2020 Vol. 46, No. 3

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5G communication technology and its application conception in coal mine
HUO Zhenlong, ZHANG Yuanhao
2020, 46(3): 1-5. doi: 10.13272/j.issn.1671-251x.17553
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Abstract:
In recent years, WiFi and 4G communication technology are preferred in coal mine wireless communication system in China. With development of intelligent construction of coal mine, the performance of coal mine wireless communication system cannot meet needs of intelligent development of coal mine. The paper described key technologies and performance advantages of the fifth generation mobile communication technology (5G) by comparing with previous generation mobile communication technologies. It also discussed composition and networking mode of mine-used 5G wireless communication system. Combined with characteristics of 5G communication technology and needs of coal mine intelligentization development, it put forward application scenarios of 5G communication technology in coal mine, such as underground unmanned driving and intelligent transportation, whole mine location service, equipment remote control, fault remote diagnosis, large broadband service data transmission, coal mine robot cloud control, whole mine safety monitoring information collection, virtual reality/augmented reality mine. It is pointed out that 5G technology application scenarios for coal industry still need to be continuously explored and improved, and since 5G network has high requirements for carrying network, coal mine should estimate deployment cost, and build mine 5G communication network based on its own development status and needs.
Research on coupling law of gas and coal spontaneous combustion in goaf of high gas mine
XING Zhen
2020, 46(3): 6-11. doi: 10.13272/j.issn.1671-251x.2019010084
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In view of problem that current numerical simulation of combined hazards of gas and coal spontaneous combustion in goaf only considers fluid effects, and does not consider influence of other physical fields, multi-field coupling numerical simulation software Comsol-Multiphysics is used to establish coupling model of gas and coal spontaneous combustion in goaf. Distribution law of gas and O2 in stope of working face and goaf is analyzed, and influence of drainage volume and air intake volume on gas concentration in high-level drainage roadway and O2 concentration in floor of goaf is explored to comprehensively determine the optimal drainage volume and air intake volume. The results show that with the increase of drainage volume, gas drainage concentration increases first and then decreases, and the width of oxidation temperature rise zone in goaf has a positive correlation with growth,comprehensively considering gas drainage effect and natural ignition prevention, the optimal drainage volume 90 m3/min is recommended for high-level drainage roadway; with the increase of air intake volume, gas concentration and scalar quantity of the high-level drainage roadway first increase and then decrease, the width of oxidation temperature rise zone on the air intake side of the goaf obviously increases, and the maximum at 109.3 m, the width of oxidation temperature rise zone on the return air side has a small change,comprehensively considering gas drainage effect and natural ignition prevention, the optimal air intake volume at the test face is 1 500 m3/min.
Research on gas drainage drilling parameters and nitrogen injection for fire prevention in goaf
CUI Chuanfa
2020, 46(3): 12-20. doi: 10.13272/j.issn.1671-251x.2019050049
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Abstract:
Drilling and drainage can affect movement of air flow in goaf, thus leading to changes in goaf flow field, and increasing air leakage in goaf. At the same time, there is a state of negative pressure around the borehole, and the air leakage and air flow are constantly replenishing around the drilling. The coal body in goaf presents a state of oxidation and temperature rise in the area where the air leakage is concentrated, so there is a problem of spontaneous combustion of residual coal in goaf. For the above problem, the optimal nitrogen injection for fire prevention scheme in goaf under the condition of drilling drainage was studied. The 10201 working face of Bailongshan Coal Mine was used as the background for goaf simulation by numerical simulation software. The distribution of flow field and temperature field in goaf under different drainage parameters is analyzed, and the optimal nitrogen injection condition was determined according to the reasonable drilling parameters.The results show that the gas drainage effect is good when drainage pressure is 30 kPa, and the increase of the oxidation temperature rise zone is relatively low; the drainage effect is good and the engineering amount is low when drilling interval is 6 m; when the distance between working surface and intake side nitrogen injection port is 75 m and the nitrogen injection flow is 1 500 m3/h, the width of oxidation temperature rise zone can be reduced and the cost can be saved. The actual application results show that the gas volume fractions of fully mechanized working face and the upper corner are effectively controlled, both of which are lower than 1%; the CO volume fraction of extraction pipe and upper corner is lower than 0.040% and 0.032% respectively,no spontaneous combustion occurred in the goaf, and gas drainage and nitrogen injection in the goaf achieved good application results.
Research on application of blockchain technology in mine Internet of things
QIN Xiaowei, WANG Libing, WANG Lei, LI Jingzhao, ZHANG Xiaobo
2020, 46(3): 21-26. doi: 10.13272/j.issn.1671-251x.17542
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Abstract:
Aiming at problems of data loss and tampering during data transmission and storage of mine Internet of things(IoT), blockchain technology was applied to data transmission and storage of mine IoT. Mine private blockchain architecture with data layer, transmission layer and consensus layer as core was constructed. Protection schemes for data transmission and storage of mine IoT based on consensus module and data block were designed. Practical Byzantine fault tolerance algorithm was used to design data consensus process. Consensus module was set up between every two nodes of distributed structured P2P network and P2P protocol was optimized to achieve mine data security consensus. The test results show that application of private blockchain guarantees accurate transmission and reliable storage of mine IoT data.
Automatic semantic annotation method for mine Semantic Web of things
ZHANG Nan, XIE Guojun, YE Qing, ZHAO Xiaohu
2020, 46(3): 27-33. doi: 10.13272/j.issn.1671-251x.17512
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In view of problem of difficulties in obtaining prior knowledge during fusion of heterogeneous data in mining field, poor real-time performance of IoT ontology database,and low efficiency of manual annotation of instance object data, an automatic semantic annotation method for mine Semantic Web of things was proposed. Framework of semantic processing of sensory data was given: on the one hand, professional domain and category of ontology are determined, and the domain ontology is constructed by reusing SAO as the basis for driving semantic annotation; on the other hand, machine learning method is used for feature extraction and data analysis of perceptual data stream, and relationship between concepts is mined from massive data; finally, data mining knowledge is used to drive the update and improvement of the ontology, so as to realize dynamic update, expansion and more accurate semantic annotation of the ontology, and enhance the machine's understanding. Spindle fault of mine hoisting system is used as an example to explain the process of semantic annotation from ontology to instantiation: combining the domain expert's knowledge and ontology reuse, the “seven-step method” is used to establish fault ontology of the main drive of mine hoisting system; in order to enhance the accuracy of the instance data attribute description, PCA dimensionality reduction method and K-means clustering method are used to group the data set to extract the relationship between data attributes and concepts;finally, the relationship between specific preconditions and subsequent concepts is marked by SWRL to optimize the domain ontology. The experimental results show that in the process of ontology instantiation, machine learning technology can be used to automatically extract concepts from sensing data and realize automatic semantic annotation of sensing data.
Coal mine information comprehensive perception and intelligent decision system
LI Tengfei, LI Changyou, LI Jingzhao
2020, 46(3): 34-37. doi: 10.13272/j.issn.1671-251x.17541
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Aiming at problems of poor information perception ability and low decision level in coal mine safety production, a coal mine information comprehensive perception and intelligent decision system was proposed, which was composed of capsule network layer, data transmission layer and cloud service layer. The capsule network layer is composed of personnel position and behavior perception capsule, equipment status perception capsule and environment perception capsule to realize comprehensive perception of "person, machine and ring" in coal mine. The data transmission layer adopts method of combining wireless sensor network and wired network to realize reliable data transmission in underground coal mine. The cloud service layer provides guarantee for efficient and reliable decision for coal mine production through intelligent decision mechanism based on random forest. The experimental results verify effectiveness of the system.
Intelligent multi-node communication strategy of mine cyber-physical system
MA Yangjin, FU Maoquan, XU Zhi, LI Jingzhao
2020, 46(3): 38-42. doi: 10.13272/j.issn.1671-251x.17544
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Abstract:
Aiming at problem that communication nodes and perception nodes based on different wireless communication protocols could not achieve intelligent connection in current mine cyber-physical system (CPS), a multi-mode communication node was constructed by integrating multiple communication modules on the communication node, and an intelligent multi-node communication strategy of mine CPS based on progressive neural network was proposed. The progressive neural network is used to control the multi-mode communication node to switch working mode accurately and realize independent establishment of heterogeneous wireless communication network. The asynchronous advantage actor-critic algorithm is used to perform deep training on the progressive neural network to improve convergence speed and training accuracy of the progressive neural network. The experimental results show that the strategy can realize accurate and reliable communication between multi-mode communication nodes and multi-class perception nodes.
Optimization of PWSN transmission performance on coal mining face
FANG Zuhao, ZHAO Xiaohu, WANG Haibo, WANG Jingjing
2020, 46(3): 43-48. doi: 10.13272/j.issn.1671-251x.17515
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In view of problems of long end-to-end time and high packet loss rate of positioning wireless sensor network (PWSN) on coal mining face, a guaranteed greedy scheduling (GGS) algorithm was proposed to optimize network transmission performance. The GGS algorithm combines the particle swarm optimization (PSO) algorithm and the greedy algorithm. The PSO algorithm is used to orderly process the message population in the channel to ensure the population. The greedy algorithm is used to form a multi-level, iterative processing mechanism for specific service requests during network transmission, so as to optimize the quality of the message population. The PSO mutation algorithm is used to check and update the population to ensure that the optimal solution is obtained. The simulation results show that compared with the existing MA and DE-ABC algorithms, the GGS algorithm can shorten the transmission time and improve the overall network performance while controlling the packet loss rate.
Relay selection in wireless cooperative networks based on energy collection technology
ZONG Zhengxue, DING Enjie, LIU Yan, ZHANG Bingxin, ZHAO Duan
2020, 46(3): 49-54. doi: 10.13272/j.issn.1671-251x.17514
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In view of problem that available energy collected by current energy collection technologies is limited which leads to energy shortboards at relay nodes in wireless cooperative networks, in order to avoid paralysis of the entire network due to large number of deaths of relay nodes, a relay selection scheme in wireless cooperative networks based on energy collection technology, namely a relay selection scheme for combined maximum energy and maximum data transmission link was proposed. First, based on energy collection status of the nodes, the node with the highest energy in each hop is selected for decoding and forwarding; then, based on link transmission status of each two consecutive hops, the relay node is selected which can optimize the data transmission channel between the source node and the destination node. Combined with Nakagami-m channel fading model, the proposed scheme is compared with the random selection scheme, MaDs scheme and BNBF scheme. The results show that under the premise that the collected energy is sufficient for energy collection and data transmission in the next time slot, the smaller the proportion of energy collection used, the smaller the probability of network interruption; the relay selection scheme that joints maximum energy and maximum data transmission link is superior to other schemes in terms of network interruption performance, its interruption probability decreases as the signal-to-noise ratio increases, especially when the average signal-to-noise ratio is 38 dB, the network interruption probability drops to 10-5.
Application of principal component-Fisher discrimination model in grade prediction of coal and gas outburst
CHEN Lian, YUAN Mei, GAO Qiang, XU Shiqing, CHEN Wen, LI Xinling, LONG Nengzeng
2020, 46(3): 55-62. doi: 10.13272/j.issn.1671-251x.2019070057
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In view of problems of complicated calculation process, strong subjectivity and low accuracy in existing prediction methods of coal and gas outburst, a principal component-Fisher discriminant model was constructed and applied to the prediction of coal and gas outburst grade in a coal mine. Based on analysis of gas factors, coal structure and geological structure, the factors that affect coal and gas outburst of the coal mine included gas pressure, gas content and initial velocity of gas release and so on were obtained. On the basis of 23 groups measured data of coal and gas outburst of the coal mine, firstly, the principal component analysis model was used to do dimension reduction of influencing factors of the mine coal and gas outburst, 5 principal components with high index correlation were extracted. Then the 5 principal components were input into Fisher discriminant model, and the grade of coal and gas outburst of samples was predicted according to discriminant function. The application results show that the principal component-Fisher discriminant model has high credibility, and can accurately predict coal and gas outburst grade, the training sample accuracy is 100%, the predicted results of the tested sample are also consistent with the actual situation of coal and gas outburst of the coal mine, misjudgment rate of 0, which provides a new method of accurate prediction of coal and gas outburst.
Research on improved region division method in underground WLAN location fingerprints positioning
SONG Mingzhi, QIAN Jiansheng, HU Qingsong
2020, 46(3): 63-68. doi: 10.13272/j.issn.1671-251x.2019110032
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Underground WLAN location fingerprinting personnel positioning system mainly realizes overall division of location fingerprinting samples through clustering algorithm, but existing clustering algorithm only carries out the clustering division according to the statistical distribution characteristics of received signal strength (RSS), and does not fully consider singularity problem. For the above problem, a class relationship K-Means (CRK-Means) algorithm was proposed. CRK-Means algorithm takes the ratio of intra class dispersion and inter class dispersion as the objective function, and the optimal clustering without singularity problem can be achieved by aggregation and separation process of clustering with the minimum ratio, so as to complete reasonable division of positioning area. Genetic Algorithm-Random Forets (GA-RF) algorithm was proposed to solve the problem of misjudgment in rough localization of clustering area by using Random Forest(RF) algorithm. The optimization process of selection, crossover and mutation in GA ensures the optimal value of the total number of selection trees and the feature number of location fingerprints reference points in RF algorithm. The experimental results show that the CRK-Means algorithm solves the singularity problem effectively, and improves the positioning accuracy of the positioning system. The accuracy of sub-region rough positioning by CRK-Means algorithm and GA-RF algorithm is 4% and higher than RF algorithm, it is 98%. The minimum positioning error with a confidence probability greater than 90% is 3 m, which is better than the traditional clustering algorithms.
Coal-gangue image classification method
RAO Zhongyu, WU Jingtao, LI Ming
2020, 46(3): 69-73. doi: 10.13272/j.issn.1671-251x.17495
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For problems that traditional coal-gangue separation methods such as manual separation method, mechanical wet-separation method, γ-ray separation method and so on could not give consideration to high efficiency, safety and easy operation, a coal-gangue image classification method based on machine vision was proposed. Coal-gangue image is pre-processed with enhancement, smoothing and denoising, then segmented and extracted by watershed algorithm based on distance conversion. HOG feature and gray-level co-occurrence matrix of the coal-gangue image are selected, and coal-gangue classification based on feature extraction is carried out by taking support vector machine, random forest and K-nearest neighbor algorithm as classifier separately. Coal-gangue image classification based on convolutional neural network is carried out by building shallow-level convolutional neural network and VGG16 network pre-trained by ImageNet dataset separately. The research results show that the maximum accuracy rate of the coal-gangue image classification method based on VGG16 is 99.7%, which is higher than that of the method based on feature extraction with 91.9% or the method based on shallow convolutional neural network with 92.5%.
Research on load adaptive impedance matching of magnetic resonant wireless power transfer system
BAI Jingcai, FAN Zheng, WANG Guozhu, DU Zhiyong
2020, 46(3): 74-78. doi: 10.13272/j.issn.1671-251x.2019050076
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In view of problem that current impedance matching methods ca't automatically adjust load impedance of magnetic resonant wireless power transfer system(MR-WPT) when load changes, which leads to reduction of energy transfer efficiency of the system, a load adaptive impedance matching method of MR-WPT system was proposed. In order to improve power transmission efficiency of MR-WPT system by using high frequency, class E power amplifier is used as high frequency inverter circuit. A DC/DC converter is added between magnetic resonance device and load. When the load impedance changes, the load resistance is transformed to the maximum efficiency transmission resistance by adjusting the duty cycle of the DC/DC converter, thus ensuring that the MR-WPT system always works at maximum efficiency. The simulation and experimental results show that the proposed impedance matching method is feasible and can optimize transmission efficiency of MR-WPT system. When the output power is 3.5 W, the transmission efficiency reaches 35%.
Application of comprehensive exploration technology for water-hazard prevention in coal mine working face
JI Qianhui, HAO Shijun, WANG Cheng, LIU Weiwei
2020, 46(3): 79-83. doi: 10.13272/j.issn.1671-251x.2020020031
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Most of existing comprehensive exploration technologies for water-hazard on coal mine working face adopt conventional rotary drilling method with lots of boreholes and heavy workload. In addition, blending deformation of drill pipes, geological condition variation in boreholes and alterations of drilling parameters during construction process would lead to borehole deflection, which may cause wrong decision about water-hazard exploration. For above problems, a comprehensive exploration technology based on directional drilling was proposed and applied to water-hazard detection on fully mechanized mining face of a coal mine. The application process is as follows: Firstly, mine audio-frequency electric penetration technology is used in the comprehensive exploration technology to detect anomalous area with low apparent resistivity on the working face, and then directional drilling technology is adopted to directly expose water-rich zone. It is determined that there is a water-conductive collapse column of Ordovician limestone karst in the anomalous area through observing water gushing in the boreholes and chemically examine quality of the water. Meanwhile, extension state and boundary of the water-conductive collapse column in the working face are delineated. Position of open-off cut is redesigned according to comprehensive exploration results, so as to effectively eliminate hidden water-inrush danger caused by exposing the water-conductive collapse column during mining process.
Gas control technology of directional high-level long borehole at upper corner
BAI Gang, YANG Zhong, DUAN Huiju
2020, 46(3): 84-88. doi: 10.13272/j.issn.1671-251x.2019080005
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For problems that normal roof high-level borehole hardly drilled to design position because borehole direction and dip-angle cannot be controlled, and had short effective extraction hole segment, many drainage blind areas, discontinuous drainage and so on, taking upper corner gas control of Wangjialing Coal Mine as research background, a group of directional high-level long borehole and four groups of normal high-level borehole were constructed for gas drainage in return airway of 20103 fully mechanized working face. Gas drainage effect of the two kinds of high-level boreholes were compared and analyzed. The results show that the effective drainage hole section of the directional high-level long borehole is long, the blind area of gas drainage is few, meanwhile, continuous drainage can be achieved. The average gas drainage flow from the directional high-level long borehole is 2.11 m3/min and the maximum value achieves 2.9 m3/min. Compared with normal high-level borehole, the average gas drainage flow from the directional high-level long borehole increases about 2.77 times, the gas drainage rate of working face increases nearly 2 times, and the effect drainage time increases about 3.15 times. The gas volume fraction at upper corner is reduced from more than 1.0% under the condition of only draining gas from normal high-level borehole to less than 0.6% only draining from the directional high-level long borehole, which verifies that the directional high-level long borehole has obvious technical advantages of controlling upper corner gas on working face.
Monitoring system for accurate coalbed methane drainage
LIU Lei
2020, 46(3): 89-94. doi: 10.13272/j.issn.1671-251x.2019090027
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In view of problems existing in conventional coalbed methane drainage system, such as low control accuracy, high labor intensity, inability to operate according to drainage and extraction rules, and high production cost, a monitoring system for accurate coalbed methane drainage was designed. The system uses STM32F107 Connectivity series microcontrollers as the control center, and adopts field acquisition units to collect real-time downhole flow pressure, temperature, casing pressure value, frequency and other signals, and transmits the signals to the control center through RS485 communication interface and 4-20 mA analog interface. The deviation signal is obtained by comparing the measured value of downhole flow pressure with the given value. According to the deviation signal, the control center controls the output frequency of the converter in real time through the drainage control algorithm, and then adjusts the operation speed of the drainage equipment to realize the automatic closed-loop control of downhole flow pressure. 4G wireless transmission module is used to send control and adjustment command to drainage control unit to realize real-time monitoring and control of the drainage process. The field test results show that the system can execute the operation according to the real-time scheduling system, the regulation of downhole flow pressure is accurate, the average error is within 0.5%, which can meet the requirements of accurate coalbed methane drainage.
Research on dynamic simulation of coordinated development of coalbed methane and coal in typical mining areas
XU Hualong
2020, 46(3): 95-99. doi: 10.13272/j.issn.1671-251x.2019080092
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In view of problem that traditional methods is difficult to show coordinated development process of coalbed methane and coal, a new 3D dynamic simulation idea was proposed. The coordinated development model of coalbed methane and coal is demonstrated using technologies of 3D visualization and animation deduction. With "Jincheng Mode" as the background, based on the digital mine 3D platform MineSystem, key technologies of 3D integrated rapid modeling of up and down well, 3D visual dynamic editing for coordinated development, animation deduction of three-region linked 3D drainage are used to complete dynamic simulation of three-region linked coalbed methane development model of overall drainage up and down well. The 3D integrated display of the production planning area, development preparation area, and coal production area are realized, which provides technical support for the promotion and application of the coordinated development and utilization process of coalbed methane and coal.
Research on vibration signal prediction of coal mine machinery
XIAO Yajing, LI Xu, GUO Xi
2020, 46(3): 100-104. doi: 10.13272/j.issn.1671-251x.2019090085
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According to variation differences of high frequency and low frequency components of coal mine machinery vibration signal, a combined vibration signal prediction method of coal mine machinery based on empirical mode decomposition (EMD) and support vector machine (SVM) is proposed. The vibration signal of rolling bearing is decomposed by EMD to obtain relatively stable instrinsic mode function (IMF) components, and the IMF components with similar degree of the fluctuation are reconstructed to obtain high-frequency and low-frequency subsequences. The high-frequency subsequence and low-frequency subsequence are predicted by SVM respectively, and then the final prediction value is obtained after superposing the two prediction results. The bearing experimental data are selected to verify effectiveness of the method. The results show that the root mean square error, average absolute error and average absolute percentage error of the method are smaller than that of the direct prediction method.The results show that the root mean square error, average absolute error and average absolute percentage error of the combined predition method are all smaller than those of direct prediction method. The combined prediction method is applied to condition prediction of rolling bearing of the belt conveyor in main shaft of a coal preparation plant, and the prediction results are consistent with actual situation.
Design of coal mine safety risk prevention and control and early warning system
XU Xiaojia
2020, 46(3): 105-108. doi: 10.13272/j.issn.1671-251x.17554
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Aiming at problems of lack of systematization, poor timeliness and passive response in coal mine safety risk prevention and control, a coal mine safety risk prevention and control and early warning system was designed. Based on coal mine safety risk database, the system uses risk map to realize dynamic monitoring of each link of risk state change. According to level of abnormal event, hierarchical message push and on-site abnormal linkage disposal are carried out, which improve response and disposal efficiency of abnormal event. Safety grid is used to refine spatial granularity of risk prevention and control, safety index and safety grade assessment of safety grid, operation area and whole mine are realized, and main responsibility of safety management at all levels is effectively implemented. The system is helpful for coal mine to establish comprehensive and multiple safety risk prevention and control system, and effectively improve coal mine safety production guarantee capacity.

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