Research And Development Of Real Time Traffic Flow Unit At Intelligent Traffic Crossing

Intelligent transport system (ITS) is a principal researching direction that aims at makingthe road transit safe, convenient and environmental friendly. So the studying of roadinformation abstracting unit, as a fundamental part of the ITS, is of great significance. Averagespeed and length of the car are two main parameters among them. This paper aims at describingthe realization and function of this real-time traffic flow monitoring system at intelligent trafficcrossing. In this design, a real-time monitoring system is consisted of four road informationabstracting units at each entrance of a traffic crossing and a data processing and transmissionmodule by the side of the road. It bases on the cross-correlation algorithm, which realizesthe function of extracting the average speed and length of vehicles passing by.Through signal analysis, a conclusion can be drawn that the correlation coefficient is relatedto the delay of signals. So this system is different from traditional road information gatheringunit. With the adaptation of cross-correlation algorithm into information gathering, appropriatesensors are available under different circumstances. On the basis of characteristics andparameters of moving cars, the system is designed to implant a set of sensors at each ofthe four entrances of the traffic crossing so that the road information is converted to electricsignals. The electric signals are sent into the MCU to do the data processing. And the roadinformation could be obtained in a reliable and intuitive way.This design uses ARM11as the data processing and transmission module out of theconsideration of its functional realization and reliability in engineering. Since the signalscoming out from the sensors are analog ones, and the MCU is well capable of digital signalcalculating, there should be one step that changes the analog signals to digital signals. ARM11has eight10-bit ADC on chip which perfectly meets the needs of analog-to-digital-convertingof totally eight groups of signals drawn by sensors in four lanes at a crossroad. Besides,the electric signals that extracted by the sensors are capacitance signals that can’t be sentinto ADC of ARM11. There should be a series of conversion. So the adapting circuitriesare brought into the system. The capacitance-to-voltage converting IC (integrated circuit)CAV444and voltage-to-current converting IC AM402, accompanied by their peripheral circuitsmake the signal transmitted in form of electric current, which can be transmitted in a long distance with no power attenuation. What is more the layout of the design can be free fromthe limitation of the actual situation of the crossroad.The article is structured after having a comprehensive knowledge of the system. This designsuccessfully fulfills the hardware circuit design, structure of the host computer platform,interface driving, process designing and debugging, and program downloading and solidifyingon the target board based on the algorithm credibility analysis, and reached the final goalI anticipated.