The development and evaluation of a two-axis indexing NFFDLG INS for marine navigation

This paper discusses the development and evaluation of an inertial navigation system (INS) for marine navigation applications. Marine navigation is generally a challenging mission, because, compared with the aviation or land navigation, the marine navigation often needs to endure for a long term and the navigation accuracy is demanding. The commonly used strapdown INS generally cannot satisfy the requirements of the long term marine navigation, because the residual calibration errors of the inertial sensors, such as the constant drifts of the gyros and the biases of the accelerometers, and the slow changes of the calibration errors with time may seriously degrade the long term navigation performances. Our research group in National University of Defense Technology (NUDT) develops the Nonplanar Four-Frequency Differential Laser Gyro (NFFDLG), which is a kind of ring laser gyro designed on the basis of the similar theory with Zero-Lock Gyro (ZLG). The NFFDLG has no mechanical dithering part, and is expected to have a better performance. This paper illustrates the development and evaluation of a NFFDLG INS including a two-axis indexing mechanism to remove the residual errors of the inertial sensors.