铁磁管道环境下极低频微弱磁场的分布及检测  

Distribution and detection of ELF weak magnetic field in ferromagnetic pipeline environment

作　　者：陈水平[1] 郭静波[1] 胡铁华[2] 

机构地区：[1]清华大学电机系国家重点实验室,北京100084 [2]机械科学研究总院,北京100082

出　　处：《仪器仪表学报》2011年第10期2348-2356,共9页Chinese Journal of Scientific Instrument

基　　金：科技部科研院所技术开发专项(2209004S1J)资助项目

摘　　要：极低频信号对金属管道、土壤等介质具有良好的穿透性能,可以应用于管道中的目标定位。实现这个目标包括2方面的内容:一是认识极低频磁场在管道环境下的分布;二是对接收的混有噪声的极低频信号进行检测与判决。其中极低频磁场的分布特性是信号检测、判决与系统设计的基础。首先建立了管道环境下极低频磁场的对称模型,推导了管道内外各层介质中极低频磁场的解析表达式并给出数值计算结果,通过ANSYS软件建模仿真进行验证。在此基础上,得到了接收天线上感应磁场随距离的变化曲线,通过对信号与噪声的比较,设计了接收系统的整体方案。针对接收信号的特性,选择最小二乘法进行实时检测和判决。通过分析核心判决统计量与归一化自相关系数的关系,采用深度叠接相加预处理技术,明显地改善了系统的接收效果,扩展了叠接相加法的应用范围。Extremely low frequency（ELF） signal is widely used for target locating in ferromagnetic pipeline because of its ability to pass through metal,soil and other mediums.In order to achieve this goal,two important problems should be solved.One is the distribution of ELF magnetic field and the other is the detection and decision of the ELF signal mixed with noise.The distribution characteristic of ELF magnetic field is the basis of the detection and decision,as well as system design.Firstly,a symmetric model of ELF magnetic field in pipeline environment is established,then the analytic expression of the magnetic flux density is derived,and the numerical calculation of the magnetic field is carried out using MATLAB and verified using ANSYS.On this basis,the curve of magnetic flux density vs.distance on the receiver antenna is obtained.Through comparing the received signal with noise,the front-end of the receiver is designed.According to the property of the received signal,the least square method is selected for detection and decision.Through analyzing the relationship between the decision statistics and the normalized autocorrelation coefficients,a novel modified spliced addition method with extreme depth is proposed to improve the signal receiving effect obviously;meanwhile,the application of the Welch method is extended.

关 键 词：极低频信号 铁磁管道 磁场分布 归一化自相关系数 深度叠接相加 

分 类 号：TP274[自动化与计算机技术—检测技术与自动化装置] TN911.23[自动化与计算机技术—控制科学与工程]