Research And Design Of Wireless Vehicle Detection System Based On Magnetic Sensor

Intelligent transportation system is the most effective method to improve transport efficiency and reduce urban traffic congestion. However, as a front-end that obtaining traffic parameters, the vehicle detection system provides the immediate and effective parameter for the scientific controlling on intelligent transportation system, is a key technology in the process of developing the intelligent transportation system. It is necessary to research a wireless vehicle detector with easy installation, high precision and low cost to replace the traditional detector, since the traditional detector is not propitious to a widely application for intelligent transportation system as its low accuracy, inconvenience of wiring and high cost.The vehicle detection technology based on magnetoresistive sensor has an obvious advantage on the networking, cost, accuracy and the condition of use by further analyzing and comparing all kinds of vehicle detection technologies. However, magnetoresistive vehicle detection technology is still in the stage of researching and not applied widely. It is significative that developing the wireless intelligent transportation system based on the magnetoresistive sensor to promote the research on the vehicle detection technology. Specifically, the following is the mainly contents of this paper:Firstly, the absolute advantage and feasibility of vehicle detection technology based on magnetoresistance is obtained via analyzing urban traffic situation and comparing the advantages and disadvantages of all kinds of vehicle detection technology, and, the magnetoresistive effect, principle of magnetoresistive vehicle detection, ZigBee wireless transmission, GPRS communications and software / hardware anti-interference technology related are research deeply and elaborated.Secondly, the overall scheme of wireless vehicle detection system based on magnetoresistive sensor is determined via analyzing the overall requirements of system, and the circuit design with detection node, upper end node, coprocessor and wireless transceiver module based on the principle of low power consumption, low cost, high accuracy and anti-interference are completedThirdly, an algorithm of self-adaptive threshold finite state machine is proposed based on temperature compensated according to the characteristics of magnetoresistive sensor output signal and major factors else affecting the measurement accuracy, could detect whether a vehicle is exist or not, and, real-time online update of benchmarks and thresholds realized is realized, avoiding the problem of system detection accuracy declining caused by temperature drift, and the speed measurement algorithm of position machine based on dual sensor, which can complete accurate detection of speed without time synchronization is studied, include exploratory research on traffic parameters, such as time occupancy ratio and vehicle classification.Fourthly, the vehicle detection system on traffic route was installed to test the appropriate working condition for the system, and the real-time detection of traffic parameters including traffic flow, speed, time occupancy ratio and vehicle classification are completed. The result showed that the detection accuracy of the system is very high, which reached the target basically, could be applied to intelligent transportation system and had a good application prospect.