Design Of Traffic Flow Information Collection Unit

Transportation is the basic industry for economic and social development, efficient transportation system is an important guarantee for sustainable economic development. Since the reform and opening up, China's rapid economic development, improving people's lives, the large increase in private car ownership, the growing traffic demand and traffic conditions existing contradictions more evident, many of the large and medium cities in the traffic jam phenomenon have impact on people's quality of life, restrict the further development of the economy. In the existing hardware in the same conditions, to solve the traffic congestion and effective way line on the implementation of intelligent traffic control (intelligent transportation). The basic idea of intelligent transportation is that gathering the real-time traffic information, processing, analysis, access to traffic flow information in the distribution of the road network, and then under the theory of transportion to make decision, so traffic can be effectively induced to avoid traffic congestion, improve traffic efficiency. Get real-time, comprehensive, and accurate traffic flow information is the basis for development of transport strategy, and therefore become very important. IR section traffic flow information gathering method is an effective method of obtaining traffic flow information. This method is the use of active infrared sensor infrared light emitted radiation road network in the tested area, when vehicles pass by the infrared light reflected back to detector, the processor analyzes the signal processing to obtain traffic flow information. This method can measure the traffic flow, speed, Drive share, with gathering speed, high precision, small-interference characteristics. As the traffic flow information with real-time, stochastic characteristics , basic traffic flow information is sometimes not necessarily an objective response to detecting that the traffic flow characteristics, therefore, this design is the introduction of an exponential smoothing traffic flow algorithm . The basic idea is that the real-time traffic flow information and historical traffic flow information links, forecasting future traffic flow information.Exponential smoothing algorithm assumptions that traffic flow information has certain rules on the timing , test data not only reflect this law, and responsive random. It is using time to set the right value to the weighted average, more distant time impact on the predictive value more smaller, more closer more greater the impact on the forecast, so the forward weighting coefficients become smaller and smaller over time, weighting coefficients'value is very crucial, it is directly related to the accuracy of forecasts, which follow the selection of error approach can be continuously adjusted. Forecasting traffic flow information is very meaningful, because intelligent control of traffic need ahead of the current traffic conditions, otherwise it is meaningless. The predicted traffic flow information can be used to guide the formulation of transport strategy, simply means that you can directly control the operation of traffic signals, improving the access road junctions, reduced the incidence of traffic congestion.Traffic information gather unit is a traffic information collection, traffic information transmission , traffic signal control system as one of the embedded small. Acquisition module is used infrared active infrared sensor module YCJKYS-H, which has induced sensitive,far sensing range , higher output voltage and so on. As the traffic flow information gather require high timeliness , some choose are the ARM7 LPC2131 as processor, its kernel use von Neumann architecture, data and instructions use the same bus, the kernel has a 3-stage pipeline, the implementation of ARMv4 instruction set. It clocked up to 60MHz, meeting the design requirements.Traffic information gather unit is the smallest unit of intelligent traffic control, it can be communication with other units using the bus to achieve the purposes of sharing information. Comprehensive comparison of the various field bus, the design selected CAN Bus, CAN is an effective support of distributed control or real time control serial communication network, comparison with other field bus, with high communication rate, long communication distance, easy to implement, high reliability and high cost performance , CAN Bus is an international standard of fieldbus. CAN network can accommodate up to 110 nodes, each node with a unique identifier symbol, greatly increase the cell number of nodes. In addition there is a strong fault-tolerant CAN bus system, there are five methods to check the wrong , and the CAN node in case of serious errors will auto shut down output in order to make the operation of other nodes on the bus without affect, greatly increase the system reliability.Since wireless networks in the country's rapid development in recent years,its coverage and transmission rate increasing,people more and more used it to transmit data. The design reserved RS232, USB and other interfaces for external wireless devices to transport traffic flow data to the traffic control center, which is also the design needs to continue research.