With the increasing number of urban motor vehicles, the traditional traffic signal control mode uses timing control. Since the traffic flow is changing at any time, when no car passes, the opposite car has to wait for the green light in this direction to end. It shows that the red light can pass, and the strain performance in time and space is poor, which not only wastes time, but also aggravates traffic congestion to a certain extent. In order to overcome the phenomenon that the car-free traffic at the green road of the vehicle-less intersection or the green light-passing time of the multi-vehicle intersection is short and the traffic is jammed, this paper designs the corresponding control algorithm according to the vehicle-mounted electronic license plate to detect the traffic flow in each section, and achieves intelligent control. the goal of.
1. Electronic license plate technologyThe electronic license plate is a license plate information storage method based on the passive RFID technology of the 900MHz frequency band. The license plate is different from the traditional physical license plate and is generally made into a card shape. It is fixed on the metal license plate by ceramic anti-disassembly technology or pasted on the front windshield. Directly above the glass, the uniqueness of the electronic license plate installation is guaranteed. The electronic license plate is composed of an internal memory chip, a microstrip antenna and an anti-disassembly device, and has the advantages of high sensitivity, fast reading and writing speed, high label reflectance, and can be read in a high-speed motion state. The electronic license plate writes basic information of the vehicle in advance through the card issuing management system, such as the vehicle ID number, license plate number, driver information, vehicle type, vehicle weight and the like. Through data encryption design in RFID hardware design and software, the electronic license plate after data encryption cannot be copied, and each vehicle is equipped with only one electronic license plate. At this time, the vehicle has a unique ID card.
2. Intelligent traffic signal control system structureFixed electronic license plate monitoring base stations and supporting traffic signal control systems are installed in various urban trunk roads, crossroads and bayonet. The monitoring base station is composed of an electronic license plate reader, a reader antenna, a data processing system, and a data transmission system. The monitoring base station is connected to the data center through a communication line, and the vehicle information can be obtained in real time. The RF reader reads the encrypted vehicle information in the electronic license plate, and after decryption by the monitoring base station, obtains basic information such as the electronic license plate number. The traffic signal controller determines the real-time traffic condition according to the license plate information acquired by the license plate monitoring base station, and controls the state of the traffic light. The structure of the intelligent traffic light control system is shown in Figure 1.
Figure 1 Intelligent Traffic Light Control System
3. Traffic control model and program 3.1. Control model establishmentThe key to intelligent control of traffic lights based on real-time traffic flow is the establishment of a control model for traffic flow.
In order to ensure the traffic efficiency of the vehicle, it is necessary to obtain the number of vehicles to be trafficted within a range of 1 meter before the traffic signal section in real time. The traffic flow data model in the road section is shown in Fig. 2.
Figure 2 Vehicle flow detection and control model
It is assumed that the number of vehicles in the road section is i+1, the traveling speed is vm/s, and the position of the vehicle in the road section is: xi=lâ‹…u, where u is a random number uniformly distributed in the interval [0, 1]. The estimated time for the vehicle to pass normally is:
Traffic signal control involves urban main roads and sidewalks, intersection priority access decisions and release time calculations.
(1) Main roads. The traffic light control mode of the main road is the priority of the vehicle. The transit time is determined by the specific traffic flow. The vehicle traffic is turned into pedestrian traffic, and the pedestrian transit time is fixed. If a special vehicle passes during this time period, it will be directly released. The specific control program flow is shown in Figure 3.
Figure 3 Main road traffic light control process
(2) Crossroads. The traffic conditions at intersections are relatively complicated. The priority of lane traffic can be judged by the traffic flow of each lane. If there is a special vehicle, priority will be given. The specific control program flow is shown in Figure 4.
Figure 4 Traffic light control process at the intersection
4, the conclusionThe increase of private vehicles and the traditional traffic signal control method are the main causes of urban road traffic congestion. By collecting electronic license plate information to calculate real-time traffic flow, the traffic priority is determined according to the traffic flow of special vehicles and lanes, so as to realize the intelligent control of traffic lights. . The system will effectively alleviate traffic congestion, reduce the frequency of traffic police command, and improve the informationization and intelligence level of traffic control.
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