微机械陀螺的刻蚀误差特性分析

微陀螺仪结构上的腐蚀凹槽或腐蚀腔可以由深层反应离子刻蚀技术得到,加工过程中存在的刻蚀误差对微陀螺的固有频率、输出精度和稳定性有重要的影响.采用有限元分析软件ANSYS建立了一种梳状微机械陀螺的有限元分析模型,采用解析的方法并通过Matlab数学软件进行仿真,研究了由于加工误差导致微梁过度刻蚀对微陀螺驱动模态、检测模态、固有频率、带宽、灵敏度的影响.结果表明,微梁刚度和微陀螺固有频率随着刻蚀角度的增大而增大;最大过度刻蚀角度为±2度时,其驱动模态和检测模态的固有频率的变化率均超过了14%;刻蚀误差会导致微陀螺工作模态降阶,以及干扰模态介于与驱动和检测模态之间且与驱动模态频率相近,这会严重影响微陀螺的输出精度;带宽随过度刻蚀夹角增大而减小,灵敏度随过度刻蚀夹角的变化而发生不规律变化;当刻蚀角度介于0°~1.5°时,微陀螺的灵敏度将高于无刻蚀误差时微陀螺的灵敏度.

Characteris analysis of etching error on micro mechanical gyroscope

Corrosion grooves or corrosion cavity in the structure of micro gyroscope can be obtained by deep reactive ion etching technology. The etching error in the processing has an important influence on the natural frequency, output accuracy and stability of the micro gyroscope. A finite element model of comb micromechanical gyroscope was established by using finite element analysis software ANSYS. The influence of the micro beam over etching induced by the machining error on inherent frequencies of the driving mode and the sensitive mode was studied by finite element analysis, the influence on the bandwidth and sensitivity of micro gyroscope was also examined by analytical method. The results show that micro beam stiffness and inherent frequency of micro gyroscope increase with the increase of the over etching angle. When the maximum over etching angle is ±2°, the change rates of inherent frequencies for the driving mode and sensitive mode are more than 14%. Moreover, etching error can reduce the work mode of micro gyroscope and make the interferential mode occur between driving mode and sensitive mode. Meanwhile, the frequency of interferential mode and driving mode are nearly equal, which affects the output precision of micro gyroscope. In addition, bandwidth decreases with the increase of over etching angle. Sensitivity varies erratically with the change of over etching angle. When the etching angle is between 0° and 1.5°, the sensitivity of micro gyroscope is higher than that without etching error case.