基于相位法RFID的车辆定位研究

发布时间：2019-04-01 23:26

【摘要】：近年来,随着世界范围内车辆保有量的不断增加,建立集车辆定位与管理于一体的智能交通系统成为了人们的共识。全球定位系统(GPS)、图像法、航位推算法等传统的车辆定位与信息采集技术,在应用场景、系统复杂度、工程造价以及定位精度方面各有其局限性,而射频识别(RFID)技术以其价格低廉、精度高、自动识别等优势受到青睐。此外,RFID技术可以与现有的交通基础设施相结合,形成综合管理与定位的系统整体,因此,高精度的RFID定位在车辆定位系统中有着良好的应用前景。本文采用基于相位法的RFID定位技术,介绍了RFID车辆定位系统基本构成,说明了相位法下定位系统的工作频率与信号形式的设计。在此基础上,采用带通采样与零中频两种方式处理接收端信号以提取信号相位,并在定位仿真中引入了反射路径,提出了多标签法来提高车道判别的正确率。在非视距(NLOS)环境中,射频信号在阅读器与标签之间的传播距离大于二者间实际距离,影响了定位精度。本文针对这一问题提出了一种基于凸优化和距离逆补偿的定位算法,该算法首先将定位问题转换为一个含有众多约束条件的优化问题,再将该优化问题做Lagrange对偶以符合凸优化条件,则对偶方程的最优解即为原定位问题的解。然后利用逆补偿值对定位解进行修正,采用迭代计算减小NLOS对测距误差的影响,进一步优化定位解。仿真结果表明,基于全相位算法提取相位的RFID定位系统可以完成车辆定位与车道判别;基于凸优化和距离逆补偿的定位算法使NLOS环境下的定位精度得到了有效提升。
[Abstract]:In recent years, with the increasing of vehicle ownership in the world, it has become a common understanding to establish an intelligent transportation system that integrates vehicle positioning and management. The traditional vehicle positioning and information acquisition techniques, such as GPS (GPS), image method, flight location estimation method and so on, have their limitations in application scene, system complexity, engineering cost and positioning accuracy. Radio frequency identification (RFID) technology is favored because of its low price, high precision, automatic identification and other advantages. In addition, RFID technology can be combined with the existing traffic infrastructure to form a comprehensive management and positioning system. Therefore, high-precision RFID positioning has a good application prospect in vehicle positioning system. In this paper, the RFID positioning technology based on the phase method is used to introduce the basic structure of the RFID vehicle positioning system, and the design of the working frequency and signal form of the positioning system based on the phase method is explained. On the basis of this, the receiver signal is processed by band-pass sampling and zero intermediate frequency to extract the phase of the signal. The reflection path is introduced in the localization simulation, and the multi-label method is proposed to improve the correct rate of lane discrimination. In the non-line-of-sight (NLOS) environment, the spread distance of RF signal between reader and tag is greater than the actual distance between the reader and tag, which affects the positioning accuracy. In this paper, a localization algorithm based on convex optimization and distance inverse compensation is proposed. Firstly, the localization problem is transformed into an optimization problem with many constraints. In order to satisfy the convex optimization condition, the optimal solution of the dual equation is the solution of the original positioning problem by using the Lagrange duality to satisfy the convex optimization condition. Then the inverse compensation value is used to modify the location solution, and the iterative calculation is used to reduce the influence of NLOS on the ranging error, and the location solution is further optimized. The simulation results show that the RFID positioning system based on all-phase algorithm can complete vehicle positioning and lane discrimination, and the positioning accuracy in NLOS environment is improved effectively by the convex optimization and distance inverse compensation algorithm.
【学位授予单位】：天津大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：U495;TP391.44

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