Earth Rate Detection and Gyrocompassing Mechanics for Gyroscope Alignment
Detecting Earth rotation rate for north alignment demands gyro bias stability below 0.05 degrees per hour and accelerometer tilt correction within 0.1 mrad.
Tilt Crosstalk
Error Mechanism
An acceleration measurement error occurs when a multi-axis sensor registers a signal on one axis due to a tilt on a different axis. This tilt crosstalk is caused by mechanical misalignment of the internal sensing elements or by electronic coupling between channels. It reduces the accuracy of the heading and inclination measurements, especially in dynamic applications where the sensor undergoes continuous motion.
Understanding this coupling is essential for high-precision inertial navigation where even small errors can accumulate over time.
Angular Sensitivity
Angular deviation from the ideal mounting plane increases the severity of the crosstalk. If the sensor is mounted on an inclined surface, the gravity vector will project a constant acceleration onto the horizontal axes, which can mask the true motion of the system.
Calibration Method
Calibration algorithms use a multi-position test sequence to calculate and store correction factors that compensate for this inter-axis sensitivity. This calibration is usually performed at the factory, but can be updated in the field if the mounting conditions change.
Installation Alignment
Precision orientation fixtures are used during testing to align the sensor to the gravity vector with high accuracy. This alignment is verified by rotating the sensor through a full circle and monitoring the output of the non-aligned axes.