Research On Offshore Alignment Technology Of Marine Strapdown Inertial Navigation System

It is known that the precision of the initial alignment has a great influence on the performance of the following navigation system,so the research on the alignment has been the focus of attention.The alignment of the navigation system can be carried out in a variety of cases,such as completely static conditions,or mooring state,the mooring state carrier posture will have a certain degree of swing,the position speed also has a small change with the drift,and the most difficult alignment needs to be completed under the complex environment conditions on the sea.For the strapdown inertial navigation system for alignment at sea,the difficulty of the alignment is greatly increased because of the disturbance to the wind and waves,and the speed position is constantly changed.In this paper,marine alignment is studied.The aim is to complete the alignment task in ten to fifteen minutes and get the initial state information that can be used for navigation.Based on the alignment at sea,the velocity position integration formula is used for coarse alignment,and an optimized alignment method is combined in the alignment algorithm design.This method can make use of the speed position information of GPS and other external auxiliary speed,combined with the acceleration and angular velocity information of the inertial device to continuously update and calculate the attitude information of the carrier.Because of its integral characteristics,the method can achieve high accuracy and good stability under large internal and external interference.The simulation results show that the horizontal attitude angle of its alignment can reach a few angle seconds in a few minutes,and the accuracy of the most difficult heading angle can reach the accuracy of ten angles minutes.After coarse alignment,the misalignment angle of the carrier is small,and the precise Kalman alignment method is selected to further improve the accuracy of alignment information.The linear Kalman filtering state equation is established,the equation is measured,and the external position or velocity information is taken as the measurement.Finally,the attitude error angle and gyro drift error of the carrier are estimated through the final simulation,which lays the foundation for the verification of real data.Finally,the real data is verified,but due to the limitation of the test conditions,the final verification work of coarse alignment and fine alignment is carried out only by the vehicle test data.In this paper,we first verify the coarse alignment through real data,so as to select the appropriate time of coarse alignment,then use the precision alignment to estimate the attitude and feed back into the system,and correct the attitude error.The results of vehicle data analysis show that the alignment method is more practical in practice.