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The core idea of inertial/celestial integrated navigation system composed of SINS and star tracker is to estimate and correct SINS navigation errors through a designed kalman filter by use of star's accurate angle information measured by the star tracker. In this way, divergence of navigation errors along with time could be restricted, and thus navigation accuracy during long time flight could be improved significantly. Based on analysis of the relationship between star tracker's measurement and SINS's navigation errors, two integrated navigation algorithms called position plus azimuth correction algorithm and angle error integrated navigation correction algorithm are designed for the system Then, navigation accuracies of the two algorithms are analysed theoretically and validated by using a series of long time flight simulations. The results show that position plus azimuth correction algorithm not disturbed by initial position errors is more suitable when star tracker works intermittently; while angle error integration algorithm which doesn't disturbed by initial attitude errors is more suitable when SINS's initial position errors are small or corrected effectively before integration. [ABSTRACT FROM AUTHOR]

Coning effects must be accurately compensated in the attitude updating of the classical strapdown inertial navigation integration algorithm. These effects are not involved in the velocity updating, though the attitude change is being taken into it. The novel velocity error term induced by the coning correction is studied in this paper. These effects as the gyro angular increment data have the influence on the velocity updating in the same way. For the assumed linear ramp model, a two-sample compensation algorithm for the novel velocity error term is deduced in detail by using the two successive integrated angular rate increment and specific force increment measurements. The weighting coefficients are then optimized for best average performance in a specific environment; i. e. the body is exposed to a coning angular vibration about the x axis of the body frame combined with a linear vibration at the same frequency and in phase along the z axis. The simulation results validate that the two-sample optimization algorithm can compensate the integrated term of the novel velocity error effectively. [ABSTRACT FROM AUTHOR]

In view of the phase-shift characteristic inconsistency between gyros and accelerometers in actual SINS (Strapdown Inertial Navigation System ), it's found that non-synchronization velocity errors are considerable under SINS angular motion. Through SINS systemic test, a simple and convenient way to identify the accelerometer time-delay parameter is proposed. In this way, a rolling test in gravity fields is designed and the relations between accelerometer time-delay parameter and the system' s velocity error are obtained. Moreover, two kinds of methods for non-synchronization velocity error compensation ate given: one is the time-delay extrapolation based on the transfer function model of accelerometer and the other is the velocity error direct compensation based on SINS velocity update algorithm. Finally, by using fiber optic gyro SINS, some experiments are carried out and the results verify that the navigation system's accuracy is improved effectively and the theoretical analysis is correct. [ABSTRACT FROM AUTHOR]

In actual strap down inertial measurement unit (SIMU), special force outputs of the three accelerometers are from different measuring points. If the outputs are directly put into the SINS update algorithm, it will bring navigation velocity errors under the case of SIMU angular movement. Taking into account the non-orthogonal installation scheme of accelerometer unit and based on the traditional static calibration models , new dynamic calibration models involving inner lever arm (ILA) compensation are deduced. A universal equation for accelerometer unit ILA compensation is established by taking navigation velocity as observation. Using the laser gyro SIMU, a test scheme is designed to identify the ILA parameters. In the end, a high intensity of swaying test verifies that ILA compensation can effectively improve the navigation accuracy, with the amount of errors decreasing over 77%. [ABSTRACT FROM AUTHOR]