Fast Initialalignment Technology Reserch Of Mems Inertial Navigation Positioning System

MEMS strapdown inertial navigation system(MEMS-SINS)has the advantages of low cost and small volume,has been widely used in unmanned aerial vehicles,pedestrian navigation and other fields.And the initial alignment technique is one of the most important key technologies in the system.Based on the application conditions of personal navigation,the thesis studies the technology of rapid initial alignment under the condition of MEMS.(1)Due to the limitation of MEMS accuracy,the traditional initial alignment technology can not be realized,so a fast initial alignment scheme based on MEMS magnetometer and multi-sensor fusion is proposed,and a multi-sensor array with two MPU9250 and two MPU6500 is designed.Firstly,each MEMS accelerometer and magnetometer in the multi-sensor array is used to obtain the acceleration and magnetic field intensity information,and the initial attitude angle is solved;secondly,the attitude angle is fused at the same time;finally,take the mean of attitude angle after fusion as the final attitude angle of a position.(2)Due to the error of MEMS device is too large and needs to be corrected before it is used,therefore a six-position calibration method is adopted for the error characteristics of the accelerometer,and a new two-step correction algorithm is proposed for the online correction demand of magnetometer and the defect of ellipsoid fitting.The algorithm first uses ellipsoid fitting method to compensate partial error,and then uses dot product based on zero acceleration detection to compensate non alignment error,and can obtain more accurate magnetic field strength.(3)For the fusion of attitude angles,a weighted fusion algorithm based on MEMS device error and a fusion algorithm based on MEMS device minimum error are proposed.Among them,the former takes the square of the error of the MEMS accelerometer at every moment as the weight of the horizontal attitude angle,and the error square of MEMS magnetometer at every moment is the weight of azimuth,the method is superior to the traditional weighted fusion algorithm on the whole level,but still does not avoid the defects of the traditional weighted fusion algorithm,easily deteriorate the attitude angle at mutational points.The latter takes the attitude angle calculated by the accelerometer and magnetometer with the least square error at every moment as the final attitude angle,themethod can achieve better fusion effect for both information with mutational points and information without mutational points.Finally,the experiment proves that the alignment method based on MEMS magnetometer and multi-sensor fusion can complete the whole alignment process within 9seconds,in the static situation,and the alignment accuracy of the horizontal attitude angle is within 0.83 degrees,the alignment accuracy of the azimuth angle is within 2.62 degrees,meet the requirements of the pedestrian navigation and positioning system.