A closed-loop calibration for fiber optic gyro unit

The tradition open-loop calibration can´t satisfy the precision of marine high precision fiber optic gyro (FOG) strap-down inertial navigation system (SINS). Based on the open-loop calibration, this paper proposed a closed-loop calibration. It takes the course difference between two navigation calculations as the feedback to revise the calibration results. In initial alignment the gyro drift can be estimated by Kalman filter. The closed-loop calibration makes the results of open-loop calibration as the initial value of closed-loop calibration and makes use of the output of SINS and the information of turntable to revise the FOG scale factor and installation error. By revising the FOG error matrix, the attitude error angle trends to zero. Experiment results show that the closed-loop calibration method can improve the FOG calibration precision and decrease the static navigation fixing error.