静电悬浮重力仪测量环路线性化的理论与实验研究

For the electrostatic suspension gravimeter, the electrostatic force produced by a high-voltage drive amplifier is used to compensate the Earth gravity g0, to scale the gravity variation. A better bias stability can be achieved, which benefits to a low drift and a high accuracy, compared to the classical relative gravimeter with mechanical spring suspension. Another advantage of the gravimeter is to be able to measure gravity vectors with only one probe. However, preliminary experimental results show that the noise level of the electrostatic suspension gravimeter is only 10^(-4)m/s^2/Hz^(1/2), where the large quadratic factor existed in the measurement loop is one of the main limitations. In the view of above situation, this proposal raises a linearized actuator to reduce the nonlinear error in the measurement; the noise of the high-voltage drive amplifier is suppressed to improve the sensitivity to 1mGal level (10^(-5)m/s^2/Hz^(1/2)), to satisfy the requirement. The residual nonlinear factor will be also evaluated to correct the error, and to reject high frequency disturbance.

静电悬浮重力仪采用高压驱动电路产生静电力来平衡检验质量受到的地表重力加速度g0，静电力的波动反映了重力场的变化。相对于传统弹簧相对重力仪而言，静电悬浮重力仪有较好的零偏稳定性，因而具有漂移小和精度高的潜在优势；且只需一个探头便能实现三个正交方向的矢量重力测量，极具发展前景。但初步试验表明，静电悬浮重力仪的噪声水平仅达到10^(-4)m/s^2/Hz^(1/2)；其中较大的二次项非线性系数是测量精度的主要限制因素之一。本课题针对上述现状，通过线性化反馈执行机来减小重力测量环路的非线性误差；同时抑制高压驱动电路噪声的影响有望提高重力测量精度至毫伽量级(10^(-5)m/s^2/Hz^(1/2))，从而满足实用化需求；最后准确测量残余二次项非线性系数进行误差改正来抑制高频扰动的影响。

静电悬浮重力仪采用高压驱动电路产生静电力来平衡检验质量受到的地表重力，静电力的波动反映了重力场的变化。相对传统弹簧相对重力仪而言，静电悬浮重力仪有较好的零偏稳定性，因而具有漂移小和精度高的潜在优势；且只需一个探头便能实现三个正交方向的矢量重力测量，极具发展前景。但初步试验表明，静电悬浮重力仪噪声水平仅达到10^(-4)m/s^2/Hz^(1/2)，主要受限于二次非线性执行机。.本课题针对上述现状：首先，给出了静电悬浮重力仪的基本工作原理，分析了各组成环节的传递函数，建立了竖直高压悬浮闭环控制的仿真模型。其次，对比分析了算法线性化和执行机线性化两种测量环路线性化方案；其中算法线性化方案是根据已有执行机设计特定算法从而实现测量环路线性化，而执行机线性化方案通过在上下极板上同时施加反馈电压来实现测量环路线性化。最后，结合机械敏感探头设计实验对重力仪性能进行评估，测试结果表明采取线性化改善措施后重力仪竖直方向高压悬浮测量环路在0.1Hz处加速度噪声由10-4m/s2/Hz1/2量级降低至2×10-5m/s2/Hz1/2，改善了约5倍左右。.综上，本项目采用测量环路线性化相关技术后，使重力仪在0.1Hz频率处的噪声降至约2×10-5m/s2/Hz1/2，为静电悬浮重力仪的实际应用提供了技术基础。