Quartz MEMS Accelerometer for EMCORE Inertial Technology from Tactical to High-End Navigation

Inertial measurement units and navigation systems range from low-end tactical to strategic grade, spanning a very large spectrum of sensor performance. EMCORE makes use of its own quartz MEMS gyros for tactical grade systems, while for higher-end systems we use in-house optical gyroscopes (fiber optic and ring laser gyros). These gyroscopes and systems range from 10 °/hr down to 0.0001 °/hr performance over dynamic environment. These systems require accelerometers with suitable levels of performance for each IMU/INS grade. In a previous DGON ISS 2021 paper we described the quartz-MEMS IMU progress toward navigation grade performance [1]. This improvement was based on use of a modified conventional calibration method over a dynamic thermal environment. Here we report the latest experimental results (consistent with a high-end tactical grade accelerometer) which are much-improved due to a method of self-calibration incorporating multiple resonant modes of the accelerometer structure. The results we present are for the quartz MEMS accelerometer, which demonstrate a velocity random walk of $0.1\ \mu \mathrm{g}/\surd{\text{Hz}}$, and bias instability of 30 ng. The accelerometer bias and scale factor drift over a full temperature range (-55 °C to +90 °C) were $25\ \mu \mathrm{g}$ and 25 ppm, respectively, after we improved the conventional calibration. Using an innovative advanced operational regime, called multiple-mode operation, a new self-calibration algorithm was developed demonstrating accelerometer bias over a dynamic thermal profile of less than $2\ \mu \mathrm{g}$, thus, making the accelerometer suitable for high-end navigation grade systems.