Research On Technology And Validation Of GNSS/INS Deep Integration Seismograph

The timeliness and accuracy of early warning of strong earthquakes determine the degree of loss of life and property,while accurate measurement of displacement and velocity of strong earthquakes is the precondition for accurate early warning of strong earthquakes.At present,the commonly used seismic measurement methods include traditional seismographs and Global Navigation Satellite System(GNSS)seismographs.The traditional seismometers uses accelerometer to sense seismic motion,it has good sensitivity and a high sampling rate,but noise and permanent ground tilt will cause baseline drift in accelerometer measurements.And the GNSS seismograph uses the global navigation satellite system to measure the displacement,it can directly obtain the instantaneous displacement information,which is not easy to distort,however,due to the limitation of the receiver's tracking loop bandwidth,the measurement accuracy decreases with the increase of the movement frequency and dynamics.In this paper,the deep integration of GNSS and inertial navigation system(INS)in the navigation field is used to study the GNSS/INS deep integration seismograph.The deep integration seismograph uses INS to estimate real-time dynamic information and uses this information to assist the baseband signal processing of GNSS seismographs.Therefore,the problem of the degradation of the carrier phase observation accuracy of the GNSS seismograph under the strong earthquake dynamics is essentially solved,and real-time high-precision strong earthquake measurement of GNSS seismograph is realized.The specific research content of this paper is as follows.First,based on the characteristics of strong motion,the key technologies of GNSS/INS deep integration seismograph is studied.On the one hand,by modeling the error of the deep integration tracking loop,the transfer relationship between error sources and the loop tracking error is studied,and the tracking error of the deep integration PLL under strong earthquake dynamics is quantitatively analyzed,then the analysis results are used to guide the parameter design of the deep integration tracking PLL under the strong earthquakes.The analysis shows that,with the aid of INS,the loop is no longer subjected to the impact of strong dynamic stress,it only needs to track the minor error of the auxiliary estimation,so the carrier phase tracking accuracy can be improved by compressing the bandwidth and lengthening the integration time.Therefore,the deep integration tracking loop adopts 8Hz narrow bandwidth and 20ms long integration time.On the other hand,different INS constraint techniques is studied for static periods before strong earthquakes and high dynamic periods during strong earthquakes.In the stationary section,the zero-velocity update and zero-angle update are used to prevent the drift of the INS position,velocity,and attitude measurement values.And in the dynamic segment,the INS measurements are corrected by GNSS/INS loose integration.Moreover,the sliding window variance method is used to judge the system motion state,and the constraint method is switched according to the judgment result.Second,the GNSS/INS deep integration seismograph software is realized,and the test scheme for it is designed and verified.The software is built on PC based on C#,and the loop parameters,INS parameters,etc.can be set flexibly on it,also it can output all kinds of information at will,which is good for testing and analyzing the performance of the system at the signal level and the positioning level.In addition,a test process for the system is designed,which includes four steps:test scene preparation,signal simulation,signal acquisition and data processing,and fully verify the feasibility and correctness of the process.Thirdly,based on the hardware simulator and the vibration platform experiment,the performance of the deep integration seismograph was tested at the baseband signal processing level and positioning level,and the accuracy requirements of the deep integration seismograph for inertial devices also are tested.Among them,Based on the hardware simulator,a single-frequency sinusoidal motion scene and a real seismic motion scene are designed,and based on the vibration table,a single-frequency sinusoidal motion scene is designed.The test results show that:the tracking precision of deep integration loop is much better than the traditional loop under the strong earthquake dynamics.When the bandwidth is 8Hz,in the simulator scene,the phase error RMS of the deep integration loop is less than 2°,the maximum is about 8°,and in the shaking table scene,the phase error RMS is 4.6°,the maximum is 14.5°.2)the measurement error of Trimble will increase with the increase of motion frequency and dynamics,however,the deep integration seismograph has always maintained stable and high-precision measurements.In the simulator scene,the measurement error RMS of the deep combined seismograph is less than 0.2cm,the maximum value is about 0.7cm,and in the shaking table scene,the measurement error RMS is 0.5cm and the maximum value is 1.7cm.3)The loop tracking accuracy of the deep integration seismograph using MEMS IMU is 1 degree worse than that using the tactical IMU,and the difference of the horizontal displacement precision is 0.1cm,which indicates that the MEMS IMU can be used in deep integration seismographs.In summary,in this paper,the key technologies of the GNSS/INS deep integration seismograph are studied,and the GNSS/INS deep integration seismograph software is developed.The test analysis shows that the GNSS/INS deep integration technology improves the measurement accuracy of GNSS seismograph under the strong earthquake.Therefore,the research work in this paper provides optimized solutions and techniques for seismographs.