LAUSR

It is much important for core drilling to measure the orientation and trajectory of the drill bit precisely. Presently, with the higher and higher accuracy requirements of orientation and positioning, the utilization of inertial navigation system, especially the use of fiber optic gyroscope (FOG), has become a general trend. However, the realization of high precision and small size simultaneously is still a difficult challenge. In this article, a FOG-based single-axis rotational inertial navigation system (RINS) instrument was used to suppress the inertial sensor errors automatically through rotation modulation technology. Based on the limited movement of the drill bit in lateral and vertical directions, this article proposed a new dead reckoning (DR) algorithm, which performed much better than normal inertial navigation algorithm due to the reduction of error sources, but the actual accuracy of DR algorithm was affected by the installation errors between the axes of the instrument and the pipeline. Therefore, this article further proposed a new and practical calibration method of the installation errors to improve the accuracy of DR algorithm. To verify the rationality and the validity of the algorithm, the simulations and semi-physics simulation experiments were conducted under laboratory conditions. The results showed that the proposed DR algorithm with installation errors corrected could reach a high positioning accuracy of 0.5% utilizing FOGs with a drift of 0.015°/h. This study provided an innovative solution for high positioning precision based on a small-sized and low-cost RINS instrument in core drilling.