Intelligent city has become the fourth wave after industrialization, informatization and electrification. The construction of intelligent city is the frontier trend of global urban development. Nowadays, many urban pipes for rainwater drainage are often blocked, which seriously affected drainage, resulting in frequent water accumulation on roads, so that it seriously affected people’s life and travel. In addition, the well cover is stolen and damaged from time to time in recent years, leading pedestrians sometimes to fall into the sewer. And too much traffic on the road also affects the traffic situation and people’s travel. So it is very necessary to carry out systematic management of all aspects of municipal problems. At the same time, in terms of technology development, with the progress of intelligent sensing technology of wireless sensor, the rapid development and deployment of NB-IOT mobile communication technology as well as the rapid popularization of broadband Internet, it also provides a solid technical foundation for the construction of “municipal management of intelligent city “.
1 System function
We build an intelligent municipal management platform for city managers, which can remotely monitor the status of well covers, traffic flow, pipeline blockage and other information, at the same time, which can timely alarm when problems occur and make more efficient solutions. The product can also complete all operations in a visual way.
2 Basic design ideas
2.1 Water flow condition monitoring
Each node uses the ultrasonic module to detect the height of water level, and compares the height of water level between the adjacent nodes, so as to judge whether the blockage occurs (if the water level difference between the adjacent nodes is large, it can be considered that the drainage pipeline between the two nodes is blocked, and the severity of the blockage can be roughly judged by the height difference). The schematic diagram of blockage detection is shown in Figure 1.
Collecting the information of water level at each moment is for forming the height curve of water level. When the height of water level increases too fast, the alarm is triggered.
The module is placed at the top of the culvert near the well to eliminate the influence of uneven ground. The principle of ultrasonic ranging is to measure the time it takes for the sound wave to reflect back from an obstacle after it is launched based on the known propagation speed of the ultrasonic wave in the air, and calculate the actual distance from the launching point to the obstacle according to the time difference between the launching and receiving. When the water level of adjacent nodes is different, it can be highlighted in the upper computer software, so as to solve the problem faster.
2.2 Well cover status detection
The gyroscope module is used to detect the change of the shaft cover angle, so as to judge whether the cover is loose or opened without any reason, so as to realize the function of anti-theft and detection of looseness.
MPU6050 has the function of angular acceleration and acceleration detection, and the precision is very high. It can detect micro changes of angle. Adopting I2C communication protocol is very easy to operate. Mpu6050 can be attached to the well cover horizontally. When the well cover is opened, the module can detect the change of the angle and make feedback. If the well cover is loose, when someone or a vehicle passes through the well cover, the angle of the well cover will change slightly. The information returned by MPU6050 can be used to judge whether the well cover is loose or not. If the inclination of well cover is greater than 30 ° , it is judged that the well cover is opened; If the angle is -5°～5° with constant fluctuation, it is judged to be loose.
2.3 Surface environmental monitoring
Monitor the surface temperature and humidity, judge the weather conditions, and make certain feedback.
2.3.1 Humidity detection
Installing the humidity sensor at the inner edge of the well cover, detect the humidity status in real time and make feedback to the central processing system of each node. When the humidity is high in rainy weather or the surface water penetrates into sensor through the edge of the well cover, and the humidity exceeds a specific value, the central processing system will make some response, improve the communication frequency with the host and make feedback real-time, which will be helpful for managers to master more information in case of emergency.
2.3.2 Temperature detection
Fixing the temperature sensor under the well cover to collect and report the surface temperature information is helpful for the municipal department to grasp the temperature situation in various parts of the city and take cooling measures in the areas with too high temperature. (The upper computer can be used to generate the temperature change curve and predict the future temperature)
The temperature sensor LM35DZ is adopted. The chip is small and flexible in size and high in accuracy. The data can be accurate to two decimal places. The chip can adopt single bus communication mode and is easy to operate.
2.4 Traffic flow monitoring
The car detection module is installed on the well cover to detect the traffic flow and reflect it to the municipal management department for reference.
It is planned to use geomagnetic sensor to realize the function of the vehicle flow monitoring. The module can detect the magnetic field situation accurately. When there are vehicles passing by, it will interfere with the magnetic field. If the module detects the change of magnetic field, it can judge that there are vehicles passing by. At present, the module is mainly used in the parking space detection. The main advantages of the module are as follows:
(1) Small and flexible size. The module can be easily used in products;
(2) High sensitivity. The module is very sensitive to the change of the earth’s magnetic field, and can detect the vehicle movement beyond 3 m;
(3) Ultra low power consumption. The average working current of the module is less than 200 μA. And it is working voltage can be as low as 2.0 V, which can maximize the service life of the battery (two No. 5 Nanfu batteries can work for more than 3 months, professional large capacity industrial batteries can work for more than 5 years, super large capacity batteries can even work for more than 10 years or determined by the battery shelf life).
(4) Simple and easy to use. The module provides switch interface and UART serial port. The switch interface can provide high and low level output. High level means there is a car, low level means there is no car; UART serial port provides timing status report, parameter setting and other functions.
2.5 Data transmission
2.5.2 NB-IOT part
Nb-IOT part is used to send the information processed by Central controller (Beaglebone) to Internet. Using NB-IOT to transmit data has the following advantages:
(1) NB-IOT signal covers a wide range, which can ensure the smooth transmission of all data to the Internet;
(2) The network speed can reach about 20 K per second, which is enough to transmit data;
(3) Compared with SMS, the cost of using NB-IOT to do data transmission is lower;
(4) Using serial communication protocol is easy to operate
Considering that the IP address used by NB-IOT module is randomly assigned, users also need to log in on different IP devices, so it is difficult to send the collected information to the users’ devices directly. Therefore, it is decided to use the server platform as the data transfer station. All the collected information is sent to the server for temporary storage through NB-IOT, and the user uses the upper computer to access the server to obtain the data.
2.7 Intelligent control interface
The upper computer obtains the data from the server platform and presents it to the user in the form of visualization. Through the visual interface, the user can intuitively understand the location relationship between each node, and conveniently obtain the water level, temperature, humidity, well cover status, traffic flow and other information of each node. When there are various abnormal conditions, such as blockage, rapid rise of water level, abnormal well cover status, the user can timely feedback the status and location information.
The upper computer uses the API provided by Baidu map to display the map of the monitored area in the web page, and each node is marked on the map, which is very obvious. Using the Django architecture of Python language and HTML, JS and other languages, the data collected by each node is presented in the form of chart in the web page, and you can check it by clicking the tag. At the same time, the alarm function can inform the problems to the user in time.
- Overall block diagram
The overall block diagram of the system is shown in Figure 4, and the following functions are finally realized:
(1) Burglary alarm, use the network to inform municipal departments to solve the problem of missing well cover in time.
(2) Loose alarm, eliminate the potential safety hazard caused by the damage of well cover to pedestrians.
(3) Pipeline blockage alarm, in the visual interface to display the blockage, to assist the cleaning department to clean up in time, eliminate hidden dangers, and prevent the occurrence of urban waterlogging.
(4) Detect the ground temperature and send back the data.
(5) Detect the water level and send back the data.
(6) Detect the ground humidity and increase the transmission frequency when the humidity increases, which is helpful for heavy rain warning.
(7) Detect vehicle flow, send back data in real time, and assist traffic management.
(8) Display the returned data in the visualization interface, and carry out corresponding processing and classification, which provides convenient operation environment for municipal departments.
(9) Establish the database to store the returned data for easy use and analysis.
4 Concluding remarks
The system aims to build an intelligent municipal management platform for the city to provide a more convenient and safe life for the public. Taking the well cover as a regional convergence node, centralized transmission and intelligent processing of the collected data is a major innovation of the project. Taking drainage, traffic, road safety and other municipal information into account, building a smart city is a highlight of the project. Although there are still some problems in power supply and antenna, they are not difficult for engineers to be solved, which can provide more guarantee for people’s safety and quality of life.