2020 Vol. 46, No. 8

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Coal mine intelligence and mine-used 5G
SUN Jiping
2020, 46(8): 1-7. doi: 10.13272/j.issn.1671-251x.17648
<Abstract>(245) <HTML> (31) <PDF>(91)
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Aiming at characteristics of electrical explosion-proof and large wireless transmission attenuation in underground coal mine, 5G technology and its application scope were analyzed.Mine-used 5G should adopt intrinsically safe explosion-proof. Mine-used 5G for control should have strong anti-interference ability. Mine-used 5G should be used for remote control of coal mining face and tunneling face. Mine-used 5G should be used for ground remote control of unmanned vehicle in underground coal mine. Mine-used 5G that has not been developed for characteristics of mine mobile communication is less cost-effective than mine-used WiFi mobile communication system. It is strictly forbidden to replace mine-used wired dispatching communication system with mine-used 5G mobile communication system. Mine-used 5G that is not developed for coal mine safety monitoring characteristics cannot replace coal mine safety monitoring system. Positioning accuracy of mine-used 5G that has not been developed for precise positioning characteristics of mine moving target is lower than that of mine-used UWB precision positioning system. Transmission rate of mine-used 5G in frequency range of 450-6 000 MHz is lower than that of mine-used WiFi6. Reliability of mine-used 5G that is not developed for monitoring characteristics of fixed equipment in underground coal mine is lower than that of mine-used wired monitoring system. It is urgent to research and develop mine-used 5G based on characteristics of safe production in coal mine, not just for explosion-proof transformation of existing ground 5G products.
Research on key technologies of coal mine auxiliary transportation robot
YUAN Xiaoming, HAO Mingrui
2020, 46(8): 8-14. doi: 10.13272/j.issn.1671-251x.2020040019
<Abstract>(125) <HTML> (13) <PDF>(27)
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In view of special working conditions of coal mine auxiliary transportation robot such as fast moving speed, variable driving routes and complex driving road conditions, structural form and technical architecture of coal mine auxiliary transportation robot are given:the cabless structure design is adopted, automatic driving system is taken as control center, wheeled explosion-proof wire-controlled power chassis is used as mobile platform, and unmanned transportation of different materials underground is realized through a variety of replaceable upper loading tools. In view of three functions of environment perception, positioning navigation and path planning of coal mine auxiliary transportation robot, corresponding solutions are respectively proposed: ① Machine vision enhancement and perception fusion technology in mine low illumination environment: environment perception function of robot is realized by combining depth camera infrared imaging technology and planar lidar detection technology; ② Wireless communication and positioning technology in confined space of underground coal mine: combination of IoT wireless communication positioning and simultaneous localization and mapping(SLAM) technology is used to achieve active and precise positioning of robot during transportation operation; ③ Path planning and obstacle avoidance mechanism under complex geological conditions of coal mine: the shortest path search algorithm and dynamic window algorithm are used to realize functions of global path planning and local path planning of the robot respectively.
Research status of pose detection methods of boom-type roadheader
MA Yuan, FU Shichen, ZHANG Ziyue, WANG Dongjie
2020, 46(8): 15-20. doi: 10.13272/j.issn.1671-251x.2020030072
<Abstract>(87) <HTML> (17) <PDF>(17)
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According to principle of pose detection of boom-type roadheader, pose detection methods of roadheader respectively based on sector laser, indoor GPS (iGPS), total station, machine vision, ultra wide band (UWB) and inertial navigation were introduced. The pose detection method of roadheader based on sector laser has advantages of concise calculation, high accuracy of heading angle and X-axis (vertical direction of two sides of coal wall) coordinate measurement, but it cannot detect Y-axis (heading direction) coordinate and Z-axis (vertical direction of ground) coordinate of roadheader fuselage. The pose detection method of roadheader based on iGPS can realize full-parameter pose measurement with high detection accuracy, but effective measurement distance is small. The pose detection method of roadheader based on total station can also realize full-parameter pose measurement, but calibration and station shift are complicated. The pose detection method of roadheader based on machine vision has advantages of high measurement accuracy of cutting head position, fuselage posture of roadheader as well as X-axis and Z-axis coordinate, but it cannot detece Y-axis coordinate of roadheader. The pose detection method of roadheader based on UWB has advantages of convenient automatic station shift and high accuracy of Y-axis coordinate measurement, but Z-axis coordinate error is large. The pose detection method of roadheader based on inertial navigation has advantages of high measurement accuracy of posture angle and independent non-contact measurement process, but there is cumulative error in three-axis coordinate measurement. In order to meet practical application requirements that effective measurement distance is greater than 100 m, three-axis positioning error is less than 10 cm and posture angle error is less than 1°, it is necessary to further research combined roadheader pose detection method of machine vision, UWB and inertial navigation, so as to realize automatic, full-parameter and non-contact pose detection of roadheader.
Advanced control of dense medium coal separation process: research progresses and prospects
ZHANG Lingzhi, DAI Wei, MA Xiaoping
2020, 46(8): 21-27. doi: 10.13272/j.issn.1671-251x.2020020001
<Abstract>(123) <HTML> (18) <PDF>(17)
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Automatic control of dense medium coal separation process based on traditional control methods has problems of high energy consumption, large fluctuation of ash content and so on, while advanced control can improve dynamic performances of the process and make the system run close to the optimal state. Firstly, dense medium coal separation technology is introduced with characteristics analysis of multi-time scales and multi-rate. Based on factor analysis of strong nonlinearity, multi-variable coupling, time variant and multi-interference in dense medium coal separation process, difficulties of advanced control of dense medium coal separation process are analyzed, which are about mathematical modeling, tracking control of operation indexes, stability and accurate perception of key parameters. Secondly, research progresses of advanced control of dense medium coal separation process are summarized in terms of process modeling, density control of dense medium suspension and ash content control of clean coal. Finally, prospects about future research directions of advanced control of dense medium coal separation process are made, which involve visualization platform construction of dense medium coal separation based on big data, prior knowledge and data hybrid driven intelligent optimization and control orienting dense medium coal separation process, research on prediction methods of product quality and efficiency, and virtual experimental platform construction of dense medium coal separation.
Research on application of network slice technology in mine communication network
LIU Haipeng, ZHOU Shuqiu
2020, 46(8): 28-31. doi: 10.13272/j.issn.1671-251x.2020050074
<Abstract>(127) <HTML> (21) <PDF>(20)
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Aiming at problems of low resource sharing efficiency, difficult maintenance and upgrade, and inflexible and inefficient vertical service deployment and configuration caused by multi-source heterogeneous structure of mine communication network, network slice(NS) technology was applied to mine communication network. Mine communication network architecture based on NS was constructed. Deployment of NS in mine communication network is divided into service instance layer, network slice instance(NSI) layer and resource layer, which respectively correspond to application layer, transmission layer and perception layer in mine communication network. The service instance layer is responsible for underground service creation and life cycle maintenance. By abstracting device into independent NS, the NSI layer generates customizable, logically independent and service isolated NSI for customized use by service subscribers with different requirements. The resource layer is responsible for providing computing, storage, forwarding, wireless access and other functions to the NSI layer. By dynamically modifying key performance indicators parameters of each network in NS template, management of NSI life cycle is realized, which meets service requirements of customization and flexible use of NS. Through dynamic configuration and management of NSI isolation attributes and global operation of NSI isolation requirements, NS isolation is realized to achieve purpose of non-interference among services carried by NS. NS was divided according to latency sensitive, bandwidth sensitive and connection quantity sensitive underground services, and NS working state under typical underground services was given, which could meet flexible configuration requirements of mine communication network for differentiated vertical services.
Research on principle of supporting status classification and sensing of hydraulic support
ZHANG Desheng, WEI Xuntao, BIAN Ji, WEN Zhiguo, LI Dingyi, DU Shangyu
2020, 46(8): 32-37. doi: 10.13272/j.issn.1671-251x.2020030002
<Abstract>(317) <HTML> (16) <PDF>(14)
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Aiming at problem that single attitude measurement of hydraulic support can not fully reflect comprehensive state of hydraulic support, and can not realize accurate perception of supporting state of hydraulic support, taking two column shield hydraulic support as an example, based on three-dimensional space stress model of hydraulic support, supporting state classification and stability of hydraulic support are analyzed from two aspects of spatial geometric state and structural load, and it is pointed out that the key influencing parameters of hydraulic support are inclination angle, pressure and pin force.When hydraulic support and surrounding rock are in uncoupled state, geometric instability is easy to occur: the geometric equilibrium equation is constructed, and the height of gravity center and the dip angle of working face are the key factors affecting the stability; A method of determining the center of gravity position of hydraulic support with three inclination angles of top beam, base and front link is put forward, and the state perception is realized by using dual axis inclination sensor.When hydraulic support and surrounding rock are in coupling state, bearing instability is easy to occur: accurate solution equation of the resultant force point of the hydraulic support is constructed, the state perception of the top beam and the shield beam is realized by the force measuring pin shaft, and the bearing instability type is determined according to the balance zone theory.
Analysis of influencing factors of short-circuit spark discharge in electric potential capacitance circuit
KANG Qian, XU Chunyu, TIAN Muqin, SONG Jiancheng
2020, 46(8): 38-43. doi: 10.13272/j.issn.1671-251x.2020030006
<Abstract>(94) <HTML> (11) <PDF>(10)
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Most of existing models and methods for research of capacitive circuit spark discharge and high-power intrinsic safety power supply only consider discharge characteristics of energy storage elements during discharge process， and do not consider influence of power supply potential on discharge characteristics of capacitive circuit. Analysis of capacitive circuit discharge characteristics is carried out under condition of no load, without considering situation of load in practical application. For the above problems, based on analysis of short-circuit spark discharge characteristics of capacitive circuit, the intrinsically safe power supply is equivalent to the electric potential capacitance (EC) circuit, and spark discharge equivalent mathematical model was established by introducing power supply potential and external load, the mathematical expressions of spark discharge current, discharge voltage and discharge power is derived in the circuit failure, and combined with the mathematical model and Matlab simulation research, the influence of the power supply potential, filter capacitor, short-circuit resistance and load current before short-circuit on short-circuit spark discharge current, discharge voltage and discharge power during faults were analyzed. Theoretical analysis and simulation results show that in the short-circuit of EC circuit, the spark discharge current and spark discharge power rapidly rise to the maximum value at the initial stage, and then slowly decrease, and the spark discharge voltage quickly drops to the minimum value; in short-circuit of EC circuit, other circuit parameters are not changed, with the increase of the power supply potential, the spark discharge current and the spark discharge power increase obviously, which poses a great threat to the intrinsic safety performance of the circuit; with the increase of the filter capacitor, the spark discharge current spike increases, the discharge power increases, it is necessary to consider the output voltage ripple and intrinsic safety performance to reasonably select the capacitance value of the filter capacitor; as the loop resistance increases during a short-circuit, the spark discharge current and the spark discharge power are also significantly reduced, which can effectively improve the intrinsic safety performance of the circuit; with the increase of the load current before the short-circuit, the spark discharge current and spark discharge power increase somewhat, but the increase is not obvious, which has little influence on the intrinsic safety performance of the circuit.
Research on influence of parasitic parameters of LRC filter for mine-used inverter
SHI Han, JIANG Dezhi, RONG Xiang, WANG Yue
2020, 46(8): 44-50. doi: 10.13272/j.issn.1671-251x.17531
<Abstract>(139) <HTML> (13) <PDF>(11)
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Parasitic parameters of LRC filter are easy to cause series-parallel self-resonance, which influences filter performance of restraining peak voltage and voltage change rate at motor side in mine-used inverter long-line transmission system, and even causes element to burn out. There is a lack of research achievements from the above aspect at present. A mathematical model of inverter long-line transmission system was established. Based on the analysis of parasitic effects of LRC filter elements, the influence of parasitic parameters on filtering performance of the LRC filter was researched by use of frequency domain analysis method. It is concluded that parasitic inductance of resistance in LRC filter has the most prominent influence, which causes filtering performance degradation of the LRC filter and serious overshoot and oscillation problems in step response process of the inverter long-line transmission system, while the other parasitic parameters has little influence. Simulation and experiment were taken out to research the influence of the parasitic inductance of resistance in the LRC filter on filtering performance and dynamic characteristics of the system. The results show that when aluminum-shell power resistors are used in LRC filter, there would be distortion of voltage waveforms at motor side as well as obvious oscillation during rising and falling processes, while when thick film power non-inductive resistors are used, overshoot and oscillation caused by parasitic inductance of resistance would be eliminated, so that the LRC filter can achieve a more ideal filtering effect.
Detection test of coal seam hydraulic fracturing range based on multi-frequency synchronous electromagnetic wave CT technology
YUAN Yongbang, YI Hongchu
2020, 46(8): 51-57. doi: 10.13272/j.issn.1671-251x.2020030039
<Abstract>(108) <HTML> (18) <PDF>(11)
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At present, the detection methods for influence range of coal seam hydraulic fracturing mostly have some problems, such as complex implementation, large amount of engineering volume, high cost and low accuracy, which are difficult to meet requirements of effective guiding of optimization of fracturing construction scheme and construction quality control. And single frequency data analysis in conventional electromagnetic wave perspective detection may lead to low detection resolution and accuracy. To solve the above problems, a detection method of coal seam hydraulic fracturing range based on multi-frequency synchronous electromagnetic wave computerized tomography (CT) technology was put forward. The method is based on principle of electromagnetic wave perspective, the detection data of multiple frequencies can be obtained at one time, and the comprehensive analysis of fracturing effect from different resolutions can greatly improve the detection accuracy and efficiency. Taking the M6 coal seam of a gas outburst mine as the research object, the detection test of hydraulic fracturing range in coal seam was carried out. The response characteristics of three different frequency electromagnetic waves of 0.3, 0.5, 1.5 MHz on coal seam hydraulic fracturing were studied, and the influence range and effect of hydraulic fracturing were analyzed. The results show that after hydraulic fracturing, the fractured zone is mainly characterized by high attenuation of electromagnetic field strength. The attenuation coefficient of electromagnetic wave in the fracturing area increases obviously, and the attenuation coefficient range widens. The energy absorption gap of electromagnetic wave in fractured area and non-fractured area is widened due to hydraulic fracturing. Therefore, the fracture range of coal seam can be divided. The abnormal detection areas of 0.3 and 0.5 MHz electromagnetic wave are basically in "sheet" distribution, while the response of 1.5 MHz electromagnetic wave is more sensitive to the hydraulic fracturing area with longitudinal "strip" distribution, more obvious attenuation amplitude, and better lateral resolution. There is a positive correlation between the water injection rate and the attenuation coefficient of electromagnetic field strength, and the attenuation coefficient increases with the increase of water injection volume. The distribution range of high attenuation abnormal area has a certain correspondence. The fracturing range of the test area is mainly distributed in the abscissa of 40-90, 100-140, 210-350 m section, corresponding to the radius of surrounding rock of No.2, No.3, No.6-8 boreholes within 15-25 m, accounting for about 65% of the detection range.
Influence of hydraulic fracturing parameters of reused coal pillar roadway on pressure relief effect
ZHANG Zhen
2020, 46(8): 58-63. doi: 10.13272/j.issn.1671-251x.2020060081
<Abstract>(73) <HTML> (13) <PDF>(9)
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Hydraulic fracturing pressure relief technology is used to control surrounding rock deformation of reused coal pillar roadway. In order to determine parameters of hydraulic fracturing, 43122 reused coal pillar roadway of Changping Coal Mine of Shanxi Jincheng Anthracite Mining Group Co., Ltd. was taken as research object, influence of fracturing times and fracturing positions on pressure relief effect were numerically simulated by use of plane discrete element UDEC software. The results show that the longer the fracturing segment length is, the less the corresponding fracturing times will be, and the weaker the effect of hydraulic fracturing on roof will be. Fracturing segment length should not exceed 4 m. Fracturing borehole will increase stress of coal pillar when it is located at coal pillar side of lower section working face, and reduce stress of coal pillar when it is located at goaf side of upper section working face and above the coal pillar, and pressure relief effect is the most obvious when fracturing borehole is located at goaf side of upper section working face. The hydraulic fracturing parameters determined by numerical simulation results were tested in field, the results show that after hydraulic fracturing is used for pressure relief, deformation stability period of surrounding rock of reused coal pillar roadway is 33.3% shorter than that of non-fractured roadway, and displacement of roof and floor and two side walls of reused coal pillar roadway is 63.5% and 45.5% lower than that of non-fractured roadway, which indicates deformation of surrounding rock of reused coal pillar roadway decreased significantly.
Path planning of mine robot based on a novel heuristic algorithm with regular hexagon grids
WANG He, CHEN Jing, TENG Yingyao
2020, 46(8): 64-69. doi: 10.13272/j.issn.1671-251x.2020020003
<Abstract>(92) <HTML> (10) <PDF>(11)
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In the traditional square grid map, when robot encounters an obstacle, it is easy to collide with the obstacle when moving along diagonal direction, has poor capability in obstacle-avoiding and stability, and time consumed in each step during real-time detection cannot be uniquely determined. In view of the above problems, based on working environment of regular hexagon grid, a path optimization method for multiple parallel mobile mine robots by using improved heuristic path search algorithm is proposed. In this paper, a comparative analysis of single robot in square and regular hexagon grid modeling environment is carried out from three aspects of obstacle-avoiding angle, obstacle-avoiding ability and optimal path. The results show that for a single robot, path length cost under regular hexagon grid map is less than that in square grid map, and from path planning of a single robot, regular hexagon grid map is more conducive to obtain the shortest path, so it is concluded that regular hexagon grid is more suitable for robot working environment modeling than traditional square grid. Aiming at path planning problem of parallel movement of multiple robots in collaborative operation, an improved heuristic path search algorithm is used to optimize path of multiple robots on the basis of working environment of regular hexagon grid:Multiple collaborative robot paths are planned by use of improved heuristic estimation function, which determines the one of all adjacent grids around the current robot location to be traversed by the robot. The improved heuristic estimation function is used to plan the path of multiple cooperative robots. According to the number of grids traversed by robot and deformed Manhattan distance between candidate grid and target grid of the robot, the heuristic estimation function can evaluate fitness value of adjacent grids. The simulation results show that total path length and running time of the algorithm are reduced by more than 10% compared with the square grid map, collision between the robot and static obstacles and among the robots is effectively avoided, and safety of the robot is improved. With increase of the number of robots, the improved heuristic path search algorithm has more obvious optimization effect on robot path and algorithm running time under the regular hexagon grid map.
Rolling bearing fault diagnosis based on wavelet packet decomposition and PSO-BPN
JU Chen, ZHANG Chao, FAN Hongwei, ZHANG Xuhui, YANG Yiqing, YAN Yang
2020, 46(8): 70-74. doi: 10.13272/j.issn.1671-251x.2019120022
<Abstract>(176) <HTML> (33) <PDF>(16)
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In view of problems in existing rolling bearing fault diagnosis methods for coal mine rotating machinery, such as incomplete signal feature extraction, low fault diagnosis accuracy and low efficiency, a rolling bearing fault diagnosis method based on wavelet packet decomposition and particle swarm optimization BP neural network was proposed. The method includes signal feature extraction and fault type recognition. In the signal feature extraction part, the collected vibration signals of rolling bearing are decomposed by wavelet packet to obtain energy of each sub-frequency band and total energy of the signal. After normalization processing, feature vector representing state of rolling bearing is obtained. In the fault type recognition part, initial weight and threshold of BP neural network are optimized by particle swarm optimization to accelerate convergence speed of the network and avoid falling into local minimum. The experimental results show that the method improves fault diagnosis efficiency and accuracy of rolling bearing.
Improved DSOGI-PLL for synchronizing frequency detection of mine power grid voltage
GAO Zhengzhong, WANG Yanan, NIU Huihui, WU Mingjuan
2020, 46(8): 75-81. doi: 10.13272/j.issn.1671-251x.2019120058
<Abstract>(116) <HTML> (17) <PDF>(7)
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In view of problems that there are frequency and phase errors in extracting voltage synchronization signals of DSOGI-PLL with multiple harmonics or DC bias in mine grid, an improved DSOGI-PLL was proposed to improve DSOGI-PLL from three aspects: frequency regulation, DC bias and harmonic detection.Frequency adaptive adjustment unit is constructed to automatically adjust resonant frequency of DSOGI-PLL through real-time monitoring of frequency change of mine power grid, so as to realize frequency adaptive function of DSOGI-PLL, which can improve accuracy of frequency detection and optimize dynamic response performance.Integral feedback compensation is applied to the second-order generalized integrator-quadrature signals generator(SOGI-QSG) to remove the influence of direct-current component on the test results.Cross feedback structure of multiple DSOGIs in parallel is proposed. In this structure, the input signal of each DSOGI does not contain harmonic components detected by other DSOGIs, which weakens influence of each harmonic component on each other. Matlab simulation results show that the improved DSOGI-PLL can complete accurate detection and tracking lock of frequency and phase angle of the grid voltage when the mine grid voltage has serious interference.
Design of three-dimensional scene monitoring system for filling hydraulic support
ZHAO Hao, SHI Yannan, ZHANG Chongchong
2020, 46(8): 82-88. doi: 10.13272/j.issn.1671-251x.2020030005
<Abstract>(79) <HTML> (13) <PDF>(9)
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At present, the equipment monitoring system of filling working face mainly adopts traditional monitoring method based on two-dimensional monitoring, with underground application of filling hydraulic support increases gradually, the accuracy of movement of the parts of filling hydraulic support and group support cooperative movement has a great influence on underground filling mining efficiency. However, the two-dimensional planar motion is unable to describe complexity of the filling hydraulic support action, and needs to upgrade monitor interface to three-dimensional space, and monitor working condition of filling hydraulic support from the perspective of different locations and different angles, so as to improve mine safety coefficient. For the above problems, a three-dimensional scene monitoring system for filling hydraulic support was designed by using three-dimensional engine technology. The system is mainly composed of three-dimensional virtual simulation software, data acquisition module and data communication module. Based on Unity3d, the three-dimensional virtual simulation software is used to establish the system monitoring interface. The computer displays the dynamic changes of monitoring data such as roof pressure values of the filling hydraulic support, the angle offset between each pin shaft and the displacement of the hydraulic cylinder, so as to realize the three-dimensional real-time monitoring of the filling hydraulic support. System monitoring interface can be divided into two parts of entity scene monitoring interface and data monitoring interface:entity scene monitoring interface uses 3ds Max modeling software to establish three-dimensional entity model and three-dimensional scene model of filling mining equipment, and to optimize processing and rendering of the three-dimensional model, so as to achieve scene-driven consistent with the actual working space on filling working face; the data monitoring interface collects, analyzes and processes the working state information of the filling working face through the data acquisition module, and transmits the information to the three-dimensional virtual simulation software through the data communication module to realize the matching between the monitoring data and the software. The effectiveness of the system is verified by practical application.
Hydraulic support condition monitoring system based on LoRaWA
HAN Zhe, DU Yibo, REN Huaiwei, ZHAO Guorui, WEN Zhiguo, ZHOU Jie
2020, 46(8): 89-93. doi: 10.13272/j.issn.1671-251x.2020020024
<Abstract>(56) <HTML> (8) <PDF>(11)
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In view of unstable communication and poor anti-interference ability of the existing hydraulic support condition monitoring system, a hydraulic support condition monitoring system based on LoRaWAN was designed. Sensor nodes use rate adaptive technology to periodically upload data, and can actively upload data in case of abnormal conditions, and use sequential polling to reduce transmission error rate; gateways simultaneously transmit uplink and downlink commands through independent uplink and downlink channels, which reduces collision probability of uplink and downlink commands, and improves data forwarding efficiency. In order to ensure signal coverage of fully mechanized mining face, a gateway is installed at the corner of the roadway, and the LoRa wireless signal of the fully mechanized mining face is forwarded to application platform through a jump transmission. Experimental results show that the system can effectively cover the entire fully mechanized mining face and realize condition monitoring of hydraulic support,when communication distance is 150 m, the data transmission packet loss rate is 0, and the data transmission time of a single sensor node is about 0.29 s,the system acquisition cycle is within 200 s, which meets application requirements.
Optimization design of video monitoring system on fully-mechanized mining face
DU Chunhui
2020, 46(8): 94-100. doi: 10.13272/j.issn.1671-251x.2020020021
<Abstract>(95) <HTML> (25) <PDF>(14)
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In view of problems of current video monitoring system on fully-mechanized mining face such as occupying large network bandwidth, incomplete video storage, unobtrusive cutting pictures of the shearer, and uneven video stitching pictures, optimization design was carried out from aspects of system hardware and software, video compression and stitching algorithms, etc. In terms of hardware, hard disk video recorders are introduced to reduce network bandwidth occupancy rate and solve the problem of video transmission jam; the combination of local storage and remote storage effectively solved the problem of video storage loss. In terms of software, based on the principle of highlighting the key points and partial zooming in, combination of real-time video and animation simulation is adopted to display video images and equipment status parameters of the fully mechanized mining face, which solves the problem that the shearer cutting image is not prominent.In terms of algorithm,a video compression method based on deep learning technology is proposed, in addition to compressing the video data itself, the inter-frame data is also compressed, which effectively reduces bit rate of the algorithm; the nonlinear anti-distortion model(NAM) correction algorithm is used to eliminate image distortion, the speeded-up robust features(SURF) detection algorithm is used for feature point detection, and image fusion is realized through bilinear interpolation method, so as to achieve panoramic video stitching. Development directions of video monitoring technology for fully mechanized mining face are discussed including camera self-cleaning technology, intelligent recognition technology, panoramic video stitching technology of working face, 5G and WiFi6 fusion communication technology, coal and rock interface identification technology.
Design of a mine monitoring image restoration device based on L-R algorithm
FU Yua
2020, 46(8): 101-105. doi: 10.13272/j.issn.1671-251x.17656
<Abstract>(75) <HTML> (8) <PDF>(11)
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The intelligent technology of mine video monitoring is one of the key technologies to realize visual remote intervention intelligent unmanned mining in coal mine.However, due to bad working environment of mining face in underground coal mine, the collected mine monitoring images have serious degradation, which affects development of intelligence of coal mining. The collection process of mine monitoring images is affected by vibration of hydraulic support, shearer, crusher and belt conveyor, as well as random factors such as mineral dust and spray, so the useful information such as depth, strength and range of images degradation cannot be accurately acquired. In view of the above problems, a mine monitoring image restoration device based on L-R algorithm was designed, which includes a stream fetching module, a configuration module, an image restoration module and a forwarding module. Firstly, the device uses stream fetching module to obtain video stream of camera and decodes it into image frames. Then, it uses configuration module to configure parameters of the restoration module, and adopts degradation function model and image restoration module based on L-R algorithm to restore the image and output the restored image. Finally, it uses forwarding module to transmit the restored image frame to video monitoring end in form of video stream, so as to provide clear video information for operators to operate coal mining equipment remotely. The experimental results show that the device can improve quality of mine monitoring images, and the restored images are clear and bright.
Design of collecting and computing platform used for predictive maintenance of coal mine electromechanical equipment
ZHOU Libing
2020, 46(8): 106-111. doi: 10.13272/j.issn.1671-251x.2020040005
<Abstract>(105) <HTML> (18) <PDF>(13)
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Existing operation maintenance mode of coal mine electromechanical equipment is collecting data in underground and analyzing data by ground controller or cloud platform, which has poor real-time performance and flexibility, limited data collection amount, high cost, etc.While predictive maintenance solution scheme in general industry of edge computer plus data collection card is not applicable for operation maintenance of coal mine electromechanical equipment because of difficulty of mine-used intrinsically safe design, poor flexibility of field arrangement, too high cost, etc. For the above problems, a collecting and computing platform used for predictive maintenance of coal mine electromechanical equipment was designed, which was based on main controlling chip of STM32F4. The platform can parallel collect vibration, temperature, pressure and other data of coal mine electromechanical equipment with high speed and take out fast Fourier transform and envelope spectrum analysis real-timely, so as to obtain health status of the electromechanical equipment. The monitored data and diagnosis results can be displayed through man-machine interaction module on the spot, and be transferred to underground controller or cloud platform through Ethernet for large-scale data analysis. The test results show that the platform has measuring errors of less than 4% for vibration signals, and can correctly judge running status and faults of different components in the electromechanical equipment, which meets requirements of real-time calculation, analysis on the spot and flexible arrangement in coal mine field.
Design of automatic in and out device of hydraulic support test bench
ZHAO Rui
2020, 46(8): 112-116. doi: 10.13272/j.issn.1671-251x.2020020055
<Abstract>(73) <HTML> (12) <PDF>(10)
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In view of problems of low efficiency of entering and exiting test bench during hydraulic support inspection and prone to injury accidents, an automatic in and out device of hydraulic support test bench was designed. An in and out trolley is driven by an electric motor to transport the tested support to the designated position of the test bench on a dedicated track; In order to make the tested support transported to the specified position by the trolley, a horizontal lifting cylinder is designed.The lifting cylinder is installed in the base of the test bench to push the wedge-shaped horizontal moving block, the wedge-shaped vertical moving block is driven to move vertically up and down along the track in the base.On the wedge vertical moving block, 16 ejecting rods are arranged according to the size of the U-shaped internal space of the trolley, which pass vertically through holes reserved in the base of the test bench and enter into the tested support on the test bench to make it separate from the trolley. As a result, the trolley exits and resets, and then the tested support is put down to enter test state. Analysis and calculation results show that the rated load of the device exceeds 120 t, which meets requirements of the hydraulic support for automatic in and out the test bench. Practical application shows that the device avoids unnecessary loading of the in and out trolley, realizes the automation of the whole in and out process of hydraulic support, greatly shortens the time for the hydraulic support to enter and exit the test bench, and completely eliminates safety hazards.
Forward multi-stage large-diameter reaming technology for directional high-level borehole in roof
JIA Mingqu
2020, 46(8): 117-122. doi: 10.13272/j.issn.1671-251x.2020010044
<Abstract>(107) <HTML> (13) <PDF>(8)
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Directional high-level borehole in roof is an important means to control mining pressure-release gas in coal mine underground. Due to limitation of drilling device, the borehole diameter is small in once-through drilling, and borehole group arrangement is needed to achieve good drainage effect. In order to solve the above problem, a forward multi-stage large-diameter reaming technology for directional high-level borehole in roof was developed, which constructed directional pilot hole firstly and then enlarged the pilot hole level by level though rotating drill pipe in drilling machine driving reaming bit in borehole. Reaming diameter gradation parameters were analyzed and determined on the basis of equal torque principle, and drilling devices were developed and selected including spiral blade and combination reaming bit, reaming drill pipe with high-strength and high-toughness, high-power directional drilling machine, mud pump truck with high-pressure and large-flow, etc. The field test was carried out at W1304 working face of Sihe Mine of Shanxi Jincheng Anthracite Mining Group Co., Ltd. The test results show that the diameter of directional high-level borehole in roof can be increased from 96 mm to 153 mm by use of the forward multi-stage large-diameter reaming technology, the maximum return-air gas volume fraction is 0.47% during the working face mining, and gas drainage flow of 153 mm borehole is nearly three times than that of 96 mm borehole, which verifies 153 mm borehole has salient gas drainage effect.

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