Underground Coal Mine Environment Monitoring System Based On Optical Fiber Transmission

The underground environment of coal mine is special,and the disasters are serious.In order to ensure the safety of the underground workers,the underground environment monitoring system of coal mine plays an important role.The data of existing environmental monitoring system mainly includes CAN bus,RS485 bus and wireless transmission.CAN bus and RS485 bus generally have the problems of slow interaction rate and limited transmission distance.The wireless transmission will be repeatedly disconnected due to the electromagnetic interference generated by the power cables in the tunnel,and the wireless signal will also have great attenuation and interference,and will be limited by the transmission distance and transmission bandwidth.Therefore,combined with the technical advantages of optical fiber anti-interference long-distance large-capacity transmission,this paper proposes a coal mine underground environment monitoring system based on optical fiber transmission.This article through to the coal mine environment parameters and the analysis of the electromagnetic interference type selection of temperature,concentration of methane,carbon monoxide concentration,the concentration of oxygen,four parameters are collected,and according to the structure design of the two kinds of test scheme of the coal mine,the first solution is to separate a set of optical fiber is used for each system,the second kind of plan is a multiple systems share a set of optical fiber,In order to ensure that the data collected by each system can be completely transmitted to the receiving end,the first scheme is adopted as the optimal choice,and the hardware circuit of the system is designed.Because the difference of the output signal range of the four parameter sensors is relatively large,the circuit of methane sensor is designed to divide the voltage,the circuit of oxygen sensor and carbon monoxide sensor is designed to amplify and filter,so that the output of the four sensors are within the input range of the analog-to-digital conversion chip.In addition,in order to ensure the reliability of the data transmitted by the underground coal mine environmental monitoring system,the multiplexing problem of the analog-digital conversion chip and the delay performance of the optical fiber are analyzed to solve the problems of competition and risk in the testing system.Combined with the SPI protocol used in the output of the analog-to-digital conversion chip,through the logic design in the master chip and the test in the actual process,the problems of dislocation,missing and invalid data in the output of the system are solved,and the uniform sampling is realized.The data is encoded to improve the reliability of the data.The system adopts the electric-opto-electric transmission mode,which can make the data in the transmission process as little as possible by the interference of the external environment,which is conducive to the real-time monitoring of the underground environment of the coal mine,and ensure the life safety of the staff.Finally,the system is simulated by building a test platform,and the data transmission function of the system is tested,and the compensation calculation of relevant parameters is analyzed to verify the feasibility of the design.