Research On SINS/GNSS Integrated Navigation Fusion Algorithm

With the continuous expansion of the navigation field,all walks of life have higher and higher requirements on the positioning accuracy and cost of the navigation system.It is difficult to meet the needs of the public to achieve the positioning accuracy by relying solely on a navigation system.Therefore,the data fusion of two or more navigation systems is of great significance for improving the positioning accuracy of the navigation system.Because of the combination of Strap-down Inertial Navigation System(SINS)and Global Navigation Satellite System(GNSS)has the advantages of high positioning accuracy and good stability,so it has become one of the hot research objects of integrated navigation system.Based on this background,this paper analyzes and studies the SINS/GNSS integrated navigation fusion algorithm.The main research contents are as follows:Firstly,the initial alignment algorithm is designed.The initial alignment algorithm designed in this paper mainly includes coarse alignment and fine alignment.In the coarse alignment process,the pitch angle and roll angle are calculated according to the output of the accelerometer,and then the initial heading angle is obtained according to the horizontal component of the x and y gyros,and then rough initial attitude matrix is obtained.The precision alignment process mainly uses Kalman filtering algorithm,which is realized by zero-velocity correction.The difference between the velocity of the three northeast directions and the external reference zero velocity is taken as the observation value of the Kalman filter,and the state equation and measurement equation are established to get the accurate initial attitude matrix.The results show that the precision of pitch angle and roll angle is improved by about 1% and the precision of heading angle is improved by about 50% after accurate alignment.Secondly,the inertial navigation algorithm is designed.The inertial navigation is solved by moving azimuth arrangement,which mainly includes the establishment of updating equations of position,velocity and attitude and the establishment of relevant error models.In order to solve the instability problem of the height channel,the third-order vertical channel damping method is adopted,By introducing the external height information,the damping design is carried out to reduce the height and celestial velocity errors.The results show that the attitude calculated by the inertial navigation is close to the real situation,while the velocity and position errors begin to accumulate over time after 660 s,which verifies the problem that the accuracy of errors of pure inertial navigation system error deteriorate over time.Finally,the fusion algorithm of inertial navigation and satellite navigation is designed.In this paper,the satellite navigation system and the inertial navigation system are loosely combined.25 error state variables were selected and sate equation were established;Taking the difference of position and velocity between inertial navigation system as the observation quantity,the measurement equation is established.Through loose combination,the optimal estimation of error is obtained,and then the output navigation parameters are corrected.The results show that the loose combination has limited improvement on the accuracy of attitude and heading angle,but has a great improvement on the accuracy of position and velocity.Compared with the pure inertial navigation,the mean error of longitude and latitude after combined navigation is lower from several meters to several meters,and the velocity in the three directions of the northeast sky is also been greatly improved.On the whole,the positioning accuracy of loose combination has been significantly improved,which makes up for the low positioning accuracy of the single inertial navigation system.