【作者】 吴琼；

【导师】 滕云田； 郭有光；

【作者基本信息】 中国地震局地球物理研究所 ， 固体地球物理学， 2011， 博士

【摘要】 重力场是反映地球内部物质结构及其变迁的地球物理基本场,高精度绝对重力观测资料是地震监测预报、地球科学研究、资源勘探等领域研究的基础。国际上虽然很多国家开展了对绝对重力观测技术的探索,但实际上仅有美国Micro-G公司生产的FG5和A10两种类型的绝对重力仪实现了实用化,而且对我国施行出口管制,价格昂贵,维修周期长。我国虽然在二十世纪七八十年代由中国计量科学研究院的专家推出了与国际测量精度水平相当的NIM-Ⅰ和NIM-Ⅱ两种绝对重力仪,但仅停留在实验样机阶段,未能形成产品。同时,随着近年来我国在时间基准、长度基准、高精度数字化采集与控制、宽频带高精度振动测量技术等领域的飞速发展,使得研究具有自主知识产权的高精度绝对重力仪成为可能。本文首先对绝对重力仪研究的国内外发展动态做了综合性描述,然后针对设计中可能出现的误差源及其影响水平进行量化估计,主要集中以下三个关键技术进行研究：1、落体伺服控制技术研究。利用数字控制技术,实现了对落体控制的精确度和稳定性的要求。通过对同轴齿轮系统、拖架理论运动曲线的设计,确定了电机的动作过程。通过对落体控制机构的理论计算,确定了伺服电机的容量。从而在最小化系统自振的前提下,解决了落体的伺服跟踪技术；2、落体轨迹重建算法与振动干扰抑制技术研究。利用经过外部铷原子钟同步的高速数字化仪对光电接收器输出的干涉带信号进行采样,得到了数字化的干涉带信号。利用数字信号处理技术,提取干涉带上包含的落体相对于参考棱镜的位置和时间信息。这部分经过误差模拟计算表明,其平均误差为0.00052微伽。同时利用与干涉带信号同步采集的高精度、宽频带参考棱镜的振动信号,开发了一套振动干扰的抑制算法。实验证明该算法可以补偿地面振动带来的系统偏差和测量精度。通过本部分的研究,解决了高精度重力加速度的计算方法问题。3、干涉测量的误差补偿技术研究。通过对理想平面上反射镜对光线平行性的影响、分光镜第一面分光比的确定、光线垂直性调节技术分析以及高精度落体的有限元法设计等方面的理论分析,确定了干涉测量系统中的误差源及其对测量结果的影响水平。在实际的设计中根据这部分的分析,确定了整套干涉测量系统的测量光路,解决了绝对重力仪中的高精度干涉测量问题。通过对以上三个关键技术的分析研究,笔者所属的研究团队实现了实验样机的构建,通过在自家疃国家重力基准点的误差实验,确定其测量系统偏差为-55微伽(未经误差修正),2小时测量精度优于10微伽。基本实现了高精度绝对重力观测的设计目标,同时也为下-步进行更高精度的绝对重力仪的设计和实验样机的产品化定型准备了相关的关键技术。更多还原

【Abstract】 Gravitational field is one of the Earth’s basic fields which reflects the internal structure and change of the Earth. High precise absolute gravitate observation is the base to research the Earthquake Prediction, Solid Earth Sciences and Exploration. Although many countries have begun to design their own absolute gravitate gravimeter (AG), only the U.S.A has the breakthrough of key technologies of AG and formed their own products, for example the FG5, A10 and others, But these products are expensive and Export Control by the U.S.A, and also have a very long period to repair. Our country is one of countries who began to develop the absolute gravimeter at the first time. Last century, the NIM-Ⅰand NIM-Ⅱabsolute, which were developed by the National Institute of Metrology P.R.China, have got the High-tech level in the International Comparison of Absolute Gravimeters. But because of the investment, technology of Machining and electronics and information technology, our country has not developed our brand of the absolute gravimeter. As the progress of the precision of Time Base, Length Base, high precise digitizer and Precision Control, broadband, high precise vibration monitoring technology, it is possible to solve the key technical difficulties and develop our own high precise AG.First of all, this paper comprehensive describes the developments of AG and then quantitative estimates the possible error sources. The whole research focus on these three kinds of key technologies: First, the study on the servo controlling of the free-fall body (FB). By using the digital control technology, we achieved the requirements of precise and stability in controlling the FB. By designing of the Coaxial Gear System and the theory motion curve, the motion of the servo motor was identified. By the calculation of the mechanism of FB servo controlling, the motor power was identified. So, on the condition of minimizing the system vibration, we successfully solve technology in the FB Servo Tracking.Second, the study on the algorithm of rebuilding the trace of FB and the technology of the disturbance inhibition. The digital interference signal, which used to get the Time and distance coordinates of the FB’s trace by using the digital signal processing, can be got from the high speed digitizer. And the time base of the digitizer is provided by the Rubidium Atomic Clock. The error simulation confirmed the truth that the mean error of this algorithm is 0.0005μGal. And then, we got the vibration signal of the reference prism which was synchronously collected of the digitizer to develop a new algorithm to inhibit the disturbance which can introduce the error in the measurement result of AG.Third, the study on the compensating the error of interferometry. In this section, the influence of the mirrors to the light parallelism in the ideal plane, the study of the splitting ratio of the first side of the beam splitter, the theory of the adjustment of the light vertical were studied and the errors coming from these units have been confirmed. These studies also identified the design ideas in the interferometry system, and solved the high precise measurement of AG.Through the study of these three sections, we built the experimental prototype successfully. After the error experiments in the international absolute gravity reference point, in Beijing national geophysics observatory, the prototype’s systematic bias is-55μGal(no Error Correction), the precision is less than 10μGal during the 2 hours measurements. And we also own the ability to design the even more precision AG.更多还原