A fieldbus prototype for educational purposes

One of the problems with instrumentation systems is the interconnection between the multiple devices with different communication protocols. Exacerbating this problem are two typical requirements of interconnection: minimize cabling cost and avoid degradation of the signal during transmission. Cabling cost can be reduced through several multidrop communication systems: industrial local area networks or wireless communication. Reduction of signal to noise can restrict system performance and the quality of manufactured products, even if high-accuracy devices are used. Another problem in the field of manufacturing instrumentation networks is that industry uses multiple solutions to interconnect instrumentation with different communication protocols. This article presents the development of a prototype for an instrumentation network with the goal to study and analyze the characteristics of the different communication solutions. The overall system contains a large number of instrumentation devices, which is a great advantage for educational purposes and laboratory experiments. The students can configure, calibrate, and operate a large number of instruments connected to different segments of the DCS. We also connected some current-loop devices to the FF system to evaluate their performance when connected to a fully digital network. Results from the prototype DCS show that networking between different instrumentation devices and protocols can be successful and that a hybrid solution using conventional 4-20 mA current loop and fully digital instrumentation can work to leverage existing analogue systems. Future work will include the development of a fieldbus network analyzer to trace messages in the network and study the quality of FF service parameters, such as packet loss and delay measurement, as a function of network load.     

Bandwidth allocation scheme for cyclic-service fieldbus networks

Field devices in factory automation and process control systems generate time-critical, periodic, and time-available data that share the bandwidth of one fieldbus network medium. This paper presents a bandwidth allocation scheme that is applicable to cyclic-service fieldbus networks. The bandwidth allocation scheme transmits time-critical data as soon as the server is available. Transmission of periodic data is scheduled such that the network-induced delay will not exceed the maximum limit allowed. The bandwidth allocation scheme restricts the packet length of time-available data to satisfy the delay requirements of time-critical and periodic data. The bandwidth allocation scheme not only satisfies the real-time transmission requirements of both time-critical and periodic data, but also fully utilizes the bandwidth resources of the fieldbus network. The validity of this bandwidth allocation scheme is examined through simulation     

An improved CAN fieldbus for industrial applications

The controller area network (CAN) was originally developed to support cheap and rather simple automotive applications. However, because of its performance and low cost, it is also being considered in automated manufacturing and process control environments to interconnect intelligent devices, such as modern sensors and actuators. Unfortunately, CAN, in its current form, is not able to either share out the system bandwidth among the different devices fairly or to grant an upper bound on the transmission times experienced by the nodes connected to the communication medium as it happens, for instance, in the token-based networks. In this paper, two slight modifications of the basic CAN protocol are presented that satisfy the above-mentioned requirements at the expense of a very small degradation of the system's performance. Both these solutions exhibit a high degree of compatibility with those devices which have already been designed for the conventional CAN fieldbus. Besides introducing the new mechanisms, this paper also presents some performance figures obtained using a specially developed software simulator, while the behavior of the new mechanisms is compared to the traditional CAN systems, in order to see how effective they are     

现场总线技术评析

本文通过对近年来出现的现场总线技术的介绍，讲解了现场总线技术的特点和应用。同时，阐述了几种常见的现场总线的特点和使用情况，并加以对比，其中包括ＲＯＣＫＷＥＬＬ公司最新推出的ＣｏｎｔｒｏｌＮｅｔ。     

基于双ATmega128的安检力学试验机设计

针对当前安栓力学试验机所能完成的试验种类单一、自动化程度低等问题,提出一种以ATmega128单片机为核心控制器的安检力学试验机的设计.详细阐述了该安检力学试验机各个组成部分的设计原理和方案,并且给出了各部分的软件设计思想和操作流程.经过大量测试试验表明:设计的安检力学试验机可以完成多达十余种的力学安检试验,完全符合相关国家标准,并且具有数据采集精度高、传输速度快、操作安全简便等特点,实现了安检设备的多功能化、数字化和自动化.     

Real-time fieldbus communications using Profibus networks

This paper provides a comprehensive study on how to use Profibus fieldbus networks to support real-time industrial communications, that is, on how to ensure the transmission of real-time messages within a maximum bound time. Profibus is base on a simplified timed token (TT) protocol, which is a well-proved solution for real-time communication systems. However, Profibus differs with respect to the TT protocol, thus preventing the application of the usual TT protocol real-time analysis. In fact, real-time solutions for networks based on the TT protocol rely on the possibility of allocating specific bandwidth for the real-time traffic. This means that a minimum amount of time is always available, at each token visit, to transmit real-time messages, transversely, with the Profibus protocol, in the worst case, only one real-time message is processed per token visit. The authors propose two approaches to guarantee the real-time behavior of the Profibus protocol: (1) an unconstrained low-priority traffic profile; and (2) a constrained low-priority traffic profile. The proposed analysis shows that the first profile is a suitable approach for more responsive systems (tighter deadlines), while the second allows for increased nonreal-time traffic throughput     

一种新型的半固化片无尘裁切机

一种新型的半固化片无尘裁切机,该设备采用先进的红外加热技术,可使半固化片裁切刃口整齐、不掉粉、不发白、不烧焦,且能够自动封边,解决了传统机械裁切半固化片时带来的粉尘污染、玻璃丝掉落等困扰业界多年的问题;在裁切精度控制方面该设备采用伺服驱动技术,解决了传统剪切机高速状态下定长计量精度差的问题,提高了剪切机的定长计量精度。     

A computer-controlled electron-beam machine for microcircuit fabrication

The main advantages of electron-beam methods for the fabrication of microcircuits are: 1) improvement in resolution; and 2) ease of automation. A computer-controlled electron-beam machine has been developed from a high-resolution scanning electron microscope and has incorporated several important features for use in microfabrication, such as an LaB6gun to improve brightness and stability, and a special electron collection system based on channel multipliers, which is particularly suitable for use with large flat specimens. The control system is based on a small general-purpose computer with a flexible data input facility which can be made compatible with the output of most computer-aided mask design facilities. The input data is based upon rectangular shapes but additional nonrectangular shapes can also be handled. Several of the important technical areas of the machine have been evaluated, e.g., resolution, speed of operation, area of coverage, etc. It has been found that speed of operation and area of coverage are both related to the beam diameter used and the effect of this rather complicated interrelationship has been studied. The machine has been used to generate patterns on mask and wafers and results indicate that it has direct application to microcircuit manufacturing and one immediate use would be to develop it into a mask maker where it could produce a complete set of standard size masks (1x) in one working day.     

State of play [fieldbus technology]

It is unfortunate, to say the least, that the search for a common fieldbus standard has proved both protracted and divisive. The fieldbus approach to inter-device communications in a control environment has clear benefits. Costs are lower-the result of replacing multiple point-to-point links with a shared bus-while local intelligence enhances the functionality of field devices and reduces the demands on central computing. For the present, the great majority of fieldbus installations are based on single-link networks, but, as we move increasingly to multi-link networks, with multiple single links connected by gateways and bridges, additional performance gains are being realised. In particular, fault damage can be confined within the originating link, bus power requirements can be distributed independently across individual links, and bandwidth demands can be reduced by confining local traffic to local links. Multi-link networks also allow the characteristics of individual links to be tailored to address specific local requirements, such as high-speed communication or safety-critical design. These are all facets of the benefits available from distributed systems composed of multiple intelligent devices and made possible by fieldbus technology     

铝电解电容器测试分选机的设计方案

JHT-LD-380型高精度电容器全自动测试分选机是铝电解电容器生产专用设备。该机选用了ST-280型电解电容器测试电桥,该电桥集极性、漏电流、电容量、损耗各参数的测试及通过I/O接口对外部电路进行控制于一体,性能优异。电桥与外围电路配合良好。在测试电桥、充电片、测试头等关键点的设计上独具匠心。该机具有自动分选、操作简便、测试准确、速度快等优点,在测试精度、速度、分选准确度等方面均达到国外同类机的水平。1998年评为国家级新产品。     

A machine vision system for inspection of keyboards

A machine vision system for automatic inspection of keyboards is described. The system verifies that each location on a keyboard contains the correct, properly oriented key and that the graphics are not badly distorted. The graphics are inspected on the top and front surface of keys that vary widely in color, contour, surface texture and graphic content. Economical solutions are presented to a number of problems related to the design of the system's mechanics, optics, illumination, data reduction, pattern location and graphics discrimination. Operating procedures for training and running the system are also presented along with preliminary results.     

A model for sequential machine testing and diagnosis

A mathematical framework for the testing and diagnosis of sequential machines is developed. A very general fault model is used in which a faulty machine is represented as a sequential machine, possibly with state and output sets different from those of the good machine. A deterministic finite automaton, called observer, describes the process by which one gains information from the observation of the responses to test sequences. It generalizes the work of Hennie on distinguishing and homing sequences, by modelling all the possible conclusions that could be drawn from observing the circuit under test. A nondeterministic acceptor is derived from the observer; it accepts diagnosing sequences and can also be used to generate test sequences. We then associate probabilities with this nondeterministic acceptor which, together with a stochastic source of input symbols, provides a probabilistic diagnoser. As a particular application we consider the testing and diagnosis of random-access memories by random test sequences. Our model generalizes the work by David et al. on the calculation of the length of a random test sequence required to guarantee that the probability of detection of a fault exceeds a prescribed threshold.This work was supported by the Natural Sciences and Engineering Research Council of Canada, Grants OGP0000871 and OGP0000243, and a grant from the Information Technology Research Centre of Ontario. Preliminary papers leading to this work have appeared earlier [1] [2].     

A neuro-fuzzy approach for robot system safety

Robot safety is a critical and largely unsolved problem involving the interaction of man and machine. The paper presents a new approach to robot safety which uses an integrated sensing architecture for monitoring the robot workspace, and a new detection and decision logic for regulating the safe operation of the robot. Sensory information is fused through a trained neural network to produce a map of the hazards. Using this combined map, and information about the robot's current position and velocity, a set of fuzzy logic rules has been implemented to regulate robot activity. Simulation results presented in the paper indicate that this method is both effective in detection of potentially hazardous situations and computationally feasible     

基于TMS320F206的CAN现场总线的嵌入式网关设计

设计了以微控制器TMS320F206为核心的连接现场总线和以太网的嵌入式网关,给出了嵌入式网关的硬件接口电路,并对主要芯片进行了介绍,阐述了硬件间的通信原理;并给出了RTL8019AS的数据收发、CAN控制器和CAN总线间的数据传输以及CAN和以太网间的数据通信原理及软件流程。现场网关解决了以太网和CAN总线之间的互联问题,使得CAN-Ethernet的互联降低成本,提高了性能。     

一种基于机器视觉的引体向上计数方法

针对引体向上项目人工计数效率低、误判率高等问题,提出了一种基于机器视觉的引体向上计数方法.利用AdaBoost算法构建Haar-like特征人脸人手分类器,通过计算图像不变矩获取人手人脸面积和质心坐标,分别取人脸面积、人脸与人手质心垂直距离做阈值;利用混合高斯背景模型提取运动前景,统计图像序列中ROI区域灰度变化,然后做椭圆肤色检测,计算图像不变矩获取图像序列中人脸质心坐标,通过对每帧的灰度值和质心坐标变化做分析,并与设定阈值作比较,得到引体向上数目.实验表明,该方法能快速的对复杂环境下引体向上动作进行计数,计数准确率约为91.3％.     

A support vector machine approach for detection of microcalcifications

In this paper, we investigate an approach based on support vector machines (SVMs) for detection of microcalcification (MC) clusters in digital mammograms, and propose a successive enhancement learning scheme for improved performance. SVM is a machine-learning method, based on the principle of structural risk minimization, which performs well when applied to data outside the training set. We formulate MC detection as a supervised-learning problem and apply SVM to develop the detection algorithm. We use the SVM to detect at each location in the image whether an MC is present or not. We tested the proposed method using a database of 76 clinical mammograms containing 1120 MCs. We use free-response receiver operating characteristic curves to evaluate detection performance, and compare the proposed algorithm with several existing methods. In our experiments, the proposed SVM framework outperformed all the other methods tested. In particular, a sensitivity as high as 94% was achieved by the SVM method at an error rate of one false-positive cluster per image. The ability of SVM to out perform several well-known methods developed for the widely studied problem of MC detection suggests that SVM is a promising technique for object detection in a medical imaging application.     

太浦闸监控系统现场总线通信网络可靠性研究

针对太浦闸监控系统现场控制单元现场总线通信网络存在的问题,根据现场勘测分析,得出可能导致此问题的原因有:网络拓扑结构不合理、总线特性阻抗的连续性不好、系统保护措施不够,提出了采用RS485集线器来实现星型接法,使网络拓扑结构合理,并通过其光电隔离的防雷的功能,加强系统的保护,同时在总线的终端串接电阻来改善总线特性阻抗的连续性,对原有现场总线通信网络进行改造.改造后系统运行稳定可靠,效果良好.