Algorithm Design And Implementation Of CNS/GNSS/INS High Precision Ship-borne Real-time Attitude Determination System

Aiming at the lack of high-precision scheme for real-time attitude measurement at sea,the information fusion technology and algorithm of ship-borne high-precision CNS/GNSS/INS integrated navigation system are studied.Combined with the problems of slow initial alignment,data delay and system installation error in practical engineering,the corresponding improvement scheme is put forward.Firstly,for the problem that the traditional inertial self-alignment method is not applicable in the large swing state,the gravity vector integral indirect alignment method is used to derive and establish the initial alignment equation of the strapdown inertial navigation on large swing base.The detailed navigation parameter calculation steps are given to improve the initial alignment accuracy of ship-borne navigation system in the large swing state.At the same time,aiming at the problem that the moving base is timeconsuming for maritime navigation,an algorithm of GNSS-aided directional moving base is designed,which can correct the attitude of INS to the angular classification accuracy in a relatively short time and complete the initial alignment at sea.Secondly,a CNS/GNSS/INS high-precision real-time positioning and attitude frame is proposed.The timing function of the GNSS receiver is used to establish a unified time reference for CNS and INS sensor data.a)For the CNS data delay problem existing in the actual engineering application,the parameters of the cached observation modified filter matrix are updated and then the state transition is performed to reduce the influence of the CNS measurement data delay on the attitude error.b)Under the condition of large sway,the small field of view star sensor is reduced by the inertial data delay,and an isometric velocity extrapolation method is studied to compensate the reference attitude provided by inertial navigation to star sensor,so as to ensure the realtime searching ability of star sensor in bad sea conditions.c)Considering the installation angle error between CNS and INS in actual engineering,the influence of installation error on attitude measurement accuracy is analyzed,and a static position calibration method is proposed,and a detailed calibration scheme is given.Finally,the CNS/GNSS/INS real-time positioning and attitude determination algorithm proposed in this paper completes the software construction and implementation the hardware platform on the ship-borne high-precision attitude determination system,and verifies the land test and sea test scenarios.The land test shows that the maximum attitude error of both static and the dynamic test are within 25 arc seconds,and the CNS/GNSS/INS solution is better than the GNSS/INS solution,and its continuity and robustness are obviously excellent,which meets the requirements of high precision attitude measurement index(the maximum attitude error is within 30 angular seconds).The sea test shows that the CNS/GNSS/INS information fusion solution proposed in this paper can effectively correct the INS attitude using CNS,and the result follows self-consistency;the initial alignment method of GNSS-aided INS can converge to the angular division level within 10 minutes,and the marine start-up scheme is feasible.At the same time,it also verified that GNSS/INS has the ability of long-term attitude accuracy and stability without divergence,and when the star-gazing environment is good,it can restore the astronomical navigation in time,greatly improving the accuracy of the three-combination system in the whole process of navigation.