Research On Moving Base Alignment Techniques For Strapdown Inertial Navigation System

Nowadays, strapdown inertial navigation system (SINS) has been used in the practice inertial navigation task widely. Initial alignment is the premise of SINS, and its accuracy will determine the performance of SINS. Because the practical condition is complex, the base is hard to keep still in the process of initial alignment. Therefore it is meaningful to study the initial alignment of moving base. In this paper, the typical initial alignment methods of SINS are analyzed and studied meticulously. Adaptability of several initial alignment methods in different circumstances are compared thoroughly with simulation and practice experiments to test the performance of moving base inertial navigation method.(1) Analyse the working principle of SINS and deduce the error equation of SINS,which is used to develop the later Kalman filter model. Meanwhile, the influence of initial alignment error to SINS is tested with simulation.(2) Study the coarse alignment methods of SINS, analyse the principles of analytical coarse alignment method,horizontal leveling and location estimating coarse alignment method, and inertial system coarse alignment method. Study these methods in the simulated circumstances and compare the adaptability to the circumstance and performance of these coarse alignment methods, applying the basis for the coarse alignment scheme of moving base.(3) Study the fine alignment methods of SINS by employing compass circuit fine alignment method and Kalman filtering fine alignment method. Explore the alignment principle of these two fine alignment methods and parameters in initial alignment. Compare and analyse the performances of these fine alignment method in different circumstances with the help of simulation. Integrating the study of coarse alignment methods, a whole initial alignment scheme is given.(4) Perform experiments of initial alignment on moving base with the laser SINS and satellite navigation receiver in the laboratory. In the end of the experiment, the stationary base initial alignment result of the location where the load stays is considered as reference.Then the moving base initial alignment experiment is accomplished by employing two moving base initial alignment methods. Result of the experiment show that both of these two moving base initial alignment methods can achieve initial alignment in practice. With the help of observation information of speed, the Kalman filter method is better than compass circuit fine alignment method in time and accuracy. Compass circuit fine alignment method's tracking performance to the motion of load is not well. After the load is still, the error of azimuth angle is smaller than 0.3° by using compass circuit fine alignment method while that of Kalman filter method is smaller than 0.2° because the Kalman filter method can track the changes of load's motion.In this paper,initial alignment methods of SINS are studied in the round. Performances of different initial alignment methods are compared with simulation and moving base initial alignment experiments in theory and practice. The experiment results are hoped to supply references for the initial alignment in practice.