A Study On The City Traffic Flow Detection Techniques And Applications

As a key role in ITS (Intelligent Transportation System), the highway traffic flow detection system is becoming the hot spot in researches and development of various countries day by day. This thesis conducted the research to the urban intelligence transportation detection technology, designed a highway traffic flow detection system based on earth magnetism coil and emphatically studied the designing and the realization of the two subsystems of ITS:traffic flow data collection&detection subsystem and traffic flow data communications subsystem. The thesis also developed a client side procedure to apply the whole set system to the actual project. The major tasks in this thesis are as follows.(1) This thesis has first analyzed the municipal transportation flow characteristic, which discussed the relations of the basic parameters, analyzed the municipal transportation characteristic in the understanding of flow main parameters, established the traffic flow the separate probability mathematical model and the continual probability mathematical model and laid the rationale for the following research. Then the thesis has carried on the discussion to some related traffic flow magnitude detection technologies, and mainly discussed the method of ring-like detection coil which detected four parameters in application.(2) Based on this, this thesis discussed the traffic flow data detection subsystem and the communication subsystem’s designing. The thesis first described the working principle and the working process of ultrasonic sensors, and then focused on the designing of vehicle type judging algorithm based on the use of ultrasonic sensors. The system completed vehicle speed computing, vehicle distance calculation, identification of various anomalies, as well as the communication with upper system. The detection subsystem can detect seven kinds of vehicle (29types in all). It is the key module of the road traffic flow detection system, which can get real-time traffic information of traffic, collect and analyze important traffic data and judge the type of vehicle and so on.(3) Then, the thesis discussed the principle of communication subsystem designing, elaborated the communication subsystem with up and down the both sides procedure’s correspondence mechanism and the communication protocol, and has given the main correspondence data packet form. The communication board is designed to receive real-time vehicle information from detection boards, collect information of numbers and average speed of various vehicle, send real-time traffic data to TCP ports of Data Service Center (DSC). Furthermore, communication soft can answer commands from DSC to set its running parameters, examine the state of network and reconnect DSC when the network is broken. Finally, the thesis introduced how to develop the detection subsystem in Keil environment.(4) We tested this traffic flow detection system in Shanghai and Wuhan. Testing results show that the system could get accurate information of traffic flow, types and speed of vehicles, and lane occupancy. Then we can develop the client side statistics module with the detection subsystem and the communication subsystem, and apply to the actual traffic flow detection project.