Research,Design And Implementation Of Tunnel Multi-vehicle Positioning System

High-precision positioning of vehicles is an important issue to be solved in traffic tunnels where no GPS or GPS signals are weak.At present,vehicle-mounted video system and microwave radar system may encounter problems caused by weak light,blurred vision,and strong radar reflection.The inertial navigation system and laser radar are subject to cost and cumulative error in integrated navigation and positioning,that is,GPS is required to correct or provide initial reference position for auxiliary positioning.It becomes more and more urgent to solve the problem when ADAS or driverless cars goes into application gradually and has great research significance.This paper proposes a tunnel positioning system based on UWB,which acts as a “tunnel GPS” and seamlessly switches with the vehicle-mounted GPS signal to provide accurate and continuous positioning for the vehicle.However,when using UWB positioning for tunnel vehicle positioning,not only the system positioning accuracy,stability and coverage are to be ensured,but also the real-time problem from the slow moving indoor positioning application to the fast-moving vehicle positioning.That the system capacity may be seriously reduced due to the demand for high positioning refresh rate.In response to the above questions,the main work of this paper is as follows:(1)Design and implement the UWB positioning hardware terminal based on DW1000 chip for tunnel driving scenario,including fixed base station and vehicle tag,involving terminal layout,high frequency circuit design,chip selection,PCB drawing and final debugging.It is proposed to use the two-way ranging TW-TOF algorithm to develop a matching lower computer positioning program.At the same time,the PC-side host computer graphical interface and the implementation of the LwIP protocol for communication are developed.(2)In order to ensure the reliability of communication,the system adopts the TDMA mechanism.Faced with the high-speed vehicle positioning,the coexistence problems of update rate and system capacity of positioning system.In this paper,the improved Kalman model is used to realize error elimination and trajectory prediction at the same time,so as to realize real-time positioning and the larger system capacity.The effects of velocity,acceleration and curvature radius of curvature on the modified Kalman model are studied respectively.(3)Based on the centimeter-level positioning accuracy of UWB positioning system,this paper proposes an accident detection method based on displacement variation and velocity variation.