A case for the VMEbus architecture in embedded systems education

The VMEbus is an IEEE standard architecture upon which many embedded and real-time systems are built. The VMEbus architecture has existed for nearly 25 years and has been used extensively for military, industrial, and aerospace applications. This paper describes the general characteristics of the VMEbus architecture, specifically relating these characteristics to aspects of embedded systems education included as components of the IEEE/ACM CE2004 computer engineering model curriculum. Portions of this model curriculum are currently being implemented at universities across the country as part of an increasing effort to address the need for embedded systems education. This evaluation will identify the strengths and weaknesses of this architecture as a general-purpose embedded systems educational tool. The VMEbus architecture is used in the laboratory component of an undergraduate embedded systems course at the University of Alabama (UA), Tuscaloosa. The assessment results evaluating its effectiveness are presented.     

实现电力监控嵌入式系统可靠数据交换的串行通信Agent

基于任务Agent的设计理念,开发了一种实现电力监控嵌入式系统可靠数据交换的串行通信Agent模块。这种模块实现了串行通信的全程代理。采用这种模块的嵌入式系统,只要对接口的双口RAM进行访问即可完成不同系统间的可靠数据交换,从而使串行通信变得非常方便且更加可靠。同时,采用这种模块还能有效地缩短产品的开发周期。详细地介绍了这种串行通信Agent模块的设计思想、基本原理和实现方法。     

A distributed arithmetic hardware architecture for real-time hough-transform-based segmentation

Real-time segmentation and tracking of biopsy needles is a very important part of image-guided surgery. Since the needle appears as a straight line in medical images, the Hough transform for straight-line detection is a natural and powerful choice for needle segmentation. However, the transform is computationally expensive and in the standard form is ineffective for real-time segmentation applications. This paper proposes a dedicated hardware architecture for the Hough transform based on distributed arithmetic (DA) principles that results in a real-time implementation. The architecture exploits the inherent parallelism of the Hough transform and reduces the overall computation time. The DA Hough transform architecture has been implemented using the Xilinx field-programmable gate array (FPGA). For a 256x256-bit image, the proposed design takes between 0.1 ms and 1.2 ms to process the Hough transform when the feature points in the image are varied from 2% to 50% of the total image; these values are well within the bounds of real-time operation and thus can facilitate needle segmentation in real time.     

A Study of an FDTD‐Based Frequency‐Dependent Line Model for Electromagnetic Transient Simulations

Electromagnetic transient (EMT) simulations of power systems require accurate representation of models in a wide range of frequencies. This of course applies to the representation of transmission lines, and the phase‐domain frequency‐dependent line model is often used to this end. The phase‐domain line model does not require modal transformation in EMT simulations but requires modal decomposition at its model identification stage, and there are cases where it fails to fix switchovers of propagation modes with respect to frequency. Thus, a frequency‐dependent line model which essentially avoids modal decomposition is desired. This paper studies the possibility of a frequency‐dependent line model based on the FDTD (Finite Difference Time Domain) method as a candidate which satisfies the above‐mentioned requirements. First, improvements regarding computational efficiency and numerical stability are made to Kordi's FDTD‐based frequency‐dependent line model. Then, the following points are clarified using the developed model: (i) Waveform deformations due to propagation modes with different velocities can be reproduced completely without modal decomposition; (ii) As the time step size becomes larger, waveforms obtained by the developed model become less accurate due to the embedded filter for numerical stability. These points assure, if the error due to the embedded filter is reduced, that the developed model can become a useful frequency‐dependent line model without model identification problems.     

伺服系统CANopen协议软件植入方法分析

分析了在交流伺服系统中实现CANopen运动控制子协议CANopen DS402的两种方式:硬件嵌入实现和软件植入实现.通过对软件植入方法进行分析,探讨了在伺服控制程序中植入协议模块的关键问题,针对这些问题提出了相应的解决方案,并在伺服驱动器中实现了协议内容.实验结果验证了该方法的正确性和实用性.     

A novel physical model for partial discharge in narrow channels

In order to reveal the mechanism of partial discharge (PD) in electrical trees, an artificial single channel is studied as model for tree channels. In a long-narrow channel, the behaviour of PD is similar to that in an actual tree. When the length of the channel is decreased, the φ-q-n pattern of PD in the channel changes from wing to turtle or rabbit like, and the range of light emission in the channel increases when the applied voltage is increased. Considering the influence of a PD on the total field distribution and thus on a later PD, a physical model is put forward to describe the PD behaviour. It is assumed that PD is induced by the high field at the needle tip, then propagates along the channel, and stops propagating when the field in the channel becomes lower than a critical value due to field divergence. Mathematical analysis on an ideal needle-plane electrode system clearly explains the physical meaning of the model. And the computer simulation by using the superposition method agrees with the experimental results very well. This model is also valid to describe the behaviour of PD in electrical trees     

A laboratory testbed for embedded computer control

There has been a tremendous growth in the use of modern embedded computers in control and other applications in the past few years. While courses offered in the electrical and computer engineering disciplines cover such topics as microprocessors, digital and analog hardware, control theory, and programming languages, there exist few courses that focus on integrating these subjects for designing embedded systems. On the other hand, there is a growing need in industry for engineers who can perform software design and system integration for various applications in embedded control. Toward filling this gap, this paper describes a laboratory testbed developed for a new course on Embedded Computer Control offered at the University of Western Ontario, London, ON, Canada. An outline of the course structure, laboratory setup, and the design aspects for implementing a modern embedded control application are presented. The embedded controller performs command, control, and user interface tasks required to operate a low-cost prototype of a thermal system. Furthermore, its network connectivity allows users to tune system parameters, start and stop running the system, and observe the status of the plant via the Internet.     

交联电缆典型绝缘损伤针刺模型的局部放电试验研究

构建了交联电缆施工及运行过程中的典型绝缘损伤模型——针刺模型,设计并制作了衰减振荡波电压发生器,分别测量了针刺模型在交流电压及衰减振荡波电压下的局部放电脉冲,对比分析了针刺模型在振荡电压下的局部放电的一些基本特征,结合IEC 60060-3标准对交联电缆采用衰减振荡波的耐压试验与局放测量的可行性进行了探讨,对现场综合评估交联电缆主绝缘的状态方法进行了实验室内的初步试验研究。     

A comprehensive circuit model for partial discharge activities in cable insulation due to electrical treeing

A new comprehensive circuit model is proposed for electrical trees in cable insulation to be used in partial discharge (PD) analyses. Simple relations are presented for each of circuit components. The effect of tree’s constructional parameters (such as length, growth angle and type), cable and insulation dimension (such as conductor radius and insulation thickness), needle dimension, temperature and insulation aging are considered in the proposed model. The patterns (pulse sequences, φ–q–n and φ–n) extracted from the proposed model are in a good agreement with the published experimental patterns under different conditions. Moreover, the model is fully compatible with the software packages, such as EMTP, that can simulate pulse propagation along cable networks.     

嵌入式系统基于RTL8019AS的以太网接入设计

以太网作为局域网的骨架已经不局限于校园等一些办公场所,它开始慢慢的走向工厂、车间,所以研究和实现嵌入式系统的以太网接入具有深远的研究意义和良好的应用前景。本文介绍了一种在ARM32位嵌入式系统中实现的以太网（ETHERNET）接入设计。方案采用ARMCPU来控制网卡芯片RTL8019AS,在以太网协议上实现了ARP协议和自行设计的小型TCP／IP协议栈。本文描述了系统硬件构成,并对以太网通信中的ARP协议以及适用于嵌入式系统的精简的INTERNET网络通讯协议-TCP／IP的实现等做了介绍,最后对调试的方法也做了简单介绍。本设计方案已成功应用于新型环保黑匣子产业化项目。系统具有体积小、功耗低、可靠性与性价比高等特点,并且具有良好的可扩展性和产品开发的延续性,对于需要在嵌入式系统中进行局域网数据传输的场合有很好的借鉴意义。     

A Practical Model for Generator Maintenance Scheduling with Transmission Constraints

In this paper an optimal maintenance scheduling of generating units in a power system has been developed with transmission network representation. Here a DC load flow has been embedded in the maintenance model to include network constraints resulting in a more practical maintenance schedule. The model developed here uses the minimization of system cost (production cost plus the unserved energy cost) as the objective criterion, whereas the reliability objective function used is the minimization of unserved energy. The optimization is achieved by integer linear programming. The incorporation of transmission network adds significant complexity to maintenance scheduling. The proposed model enables almost all practical maintenance scheduling constraints to be handled easily. The optimization has been carried out to minimize the cost function considering different cases (i.e., with and without incorporation of the transmission network). The effectiveness of the proposed method has been demonstrated by obtaining numerical results on sample and real scale test systems. A comparison of the cost objective function clearly indicates that the maintenance schedule obtained from the simple generation model alone is more expensive than the one with transmission, and that there is a considerable degree of suboptimality in the former case.     

基于仿真软件对金属导体尖端放电阈值的研究

针对目前国内外对闪电始发阈值的研究较少的情况,利用实际实验冲击平台、ANSOFT Maxwell电磁仿真软件以及金属尖端电场分布模型,主要研究了先导始发的阈值电压以及阈值电场大小随金属棒之间垂直距离变化情况.研究表明:先导始发的阈值电压以及阈值电场与金属尖端之间的垂直距离存在显著性的相关性关系,下针金属棒放电电场阈值与两针间的垂直距离是负相关的,而上针恰好与下针的金属棒放电的电场阈值变化趋势相反,但上下两针的放电电压阈值与两针间的垂直距离均是正相关的.     

Use of Student Experiments for Teaching Embedded Software Development Including HW/SW Co-Design

Embedded systems have been applied widely, not only to consumer products and industrial machines, but also to new applications such as ubiquitous or sensor networking. The increasing role of software (SW) in embedded system development has caused a great demand for embedded SW engineers, and university education for embedded SW engineering has become important. The embedded software engineers should learn system architecture design and hardware (HW) technologies as well as SW technologies. However, only a few universities offer education courses for embedded software engineering that include system architecture design and HW technologies. This paper proposes a student experiment method that is designed to nurture embedded SW engineers by teaching these technologies. The proposed method includes an experiment for embedded SW development, an experiment for embedded HW development and a HW/SW co-design experiment, which help students learn system architecture design skills such as system modeling, HW/SW tradeoff design, and SW and HW module design. A model of each experiment was developed and evaluated.      

A multi-objective short term hydropower scheduling model for peak shaving

The short-term scheduling problem of a hydropower system in China Southern Power Grid (CSG) is studied. As one of the largest in China, the system consists of 92 hydro plants with total installed capacity of 41GW occupying 14.7% of the national hydropower capacity at the end of 2013. Abundant hydroelectricity of the system is transmitted from the western provinces to the eastern load centers in CSG. Obvious difficulties of the hydropower scheduling of CSG are large-scale system, complex constraints and multiple power receiving grids of single plants and cascaded systems due to huge capacity. A short-term hydropower scheduling model for peak shaving of multiple power grids is developed for the operations of the hydropower system of CSG. The model is composed of multi-objective optimal peak shaving (MOPS) model, inter grid power distribution (IGPD) model and load fluctuation balance (LFB) model. The MOPS model minimizes the maximum residual loads of each power grid in which the IGPD model is embedded to distribute power of a plant among several power grids. To solve the model, an aggregate function and a multi-objective fuzzy optimization model are combined to establish an alternative objective function, and a proposed constraint successively satisfying (CSS) algorithm is used to address the period coupling constraints in local search. A case study shows that the proposed approach is practicable, adaptable and robust to obtain near optimal results efficiently, and is applicable for large-scale hydropower systems with both multiple and single power receiving grids.     

A Predictive Controller for Autonomous Vehicle Path Tracking

This paper presents a model predictive controller (MPC) structure for solving the path-tracking problem of terrestrial autonomous vehicles. To achieve the desired performance during high-speed driving, the controller architecture considers both the kinematic and the dynamic control in a cascade structure. Our study contains a comparative study between two kinematic linear predictive control strategies: The first strategy is based on the successive linearization concept, and the other strategy combines a local reference frame with an approaching path strategy. Our goal is to search for the strategy that best comprises the performance and hardware-cost criteria. For the dynamic controller, a decentralized predictive controller based on a linearized model of the vehicle is used. Practical experiments obtained using an autonomous “Mini-Baja” vehicle equipped with an embedded computing system are presented. These results confirm that the proposed MPC structure is the solution that better matches the target criteria.      

A biointelligence system for identifying potential disease outbreaks

The development of public health surveillance systems requires multidisciplinary knowledge and advanced technologies. Scientific Technologies Corp. has developed the NH Pharmaceutical Sales Surveillance (NHPSS) for the New Hampshire Department of Health and Human Services (NH DHHS). The NHPSS was developed as a distributed information system. In addition to the database server, enterprise application servers and the Web-browser-based user interface, its architecture features knowledgebase technology, a new dynamic system model with rule systems, and automated data analysis in supporting public health surveillance. Internet mapping was also embedded in the system to provide for spatial analysis. Since its pilot application, started in December of 2002 in the Bureau of Communicable Disease Control and Surveillance, NH DHHS, the NHPSS has assisted NH DHHS in successful detections of gastrointestinal and respiratory events. This article first introduces the methodology and the technology in the NHPSS development. Next, the system functionalities are introduced. Then, a new dynamic system model with a rule system for public health surveillance is described in detail. Finally its application and preliminary results are summarized.     

Experimental validation of a model for an information-embedded power system

This paper develops a model of an electrical power system with its inherent embedded communication system for the purpose of studying the characteristics of power system measurement errors due to communication delays. This model is referred to as an "information-embedded power system" to emphasize the inclusion of information variables that represent measurements that have been delivered across the communication system and observed at a control center. These information variables are added to the standard power system model for the energy balance within the power system. A stochastic system model is developed, which is composed of both the physical infrastructure of the power system as well as the embedded computer network communication infrastructure. This type of analysis is an extension of traditional observability approaches, which usually only assume steady-state conditions in the power system and do not consider time delays in delivering measurements. An experimental platform has also been designed to validate the developed model.     

大型水电站蜗壳埋设方式对厂房振动的影响分析

如何选取水轮机蜗壳的埋设方式,是我国大型水电站厂房设计和研究的重点和难点之一。本文以三峡水电站厂房为背景,采用双结点接触非线性模型,计算三种不同蜗壳埋设方式下厂房结构的振动响应。计算结果表明：对于混凝土结构而言,保压方案的振动响应最小,垫层方案明显大于充水保压方案,直埋方案的振动响应最大;对于蜗壳等金属构件而言,保压方案的振动响应最大,而直埋方案最小,这说明直埋方案对金属构件的振动有利。为了检验计算模型与计算结果,开展了145m水位下三种不同埋设方式蜗壳的厂房振动现场测试。测试结果表明,对于混凝土结构而言,直埋方案的振动响应最大,保压方案最小,垫层方案略大于充水保压方案;而对于水轮机顶盖的振动而言,直埋方案振动最小,保压方案最大,垫层方案略小于充水保压方案。这说明测试结果与计算结果的振动响应规律基本一致。测试结果中垫层方案与保压方案基本一致的主要原因在于,在低水位下实际厂房的混凝土结构与垫层以及蜗壳之间存在缝隙,导致蜗壳的部分振动传递不到混凝土。     

蒸汽冷却器内置节流孔板孔径设计方法初探

在工程设计中,如何确定蒸汽冷却器内置节流孔板的孔径大小,尚缺乏合适的计算方法。为此,利用ANSYS Workbench 14.0软件平台,建立了某型蒸汽冷却器的管侧实体模型,并使用软件中的CFX模块进行了流体模拟,确定了U换热形管内的流体压损,通过调整U形换热管内的给水流量与节流孔板流量的分配比例,从而得到蒸汽冷却器内置节流孔板的孔径尺寸。     

Semi-empirical high-field conduction model for polyethylene andimplications thereof

A semi-empirical model for high-field conduction in polyethylene is developed on the basis of data in the literature for ac conductivity in the range of 30 to 60 kV/mm and `charge injection' from a needle in the range of 160 kV/mm. The model is used to compute high-field conduction-related phenomena by solving Poisson's equation with field-dependent conductivity and time-dependent applied voltage for a highly inhomogeneous field geometry. Parameters computed include field, current density, charge density, power density, and force density. Temperature rise in the dielectric is estimated based on the computed power density