【作者】 陈鹏；

【导师】 范继； 涂良成；

【作者基本信息】 华中科技大学 ， 无线电物理， 2022， 博士

【摘要】 重力梯度测量在资源勘探、国防军事和地球科学研究等方面有重要应用。旋转加速度计重力梯度仪是目前应用最为成熟的航空重力梯度仪,但由于技术封锁,国内无该类仪器成功应用于移动测量。提高梯度仪运动噪声的抑制能力及环境适应性是实现移动测量的关键。本文面向移动测量10 E/Hz^1/2（1 mHz到0.1 Hz）的梯度仪噪声性能指标,围绕梯度仪运动噪声传递模型与模型参数测试、运动噪声抑制方案的需求分析、梯度仪磁场效应和温度效应分析与抑制方案等方面展开了相关研究,具体内容如下:首先,针对旋转加速度计重力梯度仪运动噪声传递问题,进行了运动噪声传递模型推导。该模型强调模型项与实际物理系统的联系,系统地引入了梯度仪移动测量时面临的包含载体及转台运动在内的各类潜在运动噪声,以及影响噪声抵消效果的加速度计的标度因数不一致、安装误差、二阶非线性误差等非理想因素。基于上述与实际物理系统有对应关系的模型,对仪器面临的运动噪声、模型中的噪声传递系数进行了测试。在运动噪声测试方面,除梯度仪通常面临的载体运动干扰外,还对梯度仪内部转台存在的转速波动、轴系摆动和跳动等多种误差运动进行了测试。分析表明这些较弱的运动会与较强的外部载体运动耦合,对梯度测量的干扰不可忽视。在噪声传递系数测试方面,对构成噪声传递系数的加速度计标度因数不一致及装配误差等非理想因素进行了测试,特别提出了加速度计零偏的存在使得轴向误差角过大,进一步导致加速度计可用量程变小或梯度仪对轴向运动噪声耦合严重的问题,基于一种零偏可调的自研加速度计及零偏测量方法对轴向误差角进行精准调节,在动态环境中保证加速度计可用量程的同时,将轴向误差角减小至10μrad,将梯度仪的轴向噪声抑制能力提高了3个量级。针对运动噪声抑制需求不明确的问题,基于模型及模型参数的测试结果,在梯度仪的加速度计装配参数测试与调节的基础上,根据预期的梯度仪噪声性能,对标度因数一致性匹配技术、事后误差补偿方案、加速度计幅频、相频一致性及二阶非线性误差系数提出了系统化需求。在此,为实现移动梯度测量残余误差的补偿,针对转台运动与载体运动耦合产生的噪声,提出一种将噪声监测传感器安装在转台上的事后误差补偿方案,不同于传统方案中将监测传感器安装于载体上的方式,新方案中安装于转台上的传感器测量的运动干扰中同时包含了载体及转台运动噪声,可以实现对所有运动噪声的补偿。结果表明,此方法可以将噪声补偿效果提高2个量级。针对重力梯度仪面临的磁场及温度等非运动噪声的影响,进行了磁场和温度效应及其抑制方案的分析,并进行了测试验证。根据梯度仪的多加速度计组合差分的梯度测量原理,分析了磁场通过影响加速度计输出,进而在差分测量过程中以磁梯度的方式导致梯度测量误差。基于此模型,对加速度计进行了磁屏蔽,将梯度仪磁系数减小了1个多量级,达到0.2 E/μT/m;同时提出了一种磁梯度监测和扣除方案,实现磁场干扰的实时补偿,满足了地磁场波动下移动测量需要。此外,分析了温度通过影响加速度计零偏和标度因数两种方式影响梯度仪的性能。通过对加速度计温度系数的测试,给出了当前梯度仪的温度系数,结合预期的梯度仪噪声性能,提出温控的需求。在地面噪声环境下,从加速度计输出及梯度仪输出两个层面,进行了噪声传递模型与模型参数的正确性验证。结果表明,加速度计噪声的模型估计值与实测值相关性达到0.98,梯度仪噪声的模型估计值与实测值为同一噪声水平,符合模型分析预期。进行了梯度仪实验室的梯度信号测试实验,基于磁场和温度噪声模型,评估并排除了磁场和温度对梯度信号测试的干扰,检验了当前梯度仪对梯度信号的测量能力。更多还原

【Abstract】 Precise gravity gradient measurements could play an important role in resource exploration,national defense,earth science research,and other applications.A rotating accelerometer gravity gradiometer is currently the most mature moving-base gradiometry,but no such instrument has been successfully implemented in China.It is crucial to improve noise rejection ability and environmental adaptability for moving-based gravity gradient measurement.To achieve a noise floor of 10 E/Hz^1/2（from 1 m Hz to 0.1 Hz）,this thesis focuses on building the motion noise model,identifying the model parameters,investigating the requirement for the motion noise rejection scheme,the analysis and rejection of magnetic field errorr effect and temperature error effect.The details are as follows:Firstly,the motion noise transfer model is deduced to describe how the motion noise of the rotary accelerometer gravity gradiometer is transferred.The model emphasizes the connection between the model terms and the actual physical systems,and systematically introduces various potential motion noises including the motion of the vehicle and the rotary table that the gradiometer is experiencing during the moving-based measurement,as well as the accelerometer scale factor imbalances,the accelerometer installation error,the accelerometer second-order nonlinear error,and other non-ideal factors of the accelerometer,which affect the noise cancellation of common-mode motional disturbance.Based on the above models that correspond to the actual physical system,the motion noise faced by the instrument and the noise transfer coefficients in the model are tested.The analysis shows that the weaker motions of the rotary table lead to considerable disturbance by coupling with stronger external motions.In terms of motion noise test,in addition to the vehicle motion usually taken into account,various error motion modes such as rotational speed fluctuation,spin axis wobble,and spin axis shake existing in the rotary table of the gradiometer are also tested.In terms of the noise transfer coefficients test,the non-ideal factors such as the accelerometer scale factor imbalances and the accelerometer assembly error that constitute the noise transfer coefficients are tested.In particular,it is found that the existence of the accelerometer bias could make the axial error angle large,which further leads to the reduction of the available operational range of the accelerometer or the serious coupling of the gradiometer output to the axial motion noise.Based on a self-developed accelerometer with adjustable offset and an offset measurement method to accurately adjust the axial error angle,while ensuring the available range of the accelerometer in a dynamic environment,the axial error angle is reduced to 10 μrad,which improves the axial noise rejection of the gradiometer by three orders of magnitude.On the basis of the test and adjustment of the accelerometer assembly parameters of the gradiometer,the systematic requirements are put forward to achieve the noise floor of the gradiometer,involving the scale factor consistency matching technology,the post-error correction scheme,the accelerometer frequency response consistency,and the accelerometer second-order error compensation.Here,in order to realize the correction of the residual error of the mobile gradient measurement,a post-error correction scheme is proposed for the noise generated by the coupling of the motion of the rotary table with the motion of the vehicle.Different from the traditional scheme of mounting the monitoring sensor on the vehicle,the motion measured by the sensor mounted on the rotary table in the new scheme includes both the motion noise of the vehicle and that of the rotary table,which can correct errors resulting from all motion noises.Simulation experiments show that this scheme can improve the noise correction effect by two orders of magnitude.The error effect of the magnetic field and temperature in the environments are analyzed and the suppression schemes are provided.According to the gradient measurement principle of the combining pairs of accelerometers,it is inferred that the magnetic field affects the output of the accelerometer,and then the gradient measurement error is finally caused by the magnetic gradient in the differencing process of accelerometer outputs.Based on this model,the accelerometer is magnetically shielded,and the magnetic coefficient of the gradiometer is reduced by more than one order of magnitude,reaching 0.2 E/μT/m.At the same time,a magnetic gradient monitoring and compensation scheme are proposed to cancel out magnetic field interference in real-time.Both schemes meet the needs of geomagnetic field fluctuations during mobile measurement.In addition,analysis shows that temperature affects the performance of the gradiometer by affecting the accelerometer bias and the accelerometer scale factor.Given the measured temperature coefficient of the accelerometer,the temperature coefficient of the gradiometer is deduced,and aiming at the gradiometer noise performance,the temperature control requirements are put forward.In the laboratory,the noise transfer model is verified in terms of both the output of the accelerometer and the output of the gradiometer.The results show that the correlation coefficient between the model estimated-value of the accelerometer noise and the measured value reaches 0.98,and the model-estimated value of the gradiometer noise exhibits the same noise level as the measured value.Based on the magnetic field and temperature noise model,the interference of the magnetic field and temperature on the gradient signal test is estimated and annihilated.Measurement of the gradient signal in the laboratory demonstrates the capability of the gradiometer to detect the gradient signal.更多还原