Self-Calibrated MEMS Gyroscope with AM/FM Operational Modes, Dynamic Range of 180 dB, and In-Run Bias Stability of 0.1 deg/hr

This paper reports our cumulative progress toward the development of a gyroscope with two interchangeable modes of operation: an Amplitude Modulated (AM) mode, for a precision measurement in more conventional ranges (~300 deg/sec) and a Frequency Modulated (FM) mode, for an expanded range of operation (over 300 deg/sec and as high as 18,000 deg/sec). We demonstrate that the implemented self-calibration algorithms for AM detection effectively remove the rate random walk, allowing for a highly stable in-run bias. The FM approach is based on tracking the resonant frequency split between two, high Q-factor mechanical modes of a gyroscope, providing a frequency-based measurement of the input angular rate. Temperature characterization of the FM gyroscope exhibited less than 0.2 % variation of the angular rate response between a temperature range of 25 °C and 70 °C. This characteristics is shown to be enabled by the self-calibration capability of differential frequency detection. Measured Allan deviation of the FM gyroscope demonstrated a bias instability of 0.5 °/hr and an Angle Random Walk (ARW) of 0.08 °/√hr. Rate table characterization of the gyroscope in FM operational mode demonstrated a linear range of 18,000 °/s, representing a dynamic range of 160 dB. In the conventional AM mode, the gyroscope experimentally demonstrated a 0.1 °/hr bias instability after implementation of the temperature self-sensing calibration algorithm. Thus, the interchangeable operation of the QMG transducer provides a measured 176 dB dynamic range, making the same high-Q mechanical structure suitable for demanding high precision and wide input range applications. 1