Fast Self-Calibration and Self-Alignment of Triaxis RINS under marine mooring condition

Abstract The triaxis rotational inertial navigation system (TRINS) is crucial for underwater long-duration, high-precision navigation and positioning. The accuracy of initial alignment directly affects the position error in the navigation of the TRINS. Traditional alignment method include coarse alignment and fine alignment. In fine alignment, only bias errors are considered. However, conducting the initial alignment
while the ship is in a moored state can lead to more IMU errors, thereby reducing the alignment accuracy. Therefore, a scheme for the simultaneous self-calibration and self-alignment of TRINS under mooring is proposed, in order to suppress the impact of additional IMU errors excited by sway disturbance on the alignment. A full-parameter IMU error model including the quadratic error of accelerometers and lever arm errors is established. And a self-rotation calibration trajectory scheme with 36 position is designed. In order to reduce the calibration time and thereby enhance navigation efficiency, an iterative Kalman filtering method is employed. The entire process takes
30 minutes. Simulations and experiments both utilize the traditional 19-position method for comparison validate the efficacy of the proposed method. Furthermore, navigation testing show that errors in position and velocity are significantly decreased by calibration errors correction, demonstrating that the proposed approach could improve TRINS’ positioning accuracy.