Design And Implementation Of PDR Positioning System Based On Internet Of Things

Coal resources in China's energy supply in the long-term dominant position,can not be replaced in a short period of time.The underground environment of coal mines is harsh,and there are hidden safety hazards such as water leakage,fire,blasting,etc.These hidden dangers plague the safe production of coal mines.Therefore,ensuring the safety of coal mine personnel is of great significance to improving coal mine safety production.Although the country attaches great importance to coal mine safety issues and strengthens supervision,it is still inevitable that mining disasters will occur.After the mine disaster,the complex terrain and the high-risk environment in the coal mine have added a lot of obstacles to rescue personnel in carrying out rescue operations,making it impossible to rescue the trapped personnel timely and accurately,so the underground personnel should be monitored and located.The real-time location has important practical significance.Aiming at the problem of real-time positioning of coal mine personnel,this paper designed a Pedestrian Dead Reckoning(PDR)positioning system based on the framework of the Internet of Things.After analyzing the current domestic and foreign research status of the underground personnel positioning system,the Internet of Things technology and the PDR algorithm were combined to realize the function of remote real-time monitoring.Firstly,the requirements of the entire system was analyzes to determine functional requirements and non-functional requirements.Secondly,each module of the system was designed separately,including three modules: shoe-mounted inertial navigation module,host computer and PDR algorithm design.The shoe-mounted inertial navigation module was designed with STM32F103 as the core chip.It collected pedestrian walking data through the USART2 serial port and connected to the Inertial Measurement Unit(IMU).After processed and packaged,the data was forwarded to the external Wi-Fi module through the USART1 serial port.The Wi-Fi module sent the data to the Message Queuing Telemetry Transport(MQTT)server located in the public network.The design of the host computer included three parts: the background,the user interaction interface,and the database.The background used the SSM(Spring + Spring MVC + Mybatis)framework,which realized the way of receiving and storing the data sent by the MQTT server,using the data input and output stream and the PDR algorithm Perform data interaction,provided application programming interface(API)to the user interaction interface,and receive requests through Http Servlet.The user interaction interface used the Angular JS framework and ECharts plugin,and used http to call the API provided in the background to request data.After the response,the coordinate system was drawn,so that the final pedestrian navigation and positioning results could be displayed on the web page in the form of trajectories.The database included the design of data collection tables and the design of separation of masterslave database synchronization read-write operations.The PDR algorithm module obtained data directly from the database,using the multi-condition joint zero-speed detection algorithm to detect steps,the quaternion to update the attitude,and the Zero Velocity Update(ZUPT)algorithm to eliminate the cumulative error of the sensor.The accuracy of the heading and step length after the PDR algorithm merged the two steps of the step length estimation and the heading estimation.The actual operating results showed that the underground PDR positioning system of coal mines based on the Internet of Things framework was flexible in design,stable and easy to use.It also can monitor the position of pedestrian trajectories effectively.Finally,the simulation results of each algorithm showed that the number of steps was accurate,the cumulative error of speed can be effectively eliminated,the correctness of the step length and heading,and the trajectory of pedestrians were consistent with reality.The system provided an interface to the Python language during the development process,a practical platform for other positioning algorithms using Python.It has practical value for the positioning of underground personnel in the coal mine.