| In recent years, with the number of vehicles increasing rapidly, it is particularly important to strengthen the management of vehicles driving in or out in residential areas, parking lots and other public areas. Traditional Parking Access Control Systems (PAC System) based on IC card or RFID technique are complex to setup, hard to use, and sometimes have the security issues of replacing or stealing cars. They are unable to meet the needs in some complicated application environment.A kind of PAC System based on Vehicle License Plate Recognition (VLPR) has been designed in this thesis, for the defects of traditional PAC System. In view of the system’s functional requirements, this thesis develops the software of data service center, center client and stations local system these three parts which have functions such as whitelist management, traffic record management, stations management, user management, emergency management and synchronization mechanism of distributed lsomcrization database between stations and service center. Considering the high eal-time performance demand of releasing cars through each station, a design for educing the latency of system response from vehicle detection to lane release are presented. This design mainly focuses on three aspects -- pre-process in camera, image transmission and later-process in industrial personnel computer and realizes a kind of block transmission method combined with image region extraction, to improve the efficiency of each processing part.Experimental results show that this PAC System based on VLPR is confirmed to have met the whole requirements. At the same time, the database synchronization for data backup ensures that system can switch to local operation under the condition of network failure normally. And this system has the very good response performance and a high real-time capability, that the average total time of image transmission and processing is about 136 milliseconds while at the same time ensuring the accuracy of VLPR. |
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