高动态GPS信号跟踪算法研究及实现
发布时间：2018-10-12 16:25
【摘要】：GPS (Global Positioning System)系统是使用最为广泛的导航定位系统,为军民领域的诸多方面提供服务。随着GPS技术的不断发展,高动态环境下GPS定位系统的应用也越来越重要,但由于在高动态环境中,GPS载波上会产生较大的多普勒频率,容易造成GPS信号跟踪失锁,无法稳定跟踪。为克服多普勒频率的影响,本文对高动态下GPS信号跟踪环路算法进行了研究,主要从以下几个方面进行研究:(1)分析载噪比对传统载波跟踪环路GPS信号跟踪结果的影响。通过调整载噪比的大小,找到锁相环和锁频环的最佳工作状态,载噪比越高,锁相环和锁频环的性能越好,但由于噪声带宽过高,噪声功率会增大,当超过载波跟踪环的承受能力时,会导致环路失锁。(2)将扩展卡尔曼滤波应用到载波跟踪环路中,将传统载波跟踪环路的滤波器和鉴别器替换为扩展卡尔曼滤波器,通过对高动态中的非线性函数进行泰勒展开式,并进行一阶线性化截断,将其余高阶项去除,从而将非线性问题转换成为线性问题,实现载波跟踪。(3)将无迹卡尔曼滤波应用到载波跟踪环路中,将传统载波跟踪环路的滤波器和鉴别器替换为无迹卡尔曼滤波器,以UT变换为基础,对高动态中非线性函数的概率密度分布进行近似,采用一系列的采样点来逼近状态的后验概率密度,最终实现载波跟踪。通过仿真结果可以得出,当载噪比比较低时,传统载波跟踪环路对多普勒频率的估计误差比较大,导致跟踪失锁,提高载噪比,传统载波跟踪环路对多普勒频率的估计误差有所改善,但是对多普勒频率的一阶导数和二阶导数估计误差比较大。在低载噪比的情况下,扩展卡尔曼跟踪环路和无迹卡尔曼跟踪环路在跟踪精度和动态应力方面都比传统跟踪环路的性能好,对多普勒频率及其一阶导数、二阶导数的估计误差减小,提高载噪比,扩展卡尔曼跟踪环路和无迹卡尔曼跟踪环路的跟踪精度有所提高,而且,在跟踪精度和收敛速度方面,UKF载波跟踪算法要比EKF载波跟踪算法的性能更好一些。
[Abstract]:GPS (Global Positioning System) system is the most widely used navigation and positioning system, which provides services for many aspects of military and civilian fields. With the development of GPS technology, the application of GPS positioning system in high dynamic environment is becoming more and more important. However, in the high dynamic environment, the large Doppler frequency will occur on the GPS carrier, which will easily lead to the GPS signal tracking lose lock and can not be tracked stably. In order to overcome the influence of Doppler frequency, this paper studies the algorithm of GPS signal tracking loop in high dynamic state, mainly from the following aspects: (1) the influence of carrier noise ratio on the GPS signal tracking results of traditional carrier tracking loop is analyzed. By adjusting the ratio of carrier to noise, the optimum working state of PLL and FLL is found. The higher the ratio of carrier to noise, the better the performance of PLL and FLOL, but the higher the noise bandwidth is, the greater the noise power will be. When the capacity of carrier tracking loop is exceeded, the loop will lose lock. (2) the extended Kalman filter is applied to the carrier tracking loop, and the filter and discriminator of the traditional carrier tracking loop are replaced by the extended Kalman filter. The nonlinear function in high dynamics is transformed into a linear problem by Taylor expansion and first order linearization truncation to remove the other higher order terms. (3) the unscented Kalman filter is applied to the carrier tracking loop, and the filter and discriminator of the traditional carrier tracking loop are replaced by the unscented Kalman filter, which is based on the UT transform. The probability density distribution of nonlinear function in high dynamic state is approximated, and a series of sampling points are used to approximate the posteriori probability density of the state. Finally, carrier tracking is realized. The simulation results show that when the carrier / noise ratio is low, the estimation error of Doppler frequency in the traditional carrier tracking loop is relatively large, which leads to the tracking loss and increases the carrier noise ratio. The traditional carrier tracking loop improves the Doppler frequency estimation error, but the first and second derivative estimation errors of the Doppler frequency are relatively large. In the case of low load to noise ratio, the performance of the extended Kalman tracking loop and the unscented Kalman tracking loop is better than that of the traditional tracking loop in terms of tracking accuracy and dynamic stress, and the Doppler frequency and its first derivative are obtained. The estimation error of the second derivative is reduced, the carrier noise ratio is increased, the tracking accuracy of the extended Kalman tracking loop and the unscented Kalman tracking loop is improved, and the tracking accuracy of the extended Kalman tracking loop and the unscented Kalman tracking loop are improved. In terms of tracking accuracy and convergence speed, the performance of UKF carrier tracking algorithm is better than that of EKF carrier tracking algorithm.
【学位授予单位】：西安理工大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：P228.4
本文编号：2266797
[Abstract]:GPS (Global Positioning System) system is the most widely used navigation and positioning system, which provides services for many aspects of military and civilian fields. With the development of GPS technology, the application of GPS positioning system in high dynamic environment is becoming more and more important. However, in the high dynamic environment, the large Doppler frequency will occur on the GPS carrier, which will easily lead to the GPS signal tracking lose lock and can not be tracked stably. In order to overcome the influence of Doppler frequency, this paper studies the algorithm of GPS signal tracking loop in high dynamic state, mainly from the following aspects: (1) the influence of carrier noise ratio on the GPS signal tracking results of traditional carrier tracking loop is analyzed. By adjusting the ratio of carrier to noise, the optimum working state of PLL and FLL is found. The higher the ratio of carrier to noise, the better the performance of PLL and FLOL, but the higher the noise bandwidth is, the greater the noise power will be. When the capacity of carrier tracking loop is exceeded, the loop will lose lock. (2) the extended Kalman filter is applied to the carrier tracking loop, and the filter and discriminator of the traditional carrier tracking loop are replaced by the extended Kalman filter. The nonlinear function in high dynamics is transformed into a linear problem by Taylor expansion and first order linearization truncation to remove the other higher order terms. (3) the unscented Kalman filter is applied to the carrier tracking loop, and the filter and discriminator of the traditional carrier tracking loop are replaced by the unscented Kalman filter, which is based on the UT transform. The probability density distribution of nonlinear function in high dynamic state is approximated, and a series of sampling points are used to approximate the posteriori probability density of the state. Finally, carrier tracking is realized. The simulation results show that when the carrier / noise ratio is low, the estimation error of Doppler frequency in the traditional carrier tracking loop is relatively large, which leads to the tracking loss and increases the carrier noise ratio. The traditional carrier tracking loop improves the Doppler frequency estimation error, but the first and second derivative estimation errors of the Doppler frequency are relatively large. In the case of low load to noise ratio, the performance of the extended Kalman tracking loop and the unscented Kalman tracking loop is better than that of the traditional tracking loop in terms of tracking accuracy and dynamic stress, and the Doppler frequency and its first derivative are obtained. The estimation error of the second derivative is reduced, the carrier noise ratio is increased, the tracking accuracy of the extended Kalman tracking loop and the unscented Kalman tracking loop is improved, and the tracking accuracy of the extended Kalman tracking loop and the unscented Kalman tracking loop are improved. In terms of tracking accuracy and convergence speed, the performance of UKF carrier tracking algorithm is better than that of EKF carrier tracking algorithm.
【学位授予单位】：西安理工大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：P228.4
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