Heading stabilization for aided inertial navigation systems

A method of stabilizing heading in an inertial navigation system, the method comprising:

• operating an inertial measurement unit in an un-rotated orientation;
• calibrating at least one horizontal-sensing gyroscope and at least one horizontal-sensing accelerometer based on horizontal aiding measurements received while operating the inertial measurement unit in the un-rotated orientation;
• forward-rotating the inertial measurement unit about a horizontal-rotation axis, the horizontal-rotation axis being orthogonal to the direction sensed by at least one horizontal-sensing gyroscope;
• operating the inertial measurement unit in a rotated orientation;
• and
• calibrating a vertical gyroscope and a vertical-sensing accelerometer based on horizontal aiding measurements received while operating the inertial measurement unit in the rotated orientation.

An inertial navigation system, comprising:

• an inertial measurement unit;
• rotational device on which the inertial measurement unit is positioned, the rotational device configured to rotate the inertial measurement unit about a horizontal axis from a first orientation to a second orientation;
• a software module comprising:
• a navigation module configured to receive input from the inertial measurement unit;
• a Kalman filter communicatively coupled to the navigation module;
• a software control component configured to control the rotation of the rotational device based on input received from the Kalman filter;
• and
• at least one of a velocity sensor and a position sensor operable to measure a velocity and a position, respectively, and further operable to output the information indicative of a velocity and a position to the Kalman filter, respectively;
• and
• a navigation processor for running the software module;
• wherein the Kalman filter is configured to calibrate the inertial measurement unit in the first orientation and the second orientation and to correct output from the navigation module based on estimates of a bias in the inertial measurement unit.