Research On Tightly Coupled GNSS/INS Dynamic Deformation Monitoring Technology Of Bridge

Structural health monitoring is a necessary measure to ensure the normal operation of large bridges.In the traditional process of monitoring bridges using GNSS,there are some problems,such as insufficient sampling rate of receiver and GNSS signal is easy to be blocked and disturbed,which makes its accuracy and reliability difficult to meet the requirements of continuous and stable monitoring in engineering application.The existing GNSS/INS multi-sensor integrated monitoring scheme focuses on complementary verification at the result level or simultaneous interpreting method with simple structure,which has little effect on the system.However,the tight combination of different sensors in the actual monitoring scenario is not yet thorough.In order to further improve the accuracy and reliability of GNSS/INS integrated system in the process of deformation monitoring,this paper studies the GNSS/INS compact combination algorithm in the bridge deformation monitoring environment,and makes a detailed experimental analysis from the aspects of positioning method,accuracy,reliability and practical application.On this basis,a set of GNSS/INS compact combination core algorithm library is developed,and the GNSS/INS dynamic deformation monitoring data processing software is formed based on the algorithm library.The main work and achievements include:(1)The dynamic parameter estimation method of GNSS/INS compact combination is deduced and analyzed.On this basis,a GNSS/INS compact combination deformation monitoring method based on the constraint of bridge plane deformation velocity information is proposed.This method can increase the observability of the state in the filtering process,so as to improve the accuracy and reliability of bridge vertical displacement monitoring.Using the measured data,the influence of the noise level of accelerometer and gyroscope on the recursive process of INS system is systematically analyzed,and the optimal weight determination strategy of GNSS / INS compact combination is determined.(2)The vibration deformation device is used to simulate the dynamic displacement of the bridge,and the GNSS/INS tightly-coupled deformation monitoring method and the positioning accuracy after adding plane velocity constraints are evaluated.In the open environment,the accuracy of the latter is better than the former,and the solution accuracy is better than GNSS-RTK.In the GNSS/INS fusion solution,the multi system solution result is better than the single system solution result;In the simulated occlusion environment with a small number of satellites,the GNSS/INS compact combination solution with plane velocity constraint information can significantly improve the positioning accuracy compared with GNSS-RTK solution,up to 23%.(3)A double observation quality control method based on pre-test ins assisted outlier detection and post-test robust is proposed.The ins assisted detection method is deduced in principle,and the method is verified by simulation and actual environment.The experimental results show that the method in this paper can play a good role in the abnormal value,whether it is gross error or cycle slip.The high-precision prediction value of INS makes the method more sensitive to small gross error.(4)The GNSS/INS tightly-coupled algorithm is realized by using C++ language,and the GNSS/INS data processing software with visual interface is developed,which realizes the functions of monitoring data management,monitoring point visualization,tightly-coupled calculation and so on.The monitoring test is carried out in Sanchaji bridge in Changsha,and the displacement results are analyzed.Compared with GNSS monitoring,INS can help improve the sampling rate of the monitoring system while reducing the cost of user receiver,and obtain more modal frequency information of the bridge,which is less than 5% compared with the standard value,indicating that the algorithm and software in this paper have good practicability.