半航空电磁测量系统地空同步技术研究

发布时间：2018-05-07 03:10

本文选题：半航空 + 瞬变电磁法　；参考：《成都理工大学》2015年硕士论文

【摘要】：随着人类对矿产资源的需求迅速增加,有限的矿产资源与人类不断增长的需求之间的矛盾日益突出,使找矿工作重点逐渐转变为在隐伏区、矿区深部及矿区外围寻找隐伏矿和盲矿。半航空瞬变电磁法是近年来电法勘探领域发展较快的一种重要方法。瞬变电磁法是利用不接地回线或接地电偶源向地下发送一次场,在一次场的间歇期间利用回线或电偶极观测二次涡流场的方法。瞬变电磁勘探方法中“涡流”从产生到结束的时间十分短暂,对取样时间要求十分精确。要做到这点就必须使发射电流关断后,在精确的某一时刻开始测量,从而接收系统与发射系统就必须实现精确的同步。本文立足于国土资源部公益性行业科研项目“基于无人机的半航空瞬变电磁勘查技术研究”,主要对其数据采集系统中的地面发射系统,地面接收系统及无人机接收系统三者之间的采样信号同步技术进行了研究。本文主要研究了三种同步技术,振荡器同步技术、无线同步技术、GPS同步技术的原理及实现,并用GPS同步技术在半航空电磁测量系统中进行了实验,同时对系统的抗干扰措施进行了研究并进行了应用。振荡器同步技术用了时钟芯片PCF8563的可编程时钟输出,报警器及定时器功能,设置TI/TP=1,此时中断信号为脉冲方式。让PCF8563每秒钟在/INT端产生一个脉冲给单片机,在中断服务程序中可以读取时钟以供显示。以此时钟来作为发射系统,接收系统的同步时标。无线同步技术的实现利用了具有丰富的位时钟信息的曼彻斯特编码。在发送数据时,主控机将恒温晶振和电磁信号的数据字节逐个送往编码模块,由编码模块将其转换成曼彻斯特码。再经过平滑滤波调整、功率驱动及音频变压器隔离后,送到发射系统发射。接收过程是解码器收到发射端传来的信号后,首先将信号经过音频变压器隔离,再通过带通滤波、放大整形为矩形波信号,然后送入解码模块进行解码处理,解码器通过“结束标志字节”判断信号是否为有效信号。解调出的数据通过中断请求方式实现MCU读取。GPS同步技术的实现是,GPS接收模块通过天线接收卫星传送的授时信息,获得需要的时间信号,该信号和UTC国际标准时间高精度同步,同时,还要校正恒温晶振的秒脉冲。在FPGA中设计能够测量GPS秒时钟与恒温晶振秒信号之间误差的测量模块,主控机对数据进行存储与处理,利用测量的时间差序列,对GPS信号的随机误差的统计方差进行估计,恒温晶振输出信号做实时校正,从而产生高精度的时钟信号。由于同步采样装置在强电磁环境中长期连续工作,所受到的干扰比较严重,若不能及时正确处理,可能使装置工作不正常,造成同步采样的失败。所以,同步采样的抗干扰设计是十分必要的。本文中对于同步采样装置抗干扰措施,数据采集部分抗干扰措施,及抑制外部电磁噪声干扰进行了研究,有效减少了同步采样系统中的干扰。本文在实验时利用GPS同步技术,充分融合GPS秒时钟信号优良的长期稳定特性与恒温晶振优良的短期稳定特性,将两者的长处有机的结合起来,对GPS信号进行一定处理后,用于校正恒温晶振输出,实现一个高精度的时钟系统,使得时钟精度即使在GPS信号失效3个小时仍能保持小于±1μs,为半航空电磁测量系统供应精确的时间标准。本文中的方法与传统采用GPS脉冲信号调节压控晶振的电压来修正晶振输出频率获得同步时钟相比,同步精度得到提高,同步时序调节更加方便,通用性强,更加适合在野外工作的半航空瞬变电磁探测系统使用。
[Abstract]:With the rapid increase in the human demand for mineral resources, the contradiction between the limited mineral resources and the growing demand of human beings has become increasingly prominent, which has gradually changed the focus of prospecting work into hidden areas, deep areas and the periphery of mining areas to find hidden ore and blind ore. Semi aeronautical transient electromagnetism method has developed rapidly in the field of electrical prospecting in recent years. An important method. The transient electromagnetic method is a method of using an ungrounded return line or a grounding galvanic source to send a field to the ground, and the method of using a return line or electric dipole to observe two eddy current fields during the interval of a field. The time of "eddy current" from the generation to the end of the transient electromagnetic exploration method is ten minutes short, and the sampling time is very accurate. To do this, the emission current must be closed and measured at a precise time, so the receiving system and the launching system must be accurately synchronized. This paper is based on the research project of the public welfare industry of the Ministry of land and resources "semi aeronautical transient electromagnetic exploration based on unmanned aerial vehicle", mainly to its data acquisition system. The sampling signal synchronization technology between the ground launching system, the ground receiving system and the unmanned aerial vehicle receiving system is studied. This paper mainly studies the principle and implementation of three synchronization technologies, oscillator synchronization, wireless synchronization and GPS synchronization, and uses GPS synchronization technology in the semi aero electromagnetic measurement system. At the same time, the anti-interference measures of the system are studied and applied. The oscillator synchronization technology uses the programmable clock output of the clock chip PCF8563, the alarm and the timer function, and sets the TI/TP=1. At this time, the interrupt signal is pulse mode. PCF8563 produces a pulse at / at the INT terminal per second to the single chip microcomputer, in the interrupt service. In the program, the clock can be read for display. The clock is used as the transmitting system and the synchronization time mark of the receiving system. The implementation of the wireless synchronization technology uses the Manchester code with rich bit clock information. In sending data, the master controller sends the data bytes of the constant temperature crystal and electromagnetic signals to the coding module one by one, and the encoding is coded. The module converts it into the Manchester code. After the smoothing filter is adjusted, the power drive and the audio transformer are isolated and sent to the launch system. The receiving process is the signal that the decoder receives the transmitting end. First, the signal is isolated from the audio transformer, and then the band pass filter is used to shape the signal into a rectangular wave signal and then send it into the solution. The code module performs decoding processing. The decoder determines whether the signal is a valid signal through the "end mark bytes". The demodulated data is realized by the interrupt request mode to realize the MCU reading.GPS synchronization technology. The GPS receiving module receives the time message transmitted by the satellite through the antenna, and obtains the required time signal, the signal and the UTC international. The standard time is high precision synchronization, and at the same time, the second pulse of the constant temperature crystal oscillator should be corrected. In the FPGA, the measurement module that can measure the error between the GPS second clock and the constant temperature crystal second signal is designed. The main control machine stores and processes the data and estimates the statistical variance of the random error of the GPS signal by the time difference sequence of the measured, and the constant temperature crystal. When the synchronous sampling device works in a strong electromagnetic environment for a long time, the interference of the synchronous sampling device is more serious. If it can not be properly handled in time, it may cause the device to work unnormally and cause the failure of synchronous sampling. Therefore, the anti-interference design of synchronous sampling is very necessary. In this paper, the anti-interference measures of synchronous sampling device, the anti-interference measures of the data acquisition part and the suppression of the external electromagnetic noise interference are studied in this paper, which effectively reduces the interference in the synchronous sampling system. In this paper, the GPS synchronization technology is used in the experiment to fully fuse the good long-term stability characteristics and the constant temperature crystal vibration of the clock signal in GPS seconds. The good short-term stability characteristics, combining the strengths of both of the two, after a certain processing of the GPS signal, is used to correct the output of the constant temperature crystal vibration and achieve a high precision clock system. The clock precision can remain less than + 1 s even when the GPS signal is invalid for 3 hours, and the precise time is supplied for the semi aero electromagnetic measurement system. The method in this paper is compared with the traditional GPS pulse signal adjusting the voltage of the voltage controlled crystal oscillator to amend the output frequency of the crystal oscillator to get the synchronization clock, and the synchronization precision is improved. The synchronization timing adjustment is more convenient and versatile. It is more suitable for the use of the semi Aeronautical transient electromagnetic detection system working in the field.

【学位授予单位】：成都理工大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：P631.326

【参考文献】