【作者】 郁专；

【导师】 王砚方；

【作者基本信息】 中国科学技术大学 ， 物理电子学， 2009， 博士

【摘要】 石油是战略资源,现代社会对石油的巨大需求推动着石油勘探的快速发展,作为石油勘探主要手段的地震勘探也取得了长足的进步,主要表现为地震勘探仪器的性能指标大幅度提升以及地震资料处理和解释过程中新方法新技术的不断涌现。地震检波器是地震勘探中用于接收和转换振动信号的传感器。作为地震勘探仪器记录地震信号的第一步,地震检波器对地震资料的品质影响很大。随着地震勘探技术的进一步发展,对地震检波器的精度要求也越来越高。地震检波器应有理想的频率响应以及足够大的动态范围,否则电子学系统再精良,也无法得到高质量地震记录数据。目前陆上勘探使用的地震检波器通常包括动圈式检波器和新兴的MEMS数字检波器,这些检波器都属于惯性传感器的范畴。传统的动圈式检波器由于谐波失真的限制,日益成为整个勘探系统的瓶颈,必须加以改进。而基于MEMS技术的数字检波器,是地震检波器在技术层面的重大进展。这种检波器可以提供良好的线性度,除此之外,它还实现真正意义上的数字信号输出,且具有内在的、较高的矢量精度和优良的低频信号响应特性,成为地震检波器发展的主流。针对这样的趋势,本文的研究主要分成两个方面,一是传统动圈式检波器谐波失真的原理分析以及改进方法,二是结合当前MEMS技术以及工艺的进展,分析了使用MEMS技术实现地震检波器的各种方案,包括开环系统、模拟闭环系统以及数字闭环系统,在对各种方案进行线性化分析的基础上,在仿真工具中进行建模和仿真,最后给出了一个采用5阶Σ—Δ调制的数字检波器的原型。第二个方向是本文研究的重点。物理原理是地震勘探的基础,地震检波器的设计也必须充分了解物理背景。本文第二章首先介绍了地震勘探的基本原理,描述了地震波信号的基本特点,给出了高分辨率地震勘探的定义,结合地震勘探仪的进展,给出高分辨率地震勘探对地震检波器的具体要求,并针对当前传统的动圈式检波器的缺点提出了改进的方向。第三章从动圈式检波器的基本动力学原理出发,讨论了检波器各种参数的意义以及选择、检波器组合的作用,并结合本人参加的地震采集系统研制项目描述了动圈式检波器的在线测试。其中着重分析了检波器非线性来源,分析了磁场非均匀性和弹簧系数非线性对检波器谐波失真的贡献,针对分析结果,讨论了增大检波器阻尼对谐波失真的影响。在SIMULINK中对分析结果进行了仿真验证。第四章首先介绍了MEMS技术的背景和原理,国外主流厂商研制的数字地震检波器的工作原理和它们之间的异同,然后详细描述了MEMS加速度计的原理和模型(包括动力学模型和电学模型),结合地震勘探对检波器的噪声要求,讨论了传感部分参数的选择依据,给出了一组折中考虑的传感参数,在此基础上选择合适的读出电路。理论分析了包含读出电路的开环系统的性质,并在PSPICE中进行仿真和验证。第五章给出了模拟闭环系统的理论分析和仿真,详细分析了PID控制器对模拟闭环系统的影响,给出PID控制器中比例系数和微分系数的选择依据,线性分析和行为仿真均表明模拟闭环系统中惯性体的位移大大减小。模拟闭环系统由于反馈力的非线性而具有不稳定性,因此目前问世的地震检波器均采用数字闭环反馈。第六章是本文的重点,主要讨论了基于Σ—Δ调制的数字检波器的建模和仿真。首先给出了使用传感系统做二阶Σ—Δ调制的二阶系统,通过理论分析和SIMULINK中的模型仿真,说明其由于量化噪声的原因不能达到地震勘探的要求,需要添加额外的电子学Σ—Δ调制才能达到地震勘探所要求的动态范围。针对地震勘探对数字加速度计的噪声性能和线性度的具体要求,给出了使用5阶Σ—Δ调制的系统模型以及附加的电子学参数的限制条件。使用SIMULINK对这些模型进行仿真,验证了理论分析的结果。第七章总结了论文的主要思路:分析地震勘探队检波器的要求,分析和改进传统的动圈式检波器,研究新兴的MEMS检波器,给出了基于MEMS技术的各种方案,使用线性化理论分析各种方案,使用建模和仿真验证的手段进行验证,最后并指出今后的工作方向。更多还原

【Abstract】 Petroleum is the important strategic resource. The enormous need of petroleum in modern life promote the oil exploration industry, as a result, seismic exploration, an important method of oil exploration, has advanced a lot in past decades in two aspects: the performance of the seismic instrument is greatly improved and many new methods and new technology have been employed in seismic data processing and interpreting.In seismic exploration, seismic sensors are used to receive and convert the vibration signals. As the front-end of a seismic instrument, seismic sensors affecting the quality of seismic data directly. As seismic exploration advances further, more strict requirements are imposed on seismic sensors. Seismic sensors are required to have ideal frequency response and adequate dynamic range, otherwise high quality seismic data can’t be guaranteed even if the performance of electronic system is excellent.MEMS accelerometers and moving-coil geophones are widely used in modern land seismic exploration. These seismic sensors can be viewed as inertial sensors, moving-coil geophones have restricted the whole system increasingly because of its poor distortion performance. MEMS accelerometers, on the other hand, not only provide excellent linearity, but also provide direct digital output, inherent high vector fidelity, excellent low frequency response. MEMS accelerometers have become the mainstream of the seismic sensors. Aim at these developing trends, this thesis studies two aspect of seismic sensors, first is theoretic analysis of factors of moving-coil geophones’ distortion and the methods to improve it. The other aspect mainly deal with MEMS accelerometers. Several schemes based on MEMS technology, include analog close loop system and digital close loop system, are proposed and discussed in detail. Linear model analysis are performed on these schemes, modeling and simulation are carried out to verify the analysis results. A 5th orderΣ—Δdigital sensor model is proposed at last. The second aspect is the emphasis of this thesis.Physics principle is the theory basis of seismic exploration, It is necessary to capture full image of the physical background for seismic sensor designing,therefore, Chapter 2 in this thesis introduces the basic principles of seismic exploration first. Basic characters of the seismic wave is discussed and definition of high resolution seismic exploration is provided afterwards, the progress of seismic instrument is also introduced. Finally, requirements imposed on seismic sensor for high resolution seismic exploration are concluded and directions for improving current moving-coil geophone are proposed. Chapter 3 begins with dynamics of the moving-coil geophone and discuss the following aspects: the meaning and selection guide of geophone’s parameters, the effects of geophone grouping, geophone online testing employed in seismic data acquisition system which I took part in developing. The emphasis of this chapter is theoretic analysis of factors causing geophone distortion and their contributions. The using of overdamping geophone to reduce the mass deflection is proposed and discussed. Analysis results are verified by simulation in SIMULINK.Chapter 4 introduces background and principle of MEMS technology first, the basic principle and difference of two main kind of digital sensor provided by foreign company is also introduced. Fully description of principles and models(include dynamic model and electronic model) is provided then. Criterions for selecting mechanical parameters of digital sensor are presented for acceptable Brownian noise and a set of parameters is provided, various signal pick off circuits are discussed and compared. Finally, open loop system employed pick off circuit is studied, simulation and verification in PSPICE is carried out.In chapter 5, analysis and simulation of analog close loop system for seismic sensor are presented. A PID controller is introduced in the loop and criterions for selecting proportion gain and differential gain are derived. Both analysis and behavior simulation show the deflection of the proof mass is greatly reduced.However, analog close loop system is unstable because of the nonlinearity between the feedback force and deflection, that’s why digital close loop system is adopted in practical MEMS seismic sensors. Chapter 6 is the an emphasis of this thesis where digital sensor based onΣ—Δmodulation is modeled and simulated. A 2th orderΣ—Δmodulator implemented by the sensing element are discussed in detail. Simulation in SIMULINK shows 2th orderΣ—Δmodulator can’t meat the requirement of seismic exploration, additional electronic integrator is required to form high orderΣ—Δmodulation. It is revealed that 5th orderΣ—Δmodulation is required to suppress the quantization noise to negligible level. To point against the requirement to THD(total harmonic distortion), the formulas for THD calculation is derived, constraints to electronics parameters for THD that less than -100dB is calculated by these formulas. Modeling and simulation of the whole system are carried out, results are inspected and verified with theoretical analysis.Chapter 7 summarizes the main ideas in this thesis, which is analyze the requirement imposed on seismic sensor by seismic exploration, analyze and improve popular moving-coil geophones, study the MEMS accelerometers and proposed several scheme for seismic sensors, linearization methods are employed to analyze these schemes and modeling and simulation are used to verify the theoretic results. This chapter also pointed out the future更多还原