in the automotive domain, the configuration of the FlexRay bus is significantly more complex: It requires a large set of parameters and a predefined schedule. This chapter introduces a scheduling concept for the static segment of the FlexRay based on the transformation to a two-dimensional bin packing problem.

Designing FlexRay-based automotive architectures: a holistic OEM approach

FlexRay is likely to become the de-facto standard for upcoming in-vehicle communication. Efficient scheduling of the static and dynamic segment of the communication cycle in combination with the determination of more than 60 parameters that are part of the FlexRay protocol is a challenging task. This paper provides a formal analysis for interdependencies between the parameters as well as a scheduling approach for the static and dynamic segment. Experimental results give evidence of a significant interdependency between the subtasks such that a holistic scheduling approach becomes mandatory to provide high-quality FlexRay schedules. As a solution, this work introduces a complete functional FlexRay scheduling approach that takes parameter selection, allocation of messages to the static and dynamic segment, and concurrent scheduling into account. A real-world case study from the automotive domain gives evidence of efficiency and applicability of the proposed approach.