An Online Calibration Method of INS and Doppler Sensors

For the integrated navigation system of Inertial Navigation System (INS) /Doppler Velocity Log (DVL), the accuracy of velocity measurement from DVL is a key factor that restrain the accuracy of combined INS/DVL navigation system. Based on the viewpoint of observability, we analyze the reason why partial misalignment angles cannot be calibrated under some trajectories, and designs an improved calibration scheme according to the above analysis, which can realize the calibration of all the misalignment angles and scale factor. Nevertheless, the calibration method presented above is extremely unfavorable for underwater vehicles to keep concealment. Therefore, a more accurate model of DVL errors is employed, including scale factor, misalignment angles and constant errors, and a three-point online calibration method of INS and Doppler Sensors is proposed. The proposed method only requires the Autonomous Underwater Vehicles (AUVs) to float up twice to get the GPS signals. That is, only with the initial position and the other two positions, the calibration can be accomplished. The simulation results show that the presented method is efficient and the positioning accuracy of AUVs is evidently improved.