A State-of-the-Art Survey on Real-Time Issues in Embedded Systems Virtualization

Virtualization has gained great acceptance in the server and cloud computing arena. In recent years, it has also been widely applied to real-time embedded systems with stringent timing constraints. We present a comprehensive survey on real-time issues in virtualization for embedded systems, covering popular virtualization systems including KVM, Xen, L4 and others.

Energy-Efficient Deterministic Fault-Tolerant Scheduling for Embedded Real-Time Systems

By combining fault-tolerance with power management, this paper developed a new method for aperiodic task set for the problem of task scheduling and voltage allocation in embedded real-time systems. The scbedulability of the system was analyzed through checkpointing and the energy saving was considered via dynamic voltage and frequency scaling. Simulation results showed that the proposed algorithm had better performance compared with the existing voltage allocation techniques. The proposed technique saves 51.5% energy over FT-Only and 19.9% over FT ＋ EC on average. Therefore, the proposed method was more appropriate for aperiodic tasks in embedded real-time systems.

Partitioned k-Exclusion Real-Time Locking Protocol Motivated by Multicore Multi-GPU Systems

Graphic processing units （GPUs） have been widely recognized as cost-efficient co-processors with acceptable size, weight, and power consumption. However, adopting GPUs in real-time systems is still challenging, due to the lack in framework for real-time analysis. In order to guarantee real-time requirements while maintaining system utilization ~in modern heterogeneous systems, such as multicore multi-GPU systems, a novel suspension-based k-exclusion real-time locking protocol and the associated suspension-aware schedulability analysis are proposed. The proposed protocol provides a synchronization framework that enables multiple GPUs to be efficiently integrated in multicore real-time systems. Comparative evaluations show that the proposed methods improve upon the existing work in terms of schedulability.

A Concept of Dynamically Reconfigurable Real-time Vision System for Autonomous Mobile Robotics

This paper describes specific constraints of vision systems that are dedicated to be embedded in mobile robots. If PC-based hardware architecture is convenient in this field because of its versatility, flexibility, performance, and cost, current real-time operating systems are not completely adapted to long processing with varying duration, and it is often necessary to oversize the system to guarantee fail-safe functioning. Also, interactions with other robotic tasks having more priority are difficult to handle. To answer this problem, we have developed a dynamically reconfigurable vision processing system, based on the innovative features of Cleopatre real-time applicative layer concerning scheduling and fault tolerance. This framework allows to define emergency and optional tasks to ensure a minimal quality of service for the other subsystems of the robot, while allowing to adapt dynamically vision processing chain to an exceptional overlasting vision process or processor overload. Thus, it allows a better cohabitation of several subsystems in a single hardware, and to develop less expensive but safe systems, as they will be designed for the regular case and not rare exceptional ones. Finally, it brings a new way to think and develop vision systems, with pairs of complementary operators.

Energy Efficient Scheduler of Aperiodic Jobs for Real-time Embedded Systems

Energy consumption has become a key metric for evaluating how good an embedded system is,alongside more performance metrics like respecting operation deadlines and speed of execution.Schedulability improvement is no longer the only metric by which optimality is judged.In fact,energy efficiency is becoming a preferred choice with a fundamental objective to optimize the system's lifetime.In this work,we propose an optimal energy efficient scheduling algorithm for aperiodic real-time jobs to reduce CPU energy consumption.Specifically,we apply the concept of real-time process scheduling to a dynamic voltage and frequency scaling(DVFS)technique.We address a variant of earliest deadline first(EDF)scheduling algorithm called energy saving-dynamic voltage and frequency scaling(ES-DVFS)algorithm that is suited to unpredictable future energy production and irregular job arrivals.We prove that ES-DVFS cannot attain a total value greater than C/ˆSα,whereˆS is the minimum speed of any job and C is the available energy capacity.We also investigate the implications of having in advance,information about the largest job size and the minimum speed used for the competitive factor of ES-DVFS.We show that such advance knowledge makes possible the design of semi-on-line algorithm,ES-DVFS∗∗,that achieved a constant competitive factor of 0.5 which is proved as an optimal competitive factor.The experimental study demonstrates that substantial energy savings and highest percentage of feasible job sets can be obtained through our solution that combines EDF and DVFS optimally under the given aperiodic jobs and energy models.

Embedded Linux Device Driver Research

Based on the in-depth research of the embedded device management system,analyze the process of the driver parameters delivery on kernel level particularly.According to this,expound the device driver 's working principle,structure and design methods especially.Finally realize the drivers of the character-based devices which can be dynamically loaded.Actual result shows that mastering the realization of the device driver mechanism and the process of parameters delivery with kernel can improve the embedded device driver development efficiency and reduce error probability effectively,thus saving the development cost and development cycle of embedded products.

社区嵌入视角下日本老龄化城市养老服务与规划的经验及启示

当前,我国正面临着严峻的人口老龄化挑战,建设全龄社区和老年友好城市已成为迫切目标。本研究以日本三个老龄化城市的空间规划为案例,分析社区养老服务设施的规划布局和地域综合照护体系的构建。研究表明,日本社区养老服务设施规划以现有空间资源为规划对象,以建设友好社区环境为重要抓手,以公共场所和居住领域为空间治理单元,从医疗、照护、预防、居住和生活支援五个方面共同进行社区空间适老化改造。既考虑了规划的整体性和全面性,又兼顾了多元治理的互动性。对我国社区嵌入式养老服务设施空间规划的启示在于:要加强政策支持与协同治理,包括根据区域发展情况、社区面积、老年人占比等因素制定具体细致的政策,并引入社会力量,构建多元治理体系;同时建立社区养老服务评估体系,以共生发展为目标,合理配置空间资源;还应建立资源保障体系和运营维护团队,做到资源调度有序。

System-Level Performance Evaluation of Very High Complexity Media Applications : A H264/AVC Encoder Case Study

Given the substantially increasing complexity of embedded systems, the use of relatively detailed clock cycle-accurate simulators for the design-space exploration is impractical in the early design stages. Raising the abstraction level is nowadays widely seen as a solution to bridge the gap between the increasing system complexity and the low design productivity. For this, several system-level design tools and methodologies have been introduced to efficiently explore the design space of heterogeneous signal processing systems. In this paper, we demonstrate the effectiveness and the flexibility of the Sesame/Artemis system-level modeling and simulation methodology for efficient peformance evaluation and rapid architectural exploration of the increasing complexity heterogeneous embedded media systems. For this purpose, we have selected a system level design of a very high complexity media application;a H.264/AVC (Advanced Video Codec) video encoder. The encoding performances will be evaluated using system-level simulations targeting multiple heterogeneous multiprocessors platforms.

Energy Guarantee Scheme for Real-time Systems with Energy Harvesting Constraints

The growth of environmental energy harvesting has been explosive in wireless computing systems especially when replacing or recharging batteries manually is impracticable.This work investigates the scheduling of periodic weekly hard real-time tasks under energy constraints.Based on this motivation,we proposed a real-time scheduling algorithm,namely energy guarantee dynamic voltage and frequency scaling(EG-DVFS),that utilizes the earliest deadline-harvesting(ED-H)scheduling algorithm combined with dynamic voltage and frequency scaling.This one is qualified as real-time since tasks must satisfy their timing constraints.We assume that the preemptable tasks receive dynamic priorities according to the earliest deadline first(EDF)rule.EG-DVFS adjusts the processor's behavior by characterizing the properties of the energy source module,capacity of the stored energy as well as the harvested energy in a future duration.Specifically,tasks are executed at full processor speed if the amount of energy in the battery is enough to finish its execution.Otherwise,the processor slows down task execution to the lowest possible processor speed while still guaranteeing to meet all the timing constraints.EG-DVFS mainly depends on the on-line computation of the slack time and the slack energy with dynamic voltage and frequency selection in order to achieve an improved system performance.Experimental results show that EG-DVFS can achieve capacity savings up of up to 33%when compared to ED-H.

舰艇嵌入式训练系统时空一致性研究

针对训练系统嵌入舰艇实装后与作战系统不能保持时空一致性的问题,建立了异构系统节点时间补偿模型,用时间补偿向舰艇作战系统注入目标信息的时延;用预判武器命中目标逻辑距离消除武器命中目标的位置误差;在训练系统接口装置监听程序中建立了报文过滤流程,降低异构系统间数据传输的时延;采用了多分辨率建模方法和面向服务的软件架构,设计了训练软件在Windows+RTX下的运行流程,提高训练系统仿真的实时性。工程实践表明,综合采用上述方法可以满足舰艇实装嵌入式训练系统时空一致性的要求。

相空间重构延迟时间与嵌入维数的选择

论述相空间重构中延迟时间与嵌入维数之间的关系 ,提出广义嵌入窗长的概念 .分析已有的自关联函数法中的不足 ,提出一种改进的自关联函数法确定广义嵌入窗长 ,从而确定出相空间重构的其它参数 .同时从时间序列相关程度和不相关程度 2个方面进行考虑 ,克服了自关联函数法的缺点 .仿真实验结果验证了该方法的有效性 .

大容量NAND Flash文件系统中的地址映射算法研究

随着Flash芯片容量的日益增长,如何设计低空间复杂度的Flash管理算法已经成为RAM空间受限的嵌入式存储系统的一个关键问题.本文根据文件在Flash介质上连续存放的特性,引入区段的概念,提出基于极大映射区段的地址映射算法,并使用简单的数据结构和高效的算法来维护映射中的区段,大大减小了Flash文件系统的RAM用量.最后,通过不同应用负载的实验验证了该算法的有效性.在部分应用负载下,可降低高达95%的RAM使用量.

多变量时间序列相空间重构中参数的确定

介绍了多变量时间序列相空间重构理论.提出一种新的基于平均预测误差最小化的重构参数确定方法,阐述了该方法的算法过程及一些重要特点.此方法考虑了所有重构参数对平均预测误差的影响,能够同时确定重构系统相空间所需的恰当嵌入维数及时间延迟.最后将该方法应用于股票市场非线性动力系统的相空间重构,通过比较和分析验证了其优越性.

基于滑模变结构的异步电机直接转矩控制研究

根据异步电机在同步旋转坐标系下的数学模型和滑模变结构理论设计了一种基于转矩误差和磁链误差的滑模控制器,利用获得的参考电压矢量,通过空间电压矢量调制得到逆变器开关控制信号。仿真研究验证了该控制策略在减小转矩和磁链脉动,保证逆变器开关频率恒定的同时,对系统参数摄动和外部干扰表现出较强的鲁棒性。在此基础上,实际应用于基于VxWorks嵌入式系统的变频调速系统平台,取得了良好的控制效果。

重载铁路桥上无砟轨道扣件关键参数研究

研究目的:为研究重载铁路桥上长枕埋入式无砟轨道扣件系统关键设计参数取值,本文基于弹性地基梁理论和车辆-轨道耦合动力学理论,建立32.5 t轴重重载货车-长枕埋入式无砟轨道-桥梁垂向耦合动力学模型,分析扣件刚度、扣件间距对重载铁路桥上长枕埋入式无砟轨道静、动力学性能的影响规律,提出重载铁路桥上长枕埋入式无砟轨道扣件系统设计参数取值。研究结论:(1)钢轨垂向位移和钢轨轨底应力随扣件系统刚度的增大而减小,车体垂向振动加速度、轮重减载率、轮轨力和桥梁垂向振动加速度随扣件系统刚度的增大而增大;(2)钢轨垂向位移、钢轨轨底应力、车体垂向振动加速度、轮重减载率和桥梁垂向振动加速度随扣件间距的增大而增大,但轮轨垂向力随之减小;(3)综合考虑轨道变形以及工程造价,建议重载铁路桥上长枕埋入式无砟轨道扣件系统的静刚度取为40~60 k N/mm,扣件系统的动刚度取为80~100 k N/mm,扣件间距取为0.6~0.65 m;(4)本研究成果可为重载铁路桥上长枕埋入式无砟轨道结构设计提供参考。

四轮差动驱动型AGV嵌入式运动控制器设计与研究

设计了前两轮从动、后两轮差动驱动的四轮底盘结构AGV。在考虑非完整约束和轴承摩擦力的基础上,结合牛顿力学方法和矩阵分析方法建立了以运动速度和转弯角速度为状态变量的AGV非完整状态空间方程;使用全状态反馈的极点配置法建立了运动控制方程,采用DS87C520和PSD813F2设计了其嵌入式运动控制器。仿真和实验证明了非完整状态空间方程、运动控制方程和嵌入式运动控制系统的可靠性、实时性和稳定性。

输出间距对嵌入式复合纺纱线结构和性能的影响

分析了嵌入式复合纺纺纱过程中"V"形加捻三角区的动态变化及长丝与长丝间距、粗纱须条与长丝间距对"V"形加捻三角区形状和单纱受力的影响,认为各种间距变化会使"V"形加捻三角区夹角、单纱段长度产生变化,并以此为依据,使其他工艺参数不变,分别改变长丝与长丝间距、粗纱与长丝间距及纱纺中心点偏移进行纺纱,通过理论分析和实验比较,讨论了各种间距对成纱结构性能的影响。结果表明,随着各种间距变化,成纱毛羽、强伸性与条干均呈非单调性变化。综合考虑成纱结构和性能,在其他参数相同时,最佳成纱工艺为:长丝与长丝间距12 mm,粗纱与长丝间距4 mm,Z捻时纺纱中心点偏移距离-2 mm。

相空间重构中参数确定方法的新探讨

论述相空间重构中参数选择的方法并对其讨论,针对已有参数确定方法的主观性强的特点,从一个更新角度考虑相空间重构中的冗余和不相关问题,结合虚假邻点法及平均位移法的思想,提出延迟向量排序计算重构相空间的最佳嵌入维数,以及基于相邻向量内积计算最佳延迟时间间隔.仿真结果证明该方法不仅是有效的,同时也具有易编程的特点.

相空间中脑电近似熵和信息熵的计算

提出一种基于相空间重构脑电信号来计算脑电近似熵和信息熵的新方法.实验计算结果表明,癫痫患者脑电和正常人脑电的近似熵和信息熵随相空间嵌入维数的变化有明显的不同.

航天嵌入式操作系统的分析与验证

在介绍航天嵌入式操作系统的特点和应用概况的基础上,阐述了对航天嵌入式操作系统进行自动分析与验证的必要性,综述了自动分析和验证技术,并重点介绍了模型检测和符号执行两种分析技术,列举了领域内近年来具有代表性的工具及分析实例。结合航天嵌入式操作系统的特点,总结了嵌入式操作系统自动分析与验证技术面临的挑战,包括状态爆炸、描述不精确性、代码复杂度、实时性分析等。