Patent ID: 8566055
Filing Date: 2013-10-22
Classification: G01C

Abstract:
1. In a navigation system having two inertial measurement units, each of the two inertial measurement units including a gyroscope mounted to an object, each gyroscope having three attitude axes, each gyroscope providing a respective attitude output, each gyroscope periodically being subject to a periodic gimbal reorientation or indexing, a method for recovering attitude accuracy from the inertial measurement units, comprising: determining in a computer process, a readout error bias in each gyroscope relative to a true, unknown, long term mean bias in each attitude axis thereof due to the gimbal reorientation or indexing of each gyroscope; obtaining in a computer process, time-aligned respective attitude outputs of the gyroscopes; determining in a computer process, first differences between the respective attitude outputs of the gyroscopes; determining in a computer process, steps in the first differences between the respective attitude outputs of the gyroscopes, due to each successive index; determining in a computer process, odd cumulative sums of odd numbered ones of the steps and assigning of the odd cumulative sums to the gyroscope that gave rise to the odd numbered steps in the difference between attitude outputs; determining in a computer process, even cumulative sums of even numbered ones of the steps and assigning the even cumulative sums to the other gyroscope that gave rise to the even numbered steps in the difference between attitude outputs; determining in a computer process, a mean and linear trend of the odd cumulative sums; determining in a computer process, a mean and linear trend of the even cumulative sums; determining in a computer process, adjusted odd cumulative sums by subtracting the odd mean and linear trend, and designating the resultant values as an indexing readout error correction of the gyro associated with the odd numbered steps; determining in a computer process, adjusted even cumulative sums by subtracting the even mean and linear trend, and designating the resultant values as an indexing readout error correction of the other gyro associated with the even numbered steps; and storing a final indexing readout error bias corrections in a machine readable storage medium.