常温下硅微谐振加速度计零偏稳定性的提高

考虑环境温度会影响硅微谐振加速度计(MSRA)的测量精度,本文研究了谐振梁的频率漂移及抑制方法以便提高其在常温下的零偏稳定性。针对结构热膨胀导致的应力进行了建模仿真,并根据仿真结果优化设计了一种低热应力的双端固支梁的结构来降低热膨胀系数不匹配带来的频率漂移。实验测得新结构的单梁谐振频率的温度系数从典型结构的约30Hz/℃降为-1.5Hz/℃,与仿真结果-1.14Hz/℃基本一致。为了进一步提高该加速度计的零偏稳定性,设计了一种高精度测温电路用来补偿温漂,该电路测温灵敏度为96.25mV/℃,测量噪声约为0.000 2℃。实验结果表明,采用优化后的结构结合线性温度补偿的方法,可使该硅微谐振加速度计的1h零偏稳定性在常温下达到10μg以下,比改进前实验室获得的52μg水平提升了80%,满足了高精度加速度测量的要求。

Improvement of bias stability of micromechanical silicon resonant accelerometer at room temperature

In consideration of the effect of ambient temperature on the precise measurement of a micromechanical silicon resonant accelerometer (MSRA), the frequency drift of the resonant beam and suppression methods were analyzed to improve its zero-bias stability in the ambient temperature. The stress caused by structural thermal expansion was modeled and simulated and an improved structure with a lower thermal stress was designed and fabricated to reduce the frequency shift caused by non-matching of thermal expansion coefficients. The test experiments show that the temperature coefficient of resonant frequency of the single beam decreases from about 30 Hz/℃ to-1.5 Hz/℃, which is close to the simulated value of-1.14 Hz/℃. To further improve the bias stability of the MSRA, a precise temperature measurement circuit was designed to compensate the temperature shift, and the circuit shows its temperature sensitivity to be 96.25 mV/℃ and the noise to be 0.000 2℃. By proposed optimizing structure and linear temperature compensation method, the bias stability of the optimized MSRA is superior to 10 μg within 1 h at the room temperature, which is 80% higher than previous level of our laboratory (52 μg) and satisfies the requirements of high-precision acceleration measurement.