FlexRay Bus Research Articles

Network Optimization of X-by-Wire System Based on FlexRay Bus

X-by-Wire system is a typical automotive network control system. The control of x-by-wire system depends on communication network (like CAN, TTCAN or FlexRay), it must meet not only the control performance, but also the real-time performance and reliability requirement. Network optimization in x-by-wire system is great significant for achieving these targets. In this paper, first task graph was designed for the x-by-wire system, and different control links were distinguished from the task graph. Then the network optimization algorithm was designed to implement message slot arrangement coordinated with task execution time in the control links, and the principle of the network optimization algorithm design is reducing the control link response time for the best effort. Through a typical car x-by-wire control system, we can see that the network optimization algorithm research has important guidance for the optimization of the system message transmission, and can improve the system's real-time performance.

Sampling Period Selection of Control Application Connected to FlexRay Bus

Flexray is a high speed communication protocol designed for distributive control in automotive control applications. Control performance not only depends on the control algorithm but also on the scheduling constraints in communication. A balance between the control performance and communication constraints must required for the choice of the sampling rates of the control loops in a node. In this paper, an optimum sampling period of control loops to minimize the cost function, satisfying the scheduling constraints is obtained. An algorithm to obtain the delay in service of each task in a node of the control loop in the hyper period has been also developed.

Research on FlexRay Bus Software Testing Technology Based on Data Acquisition and Analysis

This paper mainly introduces FlexRay, a high speed, real-time and high reliability bus technology, and researches network topology structure and network communication protocol of FlexRay bus. Then this paper points out that the premise of analyzing FlexRay protocol is catching the bus data transmission, and designs a data acquisition and analysis system with FreeMASTER software and Tektronix TDS3012B digital phosphor oscilloscope. In order to verify the accuracy of the software FlexRay interface design, this paper also describes the analysis and verification procedure of the timing sequence of FlexRay bus. Lastly, this paper reminds of the application prospect of this system.

Application Research Based on FlexRay Bus for All-Electronic Computer Interlocking System of Railway Signal

This paper researches the FlexRay bus main features, communication mechanism and topological structure, and then applies the FlexRay bus to all-electronic computer interlocking system communication network structure. Considering the fail-safe principle ,The paper studies the node design and bus configuration based on all-electronic execution units core , It realizes safe and reliable data communication between the all-electronic execution units and the interlocking machine, the maintenance monitoring machine. At last with real-time comparision between the FlexRay bus and the CAN bus in all-electronic computer interlocking system. it indicates that the FlexRay bus meets the data communication requirements in the computer interlocking system.

Minimization of FlexRay Bus Bandwidth for Hard Real-Time Applications

Minimization of FlexRay Bus Bandwidth for Hard Real-Time Applications

Slot Multiplexing Optimization for Minimizing the Operating Frequency of a FlexRay Bus under Hard Real-time Constraints

Slot Multiplexing Optimization for Minimizing the Operating Frequency of a FlexRay Bus under Hard Real-time Constraints

Minimization of FlexRay Bus Bandwidth for Hard Real-Time Applications

Minimization of FlexRay Bus Bandwidth for Hard Real-Time Applications

Research on In-Vehicle FlexRay Bus Network Nodes

Network node designs of hardware system and software system based on in-vehicle FlexRay Bus were put forward. Structure and theory of node’s MCU, communication controller and Bus drive were analyzed. The simplest system of FlexRay Bus node was structured, and main files program, clock program, interruption program, and FlexRay Bus communication program were configured. The operation status of FlexRay Bus protocol was analyzed, and programs of receiving and transmitting data were designed. The experimental system based on MC9S12XF512 was established, and in development environment of CodeWarrior IDE, FlexRay Bus networks nodes communication was accomplished based on TDMA and FTDMA mechanism.

TEST OF ELECTRONIC CONTROL UNITS

Despite all efforts on standardisation, the small number of bus systems for control device interconnection in vehicles is facing a flood of communication protocols with individual functional ranges. When a design or test engineer tries to address a control device for testing purposes via its communication interface, his most demanding task will be to simulate a control device communication that matches the real conditions of a vehicle. He must not limit his attention to only the range of communication facets needed to control the very functionality of the device. Additionally, requirements like network management or component protection must be carefully considered and simulated to ensure the desired functioning of the control device under test. With these constraints in mind, the development of Net2Run, ❶, has been started to provide the user with a complete, database-supported residual bus simulation for the control device. The Autosar approach of unified signal access as well as the Protocol Data Unit concept (PDU) for CAN, LIN, and FlexRay bus has been implemented. Open image in new window ❶ Feature set of the Net2Run software suite

Analysing Real Time Communications on DDS over FlexRay

In this paper we present an approach to timing analysis of applications communicating over a FlexRay bus, taking into consideration the specific aspects of the publish subscribe paradigm. We give an overview of works dealing with Data Distribution Service (DDS), scheduling over FlexRay and scheduling over the Control area Network (CAN). We are interesting in real time Quality of Service (QoS) for DDS. We specially focus on real time communication on static and dynamic FlexRay bus. We give our approach to calculate deadline on a DDS distribution using the equal Flexibility. We give also DDS and the task models for the computation.

Analyzing Real Time Communication Over FlexRay

In this paper we present an approach to timing analysis of applications communicating over a FlexRay bus, taking into consideration the specific aspects of the publish subscribe paradigm. We give an overview of works dealing with Data Distribution Service (DDS), scheduling over FlexRay and scheduling over the Control area Network (CAN). We are interesting in real time Quality of Service (QoS) for DDS. We specially focus on real time communication on static and dynamic FlexRay bus. We give our approach to calculate deadline on a DDS distribution using the equal Flexibility. We give also DDS and the task models for the computation. In Many distributed embedded real-time applications, like military, automobile, aeronautique data produced in one component of the system needs to be shared with other components of the system. The middleware Data Distribution Service DDS is divided into two components: the Data-Centric Publish-Subscribe DCPS layerand the Data local Reconstruction Layer DLRL. The DCPS layer transports data from publishers to subscribers according to Quality of Service QoS constraints associated with the data topic, publisher, and subscriber. The DLRL allows distributed data to be shared by local objects located remotely from each other as if the data is local. The DLRL is built on top of the DCPS layer. DDS impose of Service in transmission between publishers and subscribers. The transmission of data is managed by the real time bus. Real time applications use CAN or FlexRay bus. The challenge is to deal with a configuration using DDS middleware over FlexRay bus. The goal of using QoS in DDS is that all DataReaders read temporally valid data. DDS proveides QosPolicies specifically targeted to minimum latency, predictable real-time operation in high performance distributed data-critical systems. The DEADLINE QosPolicy expresses the maximum duration within which a DataReader expects a data-object instance to be updated. Our research team was interested in the LifeSpan (LS) Qos which concerns the Topic and the Data Writer entities. It specifies the maximum duration of validity of the data written by the DataWriter. They developed [6] an algorithm that calculate data distribution deadline. The following assumptions are considered: all nodes, data objects, and scheduling parameters are known a priori; each DataReader/DataWriter has a local node, where it originates.; the period of a DataWriter is always less than its Lifespan; and the offered deadline period is always less then the requested deadline period. This work gives an analysis for deadline computation on a FlexRay bus. The goal is to consider the data-centric publish- subscribe (DCPS) and to use DDS Qos. Both Dynamic segment and static segment are considered. We are currently working on a project to implement deadline computation with C language in order to finalize our works dealing with our DDS implementation.

Implement of Intelligent Node for Vehicles Based on FlexRay Bus

The car can meet the high demand of the security and stability of the system by using FlexRay bus, while it also can implement optimization of the cost. The paper introduces a system of nodes’ communication based on FlexRay technology, and the system constructed two nodes which are composed of main processors, communication controllers and bus transceivers. The paper implements the transmission of data between main processors and communication controllers by EBI (external bus interface). It is succeed in implementing the communication process of receiving data and sending data among different nodes. The results show that the data completely correct while the data rate is 10Mbps. Therefore, it verifies the reliability and real-time communication of FlexRay. And it also means that the designed node will play a significant role in X-By-Wire.

FlexRay Network Parameter Optimization Method for Automotive Applications

This paper describes a new FlexRay network parameter optimization (NPO) method consisting of two straightforward steps: design the lengths of the static (ST) slot and the communication cycle. In the first step, we formulate an optimal problem for designing the ST slot length. The bandwidth limitation, composed of protocol overhead and unused network resources, is considered as optimal criterion for efficient network usage. With the exploration of design space (i.e., ST slot lengths which satisfy the constraints of the FlexRay specifications), the optimal ST slot length is determined. Based on the result of the first step, the optimal communication-cycle length is designed in the next step. In this step, we proposed an algorithm for analyzing the worst case response times (WCRTs) for the ST and dynamic frames. Using this algorithm, the optimal communication-cycle length with minimum network delays is derived. The NPO method formalizes the FlexRay network configuration process in two steps for simplicity. Furthermore, the method enables the efficient usage of FlexRay bus with minimum WCRT. Finally, vehicle chassis control system based on FlexRay network is designed using the proposed NPO method. In this example system, we verified the parameter-optimization algorithm, and analysis results are confirmed.

Schedule Optimization of Time-Triggered Systems Communicating Over the FlexRay Static Segment

FlexRay is a new high-bandwidth communication protocol for the automotive domain, providing support for the transmission of time-critical periodic frames in a static segment and priority-based scheduling of event-triggered frames in a dynamic segment. The design of a system scheduling with communication over the FlexRay static segment is not an easy task because of protocol constraints and the demand for extensibility and flexibility. We study the problem of the ECU and FlexRay bus scheduling synthesis from the perspective of the application designer, interested in optimizing the scheduling subject to timing constraints with respect to latency- or extensibility-related metric functions. We provide solutions for a task and signal scheduling problem, including different task scheduling policies based on existing industry standards. The solutions are based on the Mixed-Integer Linear Programming optimization framework. We show the results of the application of the method to case studies consisting of an X-by-wire system on actual prototype vehicles.

A little bit more attentive audi active lane assist

“Audi active lane assist”, which was presented for the first time in the Audi A7, represents a new generation of lane assist systems. The driver assistance system is capable of warning the drivers when they are about to leave their lane unintentionally but also provides continuous assistance in keeping the vehicle in the middle of the lane during normal driving. The basis is provided by the networking of electronic control units over the Flexray bus.

Classification of Activated Faults in the FlexRay-Based Networks

FlexRay communication protocol is expected to become the de-facto standard for distributed safety-critical systems. This paper classifies the effects of transient single bit-flip fault injections into the FlexRay communication controller. In this protocol, when an injected fault is activated, this may result in one or more error types, i.e.: Boundary violation, Conflict, Content, Freeze, Synchronization, Syntax, and Invalid frame. To study the activated faults, a FlexRay bus network, composed of four nodes, was modeled by Verilog HDL; and a total of 135,600 transient faults was injected in only one node, called the target node. The results show that only 9,342 of the faults (about 6.9%) were activated and their effects were observed in the network nodes. The results also show that the Synchronization error is the widespread error with the occurrence rate of 70.1%. The Invalid frame, Boundary violation, Syntax, Content, Freeze, and Conflict errors have the occurrence rates of 51.1%, 32.4%, 24.6%, 20.6%, 17.3%, and 0.0%, respectively. Among the error types, the Freeze errors are the most critical errors as they mostly result in system failures. The results also show that most of the activated faults, about 75.3%, were observed simultaneously in the target node and a neighbor node. About 11.1% of the activated faults were observed only in the target node and about 13.5% only in the neighbor node.

A FlexRay parameter calculation methodology based on the electric/electronic architecture of vehicles

The well established FlexRay bus system allows the adjustment to many configurations and applications. This flexibility comes for the price of a huge set of parameters which have to be mandatory correct, to operate the bus system robust and reliable. In this paper we provide a methodology to determine the necessary settings directly from the electric and electronic architecture description, which is developed in the design phase of a vehicle. Our approach includes the calculation of all global and local parameters, frame packing and scheduling. The implementation of the methodology was tested with various modeling data sets. The calculated parameters could be exported in a predefined data structure which was used to seamlessly configure target FlexRay controllers, successfully running a real hardware network.

An Experimental Study of the FlexRay Dynamic Segment

It is expected that the time-triggered FlexRay bus will replace the event-triggered Controller Area Network (CAN) for the high-speed in-vehicle communication in future automobiles. To this end, FlexRay provides a static segment for the transmission of periodic messages and a dynamic segment that is suitable for exchanging event-based (sporadic) messages. In this paper, we experimentally evaluate the operation of the FlexRay dynamic segment. In particular, we study how the maximum and average message delays are affected if the length of the dynamic segment, the message payload, the utilization of the dynamic segment and the priority assignment changes. Our experiments are carried out on a FlexRay network with 6 nodes.

Powerful tools for the communication with the Flexray bus

Three years ago, the first FlexCard was developed. This made TZM one of the first manufacturers of monitoring and analysing tools for the rapidly growing Flexray market. In the meantime, the development of the FlexCard kept being a dynamic process because also the target system Flexray itself was encountering permanent changes. In this article TZ Mikroelektronik (TZM), Goppingen, Germany, present their FlexCard family.