工矿自动化

Management and control mode of underground coal mining based on medium and high-level intelligent technology

LI Haodang, DING Zhen, ZHANG Kai, LUO Huiqiang, CAO Zhengyuan, CUI Wen, YOU Xiusong, ZHAO Xingyu, MENG Guangrui, SUN Jiang, DENG Wenge

2022, 48(2): 1-10. doi: 10.13272/j.issn.1671-251x.17877

<Abstract>(520) <HTML> (73) <PDF>(92)

Abstract:
Coal is the guarantee energy in China, and its dominant position in energy will not change for a period of time in the future. Coal intelligent mining will show a rapid development trend and enter into a new stage of development. Through induction and analysis, the great significance, development law, contradiction, construction method and future development direction of intelligent construction of coal mine are summarized in this paper. This paper systematically expounds the reform process of coal mining technology and management mode in China, and summarizes the five stages of manual mining, ordinary mining, comprehensive mechanized mining, automatic mining, primary intelligent mining, as well as the corresponding technical modes. Breaking through the intelligent research ideas such as traditional coal roadheader mining, this paper puts forward 10 characteristics of medium and high-level intelligent mining technology of coal, namely, complete transparency of coal mine, comprehensive intelligence of perception, high-end intelligence of equipment, real-time reliability of network, integrated platform control, intelligent analysis of data, group collaboration intelligence, professional team employees, dynamic decision-making intelligence, disaster prevention and control matching, and gives the definition, characteristics, content and function of each characteristic. Based on the premise of medium and high-level intelligent technology, the corresponding ‘1+1’ management and control mode of coal mine mining is conceived, that is, one level is set in one coal mine, and a new flat platform management and control mode of ‘one command and control center+one professional team’ is constructed. Therefore, the mode can promote the reform of production mode, match the requirements of corresponding mining mode in the future intelligent rapid development and realize the real meaning of reducing personnel, increasing safety and improving efficiency. Finally, the further development of intelligent mining technology and mode in coal mine is prospected.

Research status of intelligent technology of shearer in fully mechanized working face

ZHAO Yihui, ZHAO Youjun, ZHOU Zhan

2022, 48(2): 11-18,28. doi: 10.13272/j.issn.1671-251x.2021090024

<Abstract>(1121) <HTML> (111) <PDF>(226)

Abstract:
This paper introduces the research status of intelligent technology of shearer at home and abroad. Since the 1990s, the intelligent technology of shearers has entered a mature stage of development abroad, and leading innovations have been made in shearer memory cutting, coal and rock identification, airborne main control software and remote monitoring. The intelligent development of domestic shearers has shifted from introduction and absorption to independent innovation, basically realizing primary intelligent fully mechanized mining. According to the different functions of shearers, intelligent horizontal classification is divided into four categories, intelligent perception, intelligent control, intelligent diagnosis and intelligent communication. The key technologies of intelligent perception include posture perception, operating environment state perception, airborne video perception, personnel proximity identification, intelligent anti-collision detection, straightness perception and coal rock identification perception. The key technologies of intelligent control include drum automatic height adjustment control, adaptive speed adjustment control, environmental gas linkage control, coal flow load balance control, and pitch guidance control. The key technologies of intelligent diagnosis include real-time online diagnosis technology and the whole life cycle management of shearer. The key technologies of intelligent communication include wired communication technology and wireless communication technology. According to the human intervention in the coal cutting process of shearer, intelligent longitudinal gradation is divided into four grades, auxiliary automation, primary automation, advanced automation and intelligence. Through the intelligent classification and gradation of the shearer, the intelligent function of shearer can be visually consulted, and the intelligent grade of shearer can be determined by judging conditions, which provides quantitative reference for intelligent mine construction rating, and also shows the context of intelligent development of shearer more clearly.

Research on precise detection method of personnel in shearer operation area

WEI Dong, WANG Zhongbin, SI Lei, TAN Chao, LU Xuliang

2022, 48(2): 19-28. doi: 10.13272/j.issn.1671-251x.2021110069

<Abstract>(354) <HTML> (35) <PDF>(60)

Abstract:

The current intelligent shearer has the functions of three-dimensional positioning, memory cutting and remote monitoring, but it lacks the detection and early warning protection function of personnel entering the shearer operation area by mistake. Therefore, the precise detection of personnel is one of the key problems to be solved urgently. Affected by the low illumination and complex working conditions of fully mechanized working face, the application of active anti-collision warning technology for coal mine electromechanical equipment based on laser, radio frequency, ultrasonic and other sensors is limited, and the anti-collision technology based on visible light sensor cannot meet the requirements of accuracy and stability. The system architecture of precise detection of personnel in shearer operation area based on infrared thermal imaging technology is built, and then the precise detection method of personnel is proposed. Aiming at the high intensity and uneven characteristics of the infrared image noise in fully mechanized working face, an improved multi-layer guided filter model based on Gauss mask-code is used to filter out infrared image noise effectively and retain the edge information. The moving foreground target motion information under dynamic background is extracted by optical flow method that based on Lucas-Kanade. The intuitionistic fuzzy C-means clustering algorithm based on the weight of local image information is used to segment the infrared image information of the shearer operation area so as to obtain the position information of the moving target. Based on the morphological weighted voting method, the extraction results of the moving target motion information and the infrared image information segmentation results are fused to realize the precise detection of personnel in the shearer operation area. The underground industrial test is carried out in 21208 fully mechanized working face of Gengcun Coal Mine. The results show that the average tracking deviation of the precise detection method for personnel in the shearer operation area is 0.106 5 pixel, the average overlap ratio is 96.10%, and the average single processing time is 0.490 8 s, which meet the needs of field application.

Research on UWB personnel positioning system in coal mine

ZHANG Haijun, SUN Xuecheng, ZHAO Xiaohu, YAN Kuncheng

2022, 48(2): 29-34,41. doi: 10.13272/j.issn.1671-251x.17824

<Abstract>(519) <HTML> (25) <PDF>(120)

Abstract:
In order to solve the problem that non-line-of-sight(NLOS) interference affects wireless signal transmission in complex underground environment of coal mines, an ultra wide band(UWB) personnel positioning system in coal mine is designed. The system uses asymmetric double-sided two-way ranging algorithm with return frame mechanism for ranging without clock synchronization, which ensures the ranging precision. The positioning area is divided by the area discrimination strategy and the area correction strategy, so that the tag can only communicate with the base station in the positioning area to achieve positioning, which avoids a large number of invalid frames in the positioning process and improves the positioning efficiency. The weighted least squares method and the unscented Kalman filter joint positioning algorithm are used to solve the tag position coordinates, which improves the positioning precision. A backup power supply is configured in the base station to ensure emergency power supply in case of power failure. Two communication modes, Ethernet and LoRa, are adopted. When the Ethernet is disconnected, the ranging data is transmitted in the LoRa mode, which ensures the emergency communication of the system. The test results show that the system has high dynamic and static positioning precision and strong anti-NLOS interference capability. When the base station is powered off or the Ethernet is disconnected, the system can realize emergency communication for a period of time.

Research on 3D target detection of unmanned trackless rubber-tyred vehicle in coal mine

QIN Peilin, ZHANG Chuanwei, ZHOU Libing, WANG Jianlong

2022, 48(2): 35-41. doi: 10.13272/j.issn.1671-251x.2021110068

<Abstract>(1617) <HTML> (37) <PDF>(80)

Abstract:
The environment perception based on 3D detection is the basis of unmanned driving technology of trackless rubber-tyred vehicle in coal mine. Due to the lack of light in the underground environment, the RGB image information is missing, and the narrow roadway space leads to more noise in the point cloud data collected by laser radar, so the existing 3D target detection methods based on image or radar point cloud can not achieve good detection effect in the underground. In order to solve this problem, a 3D target detection method for unmanned trackless rubber-tyred vehicle is proposed, which fuses image and radar point cloud. The obtained driving environment data of the trackless rubber-tyred vehicle is preprocessed. The global histogram equalization method is used to improve the brightness of RGB images and reduce the effect of uneven lighting in coal mine. The bilateral filtering and denoising and principal component analysis dimensionality reduction processing are performed on radar point cloud data to improve the quality of point cloud data and reduce computing time. A fusion image and radar point cloud detection model is designed. The region proposal network is used to generate 2D image candidate regions, which are fused with the point cloud data at the early characteristic level to generate 3D candidate regions, and then fused with the pooled image and point cloud data at the later region level to output the 3D detection anchor frame to realize target detection. The experimental results show that compared with the detection methods based on YOLO3D and MV3D models, the proposed method has higher detection precision of the target to be tested, and achieves a better balance between precision and detection speed. The underground test results show that the method can accurately detect the position of pedestrians or vehicles in the driving environment of trackless rubber-tyred vehicle, and has good underground adaptability.

Information model of intelligent fully mechanized working face based on OPC UA

DU Yibo, ZHANG Chengfeng, GONG Shixin

2022, 48(2): 42-48. doi: 10.13272/j.issn.1671-251x.2021090040

<Abstract>(286) <HTML> (23) <PDF>(42)

Abstract:
In the process of data connection of each system in fully mechanized working face, it is necessary to perform frequent correspondence between the data point table and the semantics, which leads to the surge of system interconnection and data sharing cost of fully mechanized working face. An information model of intelligent fully mechanized working face based on OLE for process control unified architecture(OPC UA) is proposed. According to the physical composition, functional modules and the information flow requirements between modules of intelligent fully mechanized working face, the information model architecture of intelligent fully mechanized working face is proposed by using object-oriented method. On the basis of this architecture, the physical objects and mining process data in fully mechanized working face are digitized and modeled to form a face-level information model. The static attribute set and process attribute set of basic component, monitoring component set and functional component set objects in information model are introduced in detail. The information model of the intelligent fully mechanized working face is instantiated by adopting the combined modeling mode of the OPC UA and the unified modeling language(UML). The UML class diagram is used to assist in the description of the information model structure, and then converted into the OPC UA information model XML description file. The information model structure data and attribute data are mapped to the OPC UA address space model, and the OPC UA server is started. The practical application results show that each system of fully mechanized working face can access the server address space, and successfully obtain the structure of intelligent fully mechanized working face information model and object data semantics, so as to complete the data collection, storage and update quickly. In order to verify the application effect of the information model, based on the OPC UA server, the information management and integrated analysis platform of fully mechanized working face is developed. The field application test show that the monitoring data displayed by the platform is consistent with the actual operation results (the background data are all from the address space information model), thus verifying the feasibility of the information model combined with the OPC UA protocol to realize the information interconnection of fully mechanized working face.

Research on moving trajectory of intelligent sensor in underground roadway

BAI Sizhong

2022, 48(2): 49-54. doi: 10.13272/j.issn.1671-251x.2021080081

<Abstract>(153) <HTML> (12) <PDF>(29)

Abstract:
In order to solve the problem that the existing integrated inertial navigation method loses completely autonomous advantage and increases cost when applied to intelligent sensors in underground roadway, the underground roadways are firstly decomposed into multiple two-dimensional planes with certain vertical height. And multiple established paths are formed in the two-dimensional planes, and the positioning problem of intelligent sensors is converted into the tracking problem of moving tracks on the established paths. Secondly, the inertial measurement unit based on the micro electro-mechanical system (MEMS-based IMU) is used to realize the inertial navigation of the intelligent sensor in the underground roadway, and the moving track is inverted by combining the zero velocity update and the established path calibration. After the zero velocity update of the intelligent sensor at the starting point of the established path, the moving of the whole established path can be divided into two modes, namely linear inertial navigation mode and intersection calibration mode. Linear inertial navigation: when the change values of the heading angle and the roll angle of the sensor do not exceed the threshold value, the speed, the position and the attitude angle of the sensor are calculated through the inertial navigation component, and the real-time relative coordinates and the motion path are calculated. Intersection calibration: when the sensor moves to the intersection, the current real-time value is calibrated according to the known coordinate value of the intersection so as to eliminate the accumulated error of inertial navigation. The results of the test on the ground ring road show that in the context of uncalibrated, the heading deviation of pure inertial navigation is about 30°, and the relative error of moving distance is 5.5%. After the calibration of the established path intersections, the heading deviation is about 2°, and the relative error of the moving distance is 0.8%. After calibration, the moving track is more consistent with the actual road.

Study on effective extraction radius of bedding borehole under the impact of normal fault

JIANG Mingquan, KANG Xiangtao, YAN Chaoxing, TANG Meng, WANG Ziyi

2022, 48(2): 55-60. doi: 10.13272/j.issn.1671-251x.2021070015

<Abstract>(146) <HTML> (9) <PDF>(18)

Abstract:
The reasonable effective extraction radius of borehole is the key to ensure gas extraction effect. However, the research of effective extraction radius mainly focuses on the measurement method of effective extraction radius of borehole, and there is a lack of research on the effective extraction radius of borehole under special geological conditions of normal fault. Taking a coal working face in Guizhou as the engineering background, the fluid-solid coupling model is established, and the variation law of effective extraction radius of bedding borehole without fault impact is analyzed by means of mutual verification between numerical simulation and borehole gas extraction method. The results show that when the gas is extracted for 120 days, the effective extraction radius of the numerical simulation is 3.10 m, and that of the field test is 2.93 m. The field results are basically consistent with the numerical simulation results, which verifies the reliability of the fluid-solid coupling model. By using multi-physics field coupling simulation software, the variation law of effective extraction radius of bedding borehole under the impact of normal fault is analyzed. The results show that within a certain extraction time range, when the borehole is at a certain distance from the normal fault, the gas pressure curve will have a hump-like distribution, and the peak interval is about 3.5 m. The effective extraction radius of the borehole near the normal fault increases with the increase of the distance from the fault. The impact of the normal fault on the effective extraction radius of the borehole is within 70 m from the fault. Combined with the analysis results under the impact of normal faults, the spacing of gas drainage boreholes near the normal fault is arranged in sections under the premise of ensuring the extraction effect and not prolonging the extraction time. Within 30 m from the fault, the boreholes are densely arranged, and the spacing between the boreholes should not be greater than the effective extraction radius (1.83 m) when the distance from the fault is 10 m. Within the range of 30-70 m from the fault, under the condition of ensuring safety, the spacing of boreholes can be appropriately increased. After 70 m from the fault, the spacing can be gradually restored to the borehole spacing layout of bedding boreholes without the impact of the normal fault.

Analysis of coal drawing law and parameter research in shallow buried double hard and extra-thick coal seam

SUN Qiang, SHAN Chengfang, LI Yafeng, WANG Jianjian, ZHANG Hao, ZHANG Jiaqi, WU Zhongya

2022, 48(2): 61-69. doi: 10.13272/j.issn.1671-251x.2021070054

<Abstract>(186) <HTML> (15) <PDF>(19)

Abstract:
The coal resources in Xinjiang are shallowly buried, the coal seam is thick, resulting in poor top coal caving and drawing. And the roof is overhanging in a large area, which makes it impossible to achieve safe and efficient top coal mining. And at present, there are few related researches on efficient coal drawing in fully mechanized working face of shallow buried double hard and extra thick coal seam. In order to solve the above problems, taking 110501 fully mechanized working face of Yushuling Coal Mine as engineering background, the paper studies the coal drawing law of shallow buried double hard and extra thick coal seam, so as to determine reasonable mining-drawing rate and coal drawing technology, and improve the recovery rate. FLAC3D software is used to analyze the coal and rock failure law in the mining process of fully mechanized working face, so as to design reasonable mining-drawing ratio. The results are listed as follows. ① With the increase of the mining height of the working face, the yield failure coefficient of the top coal and the coal wall continues to increase, and the maximum value of the advance support stress and the affected area of the coal wall on the working face gradually increase. ② Considering the stability and caving and drawing of top coal and coal wall, the designed mining height is 4.0 m, the top coal drawing height is 4.6 m, and the mining-drawing ratio is 1∶1.15. The top coal drawing law of fully mechanized working face is analyzed by using PFC2D software, so as to design reasonable coal drawing technology (including the design of coal drawing step distance and coal drawing mode). The results are listed as follows. ① The gangue content of ‘one coal mining and one top coal drawing’ is higher than that of ‘two coal mining and one top coal drawing’ and ‘three coal mining and one top coal drawing’, but the overall drawing rate is higher than that of ‘two coal mining and one top coal drawing’ and ‘three coal mining and one top coal drawing’ due to the small coal drawing step distance. Therefore, the coal drawing step distance of ‘one coal mining and one top drawing’ is selected. ② Compared with two rounds coal drawing, single round coal drawing has higher coal drawing speed, but gangue content is higher and coal drawing rate is lower. Compared with two rounds sequential coal drawing, the two rounds interval coal drawing has a higher drawing rate. Therefore, the tow rounds interval coal drawing method is selected. The designed mining drawing rate and coal drawing process are applied to the engineering practice of 110501 fully mechanized working face, the results show that the top coal drawing rate of this working face is 82%-87%, the average drawing rate is higher than 82%, and the coal drawing effect is good.

Analysis of coal pillar rock burst appearance in multi-seam mining with thick and hard roof

YANG Wei, LAN Shirui, LI Zhenlei, ZHANG Chuanjiu, LI Hongping, ZHONG Taoping, SONG Dazhao, ZHOU Chao

2022, 48(2): 70-76. doi: 10.13272/j.issn.1671-251x.2021050071

<Abstract>(187) <HTML> (13) <PDF>(12)

Abstract:
The existing research only analyzes the rock burst appearance characteristics under specific conditions, lacks research on the rock burst appearance induced by coal pillar under the condition of thick and hard roof. In order to solve this problem, taking I010203 working face of a mine in Xinjiang as the research object, the paper analyzes the characteristics and causes of working face rock burst under the condition of thick and hard roof multi-seam mining by means of field monitoring and numerical simulation. By analyzing the spatial distribution law of microseismic and large energy events monitored on site, the distribution characteristics of support pressure, and the distribution characteristics of surrounding rock stress during the mining of the working face simulated by numerical simulation, this paper obtained the following results. The stress concentration and the microseismic event density in the transport roadway area of the working face are higher than those in the return air roadway area. And the stress concentration and microseismic event density in the roof and coal seam area are higher than those in the floor area. Based on the above results, the causes of coal pillar rock burst appearance in the mining process of I010203 working face are analyzed by using rock burst caused by dynamic and static combined load theory. ① It is easy to produce lateral overhanging roof above the coal pillar in the transport roadway section. The sudden breaking of the long overhanging roof generates a large amount of dynamic loads. At the same time, a large amount of static loads accumulate on the coal pillars and the roof during the mining process. When the superposition of the two exceeds the critical load, it may cause the rock burst appearance of the working face or a large energy event. The mining process of the I010203 working face mainly includes the main controlling factors such as coal pillar concentrated stress, overlying roof and surrounding rock supporting stress. Therefore, it is easy to produce coal pillar type and thick hard roof caving type rock burst appearance. ② When the mining position of the working face gradually approaches the boundary of the ‘knife shape’ goaf, the boundary stress is transferred downward to the I010203 working face, which leads to the further increase of the rock burst risk of the I010203 working face.

Study on the effect mechanism of CO on gas explosion reaction

HUO Xiaoquan, KOU Yimin, YAN Zhenguo, FAN Zhihai, HE Yanpeng

2022, 48(2): 77-82. doi: 10.13272/j.issn.1671-251x.2021080033

<Abstract>(203) <HTML> (20) <PDF>(14)

Abstract:
At present, most of the research on gas explosion takes the mixed gas of CH₄ and air as the research object, but the gas explosion in coal mine is not a separate CH₄ explosion, there are often CO and other components, which have a certain effect on gas explosion. In order to reveal the effect mechanism of CO on gas explosion reaction, the explosion pressure of 9.5% CH₄ and 0-4% CO mixed gas is measured in a 20 L spherical explosion tank. The results show that with the increase of CO concentration, the maximum explosion pressure of the mixed gas increases first and then decreases, and the maximum explosion pressure is 624.9 kPa when the CO volume fraction is 2%. In the numerical simulation software of Chemkin-Pro, the temperature sensitivity and key free radicals of the gas explosion reaction of CO, CH₄ and air mixed gas are analyze from the chemical kinetics point of view by adopting the GRI-mech 3.0 mechanism, and the effect mechanism of CO on gas explosion reaction is obtained. Adding a small amount of CO to 9.5% CH₄ can make the fuel concentration in the explosion reaction system close to the actual stoichiometric value. At this time, the promotion effect of CO on the gas explosion reaction is dominant. Macroscopically, the maximum explosion pressure increases with the increase of CO concentration. As the concentration of CO continues to increase, the explosion reaction system appears lean oxygen state, the 98 and 120 elementary reactions that hinder the temperature increase are promoted, and the 57 and 170 elementary reactions that promote the temperature increase are inhibited. Macroscopically, it is reflected that with the increase of CO concentration, the temperature of the explosion reaction system decreases, and the maximum explosion pressure decreases. CO delays the appearance time of the peak amount of substance concentration of free radicals, and the ignition delay time of the explosion reaction increases after adding CO, thereby reducing the explosion reaction rate.

Analysis of full resonance characteristics of underground magnetic coupling wireless power transfer system

ZHANG Lian, YANG Hongjie, JING Tingwei, LI Tao, ZHANG Lu

2022, 48(2): 83-92. doi: 10.13272/j.issn.1671-251x.2021110064

<Abstract>(223) <HTML> (18) <PDF>(18)

Abstract:
When the magnetic coupling wireless power transfer (MC-WPT) system is used for power supply underground, if the system parameters are not properly configured, the input impedance of the system will show non pure resistance, which will cause the system detuning and affect the power supply efficiency of underground power equipment. When the series compensation (S) is used in the secondary side of MC WPT system, it is easy to realize resonance. However, when the parallel compensation (P) is used in the secondary side, the existing research is based on the fact that the system only resonates at the primary side and the system does not fully resonate due to the non-resonance at the secondary side. In order to solve the above problems, a full resonance compensation method for magnetic coupling wireless power transfer (MC-WPT) system is proposed. In this paper, SP-type, PP-type, LCC-P type and LCL-P type compensation topologies are taken as the research object of the secondary side parallel MC-WPT system. The parameter constraint relation of the system in full resonance state is obtained by using impedance analysis method. The simulation comparison between the traditional compensation method and the full resonance compensation method is carry out by using Matlab/Simulink. The results show that the output power of SP type, PP type and LCL-P type compensation topology under the full resonance compensation method is greater than that under the traditional compensation method, and the output power of the LCC-P type compensation topology is less than that under the traditional compensation method. In the full resonance compensation method, the efficiency of SP-type and PP-type topology is not much different from that under the traditional compensation method, the LCC-P-type topology efficiency is much higher than that under the traditional compensation method, and the LCL-P-type topology efficiency is slightly lower than that under the traditional compensation method. In the full resonance method, the system does not need to provide reactive power, and the apparent power is equal to the given output power. In the full resonance compensation method, the SP topology is more suitable for underground coal mines, which is not affected by the change of mutual inductance, but is greatly affected by the resistance load. In order to solve the problem that the resonant frequency of SP Type MC WPT system is affected by the resistance load and the resistance load has a lower limit value under the full resonance compensation method, a DC-DC converter is used to combine impedance matching with active power factor correction. Therefore, the equivalent impedance of the input side of the rectifier bridge of the system is always equal to the corresponding resistance value of the preset resonant frequency. At the same time, it also ensures that the system rectifier bridge input current is in phase with the voltage, reducing the impact of the DC-DC converter introduction on the system impedance. The SP MC WPT system is taken as the experimental object for verification. The results show that the SP-type MC-WPT system can be free from the constraints of the resistance load in the full resonance compensation optimization method, the system is not affected by the mutual inductance and load changes, and is stable in the full resonance method, which improves the output power and output efficiency.

Post-disaster reconstruction algorithm of wireless ad hoc network in coal mine

HU Qingsong, WANG Shengnan

2022, 48(2): 93-99. doi: 10.13272/j.issn.1671-251x.17865

<Abstract>(185) <HTML> (23) <PDF>(26)

Abstract:
Mine accidents often lead to partial communication link damage and communication network connectivity deterioration. Using residual nodes and limited new nodes, reconstructing coal mine rescue network by constructing local virtual backbone network can reduce the network energy overhead and enhance the connectivity and coverage control ability. A post-disaster reconstruction algorithm of wireless ad hoc network in coal mine based on multi-dimensional virtual backbone network is proposed. Considering the three dimensions of betweenness centrality, node closeness and residual energy screening mechanism of wireless sensor networks, a comprehensive evaluation index of virtual backbone nodes is constructed. The nodes with large comprehensive evaluation index are selected as the dominant nodes so as to enhance the robustness of virtual backbone network and prolong the network lifetime. This paper introduces the construction process of virtual backbone network. In the initial stage, the dominant nodes are generated through multiple rounds of election and the dominating set is updated. In the connecting stage of the dominating set, the relay nodes are elected, and the each dominant node and relay node are connected to form a connected dominating set. First-order radio energy consumption model is used to analyze the energy consumption of virtual backbone network. The Matlab R2017A platform is used to conduct simulation experiments on the network reconstructed based on this algorithm. The results show that the network residual energy, the number of dominant nodes and node coverage are better than the network constructed by sleep and energy balance-based connected dominating set algorithm and energy balance minimum connected dominating set algorithm.

Research on underground crawler detection robot and its motion anti-disturbance control

SHAN Jie, GUAN Binghuo

2022, 48(2): 100-106,146. doi: 10.13272/j.issn.1671-251x.2021050033

<Abstract>(779) <HTML> (11) <PDF>(27)

Abstract:
The underground crawler detection robot has a complex working environment, and needs to carry a variety of detection or rescue equipment and climb obstacles, which easily leads to load disturbance and has strong nonlinearity and uncertainty. In addition, the permanent magnet synchronous motor (PMSM) system used for robot power drive is a multivariable and strong coupling nonlinear system, and the conventional proportional integral derivative(PID) controller based on error can not meet the control requirements. In order to solve the above problems, a four-arm underground crawler detection robot is designed, and the climbing performance is analyzed. The torque and rotational speed of robot PMSM are obtained under two working conditions of straight driving on flat ground and straight climbing. The PMSM is modeled and analyzed, the speed loop adopts the active disturbance rejection controller (ADRC), the current loop adopts proportion integration (PI) controller, and the ADRC+PI disturbance rejection control scheme is designed. The PMSM is driven by the field oriented control (FOC) technology, thereby improving the response performance and anti-disturbance performance of the robot when operating underground. The ADRC+PI control scheme and the conventional PI+PI control scheme are simulated and compared, and the speed, torque and phase current response curves of PMSM under two working conditions are obtained. The results show that under the two working conditions, when the ADRC+PI control scheme is used, the speed and torque response control of the robot PMSM is more accurate, with smaller overshoot and shorter adjustment time, and the PMSM has stronger capability to deal with external sudden disturbance. The scheme can improve the obstacle climbing performance and operation stability of the underground crawler detection robot effectively.

Prediction method of operation state of mine belt conveyor

LI Jingzhao, SUN Jiechen, YE Tongzhou

2022, 48(2): 107-113. doi: 10.13272/j.issn.1671-251x.2021080074

<Abstract>(227) <HTML> (10) <PDF>(28)

Abstract:
The sensor monitoring data combined with neural network prediction model is the mainstream method of mine belt conveyor operation state prediction. However, using contact sensor to monitor the belt conveyor running state has some problems, such as inconvenient installation and large data error, resulting in low prediction precision of belt conveyor operation state. In order to solve this problem, a prediction method of mine belt conveyor operation state based on audio signal is proposed. Firstly, the high-pass filter and Boll spectral subtraction are used to filter and reduce the noise of the original audio signal during belt conveyor operation. Secondly, the first dimension component (MFCC₀) of Mel-frequency cepstral coefficients (MFCC) of audio signal is extracted by pre-emphasis, framing and windowing, Fourier transform, Mel filter energy calculation, discrete cosine transform, and input to the residual block optimized convolutional neural network combined with long and short term memory network (Res-CNN-LSTM) prediction model to reduce the amount of input data of the prediction model. Finally, the MFCC₀ spatial characteristics of the belt conveyor audio signal are extracted adaptively by CNN with residual blocks, and the dimension of the data is reduced. Moreover, the temporal characteristics of the dimension-reduced data are extracted based on LSTM, so as to improve the prediction precision of the belt conveyor operation state. The experimental results show that MFCC₀ can effectively characterize the audio signal characteristics of belt conveyor in different operation states. Compared with CNN, LSTM, and CNN-LSTM models, the Res-CNN-LSTM model is more accurate in predicting the operation state of the belt conveyor.

Fatigue state perception in underground production operation practice

LIU Yi, ZHANG Weitao, ZHANG Fan

2022, 48(2): 114-118,130. doi: 10.13272/j.issn.1671-251x.17875

<Abstract>(253) <HTML> (25) <PDF>(19)

Abstract:
The accidents caused by human factors in coal mine accidents are mainly caused by misoperation caused by fatigue and inattention of underground operating personnel. The existing personnel fatigue detection method based on physiological signals or eye images has the problems of complex implementation, poor adaptability, low accuracy and easy false negatives and false positives. In order to solve the above problems, a perception device of fatigue state of underground personnel based on head posture monitoring is designed. When the underground personnel is in a fatigue state, the head droop motion will occur, and the brain senses the head imbalance through the cochlea. In order to restore balance and keep awake, the brain will control the neck to carry out recovery head-raising motion, thus forming a periodic nodding motion. A nine-axis posture sensor is installed on the safety helmet to collect angular velocity, acceleration and magnetic field strength, and head posture data is obtained through data fusion. The head posture angle is calculated by using the quaternion method, and nodding motion is captured according to the head posture angle. When the proportion of nodding motion in unit time exceeds a threshold value, it is judged that the personnel is in a fatigue state, voice and light early warning occurs and an early warning signal is sent to a monitoring terminal on the ground through a wireless mode. The experimental results show that the device can accurately obtain the head posture angle, capture the fatigue characteristic motion, and judge whether the underground personnel is in a fatigue state effectively. The device has the characteristics of small volume, light weight, low power consumption and easy implementation, which can provide technical reference for operation fatigue monitoring in production operation practice.

Design of high precision mine ultrasonic anemometer

LI Bingrui, LIU Na, INOUE Masahiro

2022, 48(2): 119-124. doi: 10.13272/j.issn.1671-251x.2021090012

<Abstract>(308) <HTML> (11) <PDF>(29)

Abstract:
The minimum measured wind speed of the existing anemometer can not meet the requirements of precise wind measurement under the condition of low wind speed in mines. In order to solve this problem, based on the principle of ultrasonic time difference method wind speed measurement, a high-precision mine ultrasonic anemometer with low starting wind speed is designed. Two ultrasonic transmitting probes and two ultrasonic receiving probes are arranged alternately to form two ultrasonic propagation paths. The downwind and upwind propagation times of ultrasonic waves in a specific wind speed field are measured respectively, and the average wind speed between the transmitting probes and the receiving probes is solved by using the superposition effect of the propagation speed of ultrasonic waves in the air and the wind speed (the effect of temperature on the wind speed measurement can be ignored). In order to analyze the effect of ultrasonic probe direction on the accuracy and reliability of measurement, four different probe arrangement modes are used to carry out the experiment. The results show that the more serious the ultrasonic probe direction dislocation is, the larger the standard deviation and fluctuation range of wind speed. Therefore, the infrared orientation device is used to calibrate the installation position of the anemometer to reduce the measurement error caused by the ultrasonic probe direction dislocation. The moving average method is used to smooth the original wind speed waveform curve to eliminate random noise and improve the stability of output wind speed. By analyzing the factors affecting measurement precision, it is determined that the ultrasonic emission frequency is 40 kHz and the standby time is 100 ms. The theoretical calculation and experimental results show that the resolution of the anemometer is 0.01 m/s, the measurement error is ±0.1 m/s, and the starting wind speed is lower than 0.1 m/s, which can meet the precise wind measurement requirements of the mine roadway with low wind speed.

Study on coal full pore aperture distribution characteristics considering coal matrix compression effect

LIU Jikun, REN Bang, WANG Cuixia

2022, 48(2): 125-130. doi: 10.13272/j.issn.1671-251x.2021060077

<Abstract>(202) <HTML> (25) <PDF>(19)

Abstract:
The single pore structure characterization method can only characterize the pore structure within a certain pore aperture range, the combined Mercury intrusion porosimetry and low-temperature liquid nitrogen adsorption method can characterize the full pore aperture distribution characteristics of coal. However, the coal matrix compression effect will bring errors to the pore aperture distribution measurement results, and the current research has not considered the impact of coal matrix compression effect on the pore aperture distribution measurement results. In order to study the full pore aperture distribution characteristics of coal with different metamorphic degrees, Mercury intrusion porosimetry and low-temperature liquid nitrogen adsorption experiments are carried out on four kinds of coal samples. When the mercury pressure is 0.124-20 MPa, the coal matrix is compressed and the pore structure is deformed. With the increase of mercury pressure, the compression effect of coal matrix becomes obvious and the deformation degree of pore structure increases gradually. When the mercury pressure is 20-206 MPa, the compression effect of coal matrix is significant, and the pore structure is destroyed. Considering the impact of coal matrix compression effect, a joint pores analysis principle is proposed. The boundary point of the joint pores is set at 62.35 nm (the corresponding pore aperture is 62.35 nm when the mercury pressure is 20 MPa). When the pore diameter is less than 62.35 nm, the pore volume and specific surface area are analyzed by low-temperature liquid nitrogen adsorption. When the pore aperture is greater than 62.35 nm, the cumulative mercury intrusion volume measured by mercury intrusion method is corrected in combination with the compressibility coefficient of coal matrix so as to analyze the pore volume and specific surface area. The results show that micropore and transition pore contribute the most to the surface area, mesopore and macropore contribute the most to the pore volume. The greater the degree of coal metamorphism, the greater the contribution of micropores and transition pores to the specific surface area, and the greater the contribution of mesopores and macropores to the pore volume.

Study on variation law and mechanism of coal potential signal with different lithology

WANG Zhongqiang, LI Zhonghui, ZHANG Xin, ZANG Zesheng, ZHANG Quancong, WANG Xuebing

2022, 48(2): 131-137. doi: 10.13272/j.issn.1671-251x.2021100018

<Abstract>(261) <HTML> (33) <PDF>(21)

Abstract:
The potential signal generated in the process of coal rock deformation and failure can better characterize the damage evolution process of coal rock, and has a good application prospect in the field of coal rock dynamic disaster monitoring and early warning. At present, most of the researches focus on the potential characteristics and laws of the same type of coal rock failure, and there is a lack of systematic research on the comparative analysis of potential characteristics of different types of coal rocks. At the same time, there are few comparative studies on the effect of different lithology coal rock structure failure process and components on the surface potential signal generation mechanism at the micro level. In order to deeply study the response law and difference of potential signal of coal and rock with different lithology, four kinds of samples, graphite, raw coal, sandstone and granite, are selected for uniaxial loading and the potential signals generated in the process of damage and failure are collected synchronously. The variation characteristics of potential signals of four samples under loading and failure are analyzed. The results show that the potential signal value of graphite sample is relatively low, and the potential signal fluctuates greatly during the crack damage and unstable crack propagation stages. The fluctuation of the potential signal of the raw coal sample is consistent with the fluctuation of the load, and the variation of the overall potential signal is relatively stable. The potential signal value of the sandstone sample increases rapidly in the compaction stage and the elastic deformation stage. The potential signal of the granite sample fluctuates greatly in the crack damage and unstable crack propagation stages, and the potential signal value increases faster. By scanning electron microscope and X-ray fluorescence spectrometer, the generation mechanism of potential signals of coal samples with different lithology is explained from the aspects of microstructure and components. The results show that there are more mylonic scratches from the microscopic point of view in the graphite and raw coal samples in the compaction and elastic deformation stages of coal rock loading, which indicates that the friction effect is the important reason for the electrification of the graphite and raw coal samples. The sandstone and granite samples contain more O and Si elements, and the piezoelectric effect is the key reason for the electrification of the sandstone and granite samples, and the potential signal of the sandstone sample is more affected by the piezoelectric effect. In the crack initiation and stable crack growth stage, crack damage and unstable crack propagation and unloading stage, the potential signal generation of each coal sample is mainly caused by the crack propagation and friction effect inside the sample. Among them, crack propagation is an important reason for the generation of coal-rock potential signals. The charge separation at the crack tip mainly includes three aspects, including electron escape caused by stress concentration at the crack tip, crack surface charge separation caused by crack propagation and crack tip discharge.

Transient condition characteristics and parameter optimization of mine explosion-proof diesel engine

WEI Xiao, BAO Jiusheng, TAN Fei, YUAN Xiaoming, YIN Yan, ZHANG Lei

2022, 48(2): 138-146. doi: 10.13272/j.issn.1671-251x.2021080060

<Abstract>(188) <HTML> (21) <PDF>(21)

Abstract:
The existing explosion-proof diesel engine is transformed by adding explosion-proof flame arrester to the intake system and exhaust system of ground diesel engine. Coal mine underground conditions are complex, explosion-proof diesel engine is often in start-stop, acceleration and deceleration and other transient conditions. And the installation of explosion-proof flame arrester leads to serious obstruction of diesel intake and exhaust, aggravating the hysteresis of intake and exhaust system under transient conditions, and seriously deteriorating the transient conditions characteristics. In order to solve this problem, the steady-state simulation model of explosion-proof diesel engine is established by GT-POWER, and the transient condition control model of explosion-proof diesel engine is established by Simulink, and the transient simulation model of explosion-proof diesel engine is formed by coupling the transient condition control model with the steady-state simulation model. Based on the transient simulation model of explosion-proof diesel engine, the dynamic performance of explosion-proof diesel engine under two typical transient conditions of constant speed and variable torque and constant torque and variable speed is simulated and analyzed. The results show that under the transient condition of constant speed and variable torque, compared with the diesel engine before the explosion-proof transformation, the air-fuel ratio of the explosion-proof diesel engine decreases faster, the maximum burst pressure in the cylinder decreases, and the torque hysteresis is more obvious. Moreover, the faster torque rises, the more serious the hysteresis effect. Under the transient condition of constant torque and variable speed, the air-fuel ratio of explosion-proof diesel engine decreases with the increase of speed, but the process of increasing speed with small load has little effect on the air-fuel ratio. In order to optimize the parameters of explosion-proof diesel engine, the effects of injection advance angle and the number of flame arrester barriers on the power and emission performance of explosion-proof diesel engine are analyzed by simulation. The results show that the maximum burst pressure, maximum combustion temperature, friction torque and power in the cylinder all increase with the increase of the injection advance angle, the volume fraction of CO and HC decreases with the increase of the injection advance angle, and the volume fraction of NO_x increases with the increase of the injection advance angle. With the increase in the number of intake and exhaust explosion-proof flame arrester fences, the maximum burst pressure in the cylinder of the explosion-proof diesel engine increases and the maximum combustion temperature decreases. The increase of the number of intake and exhaust explosion-proof flame arrester fences has a negligible effect on the friction torque and power of the explosion-proof diesel engine, but it can inhibit the exhaust emission concentration to a certain extent. Properly increasing the fuel injection advance angle and the number of intake and exhaust explosion-proof flame arrester fences can improve the transient condition characteristics of explosion-proof diesel engines to a certain extent.

2022 Vol. 48, No. 2

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