Research On Transfer Alignment Of Carrier-Based Aircraft Strapdown Intertial Navigation System With Large Azimuth Misalignment

Carrier-based aircraft plays a very important role in modern warfare. In order to improve the carrier-based aircraft's ability to survive and the hit ratio of airborne missile, initial alignment must be finished quickly and accurately. Due to the effects of complex marine environment and interference factors, transfer alignment method is often used to solve the problem of carrier-based aircraft inertial navigation system's initial alignment. Carrier-based aircraft often docks on the deck at random while the main inertial navigation system (MINS) is installed in the navigation room under the deck. Consequently, the difference of azimuth misalignment between the MINS and SINS (slave inertial navigation system) is considerable. In view of this situation, transfer alignment of carrier-based aircraft inertial navigation system with large azimuth misalignment is mainly researched in the dissertation.Nonlinear attitude error and velocity error equations of strapdown inertial navigation system under large azimuth misalignment are derived in detail firstly. And then, the relationships of velocity, acceleration, angular velocity and position between MINS and SINS are deeply studied based on the principle of euler kinematics.Both extended kalman filter (EKF) and unscented kalman filter (UKF) method are studied to deal with the problem of filtering of nonlinear models. First of all, basic principle and filtering equations of EKF are studied. After that, UKF method is researched in detail, including key concepts, sampling strategy. Besides, the UKF realization algorithm of nonlinear system is also studied. When the measurement equation is linear, simplified UKF equations are given. What's more, the filtering performances between EKF and UKF method are compared by simulation experiments.Three matching methods, including velocity matching, velocity plus attitude matching and velocity plus angular velocity matching under large azimuth misalignment are researched in depth. According to different matching method, different nonlinear error models and corresponding filtering models are deduced at first. And then, simulation experiments are adopted to research the three matching methods using UKF algorithm. Comparative studies of the alignment effect for each matching method are researched under different simulation conditions.To deal with the problem of getting accurate lever arm length, computing method and online real-time estimating method are proposed. After acquiring the lever arm length, compensation method of lever arm effect is studied by compensating accelerometer's output. Then, compensation method of flexure deformation is studied deeply. In consideration of ship's no-rigid situations, new expressions of lever arm acceleration and velocity are derived based on the flexure deformation model. A new compensation method is then proposed to compensate both the flexible lever arm effect and flexible deformation by establishing a unified model of them.