| Among the major natural disaster in the coal mine, the gas is one of the sources. Fire damp explosion not only influences the normal production of the mineral, but also threatens to the safety of the coal mine workers seriously. It is very important to measure the distribution of methane concentration in real-time.According to the specific requirements and the current situation of the coal mine gas monitor, this paper design the underground gas monitoring system based on optical fiber sensing. Surveillance system includes the gas sensors, the security protection power supply, actuators, relays, monitoring stations, transmission interface, the center computer and network switches equipment.The issue makes full use of the sensor, communication, embedded microcontroller, computer software programming and various aspects of the knowledge.At last,the paper complete the collection and management of gas concentration in real time. The main work of the paper are as follows:(1)Combine the technology of industrial Ethernet and the optical fiber sensor, construct the gigabit ring redundant network based on optical fiber, extend the application to the underground coal mine. Using optical as transmission medium, industrial switches for the core equipment, through the industrial ring net switch connecting each monitoring stations on site, the system established a stable, safe, reliable transmission link.(2) The key of the design is the gas sensor.Based on the principle of the gas spectrum absorption and tuned semiconductor laser spectrum absorption technology, the paper designs the superior optical fiber sensor. The design divides the function module reasonably, and completes the hardware and software design of the overall. The shell of sensor and the structure of gas chamber are both water proof and dust proof. It also designs the infrared remote control, digital pipe display,the audible and visual alarm circuit. Optical fiber sensor achieve the requirements of stability and reliability, and reduce the overall power consumption, realize the transmition over a long distance.(3)The monitoring stations choose S3C44BOX as the central processor.Compared to the traditional89C51, it improves the processing speed greatly. Peripheral circuit take a series of measures to reduce power, such as using multilevel power mode, LCD screen, with low power consumption of control chip, etc.; At the same time, the touch screen and LCD display make the station intelligent, easy to operate.(4) Using VB and SQL Sever2000to complete the software design of the center computer, to achieve the maintenance of parameters, real-time display of the data and alarm display. Write the communication protocol based on Modbus, complete the communication of the whole system.(5) Test and experiment the system. The tests simulate the environment of underground coal mine. The main content of the tests include the sensor's stability and error, response time, sound intensity and visibility; the data collection and stations'communication, power-off response and the operation of the center computer, etc. |
