Research And Design Of Bei Dou Positioning Terminal Based On FPGA

With the continuous progress of navigation and positioning technology,Bei Dou navigation satellites system(BDS)is widely used in vehicle navigation,tracking and monitoring,transportation and other fields.In order to meet people's demand for high-precision positioning,it is necessary to improve the positioning accuracy of BDS positioning algorithm.At present,the common positioning algorithm in BDS application is Extended Kalman Filter(EKF),but it has the problems that the measurement noise cannot be adjusted online according to the external changes,and the estimation of system noise and measurement noise is inaccurate.Therefore,this paper uses an intelligent calculation method to optimize EKF to improve BDS positioning accuracy,and designs BDS positioning terminal based on FPGA.The specific research contents are as follows:(1)This paper expounds the research background and significance of this paper,introduces the principle of BDS pseudo range positioning,and deduces the pseudo range positioning algorithm based on LS and EKF.Compared with LS,EKF can reduce the difficulty of positioning solution and the required storage space.Thus,the research content is determined and the EKF is intelligently optimized.(2)Aiming at the problem that EKF can not adjust the measurement noise in real time according to the external changes,an algorithm based on fuzzy control to optimize EKF is proposed.The algorithm calculates the matching factor through variance matching,then establishes Mamdani fuzzy inference system,and takes the matching factor as the system input to obtain the measurement noise adjustment factor.Finally,the adjustment factor is substituted into the EKF filter gain matrix to complete the correction of EKF measurement noise.Compared with EKF simulation,the proposed method effectively suppresses the filter divergence,and the positioning error value is lower than EKF algorithm,which effectively ameliorates the positioning precision of BDS.(3)Aiming at the inaccurate estimation of system noise and measurement noise in EKF,an algorithm based on Chaotic Particle Swarm Optimization EKF is proposed.The procedure determines whether the particle swarm optimization algorithm is in the premature convergence state through the fitness variance and the critical value of fitness variance.Then,according to the chaotic search mechanism,the chaotic variables are mapped to the optimized variable interval through the chaotic tent mapping function.The optimal value obtained by chaotic search is reflected in the original search interval and replaces the original particles.Continue the optimization process until the optimal solution is founded.At the same time,the optimal solution is assigned to the noise covariance matrix of EKF to obtain the accurate system state estimation.Compared with the traditional particle swarm optimization EKF algorithm,the proposed method has faster convergence speed and less positioning error.(4)The Bei Dou navigation and positioning terminal is designed with FPGA.Specifically,it includes main control module,clock module,fuzzy EKF module,chaotic particle swarm optimization EKF module,storage module,and interface module,etc.Firstly,the functions and logical interfaces of per module are described in depth,and the state transition diagram of the main control module is given.Secondly,each module is designed with Verilog language,and the conforming functional simulation verification is processed under Modelsim software.In this paper,chaotic particle swarm and fuzzy control optimization EKF algorithm are used to improve the positioning accuracy of BDS,and the Bei Dou Positioning Terminal is designed based on FPGA.The simulation results in Quartus II + Modelsim environment show that the designed terminal has good performance and can be widely used in navigation and positioning,aviation rescue,marine platform positioning and other fields.It not only provides a theoretical basis for the improvement of BDS positioning accuracy,but also provides a reference for the popularization and use of BDS positioning system.