Research On Positioning Of BD-2/GPS Integrated Navigation Based On School Bus Safety Service System

In recent years, the school bus accidents continue to occur which the mainly reason is thecollision, rollover and overload. The school bus safety service platform based on the BD-2/GP-S integrated navigation system reduces the number of primary and secondary school studentscasualties caused by the school bus accidents. This platform can be achieved on the school buspositioning and real-time running status monitoring and management, but the positioning datais easily affected by external environment, which deteriorates the positioning accuracy, unableto accurately locate the position of the bus. Aimed at the school bus safety service system to improve the method of BD-2/GPS integrated navigation system positioning precision, the maincontributions of the paper include:First of all, the paper analyzes the BD-2and GPS positioning feasibility ans advantages.Secondly, the calculation method of BD-2and GPS satellite position and velocity are given.Then, introduces two different time-systems of BD-2and GPS, and through analysis andcomparison, the conversion formula between the two time-systems is given. Meanwhile, westudy the basic methods and mathematical modela of the conversion between CGS2000ofBD-2and WGS-84of GPS coorfinate. Finally, we establish a mathematical model ofBD-2/GPS integrated navigation based on pseudo-range and pseudo-range rate, and integratednavigation positioning performance is evaluated.For the characteristics of non-linear observation model based on pseudo-range andpseudo-range rate, the basic theory of kalman filter is further studied, then analyzes twoalgorithms that are widely used in nonlinear filtering methods, which are extended Kalmanfilter (EKF) and unscented Kalman filter (UKF). Then EKF and UKF algorithms are appliedto the BD-2/GPS integrated navigation system, simulation results show that UKF algorithm ismore superiority than EKF algorithm.A robust UKF algorithm based on the robust estimation theory is researched aimed at thegross errors of integrated navigation observations. The robust UKF filter is used in the data processing of BD-2/GPS integrated navigation system, compared with the standard UKFfiltering algorithm, results show that the robust UKF algorithm can reduce the effect of theobservations gross error to the navigation system precision.An adaptive-robust UKF filtering based on the robust Helmert variance componentestimation is proposed. This new algorithm is mainly used to solve the error problem causedby observation gross error and the model error. The gain matrix is adjusted of the robust UKFaccording to adaptive factor which designed by the ratio between the observation variancecomponents and the state variance components, and then this algorithm is used for navigationcalculation in BD-2/GPS integrated navigation data. The results show that the adaptive robustUKF algorithm can effectively weaken the influence of observation gross error and dynamicmodel precision influence factors to the precision of the navigation system, so that theintegrated navigation system can be used in harsh navigation environment.