A two-position rotation alignment scheme for rotational fiber optic inertial navigation system

Abstract Compared with ring laser gyro, fiber optic gyro (FOG) have two inherent performance defects: poor start-up temperature characteristics and poor scale factor error repeatability. Both defects will degrade the heading angle alignment accuracy of the rotational fiber optic inertial navigation system when conventional self-alignment schemes are adopted. Previous studies mainly focused on improving alignment schemes to reduce the impact of only one of the two FOG defects on self-alignment accuracy. However, in practical engineering applications, these two defects of FOGs exhibit a synergistic effect, synchronously introducing heading angle alignment errors into the rotational fiber optic inertial navigation system. To address this issue, this paper analyzes the underlying mathematical mechanism of this phenomenon. On the basis of inheriting the advantages of the conventional two-position and continuous rotation alignment methods, a novel two-position rotation self-alignment scheme is proposed. By designing a reasonable indexing scheme, the filtering estimation error of the azimuth misalignment angle during the rotation process is offset against the attitude tracking error caused by indexing, thereby synchronously suppressing the heading angle alignment errors introduced by the FOG scale factor error and start-up temperature characteristics. The high and low temperature alignment test data show that the alignment accuracy of the two-position rotation alignment method is improved by approximately 35″ and 86″ relative to the former two schemes, respectively.