Research On The Method Based On Double Antenna In Vehicular GNSS/INS Integration

GNSS has the advantage of high precision in a long time and.But GNSS has many disadvantages:its signal is easy to be blocked or interference,low data rate,and no attitude information.INS has high precision in short-term,high data rate.INS can output attitude information and not affected by weather conditions.Because GNSS and INS are complementary to each other,GNSS and INS are combined to use the Kalman filter technique to optimize the integrated navigation system.Nowadays GNSS/INS integrated navigation system is wide used in military and geodetic fields,because of its high precision,high autonomy,and strong reliability.In the vehicle GNSS/INS integration,when the vehicle is in rectilinear motion,the heading is not observable,which will reduce the precision of system especially to low grade precision IMU.Two GNSS antennas can provide two-dimensional attitude observation:heading and pitch.The principle is that the antenna baseline is expressed as different vectors in different coordinates,the attitude value can solved according to the direction cosine matrix.Many research show that the heading accuracy is about 0.2°(1?)when the length of two-antenna baseline is lm,and the accuracy can reach up to 0.1°(1?)when the length reach to 3m.Therefore,two-antenna is used to provide an extra heading information to assist the vehicle GNSS/INS integration system.In practical application,the misalignments between the IMU frame and vehicle frame,and the misalignments between the IMU and two-antenna,should not be ignored.Otherwise these errors will lead to the reduction of precision,or even damage the navigation accuracy.This paper studies the effect of two-antenna auxiliary.This paper introduces the basic principle of the inertial navigation system;the principle of GNSS positioning and orientation;introduces the two-antenna GNSS/INS loose combination algorithm based on Kalman filter,and gives an easy and accurate calibration method to calibration the misalignments.With vehicular experiment in Wuhan.Vehicular experiments was made and the results show that:When the vehicle is moving in a straight line,the accuracy of roll and pitch are not changed,heading will diverge unless the vehicle take other maneuver.When use the given calibration method in this paper,the heading accuracy of two-antenna is about 0.3° when the length of baseline is 1.5m.To MEMS IMU,using two-antenna heading auxiliary,the position precision and velocity precision of the integration system has not improved significantly,there is a slight improvement on roll and pitch accuracy,the heading precision improved obviously,can reach up 50%.