Technologies For Autonomy SINS/CNS/GNSS Integrated Navigation System Of Aerospace Vehicle

Since the concealed and particular flight missions of Aerospace Vehicles,the navigation system shall be autonomous and reliable.SINS/CNS/GNSS integrated navigation system has attracted much attention because of its high-precision and high-reliability,and it will be one of the major forms to achieve the navigation of Aerospace Vehicles.SINS is independent,while its navigation error increases as time goes by.CNS has high attitude precision,but the accuracy of position is relative poor.The precision of GNSS is high,but its anti-disturbance ability is weak.Besides,GNSS is under the control of other countries except BEIDOU.In this case,it is hard to guarantee the security.Thus,as for the SINS/CNS/GNSS integrated navigation system,the pre-flight autonomous initialization method,the autonomous and reliable navigation algorithm during flight are proposed in this paper,in order to promote the capacity of autonomous initialization,improve the performance of SINS/CNS integrated navigation system,and enhance the ability of SINS/GNSS while the navigation signal is cryptographic.The methods discussed in this paper are aimed at providing theoretical basis for navigation system with high autonomy and reliability for Aerospace Vehicles in the future.To achieve the full-autonomous initialization of navigation system,the algorithm based on the cooperation of SINS and CNS is proposed.The horizontal attitude is roughly determined according to the output of accelerometers.Based on the horizontal reference provided by SINS,the initial position is obtained by using multiple circular intersection algorithm.Combining with position information,the coarse alignment is accomplished by using double-vector attitude determination theory,including directional and horizontal posture.And the attitude is applied to be the input of precision alignment.Then,the multi-position fine alignment is carried out to get initial attitude with higher precision and the errors of IMU are estimated to modify the output of gyroscopes and accelerometers.The initialization process is repeated based on the IMU output modified,and the precision of automatic initialization is improved by using the iterative method.Eventually,the horizontal installation errors of star sensor are confirmed according to the installation error model.At the same time,the positioning accuracy is improved by eliminating the installation errors it contains.Aiming at improving the accuracy of celestial positioning,the method of smoothing celestial observations with track-assisted is put forward.According to the track features,suitable order of polynomial fitting is selected to help decrease the noise of astronomical positioning results and ensure the accuracy.The navigation system model is rebuilt by the state augmentation method.Make the attitude results of CNS and the location information smoothed to be measurements,the state variables of navigation system can be estimated.In addition,once the navigation system is in fault,the parameter-restoration algorithm is put forward.To find the track information corresponding to navigation data before fault,the matching algorithm is designed.And the interpolating subdivision method is adopted to improve the accuracy of match.Combining with the increment of track information,the navigation data at restart moment is obtained by designing compensation algorithm.In the situation of codeless GNSS signal,the navigation algorithm of SINS/GNSS is proposed.The carrier phase is obtained on the premise of codeless carrier recovery technique.According to the measure-phase pseudorange equation,two measurement models are established.In one of the model,the ambiguity is eliminated,while in another,the ambiguity is retained.Make the carrier phase to be the measurements and combine it with SINS,the Kalman Filter is adopted to estimate the navigation parameters.Finally,the semi-physical experiment platform is built combining with GNSS signal simulator and receiver to verify the feasibility and reliability of the algorithm.The integrated navigation algorithm proposed in this paper can help improve the navigation accuracy while guaranteeing the autonomy of Aerospace Vehicles,and it provides a solution to solve the lack of autonomy and precision in current navigation system.