For the nested rotation inertial navigation system(NRINS) constructed by three ring fiber optic gyros nested with each other, it is analyzed that the main residual errors after rotation modulation are gyro angle random walk(ARW) and non-modulated gyro drift, It is pointed out that the different orientation of gyro sensitive axis leads to different equivalent ARW, and the non-modulated gyro drift caused by the nested installation of three ring gyros is also different. The generation mechanism of non-modulated drift in the embedded system and the general relationship with the axis sequence configuration are expounded. The equivalent ARW and non-modulated gyro drift in the inner frame rotation modulation mode and their influence on the alignment and navigation of the system are analyzed and deduced; Finally, taking the two typical applications of short-time navigation and long-time navigation as example, the influence of different gyro axis sequence configuration schemes on the navigation accuracy of the NRINS is verified through static navigation experiments, and the best axis sequence configuration scheme under the two applications is determined. By optimizing the gyro axis sequence configuration, the accuracy of navigation can be improved by about 2 times, which is of great significance. It has important reference value for further improving the accuracy of NRINS and maximizing the accuracy advantage of gyros in different applications.

The rotational inertial navigation system (RINS) could use rotational alignment to improve azimuth alignment accuracy significantly. However, due to the existence of magnetic drifts of fiber optic gyros, under the comprehensive influence of the outside world, there will be residual drifts that are unable to be averaged out along the body frame or the geographic frame, which will have a significant impact on the azimuth alignment accuracy. An innovative and effective calibration compensation strategy is proposed by analyzing the generation mechanism of the residual drift and its influence on alignment accuracy, which can significantly improve the azimuth alignment accuracy. With the aid of a high-precision total station, the experimental results of the initial alignment in four directions show that the accuracy of azimuth alignment is improved from 16.5'' to 10.3'' by compensating the residual drifts, which has significant theoretical significance and practical value of engineering application for improving the overall performance of inertial navigation.

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