工业控制网络中几种介质访问方式的分析.doc

工业控制网络中几种介质访问方式的对比分析基于组合特征的车牌字符识别* 路小波 凌小静 刘 斌张玉萍 佟为明 李辰 （东南大学教育部智能运输系统工程研究中心哈尔滨工业大学电气工程与自动化学院，哈尔滨哈尔滨工业大学 哈尔滨南京 215000196） 摘 要 本文阐述了应用于工业控制网络中应用的多种介质访问控制方式，并对其中常用的几种常用介质访问控制方式的优缺点进行了分析，重点分析了载波监听多路访问、时分复用、令牌环及总线令牌等介质访问方式，同时并给出了各种方式的应用实例。提出了基于Zernike矩和小波变换特征相结合的车牌字符识别方法。利用Zernike矩描述字符全局特征，小波变换系数描述字符细节特征，采用神经网络进行车牌字符分类。测试结果表明，这种组合了两种特征优点的方法实用有效，识别效果优于两种特征独立使用的情况。 关键词 工业控制网络车牌字符识别 介质访问控制方式Zernike矩 小波变换 CSMA 令牌 中图分类号 TP336 文献标识码 A 国家标准学科分类与代码 621. 特征提取 中图分类号 TP2 文献标识码 A 国家标准学科分类与代码 520.604 The Contrast Analysis of Several Medium Access Control Modes in Industry Control NetworksLicense Plate Character Recognition Based on the Combined Features Zhang Yuping Tong Weiming Li ChenLu Xiaobo Ling Xiaojing Liu Bin （School of Electrical Engineering and Automation, Harbin Institute of Technology, Harbin 150001, China） (Harbin Institute of Technology, Harbin 150001Engineering Research Center for Intelligent Transportation Systems under Ministry of Education, 5号楷体5号黑正体，居中，居小5号斜体，居中，下空一行5号楷 5号楷体5号黑正体，居中 ，居小5号斜体，居中，下空一行 5号楷体5号黑正体，居中 Abstract This paper introduces the common media access control modes in industry control networks and analyses the advantages and disadvantages of them, respectively.. Especially Tthe difference of CSMA、TDMA、Token-Ring and Bus-Token is especially describdetailed. And the applications of them are presented.This paper presents a method of license plate character recognition based on the combination of Zernike moment and wavelet transformation features. The Zernike moment is used to describe the global feature of the characters, and the wavelet transform coefficient for the detailed feature of the characters. A neural network is used to classify the license plate characters. Experimental results show the presented method achieves better recognition accuracy than using two features separately. Key words industry control networkslicense plate character recognition MACZernike moment CSMA Token wavelet