Real Time Deformation Monitoring And Analysis Based On Improved Single Epoch Algorithm

Health and safety monitoring of large bridges has become a hot topic in the field of engineering.The bridge monitoring is a complex project.In order to understand its deformation characteristics,the GNSS technology is often used for location calculation and the use of fast Fourier transform(FFT)to analyze its vibration characteristics.With the mature development of GNSS relative positioning technology,domestic and foreign scholars often use real-time kinematic relative positioning technology(RTK or NRTK)for deformation monitoring,and some research results have been obtained.RTK or NRTK technology generally uses the method of ambiguity resolution(OTF)for relative positioning,but if the satellite signal or network data chain is interrupted,the OTF method needs to be reinitialized.For this reason,a single epoch deforma-tion monitoring algorithm based on deformation characteristics has been developed in China,and the algorithm is simple and effective.The algorithm uses the initial value coordinates of the monitoring point to determine the double difference ambiguity in the positioning process,and does not need to be fixed in the position calculation process,so it has been well applied in the field of real-time deformation monitoring in the bridge.This paper is based on the research of the single epoch algorithm without whole cycle.(1)From the principle of GPS carrier phase measurement,the principle of single epoch similar single difference algorithm and the single epoch algorithm without whole cycle is derived,and the consistency of the two algorithms is proved by analysis.(2)The application conditions of the single epoch algorithm without whole cycle are analyzed and deduced,including the requirements for the number of satellites,the requirements of the initial value accuracy,the maximum range of deformation,the range of the initial value of the datum point or the monitoring point,and the detailed derivation and results are given.(3)Experimental verification is carried out on the application conditions of the single epoch algorithm without whole cycle,and it is verified by contrast that the accuracy of the internal and external coincidence of the result is equivalent to that of the RTKLIB+Kinematic solution.Then the location of the L1 carrier and L2 carrier observation data is calculated respectively,and the maximum deformation amount is verified to be related to the carrier wavelength.(4)Improve the monitoring range of large deformation based on the basic single epoch algorithm without whole cycle.In this paper,the basic algorithm is improved by continuous single epoch algorithm without whole cycle.Through experiments,it is proved that the improved algorithm can carry out continuous measurement of large deformation and get better results than RTKLIB+Kinematic.(5)The continuous epoch algorithm without whole cycle based on the robust Kalman filter is proposed.The algorithm is used to smooth the measurement results by the robust Kalman filtering method,and finally the influence of the gross error in the observed values is suppressed.Then it is found that the algorithm is more accurate than that of the continuous epoch algorithm without whole cycle and the RTKLIB+Kinematic algorithm,thus verifying the validity of the algorithm.(6)The program design of the continuous epoch algorithm without whole cycle based on the robust Kalman filter is realized,which mainly includes program function design,module design and algorithm flow design.(7)The real time monitoring data of Wuhan Baishazhou Bridge is analyzed and processed.The vibration frequency spectrum of bridge box girder,bridge span and bridge tower position is obtained by FFT,and the vibration frequency of the bridge is obtained.By comparing and analyzing the RTKLIB+Kinematic algorithm,continuous epoch algorithm and the continuous epoch algorithm based on the robust Kalman filter in the observation value,it is found that only the continuous epoch algorithm based on the robust Kalman filter can correctly calculate the real-time position and reverse the bridge.The validity of the algorithm is proved in engineering application.