Study Of Initial Alignment Techniques In INS/GPS Integrated Navigation System

Initial alignment of the INS/GPS integrated navigation system usually adopts transfer alignment on moving base. If the information of the INS/GPS integrated navigation system is fully used, the alignment does not need the information transferred by the outsides. And the INS/GPS will become an absolutely independent navigation system. Main work is as follows:The error model of INS/GPS is established. The paper studies two kinds of correction methods. The simulation results show that the closed-loop correction is more effective than the open-loop correction and pure inertial navigation system.The alignment of the INS/GPS gives INS the initial conditions to calculate the navigate information, and estimates the initial errors to correct the results. As small quantity, the error model of the INS can be considered as the linear time variant system. The initial states can be estimated only if the system is observable. The observability during initial alignment of the INS/GPS on moving base is deeply studied and thoroughly analyzed by means of the observability and the method of piece-wise constant systems. In alignment process of INS/GPS on moving base, both the straight motion of base and the rotation motion of base all can enhance the observability, thus increase the rapidity of convergence and accuracy of estimation. So the carrier must have horizontal maneuver during the alignment.On the base of INS, the method of initial alignment is introduced. And the state equation and observation equation are proposed. Using velocity error as exterior value of observation, We achieve the initial alignment.According to simulation model of the INS/GPS integrated navigation system, We carry on amout of simulation experiments and discuss the results, respectively. The simulation results of INS/GPS alignment prove that kalman filer method is feasible and the certain alignment accuracy can be achieved.