| Inertial navigation system (INS) is an example of reckoning navigation system. The position of the vehicle is obtained by integral velocity, and the velocity is obtained by the integral measurement of the acceleration. The attitude result is obtained by the integral measurement of the angular rate. Each iteration navigation equation must use the results of the previous navigation as its initial value, therefore, it is necessary to initialize the INS before the formal work., namely its initial alignment. The information of position, velocity and attitude is the main initialization vector. The position and velocity information is usually given by the outside ,and the initial attitude information can be provided by the external, and it also can be determined by the INS sensitive gravity vector and the earth rotation vector. A self alignment method is studied in the paper, and focus on the research of the self initial alignment algorithm of the fiber optic strapdown inertial navigation system for marching vehicles.This paper mainly from the following aspects to carry out research:(1) Research and analysis of the fiber optic gyro and the initial alignment of strapdown inertial navigation system, after fully understanding the present situation of domestic and foreign related technology research, according to the existing laboratory (including inertial gyro and accelerometer) level, determine the initial alignment of strapdown inertial navigation system precision.(2) The attitude, velocity and position of the marine strapdown inertial navigation system are deduced in detail, and the system error equations are established, and compensation the coning error of attitude updating algorithm, compensation the sculling error of velocity updating algorithm. In order to play high precision gyroscope and accelerometer advantage at the same time, improve the precision of initial alignment during initial alignment.(3) When the ship in the mooring or anchoring, or is sailing in the process of navigation system fault restart, due to wind effects, the system needs to perform its initial alignment in a dynamic environment. At this time the angular motion of the carrier far outweigh reference information on time (earth rotation rate). Therefore, the initial alignment in dynamic environment has been a difficult point in the research of inertial navigation technology.Aiming at this problem, this paper focuses on the study of GPS velocity aided moving self alignment technique, on the basis of theoretical simulation analysis, three axis shaking table test is designed, and the effectiveness of the scheme is verified by the actual sea trial data.(4) The error calibration of inertial devices can be accomplished in the alignment process of the " coarse inertial alignment + precision Kalman filter alignment" method,such as the constant drift of the gyro and the constant value of the accelerometer, therefore, the precision of the system is improved, and the system has the function of short time inertial navigation. It can be used to measure the 3D motion trajectory of underwater robot without GPS signal. In the specific implementation, through the observation of instantaneous velocity information, to determine whether the carrier is in a "pseudo stationary" state, the system implementation of zero speed correction, in order to correct the navigation system parameters. The method has been verified in deep water tank test, and the method can reach the accuracy of centimeter level (within 5 minutes).This paper derived the SINS update algorithm of attitude,velocity and position in detail,and then introduces two kinds of initial alignment method, namely inertial initial alignment method (inertial coarse alignment + Kalman filter accurate alignment) and compass initial alignment method. Initial alignment firstly to give a rough attitude value through inertial coarse alignment, and then through Kalman filter on the SINS error equation to get accurate attitude values. Compass initial alignment study the process of building gyrocompass loop,and analysis of the strapdown gyrocompass initial alignment method on the basis of original gyrocompass. Finally in the three axis... |
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