Quadrature Compensation and Demodulation Phase Reference Selection for FM Accelerometers

Inertial navigation provides a means to operate independent of external signals such as the ones provided by a GNSS (global navigation satellite system). The estimated position provided by inertial navigation will drift for a variety of reasons internal and external to the utilized sensors, but removing bias drift from the accelerometers can significantly mitigate this issue. This work aims to address this issue. The methods described herein document means to select the offset phase of frequency modulated (FM) accelerometers that can both be implemented in a real-time fashion and be used with a simple model to improve long-term stability. It provides improvements upon prior work that utilized autoregressive modeling, so this method is expected to be suitable for nonstationary acceleration. The method is based on an observation in experiments that found orthogonal channels to be highly correlated. Utilizing this approach, bias instability was improved by more than two orders of magnitude. However, as the bias instability was recorded at the longest measurement period, by increasing the measurement length, it is expected that the actual bias instability is lower. Future work to determine this as well as other areas are outlined at the end of the report.