Research On Error Mechanism For Ring Laser Gyroscope Based Strapdown Inertial/Stellar Integrated Navigation

The ring laser gyroscope based strapdown inertial/stellar integrated navigation sys-tem?named as the inertial/stellar navigation?can take advantage of the benefits of each,and provide continuous position and attitude information with high accuracy and reliabil-ity under highly dynamic conditions.It is widely used in ships,aircrafts,ballistic missiles and satellites,and plays an important role in military field.Considering the trends of the inertial/stellar navigation,the work of this thesis mainly focuses on three aspects,namely the dynamic error suppression of the star tracker,the comprehensive calibration of the integrated system,and the tightly-coupled and deeply-coupled integration methods.The research details are as follows:1.The dynamic error suppression method of the star tracker.According to the re-searches on the error characteristics of the star tracker under different dynamic conditions and the spectrum characteristics of the attitude-correlated frames?ACF?method on error suppression,a dynamic error suppression method is proposed by combining the centroid determination method based on the motion error compensation?CMEC?with ACF.The CMEC can reconstruct the star trajectory during the exposure period with gyroscope mea-surements.The dynamic error can be compensated by observing the difference between the predicted star centroid?PSC?and the reported star centroid?RSC?.Since the focus di-mension is about one order of magnitude larger than the detector dimension,the observa-tion sensitivity of the error component along the boresight direction is lower than others.Therefore,a multi-FOV star tracker can be used to increase the compensation accuracy of the dynamic error along the boresight direction.The low frequency error component can be well compensated with CMEC,then the ACF approach is implemented to suppress the high frequency error component further.Simulations under vehicle dynamic conditions show that the correlation curve deviation of ACF from the theoretic curve is less than 0.5^??.Experiments under complex dynamic conditions showed that the attitude accuracy along boresight increased by 6.7 times,and 2.2 times across boresight dirction.The correlation curve deviation is less than 0.9^??after the ACF method is applied.2.The comprehensive calibration method of the integrated system.A comprehen-sive calibration method to estimate the star tracker intrinsic parameter errors,gyroscope errors and fixed angle errors is proposed from a global perspective,which works by ob-serving the predicted star centroid error?PSCE?with a Kalman filter.Simulations with typical star tracker and 50-RLG show that the attitude accuracy of the integrated system after calibration is[0.65,0.31,0.53]^??.Simulations under different star centroid accuracies and gyroscope noise levels are alse conducted to validate the robustness of the proposed method.The decoupling of the calibration parameters is analysed,and the equivalent prin-cipal point error is chosen to evaluate the calibration accuracy of the principal point and subcomponents of fixed angles?_x??_y.Experiments show that the maximum deviation of the principal point is?1.82,0.47?pixel,and the RMS value is?0.77,0.20?pixel.The RMS value of the equivalent principal point error is?0.0430,0.0230?pixel.The mean value of the reprojection error is?0.0064,0.0011?pixel and the RMS value is?0.0732,0.0909?pixel.The dynamic calibration method for the integrated system was researched,and simula-tions under complex dynamic conditions show that the dynamic calibration accuracy is comparable to static conditions.3.The theory and simulations on the inertial/stellar navigation.The error propaga-tion characteristics of the ideal inertial/stellar navigation is analysed.The initial align-ment of the system based on the star tracker attitude is studied.A tightly-coupled in-tegration method based on the direct star cordinate observation is proposed.It can still work normally even under single star observation,and the statistical characteristic of the observation noise is more stable.Simulations under under different star centroid accura-cies and gyroscope noise levels validate the robustness of the tightly-coupled integration method.Simulations under small field of view show that the tightly-coupled integration method is more accurate than the traditional loosely-coupled method.A deeply-coupled inertial/stellar integrated method is proposed,which achieves the mutual suppression be-tween the star tracker dynamic errors and INS errors.Simulations under vehicle dynamic conditions show that the main error indicator is reduced by at least 3 times,and the atti-tude accuracy in inertial frame can reach subarcsecond level.The position accuracy can reach 10m level if the accelerometer bias is compensated.4.The inertial/stellar navigation experiments.Experiments under static conditions are conducted.The position accuracy in 2 hours is better than 0.15 nautical mile,which is much better than the accuracy of autonomous navigation?i.e.1 nautical mile?.The position accuracy of inertial/stellar navigation can reach 0.10 nautical mile when the ac-celerometer bias is compensated.Dynamic experiments of uniform linear motion of star show that the position accuracy in 1 hour is better than 0.15 nautical mile,which is much better than the accuracy of autonomous navigation?i.e.0.8 nautical mile?.The position accuracy can reach 0.05 nautical mile when the accelerometer bias is compensated.The gyroscope bias estimation of inertial/stellar navigation is much accurate than GPS/INS integration.Experiments with small field of view?1/3FOV?show that the tightly-coupled integration method is much accurate than the loosely-coupled method.Dynamic ex-periments of complex motion of star show that the position accuracy of deeply-coupled method in 1.5 hour is better than 0.5 nautical mile,wich is better than the tightly-coupled method?approximately 1 nautical mile?.