Research Of Key Algorithms For MEMS-SINS/GPS/BDS Tightly Coupled Navigation

The Micro-Elctro Mechanical Systems(MEMS)Strapdown Inertial Navigation System(SINS)is widely used due to its low cost,light weight and small size.MEMS-SINS has the fatal flaw of error diverging over time and therefore cannot work independently.Meanwhile,the positioning error of the Global Positioning System(GPS)in the United States and the BeiDou Navigation Satellite System(BDS)in China doesn't cumulate with time,ut their anti-interference ability is weak.The MEMS-SINS and GPS/BDS navigation system,which combines the above two independent navigation systems,making the performance better than the independent systems.Therefore,MEMS-SINS/GPS/BDS tightly coupled system is studied in this paper.The key to the design of MEMS-SINS/GPS/BDS tightly coupled navigation system is the data fusion algorithm of MEME-SINS and GPS/BDS.While the observability and observable degree of the system determine the accuracy of the data fusion algorithm,which naturally become a key problem of the tightly integrated navigation system.This paper focuses on the analysis and calculation of the observability and observable degrees of the tightly coupled navigation system,corrects the weights of Kalman filter according to the calculated results of observable degree.As a result,the precision and robustness of the system is improved compared with traditional tightly coupled navigation system.The research of this paper the following sections:Firstly,the basic principle of Kalman filter algorithm is studied,the structure and the error model of tightly coupled navigation system are analyzed.The centralized and distributed filter algorithm of the tightly integrated navigation system is studied,and the advantages and disadvantages of each structure are analyzed,which comes to a conclusion that analysis of the observability and observable degree for tightly coupled navigation system is necessary.Secondly,it is proved that the tight integrated navigation system satisfies the piece-wise constant system(PWCS)theorem and computes the observability and measurability of the tight integrated navigation system based on the PWCS theorem In this paper,the method of calculating the observability of tight integrated navigation system based on singular value decomposition(SVD)method is proposed.The singular value of S maneuvering state is used as the appearance measurement of tight integrated navigation system The calculation of the observability of the tight navigation system.Thirdly,based on the calculation of observability,a tightly coupled navigation system which weighs the estimated value of Kalman filter is proposed.And a fast satellite selection algorithm for GPS/BDS dual system is designed using the information of the position and speed of SINS.The performance of the designed system is tested with the flight simulation data generated by the satellite signal simulator.It is verified that the accuracy of location,speed and attitude is much better than that of the traditional tightly coupled navigation system.Finally,in order to further validate the effectiveness and practicability of tightly coupled navigation system structures based on observanle degree calculations.On the basis of completing the error analysis and error modeling to MEMS Inertial Measurement Unit(MEMS-IMU)devices and level arm effect,set up the tightly coupled navigation system data acquisition platform.The semi-physical simulation results of the vehicle data show that the accuracy of this paper proposed scheme in positioning,fixed speed and attitude setting are superior to the traditional tightly coupled navigation system.The accuracy of position and velocity both improve more than 10%.The accuracy of attitude improve more than 7%.