Traffic-balancing algorithm for can systems with dual communication channels to enhance the network capacity

The controller area network (CAN) is the dominant protocol for in-vehicle network (IVN) systems because it provides bounded transmission delay among electronic control units (ECUs) at data rates between 100 Kbps and 1 Mbps. Many automotive companies have chosen the CAN protocol for their chassis network system of intelligent vehicles. However, the increasing number of ECUs in intelligent vehicles and the need for more intelligent functions require a network system with more network capacity and real-time capability. As one approach to enhance the network capacity of a CAN system, this paper introduces a CAN system with dual communication channels. This paper also presents a traffic-balancing algorithm that predicts the traffic of each channel and allocates frames to the most appropriate channel. An experimental testbed using commercial off-the-shelf microcontrollers with two CAN controllers was used to demonstrate the feasibility of the traffic-balancing algorithm.     

Expanding transmission capacity of can systems using dual communication channels with kalman prediction

The controller area network (CAN) protocol is widely used for in-vehicle network (IVN) systems, and many automotive companies also use the CAN in chassis network systems. However, the increasing number of electronic control units (ECUs) dictated by the need for more intelligent and fuel-efficient functions requires an IVN system with a greater transmission capacity and less network delay. Automotive companies have tried several approaches such as segmenting CAN systems and developing time-triggered protocols. This paper presents a practical method for increasing the transmission capacity and reducing the network delay in CAN systems using dual communication channels with a traffic-balancing algorithm based on Kalman prediction to forecast the traffic on each channel and allocate frames to the one that is most appropriate. An experimental testbed using commercial microcontrollers with two or more CAN protocol controllers was used to demonstrate the feasibility of the Kalman traffic-balancing algorithm. Experimental results show that the traffic-balancing CAN system with Kalman prediction reduced the transmission delay of all priority messages compared to that of a simple method, such as a channel-switching CAN, without sacrificing the performance for high-priority messages.     

基于AUTOSAR标准的网络管理协议的设计

汽车开放架构标准AUTOSAR为不同的汽车解决方案提供了统一的平台,降低了汽车制造商整合的成本。AUTOSAR平台中的网络管理标准,为汽车车载总线网络管理管理协议的开发提供了标准与规范。本文设计了一套符合AUTOSAR网络管理标准的基于CAN总线网络管理协议。并将其应用于实际的车载网络中,实现了各节点同步休眠与状态检测。经过仿真分析,验证了该协议具有较高的实时性,可以保证车载总线可靠、安全地通信。相较于OSEK网络管理机制AUTOSAR网络管理控制算法简单,软硬件开销小,同时实时性较高,可以满足CAN总线以及FlexRay总线在内的多种车载总线的需求。     

汽车FlexRay总线动态段时长及消息窗口优化

为解决FlexRay网络利用率的问题,对FlexRay动态段进行了研究。在基于最小时间片的FlexRay动态段研究的基础上,进行系统建模,对动态段时长进行优化配置,并提出以最大网络利用率为基础的动态消息调度算法。以CANoe为仿真平台对优化方法进行验证,结果表明该优化方法能够有效的提高动态网络利用率。     

Optimal scheduling of the flexray static segment based on two-dimensional bin-packing algorithm

FlexRay is a reliable and hard real-time in-vehicle communication protocol that is strongly promoted by car manufacturers as the de facto standard in the automotive domain. The protocol offers both a time-triggered and an eventtriggered architecture. This paper focuses on the optimal scheduling of the time-triggered component of FlexRay known as the static (ST) segment using a two-dimensional bin-packing technique. To maximize the bandwidth utilization in the ST segment, a fast heuristic as well as an efficient integer linear programming approach are proposed. Our methods directly schedule signals into slots including frame packing, according to signal-based data scheduling and the slot/ cycle multiplexing mechanisms presented by the latest version of the FlexRay protocol. The benefits of our proposed methods are demonstrated by extensive experiments on synthetic and an automotive X-by-wire system case study. An additional test case is examined to emphasize the superior performance of the proposed approach relative to that of existing optimal scheduling approaches.     

Design framework for FlexRay network parameter optimization

Because the FlexRay protocol has more than 70 configuration parameters and these parameters correlate with each other, designing a FlexRay network is a complex and difficult task. In this study, we propose a design framework that optimizes the two main FlexRay network parameters that are highly relevant to the application algorithm. The design process is composed of two steps for optimizing parameters. In the first step, the static slot length is optimized using a frame-packing algorithm. This algorithm binds network signals into static frames based on their periods and signal groups. In the second step, the communication cycle length is optimally designed with frame-scheduling algorithm and worst-case reponse time analysis. Based on the frame-scheduling algorithm, the response times are analyzed. The proposed design framework was applied to a unified chassis control system as a case study, and the analytical results were verified.     

实时多任务系统下的CAN通信模块的设计

介绍了高压共轨柴油机控制器的CAN接口硬件电路的设计;着重进行了实时多任务系统下的CAN通信模块的软件结构设计方法的研究。研究结果表明,所设计的CAN接口硬件电路能够满足实际发动机控制系统的应用需要;所构建的CAN通信软件模块,在满足CAN通信实时性要求的同时,降低了CAN通信模块对发动机控制器CPU的资源消耗,同时为整个CAN通信软件模块的扩展提供了一个很好的开发平台。     

汽车底盘控制技术的现状和发展趋势

电子控制系统在汽车底盘技术中的广泛应用极大地改善了汽车的主动安全性。常见的底盘控制系统可分为制动控制、牵引控制、转向控制和悬挂控制。介绍通过高速网络将各控制系统联成一体形成的全方位底盘控制(GCC),汽车开放性系统构架工程(AUTOSAR)和底盘的线控技术(X-by-w ire)。     

基于GPRS的车载控制器远程监控系统

为满足车载控制器研发的需求,提出了一种基于GPRS网络通讯的远程监控系统。设计了基于GPRS模块SIM900A的硬件电路和软件程序。数据采集模块从传感器和整车CAN网络采集数据,并通过GPRS模块将所需数据发送到监控服务器。试验证明该系统能够实现对实验数据的实时采集和远程监控,系统运行稳定可靠。     

智能网联趋势下车辆网关路由缓存研究与应用

伴随汽车智能网联发展,车辆电气网络架构行业趋势由1~2路CAN总线网络快速演变为7~8路CAN总线与4~5路百兆以太网相结合的融合网络架构。其中网关作为车辆网络的数据交互中心,提供了各网络之间的无缝通信,并需要以极低的延迟将这些数据进行可靠传输,这对低成本网关是一个巨大的挑战。提出了一种基于车载融合网络下低成本网关路由软件缓存区的设计方法,以路由软件缓存区去配合CAN控制器和以太网Switch硬件缓存区,设计中断式报文存储发送进程,将收到的数据实时发送到硬件发送缓存区,当硬件发送缓存区已满,则将报文存储到软件缓存区中。通过与软硬件缓存区的这种联动方式,能够实时的接收报文,保证报文不丢帧;也能够在目标总线负载率较大时,避免漏发报文以及保证发送报文周期。     

汽车ECU通讯新平台——FLexRay(V2.1)协议规范

FlexRay是基于时间触发的车载网络通讯协议,由FlexRay共同体组织编写。本文简单介绍车载网络,详细阐述FlexRay(V2.1)协议规范。     

OSEK网络管理规范在FlexRay总线中的研究与实现

网络管理能保证车载网络的安全性和可靠性。通过分析OSEK网络管理规范及FlexRay总线的特点,提出在FlexRay总线通信周期动态段中实现OSEK网络管理的方案,给出了FlexRay总线网络管理协议数据单元的定义,分析和研究了FlexRay总线的OSEK网络管理过程及网络管理消息在动态段中延迟发送问题。最后在自行设计的实验平台上进行了实验,验证了本方案的可行性。     

汽车底盘控制系统总线的应用现状研究

简述了汽车底盘控制系统总线的种类及技术特点,给出先进的汽车车载网络拓扑结构。详细论述了在汽车控制领域得到广泛应用的控制器局域网和最具发展潜力的线控技术及其通讯特点,特别针对CAN总线介绍了SAE J1939、CANopen、DeviceNet 3种基于CAN的主流应用层协议。最后就我国车载网络的发展进行了探讨。     

Heuristic resource allocation and scheduling method for distributed automotive control systems

This paper presents a heuristic resource allocation and scheduling method, which is based on an integrated architecture that enables multiple missions to be embedded in a single electronic control unit (ECU) and a single mission to be distributed over multiple ECUs. The proposed design method is composed of resource(e.g. task and message) allocation, scheduling, and attribute assignments. From a given target application’s task graph, the method generates a scheduling table specifying the release, start, and completion timings of tasks and messages. After that, all relevant attributes(e.g. priority of tasks and messages) are automatically assigned. In order to guarantee the functional and temporal requirements of target applications, design constraints such as the worst case response time, deadline, precedence relations, and physical limitations are concurrently considered. A chassis control system consisting of electronic stability control, an electro-mechanical brake, continuous damping control, and electronic air suspension is employed for evaluating the proposed method. The conventional chassis control system which is composed of seven ECUs was redesigned by only four ECUs without the degradation of control performance. Consequently, it is expected that the development time and production cost of distributed automotive control systems can be significantly reduced by the proposed design method.     

汽车FlexRay网络的单节点容错同步算法

为了保证网络的安全性和可靠性,FlexRay协议要求网络中同步节点数目不能小于3个,这种制约限制了FlexRay协议在网络中节点数目较少情形下的应用。针对这种情况,本文提出了一种FlexRay总线单节点容错同步算法,该算法利用一个同步节点即可实现FlexRay的时钟同步,还能减少FlexRay时间测量的步骤和计算量。经实例验证,该算法可以在保证网络安全性和可靠性的前提下实现时钟同步。     

某重卡CAN总线控制系统的设计

CAN是一种有效支持分布式控制或实时控制的串行通信网络。本文以某重型卡车为例,遵守J1939协议,通过CAN网络拓扑架构的搭建,展示了车身控制系统的的工作过程和故障诊断过程,论述了CAN总线在商用车重卡领域的应用和CAN在电控系统中应用的经济性、方便性及准确性。通过CAN总线控制系统与传统线束控制对比,体现了CAN总线系统的强大优势。     

BP网络在ASM底盘测功机模型识别中的应用

针对ASM测试系统用底盘测功机,提出一种应用改进型BP神经网络对其进行模型识别及扭矩预估计的方法。根据试验数据,应用该方法建立了底盘测功机转矩的预估模型,并对其进行了试验仿真,仿真结果表明:其建模过程简洁,数据拟合精度高。不仅如此,该方法对ASM测试系统的控制也具有一定的参考价值。     

XL纯电动轿车CAN总线系统及应用层协议的开发

为了满足XL纯电动轿车控制实时性和可靠性要求，提出了基于CAN总线的分布式控制系统拓扑结构，开发的CAN总线应用层协议，包括通信内容、ID编码、数据编码、数据格式、消息调度以及底层接口定义等6部分。文中还介绍了所开发的基于CAN总线的硬件在环测试系统。通过硬件在环测试、台架联合调试和道路试验对CAN总线系统进行综合实测和评价。实际运行表明，纯电动汽车CAN总线系统具有较高的可靠性和实时性。     

Schedule construction under precedence constraints in flexray in-vehicle networks

As embedded time-triggered applications have widely replaced mechanical systems in modern automobiles, holistic scheduling of tasks and messages of such applications on in-vehicle networks has become a critical issue. For offering QoS (Quality of Service) guarantees, the holistic schedule must satisfy numerous constraints such as protocol specifications, delay constraints and precedence constraints between tasks schedules and messages transmissions. Existing approaches to this problem search through a vast design space of all possible joint task and message schedules. This leads to a high complexity and limits the scalability of such approaches for scheduling the large scale systems. To cope with this problem, we propose an approach that divides the holistic scheduling problem to two sub-problems: the sub-problem of message scheduling and the sub-problem of task scheduling, while precedence relations and end-to-end information passing between task instances and messages are preserved and the end-to-end deadlines are guaranteed. This helps to reduce the workload on the problem solvers and improves efficiency and scalability. In the first sub-problem, our approach optimizes scheduling the set of messages and allocates time windows for scheduling each task with respect to precedence constraints, end-to-end deadlines and FlexRay protocol specifications. The length of each time window helps to preserve the respective tasks schedulability and to provide flexibility for both task and message scheduling. The objective is defined with respect to extensibility issues. In the second sub-problem, our approach optimizes schedule of the set of tasks with respect to their allocated time windows and timing constraints. The objective is defined with respect to latency issues. We optimize the solution to each sub-problem using Mixed Integer Linear Programming optimization framework. Performance evaluations show that, compared with existing holistic scheduling approaches, our approach is more scalable and obtains better solutions in a reasonable amount of time.     

燃料电池客车用10ms TTCAN通信网络协议制订与测试

在自主研发的TTCAN总线通信网络的基础上,为燃料电池客车设计了新的10ms TTCAN通信网络并进行仿真与实车测试.测试结果证明,采用新的TTCAN协议提高了CAN总线的数据吞吐能力、实时性和可靠性.