地下工程轻便式全波磁共振系统接收机研制

发布时间：2018-10-16 22:56

【摘要】：随着我国基础设施建设的高速发展，地下工程施工建设所占比重越来越大。磁共振探测技术作为一种直接探测灾害水体的方法应用在地下工程中，对地下灾害防治起到积极作用。然而，现有磁共振探测仪器在地下环境探测中存在诸多不足，如仪器的体积重量较大，在狭窄的地下工程环境中不便于搬运；在数据量方面，包络采集方式记录信号及环境噪声的数据量有限，不利于后期的多种消噪算法处理；上位机系统软件操作步骤繁琐，运行耗时较长等。本文针对地下探测环境和已有仪器存在的问题，在JLMRS-III型仪器设计原理基础上，设计了地下工程轻便式全波磁共振系统接收机的整体方案，并研制了接收机样机及配套控制软件，通过对系统的室内及野外测试验证了系统可行性。本文针对地下工程环境，结合地下磁共振信号探测基本原理，从探测领域和探测方式出发对接收系统进行设计。在系统的轻便化设计方面，，本文遵循方便携带、容易操作、稳定可靠的设计原则，采用平板电脑作为上位机平台嵌入系统内部，减少仪器连线，利用不锈钢结构搭建内部骨架。系统采用模块化设计，体积小巧，重量仅为7.5kg，为在地下工程中进行磁共振探测提供轻便式接收机。在提升系统的信号接收性能设计方面，由于地下探测空间有限，本文在对接收天线建模和理论计算的基础上，提出采用接收发射分离式米级线圈感应磁共振信号，并对该系列线圈设计了前端匹配网络和后级放大单元，信号经滤波调理后可放大80.6~130.1dB；基于低噪声MPS-140801采集卡实现最高采样率128ksps的全波磁共振信号采集，同时为使信号相位叠加更加精准，设计了采集校准电路产生校准信号，使信号校准精度不大于78μs；从软件和硬件两方面构建系统时序，其中软件方面设置系统的发射、能释、切换和采集时间，硬件方面通过设计电路对发射机传送的同步信号进行精准延时，保证系统时序控制的准确性；为提高数据处理速率以及地下勘探效率，本文利用LabVIEW对系统进行上位机软件开发，从用户输入、硬件驱动和系统处理三个层面进行设计：采用主线单线程局部多线程方式，利用“生产者-消费者”架构对数据进行多线程循环处理，数据处理速率较原有系统提升4倍以上，确保接收系统在地下环境中进行大数据高效探测。最后，本文对地下工程轻便式全波磁共振系统接收机进行了整体性能测试，包括屏蔽室内噪声环境、仪器本底噪声、模拟MRS信号以及仪器的野外测试。系统本底噪声10.51nV，等效短路噪声1.76nV/Hz，满足磁共振接收系统的设计要求。并通过野外实验验证了接收系统稳定性和可靠性。
[Abstract]:With the rapid development of infrastructure construction in China, the proportion of underground construction is increasing. As a direct method of detecting water bodies, magnetic resonance (MRI) technology is used in underground engineering and plays an active role in the prevention and control of underground disasters. However, the existing magnetic resonance detection instruments have many shortcomings in the detection of underground environment, such as the large volume and weight of the instrument, which is not easy to carry in the narrow underground engineering environment; Envelope acquisition method records the data of signal and environmental noise is limited, which is not conducive to the later processing of a variety of de-noising algorithms; the upper computer system software operation steps are cumbersome, running time is longer, and so on. In this paper, aiming at the problems of underground detection environment and existing instruments, based on the design principle of JLMRS-III instrument, the whole scheme of portable full wave magnetic resonance system receiver for underground engineering is designed, and the prototype of the receiver and the corresponding control software are developed. The feasibility of the system is verified by indoor and field tests. According to the underground engineering environment and combined with the basic principle of underground magnetic resonance signal detection, this paper designs the receiving system from the detection field and detection mode. In the portable design of the system, this paper follows the design principle of easy to carry, easy to operate, stable and reliable. It uses the tablet computer as the upper computer platform to embed the system, reduces the instrument connection, and builds the internal skeleton with the stainless steel structure. The system is modular, small in volume and only 7.5 kg in weight. It provides a portable receiver for magnetic resonance detection in underground engineering. In the aspect of signal receiving performance design of lifting system, due to the limited underground detection space, based on the modeling and theoretical calculation of receiving antenna, this paper proposes to adopt the receiving and transmitting separated meter coil inductive magnetic resonance signal. The front-end matching network and the back-stage amplifier unit are designed for the series of coils, the signal can be amplified 80.6130.1 dB after filtering and conditioning, and the full wave magnetic resonance signal acquisition based on low-noise MPS-140801 acquisition card is realized for the highest sampling rate 128ksps. At the same time, in order to make the signal phase superposition more accurate, the acquisition and calibration circuit is designed to generate the calibration signal, so that the signal calibration accuracy is not greater than 78 渭 s. In the aspect of switching and collecting time and hardware, the synchronous signals transmitted by the transmitter are precisely delayed by designing circuits to ensure the accuracy of the timing control of the system, in order to improve the data processing rate and the efficiency of underground exploration, In this paper, LabVIEW is used to develop the upper computer software of the system, which is designed from three aspects: user input, hardware driver and system processing: the main thread, single thread, and local multithreading are adopted. By using the "producer-consumer" architecture to process the data in multithreading cycles, the data processing rate is more than four times higher than that of the original system, which ensures that the receiving system can efficiently detect big data in the underground environment. Finally, the overall performance of portable full-wave magnetic resonance system receiver for underground engineering is tested, including shielding indoor noise environment, background noise of instrument, analog MRS signal and field test of instrument. The background noise of the system is 10.51nV and the equivalent short-circuit noise is 1.76nV / Hz. it meets the design requirements of the magnetic resonance reception system. The stability and reliability of the receiving system are verified by field experiments.
【学位授予单位】：吉林大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：P631.2

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