High-Q and wide dynamic range inertial MEMS for north-finding and tracking applications

We report high-Q and wide dynamic range MEMS gyroscopes and accelerometers for development of an IMU capable of north finding and tracking. The vacuum sealed SOI gyroscope utilizes symmetric quadruple mass architecture with measured quality factors of 1.2 million and proven sub-°/hr Allan deviation of bias. The true north detection was accomplished in conventional amplitude modulated (AM) rate mode and showed 3 milliradian measurement uncertainty. The north (azimuth) tracking necessitates a wide dynamic range, for which the same QMG transducer is switched to a frequency modulated (FM) modality. The test results for FM operation experimentally demonstrated a wide linear input rate range of 18,000 °/s and inherent self-calibration against temperature changes. Vertical alignment is possible using resonant accelerometers with a projected bias error of 5 μg and self-calibration against temperature variations, enabled by differential frequency measurements. We believe the developed low dissipation inertial MEMS with interchangeable AM/FM modalities may enable wide dynamic range IMUs for north-finding and inertial guidance applications previously limited to optical and quartz systems.