导航级硅微静电陀螺的漂移误差抑制方法研究

Vibrating micromachined gyroscopes are opening up a wide range of applications. However, achievement of tactical-grade performances has proven to be very challenging for MEMS gyroscopes. The micromachined electrostatically suspended gyroscope (MESG), differed from conventional vibrating-type gyroscopes, is basically a spinning rotor based dual-axis rate sensor. It has the potential to deliver high performance as such macro-scale electrostatically suspended gyroscopes. The mechanism analysis and active suppression of the drift error in such gyroscopes are very effective for performance improvement of such MEMS gyroscopes. However, it has not intensively been investigated to date. We have developed a MESG with a rotor spinning at 12000rpm using silicon based microfabrication technology supported by NSFC. This project focuses on a MESG with a ring-shape rotor fabricated by bulk micromachining and suspended electrostatically in five degree-of-freedoms. The mechanism of action and physical mode of drift error will be intensively investigated firstly in order to clarify its propagation rules and potential suppression methods for these MEMS gyroscopes. The optimum design of both the torque rebalance loop and rotor constant-speed loop will then be conducted to achieve minimum drift error. The mathematical model describing dominant drift error of the MESG will be investigated for calibration procedures. An expected bias stability less than 0.1 /h will achieved by further identification and compensation of the MESG drift error experimentally. It is expected that the performance of the MESG will be improved from tactile-grade to navigation-grade when the goal of the research work is realized. The research work is significant in both theory and engineering in order to get a breakthrough in precision improvement of MEMS gyroscopes.

振动式微机械陀螺的应用日益广泛，但精度尚未取得根本突破。而微静电陀螺是一种不同于振动式陀螺、可实现双轴角速率测量的转子式微机械陀螺，具有传统静电陀螺精度高的潜力。研究其漂移误差规律及抑制方法对于提高该型陀螺仪的精度非常有效，但有待深入研究。申请人在自然科学基金资助下研制出了硅微静电陀螺样机，转速达到12000rpm。本项目拟在前期研究工作基础上，针对采用环形转子、体硅工艺、五自由度静电悬浮的微静电陀螺仪，研究该型MEMS陀螺产生漂移的机理及物理模型，阐明漂移误差的传播规律及抑制途径；以漂移误差最小为目标，探索力矩再平衡回路和转子恒速回路的优化设计方法；研究描述微静电陀螺规律性漂移误差的数学模型，开展漂移误差模型辨识与补偿方法的实验研究，实现陀螺零偏稳定性优于0.1 /h的研究目标。本项目有望将微静电陀螺的精度从战术级提升至导航级，对于突破微机械陀螺的精度极限具有重要的理论意义与应用价值。

硅微静电陀螺作为一种转子式双轴角速率陀螺仪，依靠可控静电力支承高速旋转的转子，不存在机械摩擦、磨损，精度高，寿命长。研究其漂移误差规律及抑制方法对于提高陀螺仪精度非常有效。本项目系统研究了该型陀螺产生漂移误差的产生机理、物理模型及抑制途径，完成了陀螺结构优化与体硅工艺改进研究，提出并验证了基于力矩再平衡回路解耦和转子精密恒速控制的漂移误差抑制方法。. 本项目主要研究内容及取得的成果包括：1）完成了微陀螺的体硅加工工艺优化与流片试验，提高了加工精度，器件成品率提升至93%；2）实现了陀螺转子转速的快速启动与精密恒速控制，解决了陀螺启动时间长、真空条件下转子易失步的问题，将启动时间大幅度缩短至438.5秒，恒速控制精度优于万分之一，显著提高了陀螺标度因子稳定性；3）综合利用刚度补偿、控制解耦与输出解耦方法，有效地抑制了再平衡回路的角位移与角速率耦合分量，在1Hz和10Hz处耦合分量分别被抑制了80.8%和62.7%；4）采用有限元方法建模并精确计算出了五自由度气膜阻尼系数的数值解，解决了多轴静电悬浮系统的建模与控制问题； 5）探索出硅微静电陀螺的器件级真空封装工艺，成功加工出真空度优于10-1Pa的微陀螺真空封装样机。测试表明，转子转速为1.5×104 rpm时，微陀螺样机的标度因数为20.23mV/°/s，分辨率为0.012°/s，零偏不稳定性为18.1°/h，角度随机游走为2.067°/√h。. 目前成功探索出了硅微静电陀螺的体硅工艺路线，填补了国内三层玻/硅/玻键合的MEMS器件加工工艺空白；提出的陀螺快速启动与精密恒速控制、力矩再平衡回路解耦方法是提高陀螺精度的有效途径；建立了描述硅微静电陀螺规律性漂移误差的数学模型，探索了漂移误差模型辨识与补偿的实验方法。研究工作为进一步提升硅微静电陀螺的精度指明了技术途径，对于突破MEMS陀螺的精度水平具有重要的理论意义和工程应用价值。