Vehicular node positioning needs to be quick and precise on highway for safety considera-tion.In this paper,we present a novel and practical vehicular node positioning method which can achieve a higher accuracy and mo...Vehicular node positioning needs to be quick and precise on highway for safety considera-tion.In this paper,we present a novel and practical vehicular node positioning method which can achieve a higher accuracy and more reliability than the existing global-positioning-system-based po-sitioning solutions by making use of Doppler-shifted frequency measurements taken by vehicular node itself.This positioning method uses infrastructure nodes which are placed on the roadside every several kilometers as radiation sources to estimate the relative distances of vehicle to the infrastructure node.Through coordinate conversion,we get the absolute coordinates of vehicular node based on known absolute coordinates of infrastructure node.We also analyze the optimal distance of neighbor infra-structure nodes in order to ensure a high accuracy.In addition,simulation results demonstrate that the accuracy of our method with Extended Kalman Filtering(EKF) is superior to the method without EKF.展开更多
主要研究了保罗离子阱中被囚禁离子二阶多普勒频移(The Second-order Doppler Frequency Shift,SODFS)的评估。保罗阱中离子的运动由宏运动、微运动和额外微运动三部分组成。目前,关于离子额外微运动的研究较少,文中对此进行了详细研究...主要研究了保罗离子阱中被囚禁离子二阶多普勒频移(The Second-order Doppler Frequency Shift,SODFS)的评估。保罗阱中离子的运动由宏运动、微运动和额外微运动三部分组成。目前,关于离子额外微运动的研究较少,文中对此进行了详细研究。基于离子密度在径向均匀分布的假设,文中提出了一种用于评估阱中温度低于100 mK离子系综的二阶多普勒频移的模型。该模型考虑了离子三种运动对二阶多普勒频移的贡献。通过实验以及分子动力学仿真,验证了模型的有效性。文中提出的模型能用于评估保罗阱中被囚禁离子的二阶多普勒频移,适用于离子光钟、离子微波钟,尤其适用于基于大离子云的激光冷却离子微波钟。展开更多
The existing research results show that a fixed single station must conduct three consecutive frequency shift measurements and obtain the target’s moving speed by constructing two frequency difference equations. This...The existing research results show that a fixed single station must conduct three consecutive frequency shift measurements and obtain the target’s moving speed by constructing two frequency difference equations. This article proposes a new method that requires only two consecutive measurements. While using the azimuth measurement to obtain the angular difference between two radial distances, it also conducts two consecutive Doppler frequency shift measurements at the same target azimuth. On the basis of this measurement, a frequency difference equation is first constructed and solved jointly with the Doppler frequency shift equation. By eliminating the velocity variable and using the measured angular difference to obtain the target’s lead angle, the target’s velocity can be solved by using the Doppler frequency shift equation again. The new method avoids the condition that the target must move equidistantly, which not only provides an achievable method for engineering applications but also lays a good foundation for further exploring the use of steady-state signals to achieve passive positioning.展开更多
基金Supported by the National Grand Fundamental Research Program of China (973 Program, No.2007CB310606)The National High Technology Research and Development Program of China (863 Program, No.2008AA01Z205)China Postdoctoral Science Foundation funded project
文摘Vehicular node positioning needs to be quick and precise on highway for safety considera-tion.In this paper,we present a novel and practical vehicular node positioning method which can achieve a higher accuracy and more reliability than the existing global-positioning-system-based po-sitioning solutions by making use of Doppler-shifted frequency measurements taken by vehicular node itself.This positioning method uses infrastructure nodes which are placed on the roadside every several kilometers as radiation sources to estimate the relative distances of vehicle to the infrastructure node.Through coordinate conversion,we get the absolute coordinates of vehicular node based on known absolute coordinates of infrastructure node.We also analyze the optimal distance of neighbor infra-structure nodes in order to ensure a high accuracy.In addition,simulation results demonstrate that the accuracy of our method with Extended Kalman Filtering(EKF) is superior to the method without EKF.
文摘The existing research results show that a fixed single station must conduct three consecutive frequency shift measurements and obtain the target’s moving speed by constructing two frequency difference equations. This article proposes a new method that requires only two consecutive measurements. While using the azimuth measurement to obtain the angular difference between two radial distances, it also conducts two consecutive Doppler frequency shift measurements at the same target azimuth. On the basis of this measurement, a frequency difference equation is first constructed and solved jointly with the Doppler frequency shift equation. By eliminating the velocity variable and using the measured angular difference to obtain the target’s lead angle, the target’s velocity can be solved by using the Doppler frequency shift equation again. The new method avoids the condition that the target must move equidistantly, which not only provides an achievable method for engineering applications but also lays a good foundation for further exploring the use of steady-state signals to achieve passive positioning.
