131 / 2023-06-30 22:38:52

Research on four-position Nonequal precision North Seeking Algorithm of Fiber Optic Gyroscope total Station based on iteration method with variable weights

Fiber optic gyro total station, four-position north seeking, iteration method with variable weights, non-equal precision configuration

     Fiber optic gyro orientation instrument is an inertial orientation instrument that independently determines the true north position of any target through sensitive earth rotation angular momentum, does not rely on external environmental information, and is an indispensable and important equipment for underground engineering surveying and national defense security such as mines and tunnels. The combination of fiber optic gyroscope and total station and applied to underground engineering directional measurement can effectively overcome the problems of high cost, high failure rate, heavy weight and long orientation time of mechanical gyroscope. However, due to the high sensitivity of fiber optic gyroscope, the uncertainty of external environmental interference can easily lead to a large number of coarse differences in the output value of fiber optic gyroscope, thereby reducing the orientation accuracy of the fiber optic gyro orientator. In addition, the fiber optic gyro north seeking scheme is also an important factor affecting the accuracy of fiber optic gyro north seeking, according to the number of locations for data collection during north seeking, the north seeking scheme can be divided into: two-position north seeking, four-position north seeking and multi-location north seeking. Regardless of the northfinding scheme, the conventional solution method is to treat the data collected at each location as equal-precision observations and calculate them differentially, but in practical engineering applications, it is found that there are obvious differences in the northfinding accuracy between the sampling locations of fiber optic gyroscopes. Therefore, the results of conventional north-seeking solutions cannot objectively and truly reflect the correct azimuth value, and are not suitable for the orientation of underground engineering. In view of the above problems existing in the current fiber gyro orientation, this paper proposes a new northward angle solution method based on the four-position north-seeking scheme: for the data collected at each position, the weighted iterative method based on robust estimation theory is first used for rough difference processing, and then the sampling data of each position are weighted according to the non-equal precision configuration, and then the least squares fitting calculation is performed to obtain the final north seeking result. The results obtained by the actual measurement in the Yingxiu No. 1 tunnel breakthrough project in western Sichuan show that the proposed method is superior to the traditional solution scheme, which can effectively suppress the observation roughness of the fiber optic gyro total station and significantly improve its directional accuracy in underground engineering surveying.