【作者】 王世隆；

【导师】 林君；

【作者基本信息】 吉林大学 ， 测试计量技术及仪器， 2011， 博士

【摘要】 直升机时间域航空电磁法以直升飞机作为载体,在飞行过程中,通过吊舱上发射线圈所产生的大发射磁矩,激发大地产生二次感应场,由电磁场理论解释该响应信号,从而获得地下几百米深度以内的电导率结构信息。该方法具有快速、高效并在工作时不受地形影响等特点,越来越受物探领域的发达国家重视。经过世界上近十年直升机时间域航空电磁法的飞速发展,国外仪器系统已趋于成熟,而国内仪器系统的研究尚处于空白状态。在国家高科技研究发展计划支持下,本文针对仪器系统开发过程中所遇到的数据收录系统研制、系统校准、数据现场处理及地面模拟仿真和实验等方面进行了详细研究。数据收录系统侧重研究了基于PXI总线技术的全波多通道数据采集、基于时间流基准方式的多种数据信息组织收录和信号动态范围的提高方法。在海量数据收录的过程中,研究了如何保证数据稳定和减小误差的方法。在信号动态范围研究中,采用补偿环和低噪声双通道采集相结合方法提高信号动态范围。系统校准侧重研究了同心补偿式吊舱装置的发射磁场空间分布及其对接收线圈的影响,补偿线圈空间位置和半径大小对于补偿效果的理论分析。针对采集的海量数据,现场数据处理对基于时间流基准方式的信息组织、多核并行大内存处理、定位信息校正、测线信息分割及去除高空背景测线信息等方面进行了研究。基于吊车摆动方式对地面环线的剖面异常检测实验,侧重研究了在不同高度下的不同半径异常环响应模拟,实验结果与仿真效果一致。吊舱校准装置的剖面异常检测实验,模拟了飞行中仪器扣除高空背景场的处理方法,也验证了吊舱校准装置在高空校准的可行性。通过本文的研究,为我国直升机时间域电磁法探测系统的研制工作,在数据收录和现场处理方法提供参考,促进我国在该领域的进一步发展。更多还原

【Abstract】 Helicopter-borne Time-domain Electromagnetic Method (HTEM) has rapid large-scale electromagnetic geophysical advantages and it is used for metal ore exploration, geological mapping, hydro geological surveys and environmental monitoring. After 2000, five aspects abroad has rapidly developed, such as airborne electromagnetic forward and inversion methods, the special data processing methods, helicopter electromagnetic instruments, instrument calibration methods and application. The 1D, 2D and 3D forward, invention model simulation, and conductivity depth imaging problems have been studied. Special data processing studies include the impact of the flight program of exploration, the influence of the bird posture change, data leveling and the good conductor detection. The most advanced HTEM systems are developed to wider frequency band, high-power transmitter and multi-component receiver. From the three calibration methods about the known loop detection method, the contrast correction method of the actual conductor and the performance of the system itself, this thesis is chose artificially controlled loop detection method. HTEM’s applications have become more and more widespread throughout continents, such as inland surface and groundwater exploration, shallow sea and salt water intrusion investigation, sea and ice depth detection, mineral exploration, natural disasters exploration about volcanoes, the falling rock and tunnels, underground exploration, pollutants investigation, coal, oil and gas exploration, unexploded ordnance detection, and vegetation cover survey.Because there is no airborne electromagnetic system equipment inboard, Chinese researchers just do studies about the theory and model simulation. Considering the mountainous terrain in China and HTEM detecting deep advantage, this subject is supported by the national eleventh five-year 863 plan. The target is to develop a practical HTEM system.Innovations of this thesis include that a bird calibration device of HTEM with concentric bucking loop, combination of two methods about bucking loop and lower-noise dual-channel sampling program is improved the dynamic range of the HTEM signal, multi-information fusion based on Time-flow FID method is achieved, and single-file storage method can avoid the system crashing because of the competition of a hard disk written, which is described four chapters.(1) The real-time full-wave method of huge data recording provides more information for helicopter-borne time-domain electromagnetic instrument with respect to deep exploration and spatial discrimination. Considering the lack of compatibility between large magnetic moment and full-wave recording approach in the coaxial coplanar coils’device, this thesis uses bucking coil to weaken the primary magnetic field, and applies the key technology of state-machines, the design of multi-tasking mode, information stored method and data fusion of time-based stream on the base of continuous sampling characteristics of high-precision and long time. Combination of two methods about bucking loop and lower-noise dual-channel sampling program is improved the dynamic range of the HTEM signal. Finally, the full-wave recording system with the core of PXI is developed. A series of experiments show that the system is stable and reliable, and provides application platform for method research and reference for the design of electromagnetic instruments on unmanned aerial vehicles and semi-airborne.(2) The multiple instrument calibrations of flying helicopter-borne time-domain electromagnetic method can eliminate the environmental time-varying effect on the system during the process of flying. Using the bird calibration device to solve the problem that the wire-loop method can’t achieve, this thesis considers the bird model of HTEM with the concentric bucking loop, bringing forward the bird device space models and the coil circuit models, and analyzing the transmitter magnetic field distribution, the bucking loop’s effect and the relationship between it and the receiving coil, the space information of the calibration device and its signal detected method. Conclusions are as follows: (a) The bucking loop that loses 0.89% of the transmitting area can increase 44.5dB of the signal dynamic range. (b) The calibration device is levelly placed between the bucking loop and the transmitting coils. If it has more turns, greater radius and is closer to the bucking loop, its signal response becomes stronger. (c) If the inductance of calibration coil becomes greater with less resistance, its exponential decay becomes more slowly. The signal detection time-point is directly decided by damping character of receiver coil, which has matching resistance. This thesis is based on experiments about the calibration curve characters and the device coil displacement. The relative error about the time constant of the device characteristics is less than 1.3%, which proves the validity of the coil circuit models and device space models. The proposed models and approaches are also the same as the bird calibration device research about HTEM with the eccentric bucking loop and the known wire-loop static testing on the high resistance ground.(3) The key technologies of on-site rapid processing of large amounts of data are the measured information management, the separation of information, the main sampling waveform processing, the information fusion of time-based stream, and large memory multi-core parallel processing method. The functions of the test profiles’software are time adjustment, survey line information division, survey lines of removal high-altitude background information and generating function of the standard profile file.(4) In order to verify the overall performance of the instrument and the initial flight data processing, this thesis designs the experiments that the crane swings the bird to detect the ground loop anomaly. Based on the ground loop detection theory, the mobile loop anomaly is simulated by different parameters. The measured profile curve information demonstrates the feasibility of the instrument movement measuring. The loop processing of the onboard calibration profile can simulate the real flight data processing.In this thesis, the system has done many ground experiments Geological Palace, Big Goose Island, Karen Lake and Shaoguo town in Changchun, and it is successfully used to find water resource combined with NMR in Yunnan and Guizhou province in 2010. However, the bird framework is broken in the helicopter experiment. Further research should be emphasized on the weight reducing of the system and the the interference removing of the current modulated signal.更多还原