Abstract
A dynamic attitude measurement system (DAMS) is developed based on a laser inertial navigation system (LINS). Three factors of the dynamic attitude measurement error using LINS are analyzed: dynamic error, time synchronization and phase lag. An optimal coning errors compensation algorithm is used to reduce coning errors, and two-axis wobbling verification experiments are presented in the paper. The tests indicate that the attitude accuracy is improved 2-fold by the algorithm. In order to decrease coning errors further, the attitude updating frequency is improved from 200 Hz to 2000 Hz. At the same time, a novel finite impulse response (FIR) filter with three notches is designed to filter the dither frequency of the ring laser gyro (RLG). The comparison tests suggest that the new filter is five times more effective than the old one. The paper indicates that phase-frequency characteristics of FIR filter and first-order holder of navigation computer constitute the main sources of phase lag in LINS. A formula to calculate the LINS attitude phase lag is introduced in the paper. The expressions of dynamic attitude errors induced by phase lag are derived. The paper proposes a novel synchronization mechanism that is able to simultaneously solve the problems of dynamic test synchronization and phase compensation. A single-axis turntable and a laser interferometer are applied to verify the synchronization mechanism. The experiments results show that the theoretically calculated values of phase lag and attitude error induced by phase lag can both match perfectly with testing data. The block diagram of DAMS and physical photos are presented in the paper. The final experiments demonstrate that the real-time attitude measurement accuracy of DAMS can reach up to 20″ (1σ) and the synchronization error is less than 0.2 ms on the condition of three axes wobbling for 10 min.
Highlights
An inertial navigation system (INS) has unparalleled advantages in measuring the motion parameters of vehicles and can output the moving vehicle’s attitude, velocity, and displacement in a real-time and autonomous way
The attitude reference for synthetic aperture radar (SAR) or lidar can be offered by a position orientation system (POS), the attitude data for the servo control system of antiaircraft guns can be measured by INS, the accuracy of servo turntables or other attitude measurement systems can be verified by higher precision INS, and so on
Despite the fact the coning errors are decreased much more by the optimizing compensation algorithm, what we study in the paper is a high precision dynamic attitude system, the other factors inducing dynamic errors should be reduced as little as possible
Summary
An inertial navigation system (INS) has unparalleled advantages in measuring the motion parameters of vehicles and can output the moving vehicle’s attitude, velocity, and displacement in a real-time and autonomous way. It is widely applied in military weapon systems such as spacecraft, missiles, airplanes, ships, advanced ground vehicles, and so on. The attitude reference for synthetic aperture radar (SAR) or lidar can be offered by a position orientation system (POS), the attitude data for the servo control system of antiaircraft guns can be measured by INS, the accuracy of servo turntables or other attitude measurement systems can be verified by higher precision INS, and so on Among all such applications, INS is unexceptionally required to output high precision attitude data of the base at each sampling time. The DAMS performance test results are shown that the dynamic attitude measurement accuracy is up to 20′′ (1σ) under three axes wobbling test for 10 min
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