基于Ring-Down原理的高Q值硅微谐振式加速度计ASIC测控方法研究

MEMS silicon oscillating accelerometer (SOA) is a kind of inertial sensor, whose oscillating frequency represents the input acceleration, providing an alternative solution to pendulous integrating gyro accelerometer(PIGA) in high precision navigation systems. Most of published SOAs employ closed-loop oscillation control method with constant oscillation amplitude. In this mode, the feedthrough capacitance could alter resonator's frequency response and worsen the stability of oscillation loop in high frequency range. Besides, the SOA' bias-instability is limited by the flicker noise in amplitude control circuits. In addition, the time lag between extra temperature sensor and SOA is inevitable and leads to hysteresis in temperature varied condition. This project intends to propose a Ring-Down based ASIC measurement and control method to overcome the shortages in closed-loop oscillation mode. The resonant frequency of SOA is read out in free oscillating period, the effects of feedthrough capacitance and 1/f noise in amplitude control circuits are inherently eliminated. The Q-factor extracted from Ring-Down period servers as an ideal temperature indicator of SOA without time lag, which gets rid of hysteresis error. This project intends to enable an ASIC measurement and control technique for SOA employed in high accurate navigation system.

硅微谐振式加速度计是一种基于力频转换原理实现载体加速度测量的惯性仪表，是高精度导航系统用摆式陀螺积分加速度计的潜在替代技术。硅微谐振式加速度计常采用稳幅闭环自激振荡测控方式，该模式下，馈通电容可显著改变其频率特性，破坏振荡环路稳定性；幅度控制电路中闪频（1/f）噪声会通过Duffing效应耦合为频率噪声，制约其零偏不稳定性；外置温度传感器提取的温度与加速度计内部存在测温延时，会在温变环境下引入较大的滞回误差。本项目拟研究一种基于Ring-Down原理的ASIC测控方法，解决稳幅闭环自激振荡模式存在的上述不足。拟通过在谐振器自由振荡阶段进行频率读出的方法，避免馈通效应及幅度控制电路1/f噪声对频率稳定性的影响；并利用Ring-Down过程中谐振器的品质因数信息作为温度源，降低测温延时，抑制温度滞回误差。通过本项目的研究，可得到一种适用于高精度导航系统用硅微谐振式加速度计的ASIC测控技术。

本项目研究了一种基于Ring-Down模式的ASIC测控方法，解决了硅微谐振式加速度计传统稳幅闭环自激振荡模式中馈通效应、测控电路相移及1/f噪声对其零偏稳定性的制约；研究了一种基于谐振器品质因数的温度提取方法，实现了加速度敏感元件与测温元件的统一，解决了温度滞回误差对硅微谐振式加速度计温度补偿精度的制约；研究了一种硅微谐振式加速度计Duffing效应的自标定与自补偿方法，通过自适应调节Ring-Down幅度的方式，解决了Duffing效应在Ring-Down过程中对频率稳定性的影响。采用上述技术手段，所研究的硅微谐振式加速度计的零偏不稳定性由2.58μg改善至0.2μg，通过本项目的研究，得到了一种适用于高精度导航系统用硅微谐振式加速度计的ASIC测控技术，可为工业用及军用制导系统的芯片化发展提供支撑。