小型化高精度MEMS相对重力仪样机研制

The relative gravimeter with high precision has a wide range of application requirements in the fields of the regional gravity survey and gravity mapping, the oil gas and mineral exploration, the groundwater and city underground space exploration, and the gravity field assisted navigation, etc. In the field of application, people require the gravimeter would be high precision, stable and portable for harsh environment. Compared with the traditional relative gravimeters with quartz or metal spring, the single crystal silicon-based spring structure has a higher quality factor and structural stability, which hence could greatly reduce the thermal noise of the sensor, and improve its durability. This project is aimed to develop the miniaturized high precision MEMS relative gravimeter. By referring the ideas from the structure design of the folded beam and the nonlinear spring in commercialized relative gravimeter, the intrinsic frequency of the MEMS relative gravimeter would be lower than 2Hz. The body of the sensor will be fabricated by the inductively coupled plasma technology widely used in MEMS manufacturing technology to etch through the whole wafer. The micro-motion of the test mass will be detected by the optical method. The body of the sensor and the optical displacement detector will be located in a small double-shield vacuum chamber with the precision temperature control. The final goal is to develop a miniaturized, economical high precision MEMS relative gravimeter with the noise level better than 2μGal, the mass less than 2kg, and the volume less than 1 liter, meeting the wide application requirements in the fields of geophysics and many other areas.

高精度相对重力仪在区域重力研究及重力填图、油气及矿藏勘探、地下水和城市地下空间勘察、及地球重力场辅助导航等方面有着广泛的应用需求。在对使用环境和耐用度要求极高的应用领域，要求仪器具有高精度、高稳定和便携性。与传统的石英或金属弹簧重力仪相比，基于单晶硅材料弹簧结构具有更高的品质因素和结构稳定性，能极大降低机械结构的热噪声水平，并提高其耐用性。本项目拟开展小型化高精度MEMS相对重力仪研制，其弹簧设计采用正刚度的折叠梁和非线性弹簧组合的思想，设计的本征频率低于2Hz，硅基结构的加工采用微机电系统制造工艺中的感应耦合等离子体技术实现体硅结构的穿透刻蚀，敏感质量块的运动采用非接触的光学方法进行微位移检测，最后对机械结构和光学位移检测系统进行整体精密温控，并置于双层小型真空腔中，目标是研制出精度优于2μGal、质量小于2kg、体积小于1公升的MEMS相对重力仪，满足地球物理等诸多领域的应用需求。

高精度相对重力仪在区域重力研究及重力填图、油气及矿藏勘探、地下水和城市地下空间勘察、及地球重力场辅助导航等方面有着广泛的应用需求。在对使用环境和耐用度要求极高的应用领域，要求仪器具有高精度、高稳定和便携性。与传统的石英或金属弹簧重力仪相比，基于单晶硅材料弹簧结构具有更高的品质因素和结构稳定性，能极大降低机械结构的热噪声水平，并提高其耐用性。本项目开展了小型化高精度MEMS相对重力仪研制，其弹簧设计采用正刚度的折叠梁和非线性弹簧组合的思想，结构实测本征频率达到0.3 Hz。硅基结构的加工采用微机电系统制造工艺中的感应耦合等离子体技术实现体硅结构的穿透刻蚀，敏感质量块的运动采用非接触的光学方法进行微位移检测，最后对机械结构和光学位移检测系统进行整体精密温控，并置于双层小型真空腔中，实测结果表明，研制的MEMS相对重力仪精度优于8 μGal/Hz1/2、零偏漂移系数为2.4 mGal/day，实现重力潮汐观测，满足地球物理等诸多领域的应用需求。