Traffic Flow Signal Sensing Based On LED Street Lights

With the concept of smart city,the modernization of the city is getting faster and faster.Nowadays,with the development of urban construction,the problem of traffic congestion has become an important issue that restricts urban development.As a new emerging sensing technology in recent years,visible light sensing has the advantages of good confidentiality,low cost and fast response.It has broad application prospects in traffic flow detection.In this paper,the research on the performance of the light-emitting diode(LED)and its equivalent circuit model in photovoltaic mode is carried out.Based on this research,the design of the all-passive traffic flow detection system with visible light sensing is proposed and demonstrated.The scheme uses sunlight as the light source,uses the LED as a light detector,and utilizes the photoelectric effect of the LED module in the street light to realize the perception of the traffic flow signal.Due to the reflection of sunlight on the outer surface of the vehicle,the vehicle in the area below the LED street lamp changes the light intensity reaching the LED module,thereby induces the low frequency optoelectric signal response of the LED module.Furthermore,traffic flow is detected by collecting and detecting characteristics of the response signal.In order to maximize the perceived performance of LED street light,we investi-gate the equivalent circuit model of LED in photovoltaic mode both from the physical mechanism and experimental aspects of LED,and propose an LED array structure op-timization scheme based on the model.Road traffic is a time-varying background environment.In order to extract traffic flow information from LED sensing signals in this scenario,we propose a traffic vector detection algorithm based on Support Vector Machine(SVM).The algorithm can iden-tify the characteristic waveform of the vehicle when it passes under the LED street light from the perceived signal under different background light intensities,and calculate the traffic flow based on this.In order to make the LEDs more responsive to the perceived signals,we designed the array structure and optical antennas of the LED street light.In order to achieve long-term monitoring of AC traffic,we designed the system's drive circuit to enable it to upload the sensory signals to the cloud server through the wireless transmission terminal.Finally,a relatively complete traffic flow sensing experimental platform is built.The stability of the system was tested by the long-term signal moni-toring on the road and the accuracy of the algorithm was verified.