Inertial navigation system

摘要

An inertial measurement system for a longitudinal projectile comprising: a first roll gyro oriented parallel to the projectile longitudinal axis and second and third gyros arranged with respect to the roll gyro to define a three dimensional coordinate system. A current projectile attitude comprising a roll angle, a pitch angle and a yaw angle is determined from the gyros. For at least two time points, the determined pitch and yaw angles are compared with expected values and a roll angle error is determined based on the difference between the determined and the expected pitch and yaw angles. A roll angle error difference and total roll angle subtended are calculated between the two time points. A roll angle scale factor error is determined based on said roll angle error difference and total subtended roll angle and is applied to the output of the roll gyro. This provides improved calibration of the roll axis rate gyro scale factor even during the high roll rate phase immediately after launch.