【作者】 韩磊；

【导师】 张一鸣；

【作者基本信息】 北京工业大学 ， 控制科学与工程， 2015， 硕士

【摘要】 可控源音频大地电磁法(Controlled Source Audio-frequency Magnetotelluric,CSAMT)是一种人工源频率域电磁测深方法,具有勘探深度范围大、测量效率高等优点,广泛应用于找矿、地下水探测、环境污染探测、石油勘探、工程地质勘查等领域。人工场源电磁勘探系统由发射机和接收机组成,发射机负责向大地提供具有一定功率的脉冲电流作为场源;接收机实现高效的电磁信号数据采集工作,再通过地球物理反演将原始观测数据转变成地球物理模型,从而能够反映地质状况。作为可控源人工电磁场的激励源,地面电磁探测(Surface Electromagnetics Prospecting,SEP)发射机的研制是整个电磁勘探研究中的重要环节。全球定位系统(Global Positioning System,GPS)时间同步和数据采集与处理系统是整个SEP发射系统的重要组成部分,其主要功能是提供发射机精准的GPS同步时间和实时的采集处理发射电压、发射电流、发射频率数据,并将这些数据上传到上位机显示和存储。本文对GPS时间同步和数据采集与处理系统进行了理论分析、软硬件设计与实验验证,完成了基于DSP+FPGA的低噪声、低漂移、高精度的SEP发射机GPS时间同步和数据采集与处理系统的研制任务,论文的主要工作包括四部分:第一部分,GPS时间同步模块的设计。首先分析了GPS的授时原理和GPS授时误差的来源,引出了GPS失锁的问题,进而提出了利用GPS/本地时钟双模授时的时间同步技术,给出了时间同步系统的总体设计方案和原理框图,并阐述了各个功能模块的所要实现的功能;其次,对时间同步方案软硬件进行了详细设计,重点介绍了恒温晶振频率校正和授时工作模式切换的方法;最后对时间同步精度进行了试验验证及分析。第二部分,数据采集和处理模块的设计。首先给出了数据采集和处理系统的总体设计方案和原理框图,采用DSP和FPGA作为主控制器,对发射电压、电流和频率进行实时测量和显示;其次,详细阐述了数据采集和处理系统硬件组成和软件设计流程;最后重点介绍了DSP对发射电压、发射电流信号的采样和处理及FPGA对发射频率测量的方法。第三部分,人机交互界面的设计。利用Labview软件设计了良好的人机交互界面,可以在线配置发射机的工作模式和发射参数,并具有数据显示和波形显示的双重功能,对发射机的运行状况进行实时监视,此外还具有自动存储功能,以便后期数据分析。第四部分,实验验证。首先通过实验对GPS时间同步精度、数据采集与处理系统采样精度进行测试,测试结果表明设计的时间同步系统同步精度优于±0.1μs,数据采集和处理系统采样精度也达到99%以上,符合系统设计要求。最后与代表国外先进水平的发射机同时于野外进行发射对比实验,通过发射频率对比分析验证了本文所设计的发射机发射性能上接近代表国外先进水平的发射机,能胜任野外地质勘探的性能需求。更多还原

【Abstract】 Controlled Source Audio-frequency Magnetotelluric(CSAMT), controlled source audio frequency magnetotelluric method is a kind of artificial source frequency domain electromagnetic sounding method, with a wide range of exploration depth, high measurement efficiency and other advantages, which has been widely used in ore prospecting, groundwater detection, environmental pollution detection, oil exploration, engineering geological exploration and other fields. Artificial source electromagnetic exploration system consists of a transmitter and a receiver, the transmitter responsible for providing pulse current to the earth as its source of power; the receiver receives magnetotelluric response information efficiently, and then through the geophysical inversion original observation into geophysical model data, which can reflect the geological condition. As the controlled source electromagnetic excitation field source, the development of Surface Electromagnetics Prospecting(SEP) transmitter is an important part of the research in electromagnetic prospecting.(Global Positioning System(GPS) time synchronization and data acquisition and processing system is an important part of the overall SEP transmitter system, whose main function is to provide accurate GPS time synchronization of transmitter, real-time acquisition and processing of transmitting voltage, current, frequency data, and these data will be uploaded to the host computer display and storage.This paper study the theoretical analysis, hardware and software design and experimental verification of GPS time synchronization and data acquisition and processing system, and complete a low noise, low drift, high precision SEP transmitter GPS time synchronization and data acquisition and processing system based on DSP and FPGA. The main work of this paper includes four parts:The first part designs the GPS time synchronization module. Fristly, analysis of the principle of GPS timing and the source of GPS timing error, in view of the problem of GPS losing lock, proposing the use of GPS/local clock dual-mode timing synchronization technology, the overall design scheme and principle of time synchronization system is presented, and describes each functional module to achieve the function; secondly, the time synchronization scheme of hardware and software designed in detail, focusing on the methods of OCXO frequency correction and timing work mode switch; at the end of the time synchronization precision of experimental verification and analysis.The second part designs the data acquisition and processing module. Firstly, the overall design scheme and the principle of data acquisition and processing system is presented, using DSP and FPGA as the main controller, the transmitting voltage, current and frequency of real-time measurement and display; secondly, describes the data acquisition and processing system hardware and software design process; finally focus the method of transmitting voltage, current, frequency signal processing by DSP and frequency measurement by FPGA.The third part designs the human-computer interface. A good man-machine interface is designed by using Labview software, which can online configuration transmitter work mode and emission parameters, and has dual functions of data display and waveform display, real-time monitoring the operation status of the transmitter, in addition also has automatic storage function to post-data analysis.The fourth part accomplishes experimental verification. The experiment of GPS time synchronization precision and data acquisition system sampling accuracy are completed in the laboratory, the experiment results show that the synchronization accuracy is improved up to ±0.1μs and the sampling precision of data acquisition and processing system can reach more than 99%, meet the design requirements of the system. Finally, through the transmitting contrast experiments outdoors with the foreign advanced and representative transmitter, by the quality of the transmitting frequency, the design of the transmitter being close to representative of foreign advanced level transmitter is verified. The outdoors geological exploration experiments show that the performance of electromagnetic transmitter which designed in this paper can be competent for the outdoor geological exploration.更多还原