The Research Of The Wireless Vehicle Detection System

Nowadays,many factors have led to transport congestion,such as the rapid development of automobile industry,accelerated urbanization,rapidly population growth.To relive the traffic pressure,the measure of increasing road capacity is adopted.But it is still cannot meet the demand of people's travel.With the development of sensor technology,communications technology and other new technology,intelligent transportation system is coming.As a fundamental part of intelligent transportation systems,Vehicle Detection System can get traffic information through analyzing the data of vehicles magnetic field.So that people can easily determine travel arrangements to ease traffic congestion and reduce air pollution.As a bipolar ferromagnetic substance,the move of vehicle will disturb the magnetic field of earth.And this disturbance can be detected by the magnetoresistive sensor which has a special internal design.According to these two points,a Wireless Sensor Network built by magnetoresistive sensor nodes can realize the collection,processing and transmission of the magnetic field data.In this paper,a wireless vehicle detection system consists of ZigBee wireless sensor technology and Honeywell magnetoresistive sensors,extracting the vehicle traffic information such as the traffic flow and the speed of a motor vehicle.In the system,the magnetoresistive sensor detects the fluctuation of the magnetic field signal caused by the moving vehicle,the only coordinator and multiple terminals nodes that have detection ability compose the wireless network to communicate the data.The main research contents in this paper are as follows:1.The overall design of the vehicle wireless detection systemThrough the depth study of short-range wireless sensor networks –ZigBee and the analysis the network reference model and protocol architecture,the network communication model of the system is initially established.At the same time,the wording principle of magnetoresistive sensor is researched in vehicle detection field.Combined these two parts,the overall architecture of the wireless vehicle detection system is proposed.2.The hardware design of the vehicle wireless detection systemOn the basis of analyzing the hardware of the system nodes,the hardware circuit of the vehicle wireless detection system is designed.The digital magnetoresistive sensor HMC5883 L which has high integration is chosen as the sensing chip.It can measure X,Y,Z axis magnetic data at the same time and output them with digital signal,which reduce the he signal processing circuit.CC2530 is selected as the hardware support to ZigBee.It integrates a radio frequency chip and a micro processing unit and has a simple peripheral circuit,which provides conditions for the system low-power design.3.The software design of the vehicle wireless detection systemThe ZStack protocol stack is analyzed and the networking of the nodes of star network is designed in this part.Meanwhile,magnetoresistive sensor-driven program is embedded tocollect and transmit magnetic field data.Thought calculating and analyzing the magnetic field data with an improved multi-state machine detection algorithm and a Two-node speed detection algorithm,the vehicle data is come out and displayed by PC software written in C++.The test result shows that this system has a strong ZigBee wireless communication quality and a high accuracy of detection algorithm.At the same time,it has advantages of small size,low power consumption,easy installation,which makes it suitable for vehicle detection.