Effect of the outer lever arm on in-motion gyrocompass alignment for fiber-optic gyro strapdown inertial navigation system

Fiber-optic gyro strapdown inertial navigation system is typically physically separated from the log giving an aiding velocity. This results in a velocity difference under angular motions, otherwise known as the outer lever arm effect. The mathematical relationship between the velocity difference and the outer lever arm is derived, and the effect of the outer lever arm on angular velocity compensation and harmful acceleration compensation is analyzed using the structure of in-motion gyrocompass alignment. Based on this analysis, a method for outer lever arm correction is given to counteract the outer lever arm effect on the performance of the alignment. Simulation and trial tests are then used to verify the analysis results.