工矿自动化

Coal mine 5G wireless communication system construction concept

GU Yidong, MENG Wei

2021, 47(10): 1-7. doi: 10.13272/j.issn.1671-251x.17850

<Abstract>(295) <HTML> (87) <PDF>(51)

Abstract:
The basic architecture of 5G wireless communication system in coal mine is proposed: 5G core network, base band unit (BBU), remote radio unit hub (RHUB) and 5G base station are connected by 5G bearer network to realize signaling transmission among network elements. Underground 5G base stations and antenna are used to realize underground wireless signal coverage. After the base stations are converged through a RHUB, they are connected to BBU and connected to the 5G core network. The advantages and disadvantages of two kinds of 5G core network construction schemes are compared, namely user plane function/mobile edge computing (UPF/MEC) sinking and independent private network. This paper studies the bearer networks between 5G core network and BBU, between BBU and RHUB, between RHUB and 5G base station. This study focuses on the characteristics and application scenes of the three bearing methods commonly used in the bearer network between the 5G core network and the BBU, namely the optical fiber direct connection, the slicing packet network (SPN) and the 5th generation fixed network (F5G). The design schemes of coal mine 5G base stations, 5G terminals and 5G communication modules are proposed. Combining the characteristics of 5G communication technology and the requirements of coal mine intelligence development, the typical applications of 5G wireless communication systems in coal mines are discussed, such as integrated communication, high-bandwidth service applications, intelligent working face service application, remote control of mining vehicles or unmanned driving, etc. It is pointed out the further optimization directions of the coal mine 5G wireless communication system, including the design of miniaturization industry 5G core network, the low-power and intrinsically safe design of coal mine 5G base stations and other equipment, the underground application of 5G equipment in the 700 MHz frequency band to improve the coverage of 5G base stations, the customization of coal mine 5G mobile terminals and the development of industry APPs, the development of low-power 5G communication modules, industry application scenes in combination with on-site needs, etc.

Impact hazard analysis and prevention research of square structure area in fully mechanized working face

YAN Yaodong, PAN Junfeng, XI Guojun, JIAO Biao, SHI Xing

2021, 47(10): 7-13. doi: 10.13272/j.issn.1671-251x.2021030070

<Abstract>(163) <HTML> (21) <PDF>(11)

Abstract:
At present, the impact hazard analysis of fully mechanized working face is only carried out from a single geological structure or square effect factor. However, the mining conditions of rock burst mines are always changing, and the influencing factors are complex and diverse. Therefore, it is necessary to specifically analyze the impact hazard in the coupled area of geological structure and square effect in fully mechanized working face. Taking the 401111 working face of Hujiahe Coal Mine as the engineering background, the energy and frequency distribution characteristics of microseismic events of square structure area are obtained by microseismic network monitoring technology, and the impact hazard of square structure area is studied. The conclusions are listed as follows. ① The impact hazard is high in the square structure area, and the faults and folds in the area affect the continuity and deformation characteristics of the coal seam respectively, resulting in abnormal tectonic stress. ② The pressure of the overlying rock seam gradually transfers to the coal seam along with the excavation of the working face, and the concentration of static load in the area is significant. The square effect of the working face advancement process leads to frequent roof movement, resulting in a high level of concentrated dynamic load. ③ When the square effect and geological structure are combined, the concentrated static load in the coal body near the working face is at the highest level. The far-field concentrated dynamic load disturbance is the most frequent, and the potential hazard of regional impact under the coupling effect of the two is extremely great. In order to solve the problem of the impact hazards in the square structure area, specific prevention and control measures are taken for the three layers of the square structure area from top to bottom of the spatial dimension. ① The fracture of the thick hard roof will generate a high level of dynamic load, and pre-splitting blasting is carried out to reduce the connection between the roof and the adjacent goaf. ② The coal pillars and solid coal between the working faces are affected by the pressure of the overlying rock layer, and the static load concentration is high. It is proposed to implement large diameter drill holes to unload pressure and reduce the transfer of coal wall integrity support pressure to deep coal seams.③ It is proposed to implement large-diameter drilling + blasting pressure relief technology on the bottom plate to block the transfer path of the support pressure of the wall to the bottom plate and reduce the deformation of the bottom heave of the roadway. The results of engineering practice show that the prevention and control measures have good effect of pressure relief. The roof periodic weighting in the square structure area is shortened, which is basically below 15 m. The energy of the microseismic events at the working face is less than 104 J, and there is no large energy event. The proposed measures can provide reference for the prevention and control of rock burst in the same type of mine conditions.

Fault diagnosis of rolling bearing of mine ventilator based on characteristic fusion and DB

GUO Xiucai, WU Ni, CAO Xin

2021, 47(10): 14-20. doi: 10.13272/j.issn.1671-251x.2021070050

<Abstract>(160) <HTML> (17) <PDF>(19)

Abstract:
The existing mine ventilator rolling bearing fault diagnosis method only extracts time-frequency component characteristics and adopts shallow network structure, thus causing low fault diagnosis accuracy. In order to solve this problem, a fault diagnosis method of rolling bearing of mine ventilator based on multi-domain characteristic fusion and deep belief network (DBN) is proposed. Firstly, the method performs wavelet packet noise reduction on the bearing vibration signal, and extracts time domain characteristics, frequency domain characteristics and IMF energy characteristics from the bearing vibration signal after noise reduction to obtain a relatively comprehensive set of high-dimensional characteristic set. Secondly, the characteristic selection method based on intra-class and inter-class standard deviation is used to eliminate the characteristics that are not effective for classification and characteristics with no obvious effect so as to filter out high-efficiency characteristics. Finally, kernel principal component analysis (KPCA) is used to reduce and fuse the high-dimensional screening characteristics, eliminate the redundancy between characteristics, and input the fused characteristics into DBN to complete the fault diagnosis. The experimental results show that compared with the diagnosis method based on single characteristic and shallow network, the average accuracy of mine ventilator rolling bearing fault diagnosis method based on multi-domain characteristic fusion and DBN has average accuracy and less average diagnosis time showing good stability and generalization ability for different damage fault data.

Research on subsidence law of overlying strata in full mining of extra-thick coal seam

WANG Jun, ZHU Weibing, XIE Jianlin

2021, 47(10): 21-26. doi: 10.13272/j.issn.1671-251x.17848

<Abstract>(127) <HTML> (20) <PDF>(12)

Abstract:
The problem of strong mine pressure during the mining of the near goaf working face in Datong coalfield is more serious than that of the first mining face. In order to study the overlying strata movement law under the full mining conditions of extra-thick coal seam, the overlying strata movement of 8202 working face in Tongxin Coal Mine is monitored and analyzed by using a wireless remote monitoring system for internal strata movement of overlying strata under mining condition and borehole TV observing technology. The results show that in the early stage of large space mining of extra-thick coal seam, the overlying strata will be deformed and damaged from top to bottom in the advance working face, and then the layer group will break down and move normally from bottom to top. The overlying strata deformation and destruction in the mining site shows the change characteristics of stage step-up jump, which has a consistent correspondence with the location of the key strata, indicating that the key strata play the main control role in the strata movement. Under the condition of full mining, the overlying strata movement appears linkage subsidence phenomenon. Through physical simulation experiments, this paper further studies the nature of the whole-strata linkage subsidence of the overlying strata during full mining. The results show that before the initial breaking of the main key stratum, the grouped layered movement trend of each key layer is more obvious. After the main key stratum breaks for the first time, affected by the periodic breaking length of each key stratum and the compound breaking law of the upper and lower rock layers, the overlying strata subsidence and movement is more likely to show the whole-stratum linkage phenomenon.

Research on multi-view image stitching method in mine

WANG Hongyao, WU Jiaqi, LIN Song, WANG Mengya, ZHAO Guorui

2021, 47(10): 27-32. doi: 10.13272/j.issn.1671-251x.17767

<Abstract>(179) <HTML> (18) <PDF>(15)

Abstract:
In order to solve the problems of small field of view and unclear detail features of monitoring images in coal mines, a multi-view image stitching method in mine is proposed. Firstly, an improved adaptive histogram equalization method with contrast limitation is used to pre-process the images to highlight the image details and improve the contrast. Secondly, the ORB algorithm is used to extract the image feature points, and the improved Brief algorithm is used to calculate the feature descriptors. Thirdly, the K-nearest neighbor(KNN) algorithm is used to achieve rough matching of feature point pairs, and the random sample consensus(RANSAC) algorithm is used to filter and eliminate the mismatched feature point pairs, and the optimal perspective transformation matrix is solved to transform the coordinates of the pixel points of the image to be matched. Finally, the hat function weighted average fusion algorithm is used to stitch and fuse the fixed image and the image to be matched. The experimental results show that compared with the speeded up robust features(SIFT) and KAZE algorithms, the ORB algorithm reduces the number of feature points extracted for a single image by 48% and 33% respectively, which improves the effective feature point extraction capability. The feature point extraction time is reduced by 17% and 34% respectively, which improves the calculation efficiency. The images stitched by this method avoid the phenomenon of cracks and black lines at the joints, the image transition is natural, and the definition is high.

A mine low illumination image enhancement algorithm

TANG Shoufeng, SHI Ke, TONG Guangming, SHI Jingcan, LI Huashuo

2021, 47(10): 32-36. doi: 10.13272/j.issn.1671-251x.2021060052

<Abstract>(163) <HTML> (20) <PDF>(25)

Abstract:
The wavelet transform cannot maintain a balance in image edge preservation and detail processing and the multi-scale Retinex algorithm is prone to halo artifacts and serious noise pollution in images. In order to solve the above problems, a mine low illumination image enhancement algorithm is proposed by combining the wavelet transform with the multi-scale Retinex algorithm based on multi-scale guided filtering. Firstly, the algorithm decomposes the low illumination image into wavelets to obtain the high-frequency and low-frequency components. Secondly, the wavelet denoising is applied to the high-frequency components of the image using a three-stage threshold function, and nonlinear global luminance correction is applied to the low-frequency components of the image to enhance the image luminance. Moreover, the multi-scale guided filter function is used to estimate the illumination components instead of the Gaussian filter function of the traditional multi-scale Retinex algorithm, and then the reflection components are obtained. The principal component analysis method is used to fuse the reflection component and the non-linear global luminance correction image so as to improve image edge detail preservation effect effectively. Finally, the wavelet reconstruction is performed on the high-frequency components and low-frequency components of the image, and the wavelet reconstructed image is nonlinearly transformed to solve the image graying problem. The experimental results show that the algorithm has strong noise suppression capability, can improve the image luminance and contrast effectively, make the image edge preservation performance and detail information richness effectively balanced, and avoid the image halo artifacts and color distortion.

Underground image matching algorithm combining homomorphic filtering and histogram equalizatio

GONG Yun, YANG Pangbin, JIE Xinyu

2021, 47(10): 37-41. doi: 10.13272/j.issn.1671-251x.2021070018

<Abstract>(127) <HTML> (19) <PDF>(11)

Abstract:
In order to solve the problem of inaccurate feature point extraction and poor matching effect of existing underground image matching algorithms, an underground image matching algorithm combining homomorphic filtering and histogram equalization is proposed. The image is sharpened by homomorphic filtering to improve the image clarity, and the image is processed by the contrast-limited adaptive histogram equalization (CLAHE) algorithm to highlight the edge detail information of the image and improve the image contrast. In order to solve the problem of mis-matching in the traditional AKAZE algorithm, on the basis of rough matching by the brute force matching algorithm, the random sampling consensus (RANSAC) algorithm based on the homography matrix is used to perform accurate matching and eliminate the mis-matched point pairs. The experimental results show that using single-parameter homomorphic filtering and CLAHE algorithm to enhance the image can stretch the gray level of the image, reduce the number of dark pixels and increase the number of bright pixels, which makes the gray level distribution smoother and helps to preserve the details and boundary information of the image. Using RANSAC algorithm based on the homography matrix for accurate matching can detect more feature points and improve the matching accuracy. The matching effect is better than that of SURF algorithm and traditional AKAZE algorithm with a maximum of 96.09%.

Research on the positioning method of continuous shearer in coal mines

HE Jianwei

2021, 47(10): 42-48. doi: 10.13272/j.issn.1671-251x.2020120011

<Abstract>(99) <HTML> (8) <PDF>(13)

Abstract:
At present, most of the underground mining equipment positioning methods use inertial navigation plus odometer, visual measurement, ranging radar and other auxiliary measurement methods to reduce the position error drift accumulated by inertial navigation over time. However, these methods requires high reliability and measurement accuracy of the auxiliary measurement methods, and the centralized Kalman filter is used to filter and solve the data. There are problems such as a large amount of calculation and poor fault tolerance. In order to solve the above problems, a continuous shearer positioning method consisting of strapdown inertial navigation, ranging radar and odometer is proposed, using the ranging radar and odometer to measure the displacement of the continuous shearer respectively. The dead reckoning method is used to calculate the two-dimensional position information of the machine body, and the two-dimensional position information is applied to correct the inertial navigation position solution information so as to reduce the position drift error accumulated by inertial navigation over time. The federated Kalman filter is used to filter, solve and fuse the position information derived from each sensor, and reduce the calculation amount by reducing the dimension of the equation. Therefore, this method ensures the measurement accuracy while having a certain degree of fault tolerance. The simulation results show that the positioning accuracy of this positioning method can reach ±2 cm, and the orientation accuracy can reach 15′. The federated Kalman filter algorithm has small calculation amount and certain fault tolerance, which can lay the foundation for accurate measurement of the position of the continuous shearer in the roadway constrained environment, automatic roadway forming control and remote control.

Mine roadway field strength prediction based on improved convolutional neural network

WANG Anyi, ZHOU Xiaoming

2021, 47(10): 49-53. doi: 10.13272/j.issn.1671-251x.2021030073

<Abstract>(145) <HTML> (17) <PDF>(27)

Abstract:
In order to solve the problems of the complex modeling process, high computational complexity, and low prediction accuracy of the existing field strength prediction models, a mine roadway field strength prediction model based on improved convolutional neural network(CNN) is proposed. By analyzing the influence factors of electromagnetic wave transmission in large-scale fading channels in mines, using antenna operating frequency, roadway cross-sectional dimensions, roadway wall roughness, roadway wall inclination, roadway wall relative permittivity and transceiver distance as model inputs, using the electromagnetic wave propagation path loss as model outputs, the model is able to predict the changes of the roadway field strength. The improved CNN adds batch normalization layer after each convolutional layer to replace the original pooling layer so as to avoid the loss of data characteristics due to down-sampling of the pooling layer, to keep the output of each convolutional layer similarly distributed, to improve the network generalization capacity and to speed up the network convergence. The simulation results show that compared with the field strength prediction models based on CNN, BP neural network and support vector machine, the model has high consistency between the predicted value and the actual value, has stronger robustness, and improves the accuracy of mine roadway field strength prediction effectively.

Precoding design and performance analysis of wireless communication system under industrial impulsive noise

LI Xinyan, ZHANG Xiaoguang, WANG Yanfen, ZHOU Jiasi, SUN Yanjing

2021, 47(10): 54-61. doi: 10.13272/j.issn.1671-251x.17735

<Abstract>(126) <HTML> (17) <PDF>(10)

Abstract:
Industrial impulse noise in mining and other scenes can lead to burst data errors in wireless communication systems, significantly reducing data transmission reliability and communication quality. Most of the existing anti-impulse noise studies can only guarantee the effectiveness or reliability of communication systems. However, the task applications in industrial wireless communication scenes put forward high requirements on both effectiveness and reliability, and a single performance study cannot meet the needs. In order to solve the above problems, comprehensively considering the size of industrial equipment and design complexity, a multi-user multiple-input single-output (MU-MISO) orthogonal frequency division multiplexing (OFDM) system model combining receiver and transmitter design is established. At the transmitter, a precoding algorithm based on quadratic conversion is designed to maximize the system sum-rate. The quadratic type is used to decouple the coupled precoding vector to reduce computational complexity. At the receiver, a deep reduction impulse noise elimination scheme is designed to reduce the bit error rate and improve the reliability of industrial wireless communication. The simulation results show that under the Middleton Class A (MCA) noise model, the system and rate of the quadratic conversion-based precoding algorithm and the semi-definite relaxation (SDR) algorithm are very similar, verifying the effectiveness of the proposed precoding algorithm. Compared with the mainstream three nonlinear impulse noise elimination schemes of blanking, reduction and mixing, the deep reduction impulse noise elimination scheme has the highest output signal-to-noise ratio and the lowest bit error rate. The bit error rate is 24%, which is lower than that of the mainstream best scheme. The model has the optimal performance.

One-mode component-based fault section location method for mine high-voltage power network

ZHAO Jianwen, CHEN Jiali

2021, 47(10): 62-69. doi: 10.13272/j.issn.1671-251x.2021040039

<Abstract>(144) <HTML> (14) <PDF>(9)

Abstract:
After a single-phase grounding fault occurs in the mine high-voltage power network, it is important to identify the fault section quickly for the safe and stable operation of the mine power network. The existing research on fault section location in distribution networks rarely involves mine high-voltage power network, while the traditional steady-state method has a dead zone when it is used for neutral point grounding system via arc suppression coil. And the transient method needs to be used with phase selection device and has the disadvantage that the fault characteristic quantity decays with time. By analyzing the characteristics of the one-mode component of the current obtained by Clark transform under the single-phase grounding fault additional state of the mine high-voltage power network, it is concluded that the one-mode component of the current upstream of the fault point is significantly larger than that downstream of the fault point, and the one-mode component of the current is not affected by the fault phase and the arc suppression coil current. A location method of the fault section of the mine high-voltage power network based on the one-mode component without phase selection is proposed. The method uses Clark transform to obtain the current one-mode components of each monitoring point in the fault additional state of the mine high-voltage power network, and calculates the current one-mode component amplitude difference on both sides of each section. The fault path is determined according to the minimum current one-mode component amplitude difference at the fault path branch node, and then the fault section is determined according to the maximum current one-mode component amplitude difference on both sides of the fault section at the fault path. Simulation and experimental results show that the method can achieve accurate fault location when a single-phase grounding fault occurs in any phase of the mine high-voltage power network, and is not affected by the initial fault angle, fault grounding resistance, fault location and system running mode.

Mine inverter based on isolation and transformation of power electronic transformer

ZHANG Guilin, WANG Yiying, LIU Jiangong, CHEN Longfei, LIU Wenzhuang

2021, 47(10): 70-76. doi: 10.13272/j.issn.1671-251x.2020110059

<Abstract>(111) <HTML> (13) <PDF>(16)

Abstract:
At present, the mine inverter and the power frequency transformer are placed separately, which occupies too much underground working space. And the inverter output voltage has high harmonic content and poor waveform quality. In order to solve the above problems, the theoretical relationship between transformer operating frequency and volume is analyzed. It is concluded that under the same transmission power, the high-frequency transformer has a more streamlined size, smaller volume and higher power density compared with the operating frequency transformer. The intermediate filter capacitor in the common topology is replaced by power electronic transformer (DC-DC converter containing high frequency transformer). The paper proposes a composite mine inverter topology based on power electronic transformer isolation and transformation. The number of fully controlled switching devices IGBT in this topology is only half of the total number of power devices, which makes the inverter structure more compact and smaller, reduces the inverter switching losses, reduces hardware complexity and production costs, and improves efficiency and reliability. The control strategies of the three-phase rectifier input stage, the intermediate isolation transformer transmission stage and the three-phase variable frequency output stage in this topology are given. The fast space vector pulse width modulation (SVPWM) algorithm in 120° coordinate system is used to control the output stage to output the ideal variable frequency three-phase symmetric sinusoidal AC voltage. The steady-state and dynamic characteristics of the inverter at all levels are analyzed through simulation and experiment. The results show that the inverter can realize the secondary conversion of the inverter output and voltage level, and the output voltage regulation range is more flexible. The fast SVPWM algorithm in 120° coordinate system reduces the output voltage harmonic content, and the output three-phase voltage waveform is good.

Decision model of roof support based on R2-MOEA/D algorithm

HAO Qinxia, WANG Lianlian, ZHANG Jinsuo

2021, 47(10): 77-84. doi: 10.13272/j.issn.1671-251x.2020120019

<Abstract>(167) <HTML> (18) <PDF>(8)

Abstract:
The existing roof support decision methods either analyze safety factors one-sidedly or assign weights to index objectively, fail to assign weight coefficients effectively, and cannot meet the demand of high-dimensional multi-objective roof case decision. In order to solve this problem, a decision model of roof support based on R2 index differential high-dimensional multi-objective evolution (R2-MOEA/D) algorithm is proposed by analyzing the roof weighting index. Firstly, the model defines the index attributes for the roof weighting state, establishes the roof index knowledge base, and calculates the conditional index in the knowledge base using analytic hierarchy process and entropy method, and obtains the subjective and objective weights of the index. Secondly, the model introduces the weight matrix on the basis of determining the subjective and objective weights to construct the roof multi-objective decision model which based on R2-MOEA/D algorithm. Finally, based on the R2-MOEA/D algorithm, the multi-objective problem is decomposed into multiple sub-problems, and the Chebyshev function is used as the R2 index ranking criterion for individual selection to obtain the Pareto optimal solution with better convergence and diversity, i.e., the conditional index roof case with the highest similarity. And its corresponding result attributes provide the support scheme for the decision of the accident case. The experimental results show that the R2-MOEA/D algorithm has the best overall effect in terms of the convergence and distribution of the data set compared with the NSGA2 algorithm, NSGA3 algorithm and RVEA algorithm, and improves the search capability in high-dimensional space. The feasibility evaluation of the decision model of roof support based on R2-MOEA/D algorithm is carried out through the roadway 2-6011 and roadway 10-4151 in Sanjiaohe Coal Mine, Huozhou, Shanxi. The results show that the solution retrieved by R2-MOEA/D algorithm is in line with the actual support situation of the coal mine.

Research on the mechanical properties and energy evolution of pre-cracked sandstone samples

WANG Yaoqiang

2021, 47(10): 85-90. doi: 10.13272/j.issn.1671-251x.2021010030

<Abstract>(111) <HTML> (17) <PDF>(6)

Abstract:
The current research on the strength and crack expansion law of single and multiple pre-cracked rock samples mainly focuses on small-scale pre-cracked rock samples. However, in actual engineering practice, the geological scale and occurrence of rock masses are larger, and the degree of fragmentation and the possibility of dynamic hazards after being affected by mining are greater than those of intact rock masses. In order to solve this problem, uniaxial compression tests on intact fine sandstone rock samples and pre-cracked large scale rock samples are carried out. Based on the analysis of the basic mechanical properties of intact rock samples and pre-cracked rock samples, the evolution mechanism of each energy index (total strain energy, elastic strain energy and dissipated strain energy) before the stress-strain peak of rock samples is obtained, and the influence of the pre-cracked inclination on the energy density during the whole process of deformation and damage of rock samples is revealed. The research results are showed as follows. ① With the increase of the inclination of the pre-cracked, the peak strength and peak strain of the rock sample decrease, and the rock sample changes from tensile splitting damage to shear slip damage. ② Corresponding to the elastic and plastic stages of the rock sample stress-strain, the pre-cracked rock sample has an accelerated energy storage period and a sharp energy consumption period. And as the pre-cracked inclination increases, the proportion of the dissipated strain energy and surplus strain energy of the rock sample increases. The increase indicates that the dynamic ejection damage ability of the rock sample is enhanced, the rock sample is broken, and the energy evolution of the intact rock sample is relatively gentle. Based on the results of the study, it is pointed out that in practical engineering, when exposing large scale and large inclination defects (faults, joints and other geological structures), it is necessary not only to prevent and control the fragmentation of the rock around the defects, but also to monitor the energy changes around the defects so as to reduce the hazard of structural impact of the rock mass.

Analysis on the importance of factors influencing the thermal environment of the excavation roadway

DONG Xiaotong, BIAN Menglong, WANG Eryu

2021, 47(10): 91-96. doi: 10.13272/j.issn.1671-251x.2021040074

<Abstract>(87) <HTML> (13) <PDF>(15)

Abstract:
At present, most studies only discuss the impact of a single factor on the thermal environment of the extraction roadway, and do not discuss the importance of multiple factors on the thermal environment of the extraction roadway. Fluent software is used to carry out three-dimensional modeling and numerical simulation of the extraction roadway, and orthogonal test and control variate method are used to analyze the influence degree of the inlet wind speed, inlet wind temperature, surrounding rock temperature and the diameter of the air duct on the thermal environment of the extraction roadway. The numerical simulation results show that the influence degrees on the thermal environment of the extraction roadway in descending order are the surrounding rock temperature, air duct diameter, inlet wind temperature and inlet wind speed. The influence degrees of inlet wind speed, inlet wind temperature and air duct diameter on the thermal environment of the extraction roadway remain stable. The farther away from the extraction working face, the more significant the influence of surrounding rock temperature on the thermal environment of the extraction roadway. There is a negative power function relationship between the extraction roadway temperature and the inlet wind speed. Increasing the inlet wind speed can reduce the extraction roadway temperature, but if the inlet wind speed is too high, the cooling effect becomes less and less obvious. There is a linear positive correlation between the extraction roadway temperature and the inlet wind temperature and the surrounding rock temperature, and there is a linear negative correlation between the extraction roadway temperature and the diameter of the air duct. Origin is used to fit the numerical simulation results, and obtain the multiple linear regression equation between the extraction roadway temperature and the inlet wind speed, inlet wind temperature, surrounding rock temperature and air duct diameter. The goodness of fit is high, and the results can provide effective reference for engineering prediction of extraction roadway temperature.

Design of a regional coal mine supervision data service platform based on big data technology

MENG Guangwei

2021, 47(10): 97-102. doi: 10.13272/j.issn.1671-251x.2021030067

<Abstract>(475) <HTML> (86) <PDF>(96)

Abstract:
There are problems in coal mine supervision system, such as multi-level repeated uploading of networked data and data inconsistencies in the safety risk monitoring and early warning system, the lack of data storage and computing resources at all levels of safety supervision agencies, the difficulty of correlation analysis and data mining, etc. In order to solve the above problems, a regional coal mine supervision data service platform based on big data technology is designed. The platform uses Kafka distributed message queues to generate standardized Kafka data bodies from regional coal mine monitoring data, and upload them to the cloud platform Kafka cluster in batches. The platform provides monitoring real-time data consumption services through the publish-subscribe mode, which reduces network transmission overhead and avoids the adverse effects of multi-level uploading and filtering of networked data. The Spark Structured Streaming computing engine and Spark SQL are used for real-time data calculation and statistical analysis of historical data. Various data analysis and mining algorithms are integrated to provide support for data mining and prediction and early warning. HBase column storage database is used to achieve reliable storage of massive historical data. Through the Hive data warehouse associated with HBase, the platform establishes various subject data model libraries to meet the demand for multi-dimensional correlation analysis of data. The data subscription service with unified security authority authentication provides the required coal mine monitoring data, statistical analysis data and data mining results for supervision agencies at all levels, decouples the back-end data service center from the front-end supervision and monitoring business system, and provides data customization and consumer services for supervision agencies at all levels through data services so as to improve data utilization efficiency. The application results show that the platform can meet the storage, analysis and calculation and data sharing needs of regional coal mine monitoring data.

Design and application of anti-wind drill command platform based on multi-system integratio

WANG Baolai, HU Kaigeng, CHEN Anguo, HAN Guoqing, YUAN Zhiji

2021, 47(10): 103-109. doi: 10.13272/j.issn.1671-251x.2021030069

<Abstract>(97) <HTML> (11) <PDF>(11)

Abstract:
In order to solve the current problems of untimely feedback information, lack of effective analysis of big data and inconvenient real-time operation in the process of coal mine anti-wind drill, an anti-wind drill command platform based on multi-system integration is designed. The platform is based on the mine anti-wind drill process and configures the platform server and client with the existing safety monitoring system, underground personnel positioning system, mine car positioning system, integrated automation system, power monitoring system, video surveillance and other system servers in the same industrial ring network. Therefore, the server and client are able to communicate directly with each system using the corresponding protocols, and big data technology is used to obtain the corresponding data effectively, classify, filter and process the data, and complete the multi-system integration. On this basis, the real-time map system, power outage and transmission system, integrated alarm system and interactive component system are designed. Real-time map system can realize dynamic update and display of maps. The important observation data such as personnel, wind direction and gas are graphically displayed on the ventilation system schematic diagram, realizing the geographic information management, analysis and auxiliary decision-making in coal mines. The power outage and transmission system can display the status of the switch in real time on the power supply system schematic diagram to realize the function of automatic search of power supply lines and remote power outage and transmission so as to guarantee the reliability and safety of power outage and transmission. The integrated alarm system responds to the abnormal information of the anti-wind drill command platform and site in real time through text and voice, and activates the corresponding emergency plan system as needed to reduce the occurrence of on-site accidents effectively. Interactive components can quickly realize remote video calls, regional personnel view, real-time data acquisition, personnel position search, personnel track query and other functions. This improves the work efficiency of personnel participating in anti-wind drill effectively. The field application results show that the platform can reduce the number of personnel participating in anti-wind drill, improve the efficiency of power outage and transmission, ensure the safety and reliability of the drill process and can be applied to rescue and disaster relief under various actual disaster conditions in mines.

Application of improved analytic hierarchy process in the emergency treatment mechanism of precise personnel positioning system

TANG Lijun, WU Wei, LIU Shisen

2021, 47(10): 110-114. doi: 10.13272/j.issn.1671-251x.2021030050

<Abstract>(104) <HTML> (17) <PDF>(11)

Abstract:
In order to solve the problem of misjudgment of underground personnel in distress in the intelligent mining precise personnel positioning system, resulting in a waste of rescue resources, this paper proposes to apply the analytic hierarchy process to the emergency treatment mechanism of the intelligent mining personnel precise positioning system. Once the judgment matrix of the traditional analytic hierarchy process method is set, it cannot respond to the changes of the influencing factors in real time. When the value of the influencing factor changes, the judgment matrix needs to be reset to obtain the correct decision scheme. In order to solve this problem, the analytic hierarchy process method is improved and the judgment matrix of the analytic hierarchy process method is proposed to be adjusted according to the real-time data of the sensors to improve the alarm accuracy. When the management server of the precise personnel positioning system receives the alarm information reported by a person tag in the mine, the method uses the 1-9 scale method to mark the various sensor data of the personnel's position and the sensor data of vital characteristics uploaded by the tag. According to the scale value of the sensor data, the parameter values of the judgment matrix of each index layer-decision layer are adjusted in real time, and the weight value of the decision layer is calculated by the analytic hierarchy process, and the authenticity of the alarm information is judged according to the weight values. The simulation results show that after the emergency treatment mechanism of the precise personnel positioning system adopts the improved analytic hierarchy process that can adjust the parameters of the judgment matrix in real time, the authenticity of the alarm information can be judged effectively, invalid alarm information is eliminated, and the alarm accuracy of the emergency treatment mechanism is improved.

Design of wireless Mesh communication system in coal mine

WEI Zhenghua, YE Xiaolan

2021, 47(10): 115-120. doi: 10.13272/j.issn.1671-251x.2021060080

<Abstract>(155) <HTML> (23) <PDF>(28)

Abstract:
The current wireless communication technology cannot meet the requirements of high throughput rate, long-distance transmission, flexible networking, and simple installation and deployment in the special space and variable working environment of coal mine. In order to solve the above problems, a wireless Mesh communication system in coal mine is designed. The distribution of wireless Mesh network nodes in a single roadway is proposed, and the system hardware and software design method is introduced. The network node is composed of baseband board and RF front-end. The baseband board mainly realizes digital waveform generation, supports embedded system management information interaction and automatic gain control of received signal. The RF front-end mainly achieves the function of amplifying RF signal intensity to the target power. The test results are listed as follows. ① When the RF front-end transmission gain is >17 dB, adjusting the transmission average output power of AD9361 software radio module can make the system average output power 37 dBm. ② The adjacent channel power ratio of the RF front-end transmission is <-43 dBc. ③ The insertion loss of the RF front-end receiving link is <1.8 dB and the transceiver switching time is <1 μs. ④ The average throughput rate of the system is ≥45 Mbit/s, which meets the requirement of no lag in monitoring video transmission in underground coal mines. ⑤ The call quality level is ≥3, indicating that the call is relatively clear in most working hours.

Environmental monitoring system of coal preparation plant based on cloud platform

FENG Tianxin, ZHANG Xiaoguang, LIU Jingyong, WANG Yanfen

2021, 47(10): 121-126. doi: 10.13272/j.issn.1671-251x.17763

<Abstract>(189) <HTML> (121) <PDF>(25)

Abstract:
The coal preparation plant has a complex environment, a large monitoring area, a large number of monitoring points, and the points are scattered. The manual fixed-point timing sampling method of environmental parameters has poor real-time performance and low data accuracy. The wired monitoring system is inconvenient deployed, has high costs and easily damaged lines. The wireless monitoring system based on NB-IoT and LoRa technology has insufficient network coverage. In order to solve the above problems, an environmental monitoring system of coal preparation plant based on cloud platform is designed using ZigBee wireless transmission technology. The system architecture, hardware and software design of monitoring nodes (terminal nodes, routing nodes, gateway nodes) and cloud-based data management software design scheme are introduced. The system collects and processes the environmental parameters of the coal preparation plant in real time through the terminal nodes. The routing nodes summarize the monitoring data and forward them to the gateway nodes. Then the gateway nodes encapsulate the data and upload them to the cloud platform server via Ethernet. And the cloud data management software realizes data storage, analysis and display. The test results show that the system is stable in operation, accurate in data transmission, and can realize the functions of real-time monitoring and warning of environmental parameters and historical data query of coal preparation plant.

2021 Vol. 47, No. 10

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