Introduction: application of wireless sensor networks in the traffic field

The previous article described the basic knowledge and application prospects of wireless sensor networks in detail, and learned its features and advantages. This article will introduce in detail the application of wireless sensor networks in traffic. I hope you can learn more about this.

Wireless sensor networks promote the development of smart traffic

The Application of Intelligent Transportation System (ITS) in urban traffic is mainly reflected in the microscopic traffic information collection, traffic control and guidance, improve the efficiency of the transportation system by improving the effective use and management of traffic information, it is mainly composed of subsystems such as information collection input, policy control, output execution, and data transmission and communication between subsystems. The information acquisition subsystem collects vehicle and road information through sensors, and the policy control subsystem collects vehicle and road information based on the set objectives (such as the maximum traffic volume or the minimum average waiting time) use the calculation method (such as fuzzy control and Genetic Algorithm) to calculate the optimal scheme, and output the control signal to the execution subsystem (usually the traffic signal controller) to guide and control the vehicle traffic, achieve the preset goal.

Wireless sensor networks are a new technology that integrates short-range wireless communication technology, micro-electronics sensors, and embedded systems. They are gradually used in intelligent traffic systems and other fields that require data collection and detection. Based on the IEEE 802.15.4 standard ZigBee technology, it has the following good features: ① low power consumption, two common No. 5 batteries can work on one node for 6 ~ 24 months; ② strong networking ability, a maximum of nodes can be reached on the network, and support tree, Star, mesh and other networking modes; ③ long transmission distance, outdoor transmission distance between two nodes can reach several hundred meters, and the transmission power can reach several thousands of meters. ④ high reliability, multi-level security mode; ⑤ low cost, open and simplified ZigBee protocol stack, works in the GHz licensed ISM band.

Wireless sensor networks have excellent characteristics and can provide an effective means for information collection of intelligent transportation systems. They can monitor vehicles in all directions at intersections. According to the monitoring results, simplified and improved signal control algorithms to improve traffic efficiency. Wireless sensor networks can be used in the control subsystem and guide subsystem of the execution subsystem. For example, this technology can be used to improve the signal controller to implement the bus priority function of the Intelligent public transit system.

Construction of wireless sensor networks for ITS

In the wireless sensor network structure, convergence nodes on both sides of the road are installed to form a self-organizing multi-hop Mesh infrastructure, A sensor terminal node dedicated for Traffic Information Collection communicates with each adjacent aggregation node in a star network, and the final data is aggregated to the gateway node. The gateway node can be installed as a module in the traffic signal controller at the intersection. The collected data is sent to the traffic control center through the signal controller's VPC for further processing.

In wireless sensor network deployment, aggregation nodes can be installed on roadside columns, horizontal bars, and other transportation facilities. The gateway node can be integrated with the traffic signal controller at the intersection, the End Node of the dedicated sensor can be landfilled under the road or installed on the roadside, and the moving vehicle on the road can also be installed with sensor nodes dynamically added to the sensor network.

Collect traffic information using wireless sensor networks

In traffic information collection, non-contact geomagnetic sensors can be used on the terminal node to regularly collect and perceive the vehicle speed and distance in the area. When a vehicle enters the monitoring range of the sensor, the terminal node uses a magnetic sensor to collect important information such as the driving speed of the vehicle, and transmits the information to the next node that is timed to wake up. When the next node senses the vehicle, the average speed of the vehicle can be estimated based on the vehicle travel time between the two sensor nodes. Multiple terminal nodes collect and preliminarily process the collected information to the gateway node through the aggregation node for data fusion to obtain information such as road traffic flow and vehicle exercise speed, this provides precise input information for traffic signal control at intersections. By installing various sensors such as temperature and humidity, illuminance, and gas detection on the terminal node, you can also detect road conditions, visibility, and vehicle exhaust pollution.

Application of wireless sensor networks in ITS

To implement the bus priority function in the intelligent bus system, the existing traffic signal controller must be transformed. By adding sensors and other auxiliary equipment, the traffic signal controller can estimate the time (travel time) for a bus to reach the intersection ), determine whether a vehicle needs to be given priority at the intersection (the number of passengers can be selected as the priority), and then select an appropriate priority control policy to adjust the green letter ratio to give priority to the vehicle. The transformation of the traffic signal controller includes:

◆ On-board wireless communication terminal node;
◆ Wireless gateway is integrated into the traffic signal controller at the intersection;
◆ Terminal nodes used for positioning public transit vehicles;
◆ The above functions can be achieved by constructing a ZigBee-based wireless sensor network.

When the intersection is approaching, the on-board ZigBee wireless terminal node broadcasts information about public transport vehicles. After the wireless sensor network deployed on the roadside obtains information, the terminal node of the public transport vehicle is tracked to obtain information and aggregated to the gateway node of the wireless sensor network. The final information is transmitted to the traffic signal controller through internal connections for priority processing.