Research Of The Highway Speed Limit System Based On ZigBee

Statistics shows that speed-exceeding is the main cause of traffic accidents. Countries all over the world have all made laws to ban on speed-exceeding. Also, along the highway, domestic and international traffic laws are numerous warning signs to remind drivers of keeping their speed right. However, road condition can be complex and volatile, it is difficult for drivers to make their vehicles under well control at all time. In recent years, especially, air pollution has greatly reduced air transparency and contributed to traffic accidents. With the rapid development and wide application of the Internet of Things, the situation now really has a big change.Thanks to these innovative technologies, this paper has designed a highway speed-limit system based on the Zig Bee and embedded technology, aiming at automatically controlling the vehicle speed by the command of speed-limit signal under bad weather conditions. As a consequence, the system operators can get the latest weather information via the wireless sensor network and make rightful decisions to ensure driving security, Motorway speed limit system can effectively reduce vehicle traffic accidents caused by speeding, protecting the highway traffic safety.In addition, this paper studied and analyzed the localization algorithm, and proposed an improved weighted centroid localization algorithm.The main work of this paper can be summarized as follows:(1)A Mesh-Shaped Zig Bee wireless sensors network has been set up as the backbone of the system: A Zig Bee network coordinator initializes a Zig Bee network, chooses an available radio channel and then waits for router nodes and endpoint nodes to join in to eventually form a complete Zig Bee network. Endpoint nodes along the highway sample the highway ambient climate information and deliver to the control center by the relay of the routers and coordinator.(2)Design the speed-limit system with the technology of Zig Bee, transducer and ARM embedded system. The Zig Bee network is powered by CC2431 Zig Bee chips. The wireless sensor network(WSN) detects real-time highway climate information, for example, temperature and humidity. And the embedded system implements the automatic speed-limit function. The software system for the Zig Bee network and control center is developed with C and Visual Basic respectively.(3)The positioning function is natively provided by CC2431 chip, using the sensor network and the combination of the RSSI value and advanced centroid algorithm. For a better accuracy, the paper has introduced real-time environment factor into the gauging of RSSI, furthermore, computer simulation has proven the efficacy of such enhancement.System simulation shows that, the bidirectional communication network has been implemented. The ambient climate information can be delivered to the control center, simultaneously, the speed controller can receive speed-limit signal from the control center. The system can efficiently reduce the risk of traffic accident under tough weather condition. Additionally, the application of advanced centroid algorithm also has enhanced positioning accuracy.