Research On The Algorithm Of Marine Gravity Aided Attitude Measurement System With Ring Laser Gyro

The high-precision attitude measurement system with the ring laser gyroscope(RLG) as the core components have the advantages of the high reliability and strong autonomy, but its system's errors accumulate over time. For long-time navigation, it's hard to maintain the accuracy of attitude measurement. To solve this problem, we carry out the research on the gravity aided inertial attitude measurement bas ed on RLG, using the passive gravity information to correct the system's accumulated errors. The main contents of this thesis are as follows:1. The local gravity modeling method. At first, the basic mathematical principle of several interpolation methods have been introduced, and then the thesis select the dramatic gravity change and the flat region to verify the interpolation precision based on the global gravity anomaly map with resolution 1'×1'. The validation results show that the precision of second-order weight coons model is much better than the bilinear interpolation, surface fitting and Shepard methods.2. Study on the influence of gravity disturbance on attitude measurement system. Obtain the conclusion that the system's error caused by gravity anomaly can be ignored according to the update equations of attitude measurement system; the analytical expressions of system's error caused by level gravity disturbance are carried out based on the quasi-static conditions; the simulation is maded to analyze the system's error caused by the level gravity disturbance on the basis of global gravity disturbance database; the conclusion is obtained that the compensation of gravity disturbance is needed in the high-precision application field.3. The algorithm of gravity-aided inertial attitude measurement. On the basis of deeply analysis of principle of gravity aided inertial attitude measurement, this thesis selects Cubature Kalman Filter(CKF) for information fusion to solve nonlinear problem between position and gravity anomaly. The simulation based on global gravity anomaly database is carried out, which proves that the algorithm is more precision than Unscented Kalman Filter(UKF). And the algorithm is not sensitive to the initial position error and measure ment noise. The system's performance of compensation and no compensation of gravity disturbance are researched and we draw the conclusion that the precision of system can be improved obviously after gravity disturbance compensation. The semi-physical simulation based on practical ship borne data is accomplished, and the results show that the designed algorithm can improve the system's performance significantly and meet the long-endurance, high-precision attitude measurement requirements.