【作者】 陈波；

【导师】 胡宸源；

【作者基本信息】 华中科技大学 ， 物理学， 2023， 硕士

【摘要】 旋转加速度计重力梯度仪在资源勘探、自主导航、地球物理学等领域有着广泛的应用价值,其核心敏感单元为高精度加速度计,对高精度加速度计的测量性能有极高的要求。三明治摆式电容结构的MEMS加速度计采用阵列电容极板进行位移检测,可实现加速度的高精度测量。然而基于阵列电容式MEMS加速度计的旋转重力梯度仪开展动态测试时,环境中大动态范围运动噪声干扰使MEMS加速度计极易超量程,导致阵列电容跨极板进入正反馈状态,使MEMS加速度计不能回到深度负反馈下的工作平衡点,从而处于非正常工作状态。因此,本文针对阵列电容式MEMS加速度计超量程不能连续工作的问题,研制其分段线性数字闭环控制电路,旨在以分段标度因子的形式增大加速度计动态范围,为旋转重力梯度仪用MEMS加速度计动态适应性的改善提供解决思路和方法。首先,对实验室旋转重力梯度仪用阵列电容式高精度MEMS加速度计的检测原理、各级检测电路进行分析,在此基础上制定了分段线性MEMS加速度计数字闭环控制电路的整体方案。其次,考虑到实际加速度计检测控制电路电子元器件的阻容值存在偏差,对MEMS加速度计进行系统辨识,实测得到其各模块传递函数,并搭建分段线性MEMS加速度计精准闭环模型。基于该模型采用蚁群算法对分段线性MEMS加速度计方案进行了仿真验证,得到了算法优化后的分段PID控制参数。然后,设计实现了MEMS加速度计分段线性数字闭环控制电路,完成了分段PID控制及其参数规则库、IIR滤波、分段线性算法、ADC和DAC模块、在线PID参数更新模块的软硬件实现。其中,ADC模块噪声水平为1μV/√Hz@0.25 Hz,采集范围达10 V;基于千兆以太网设计实现的在线PID参数更新模块传输速率达1 Gbps。最后,联合表头对分段线性MEMS加速度计模拟检测部分和数字控制部分进行了实验验证,对分段线性MEMS加速度计进行了静态本底测试与标定测试,结果表明:分段线性数字闭环MEMS加速度计第一段标度因子对应的噪声水平为3 ng/√Hz@0.1 Hz,与模拟闭环MEMS加速度计噪声水平一致;同时数字闭环MEMS加速度计成功实现了分段标度因子功能,整体量程达320 mg,相比改进前模拟闭环MEMS加速度计的量程提高了64倍,满足设计指标需求。综上,本文针对旋转重力梯度仪动态测试时阵列电容式MEMS加速度计跨极板后无法正常工作的问题,研制了MEMS加速度计的分段线性数字闭环控制电路,推进了梯度仪动态测试进程,以满足我国地球物理研究与国民经济发展的应用需求。更多还原

【Abstract】 The rotating accelerometer gravity gradiometer has broad application value in resource exploration,autonomous navigation,geophysics,etc.Its core sensitive unit is a highprecision accelerometer,which has extremely high requirements for the measurement performance of a high-precision accelerometer.The MEMS accelerometer with sandwich pendulum capacitance structure uses an array of capacitive pole plates for displacement detection,which can achieve high accuracy measurement of acceleration.However,when the rotating gravity gradiometer based on the array capacitive MEMS accelerometer carries out dynamic testing,the considerable dynamic range motion noise interference in the environment makes the MEMS accelerometer extremely easy to over-range,which causes the array capacitive trans-polar plate to enter the positive feedback state so that the MEMS accelerometer cannot return to the operating equilibrium point under the deep negative feedback,and thus is in an abnormal working state.Therefore,in this paper,we develop a segmented linear digital closed-loop control circuit to increase the dynamic range of the accelerometer in the form of a segmented scale factor and provide a solution to improve the dynamic adaptability of the MEMS accelerometer for rotating gravity gradiometer,to address the problem of over-range MEMS accelerometer not working continuously.Firstly,the detection principle of the array capacitive high-precision MEMS accelerometer for the laboratory rotating gravity gradiometer and the detection circuit at each level are analyzed.The overall scheme of the segmented linear MEMS accelerometer digital closed-loop control circuit is developed on this basis.Secondly,considering the deviation of the resistance and capacitance values of the electronic components of the actual accelerometer detection and control circuit,the system identification of the MEMS accelerometer is carried out,the transfer functions of its modules are measured,and the accurate closed-loop model of the segmented linear MEMS accelerometer is built.Based on this model,the segmented linear MEMS accelerometer scheme is simulated and verified using the ant colony algorithm.The segmented PID control parameters are obtained after the optimization of the algorithm.Then,the MEMS accelerometer’s segmented linear digital closed-loop control circuit is then designed and implemented.The software and hardware implementation of segmented PID control and its parameter rule base,IIR filtering,segmented linear algorithm,ADC and DAC modules,and online PID parameter update module are completed.Among them,the ADC module has a noise level of 1μV/√Hz@0.25 Hz and an acquisition range of ±10 V.The online PID parameter update module based on the Gigabit Ethernet design has a transmission rate of 1 Gbps.Finally,the segmented linear MEMS accelerometer analog detection and digital control parts were experimentally verified by combining sensitive probes.The segmented linear MEMS accelerometer’s static background noise and calibration tests were conducted.The results showed that the noise level corresponding to the first segment of the segmented linear digital closed-loop MEMS accelerometer scale factor was 3 ng/√Hz@0.1 Hz,which was consistent with the analog closed-loop MEMS.At the same time,the digital closedloop MEMS accelerometer has successfully implemented the segmented scale factor function.The overall range has reached ±320 mg,which is 64 times higher than the analog closed-loop MEMS accelerometer before the improvement,meeting the design index requirements.In summary,this paper develops the segmented linear digital closed-loop control circuit of MEMS accelerometer for the problem that the array capacitive MEMS accelerometer cannot normally work after crossing the pole plate during the dynamic test of rotating gravity gradiometer and advances the dynamic test process of the gradiometer to meet the application requirements of China’s geophysical research and national economic development.更多还原