Research On Intergrated Navigation Method Under GPS Loss Of Lock

GPS is currently the most commonly used outdoor navigation system.However,in scenes such as urban canyons where signal occlusion is severe,GPS positioning accuracy may be seriously degraded.The inertial navigation system(INS)is positioned by measuring the motion information.The advantage of INS is that it is an independent navigation system and it has high measurement accuracy in a short time.But the IMU such as gyro and accelerometer have cumulative errors over long period of operation which can cause the accuracy divergence.Because GPS and INS have the characteristics mentioned above,they can be combined.GPS/INS integrated navigation system can take advantage of each subsystem,which can also perform well in complex environment.It is one of the mainstream navigation technologies.This paper mainly researched on the possible problems of integrated navigation in the case of GPS signal loss.Firstly,the INS and GPS are introduced in detail.After that,the source of error in inertial navigation system is discussed,Then the principle of GPS(including pseudorange and carrier phase)is deduced,and the GPS baseline attitude measurement technology based on carrier phase measurement is mainly studied.At last,the source of error in GPS is introduced.First,aiming at the problem of GPS measurement accuracy in complex environments such as GPS signals being occluded,this paper proposes an angle fusion algoritlim,which uses GPS gyroscope to collect satellite positioning information in a short time.When the GPS signal is not so good and the number of visible satellites is insufficient,the fusion of the absolute angle measured by the GPS attitude measuring instrument and relative angle measured by gyro can ensure the accuracy and stability of the positioning.The in-vehicle experiment shows that the average error of re-integrated navigation after the angle fusion is reduced to less than lm from the original 3m,and the mean square error is reduced from the original 1 lm to lm.Positioning accuracy and positioning stability have been enhanced.Finally,the nonlinear conditions appearing in GPS/INS integrated navigation are discussed.By UT transform,the sigma point is sampled,so that the distribution of sampling points is equal to the original state distribution,and the sampled points can replace the original nonlinear function very well.The UT transfomi also avoids the process of solving complex Jacobian matrix like Extended Kalman filtering.Simulation analysis of integrated navigation using UT-based Unscented Kalman filter(UKF).The simulation results show that the UKF-based GPS/INS integrated navigation can significantly reduce the divergence of the carrier irn terms of position and speed,and is very effective for maintaining the stability of positioning.