Carrier Aircraft Inertial Navigation System Of The Moving Base Alignment Technology

Initial alignment is a key technique of SINS (Strap-down Inertial Navigation System), which to a large extent come to a decision of the system's performance accuracy and the quick reaction ability. The aim at alignment accuracy and time and the complicated environment made the carrier aircraft in-motion alignment difficulty. Therefore in-motion alignment of the carrier aircraft is becoming a key technology of the carrier aircraft, and lots of scholars pay extensive concern to it. The main contents of the thesis are the technology of in-motion alignment and its related problem.The in-motion alignment of the carrier aircraft is usually implemented by transfer alignment method. The main contents of the thesis include:1) Basic performance principles and error equations of the strap-down inertial navigation system are stated. Then the basic theory of the transfer alignment is stated. And some related problem is also studied, such as lever arm effect and the model of the marine deck flexure. The basic matching methods of the transfer alignment are studied in this thesis. The state space models of the velocity matching, the attitude matching and the velocity and attitude matching transfer alignment are derived.2) The computer simulation environment is developed and the simulations of introduced matching method are made and the analysis of the simulation results is made. Simulation show that the velocity and attitude matching scheme is the relatively ideal transfer alignment technology.3) Considering that there maybe a large heading error, thesis also studied the problem of the nonlinear alignment of SINS under the large heading errors. The nonlinear errors model with large heading uncertainty is introduced. Then, we study the nonlinear filter UKF in the application of nonlinear alignment compared with EKF. The computer simulation validates the correctness of the nonlinear model. The simulation results also show that the UKF outperforms the standard EKF in accuracy.4) Finally the effect of the error of the master INS on the accuracy of transfer alignment is analyzed, results show that the master INS error can greatly deliver the transfer alignment performance. When the error of master INS can't be neglected, and additive method is needed. To resolve the above problems, thesis introduced the combined alignment method which combined with the GPS (Global Positioning System) information to improve the alignment accuracy. Simulations also validated that method is feasible.