Research On The Key Processing Technology Of North-Seeking Non-Stationary Data Measured By The Maglev Gyroscope

With the development of national economic construction,more and more mines,high-speed railway tunnels,urban subways,and other satellite-denied large-scale engineering projects have emerged one after another.The inability to receive satellite signals properly in these confined spaces led to the ineffectiveness of traditional space geodesy techniques.To address this issue,the Inertial Technology and Intelligent Survey E&R Center of the Chang’an University and China Space Age Electronics 16 th Research Institute developed the first high-precision maglev gyro total station(GAT)with independent intellectual property in China.The GAT is based on the non-contact torque feedback and the photoelectric auto-collimating technology to achieve continuous analog-to-digital conversion and real-time massive data acquisition.The GAT independently determines the true north azimuth of any direction by sensing the earth’s rotation,which overcomes the shortcomings of traditional satellite geodesy techniques that cannot be autonomously oriented under satellite-denied environments.Therefore,the GAT has been widely used in many national major underground projects in recent years.However,due to the complex environmental conditions in the confined space,the GAT is often affected by external interference factors such as ground vibration caused by construction or vehicle passing,the airflow generated by ventilation facilities,etc.In these interfered environments,the north-seeking data measured by the GAT exhibits periodic,time-varying,and non-linear characteristics,which reduces the north-seeking accuracy and reliability.Therefore,it is meaningful to study the physical mechanism of the non-stationary characteristics of the north-seeking data measured by the GAT in complex environments,design the adaptive bias correction algorithm of the gyro signals,establish the model to detect and eliminate the periodic systematic errors,improve the reliability of the north-seeking results of the GAT under the influence of external disturbance torques,and then provide more accurate orientation reference for the confined space,which has significant theoretical supporting and engineering application value to guarantee the accurate breakthrough of national major tunnel projects.Therefore,in this paper,based on the continuous analog-to-digital conversion and the real-time massive data acquisition technology of the GAT,relying on the major tunnel projects such as the Hanjiang-to-Weihe River Diversion Project,the key processing technology of north-seeking non-stationary data measured by the GAT was studied.The main research contents and results of this paper are as follows:(1)An analysis method and evaluation system of the GAT signal characteristics based on the autocorrelogram and the wavelet spectrum were proposed.Relying on this system,the signal characteristics of the GAT were investigated from the time domain and frequency domain respectively,and the physical mechanism of the gyro rotor current signal exhibiting non-stationary characteristics was finally revealed.(2)The characteristics of the periodic error of the damping torque rotor were analyzed,and an adaptive periodic error detection model of the GAT rotor current signal was proposed.The model combines the singular spectrum analysis and the continuous wavelet transform to achieve accurate identification and separation of the high-frequency and low-frequency period errors in the GAT signals.The processing of the data measured by the GAT verified that the method can effectively improve the external coincidence accuracy of north-seeking.(3)A self-adaptive bias correction model of the GAT based on the heuristic segmentation algorithm and the two-sample Kolmogorov-Smirnov test was established to solve the problem of signal jump caused by the external instantaneous disturbance torques during the gyro north-seeking data collection.The ability of the model to automatically detect and reject the jumps in the GAT signals has been verified by the measured data of the Qinling water conveyance tunnel of the Hanjiang-to-Weihe River Diversion Project,which improving the north-seeking reliability and environmental adaptability of the GAT.(4)An adjustment model of the survey network with maglev gyro azimuth based on iterative reweighted least squares(AGIR)was proposed to solve the problem that the adjustment models cannot accurately evaluate the orientation accuracy of the GAT.Through the application example analysis of a large-scale mining tunnel project,the comparison with the results of traditional adjustment models verified that the AGIR model can optimize the allocation of the weight of the gyro azimuth,which improves the accuracy of tunnel breakthrough.