| Mine safely is an important concern in coal production,while methane is its primary disaster.Compared wiih other mature gas detecting technology such as catalytic?thermal conductivity,semiconductor gas sensing and infrared measurement,the TDLAS technology proves to have evident advantages:long lasting,no need for calibration,long-distance optical signal transmission,possesses essential safety and anti-electromagnetic interference ability?high sensitivity,large measuring range,etc.Domestic and foreign researchers dedicated immense research to the principle and the classification of TDLAS,and to the source and the structure of detector laser light.However,practical application of the laser methane sensors in the coal mine also revealed crucial impact on measurement issues caused by environmental factors such as temperature and pressure,this issue restricts the field applications of laser methane sensor.Based on the analysis of mechanism,the theory and the methods of laser temperature control,the compensation theory and method of sensor temperature and pressure are conducted in the research to achieve technological breakthrough in four areas:improving the accuracy of laser temperature control,limiting sudden changes of laser temperature,further precising and solution to the compensation of gas temperature and pressure of multi-point detection system.Through a deep research of the relationship between the absorption lines and the laser absorbance linearity related to the spectral characteristics of laser wavelength;a research of reason behind laser measurement and methane concentrations,it has been discovered that the main factors for errors in laser measurement are the ambient temperature and pressure,based on the analysis and the comparison of laser harmonic detection method for transferring absorption process.On this basis,we proposed and built the laser sensor system structure based on the Lambert-Beer Law and the laser TDLAS,and we stimulate each module by the testing of laser gas detection;we designed the hardware and the software according to the hamionic platform of signal detection.From the analysis of the harmonic detection method for the TDLAS method,we designed the program to achieve gas concentration measurement.Through the analysis of methane concentration detection,we discovered that DFB laser output wavelength is sensitive to laser temperature,and gives absorption wavelength drift variation.By the reference of gas chamber,we proposed and realized the indirect measurement method of the light intensity value A and of the optical wavelength ?.Based on the study of DFB laser thermoelectric cooler(TEC)temperature control,we proposed optimization fuzzy temperature control algorithm based on improved PSO.The algorithm is designed to control target of the characteristics of which light intensity values A,while light wavelength X of the laser internally controls nonlinear relationships between temperatures T.Finally,we carried out experimental verifications.With the development of gas detection technology by tunable semiconductor laser absorption spectrum,the sensor based on this technology is the current focus of the area of coal mine methane monitor.The sensor is currently used in coal mines,but the influence of environmental temperature to the accuracy of movement is stronger.Aiming at this problem,an adaptive iterative compensation algorithm is proposed in which piecewise interpolation should be fused with the Lagrange bar-centric interpolation.Firstly,the influence rate of measure temperature is calculated based on the sensor calibration value.Secondly,the bar-centric interpolation function is calculated under different temperature.Thirdly,the new influence rate of measure temperature is calculated to measuree methane concentration values According to the implementation of adaptive iteration,we were able to calculate the compensation methane value by this new rate of temperature affect.Various test shows that relative measurement error is reduced to 1%in the high concentration gas conditions,while absolute measurement error is reduced to 0.01%CH4 in the low concentration gas conditions.Engineer result showed that the measurement error decreases significantly than before.This method provides a reliable guarantee for laser sensor used in coal mine.On the basis of experimental testing and analysis of mine methane sensor characteristics of the laser,the laser perimeter temperature perturbations caused the display value appears unable to track the gas concentration problems when the laser sensors was placed at high and low temperature experimental box mutation status.We proposed a method which based on temperature compensation random approximation of the expert system for the laser sensor.Firstly,according to the analysis of test data,the relationship formula between gas concentration and the temperature is deduced.Secondly,the expert rule is established by the stochastic data of test,and compensation circuit of the laser gas sensor is designed.Finally,the experiments are carried out,the experimental results show that temperature compensation method reduced the fluctuation of stochastic temperature,and improved the test time and the measurement accuracy.The method will have reference value for the safety production of mine gas detection.On the basis of discussing and analyzing the detection performance of multi-point detection of gas concentration by laser,a method for selecting the gas concentration of multi points under the condition of working condition is given.Aiming at the variation of methane concentration error,the algorithm of improving the Bayes multi point data fusion estimation algorithm is proposed.We considered the changes of environmental temperature and methane concentration at the same time in the method.The theorem of improved Bayes fusion is given with the maximum posteriori probability estimation,and optimal estimation formula is given.Not only the theorems are proved,but also the examples are given.Finally,the performance evaluation tests of the laser methane sensor that we developed based on the above research-findings was conducted in the laboratory,and its technical indicators data have obvious advantages compared to other sensor principles.We introduced the coal methane monitoring systems and experimental platform,and finally carried out on-site application experiments of laser methane sensor.Development of coal mine methane sensors and laser GJG100J GJG100J(B)laser methane sensor mine site by industrial test again to verify the advantages of laser gas detection technology,the products have been put into the coal safety monitoring system,gas extraction method system.By on-site industrial test of coal methane sensors GJG100J,GJG100J(B)that we designed was to verify the advantages of laser gas detection technology again,the products have been put into mine safety monitoring system,gas drainage system.In Yu Yang mine of Songzao Coal Company,the sensor is continuously operated for nearly two months.During operation,measured data curve of pipe laser methane sensor of GJG100J(B)is basically the same with manual test data.The sensor is stable,and its linearity and accuracy remain unchanged. |
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