Error Mechanisms and Calibration Scheme for Low Bias Mode-Matched Micro Resonant Gyroscopes Under Ocean Environment

The mode-matched high Q gyros provide an ideal signal to noise ratio. However, their bad bias repeatability poses a challenge for oceanic environments due to the perpetually existing waves, which make initial alignment difficult. This work presents a comprehensive investigation of the error principle and an advanced inherent calibration scheme for mode-matched micro gyros. Analysis of gyro dynamics and oceanic temperature experiments has shown that the main contributor to error is the frequency split between the two gyroscopic modes. To overcome this problem, an automatic frequency difference calibration (AFDC) scheme has been proposed and implemented. During the validation phase, this architecture was tested in the presence of external physical disturbances. The experimental results indicate that the bias repeatability of the mode-matched micro ring gyro can reach 9.34°/h (or 3.14°/h, 1σ), which is an improvement of three orders of magnitude compared to the original performance.