工矿自动化

Research on 5G frequency band selection and antenna optimization setting in coal mine

SUN Jiping, ZHANG Gaomi

2020, 46(5): 1-7. doi: 10.13272/j.issn.1671-251x.17592

<Abstract>(265) <HTML> (23) <PDF>(60)

Abstract:
Mine wireless communication and mine-used 5G mobile communication technology is one of the key technologies of coal mine intelligence.In order to improve wireless transmission distance and diffraction ability as well as stability and reliability of wireless communication system in underground coal mine, reduce base station consumption, networking cost and maintenance workload, the effect of mine-used 5G working frequency band and antenna position of base stations on wireless transmission loss and transmission distance is studied.The major conclusions are as follows: ① Wireless transmitting power in underground coal mine is limited by intrinsically safe explosion-proof, receiving sensitivity is limited by electromagnetic noise, and antenna gain is limited by intrinsically safe explosion-proof and tunnel space.Therefore, under the conditions of limited wireless transmitting power, receiving sensitivity and antenna gain in coal mine, it is necessary to increase wireless transmission distance and diffraction ability, improve stability and reliability of wireless communication system, and reduce base station consumption, networking cost and maintenance workload by optimizing wireless working frequency band and antenna location setting.② 700 MHz is recommended as mine-used 5G working frequency band. Compared with other 5G frequency bands such as 2.6 GHz, 3.5 GHz and 4.9 GHz, 700 MHz frequency band in underground coal mine has the advantages of low wireless transmission loss, long wireless transmission distance, strong diffraction ability, less base station consumption, low networking cost and maintenance workload and so on.③ Analysis method of transmission loss/position change rate is put forward, which is convenient to analyze the change of transmission loss caused by position change in different transversal areas of tunnel.④ The antennas of wireless base stations should be set close to tunnel side, not less than 0.01 m away from tunnel side, and the height of antennas should be about 2/5 of tunnel height.This is convenient for installation and maintenance, not only does not affect pedestrians and driving but also can satisfy the requirements of low transmission loss and long transmission distance. ⑤ In order to improve wireless transmission distance, wireless terminals used in underground coal mine, such as mobile phones, personnel positioning cards, portable wireless methane detection alarms, multi-functional wireless lamps, portable wireless cameras, portable wireless instruments and equipments, wearable wireless devices, vehicle positioning cards, vehicle wireless devices, wireless cameras, wireless sensors, Internet of things devices and so on, should be closer to the tunnel center as much as possible under the condition of not affecting normal use.

Preliminary study on application of artificial intelligence technology in mine intelligent constructio

MA Xiaoping, YANG Xuemiao, HU Yanjun, MIAO Yanzi

2020, 46(5): 8-14. doi: 10.13272/j.issn.1671-251x.17593

<Abstract>(482) <HTML> (31) <PDF>(67)

Abstract:
The paper introduced related concepts, development overview and application of artificial intelligence technology in development of coal industry, and pointed out that at present, application of artificial intelligence technology in mine is only a combination of point and shallow degree, and deep fusion between artificial intelligence technology and a certain production or management system of mine is not realized. The development process of intelligent mine was summarized. Intelligent mine is considered as a deep fusion of artificial intelligence technology, big data technology, Internet of things technology and physical mine, it combined intelligent communication, intelligent control and intelligent computing technology to realize calculation and processing of digital mine, and construct digital twin mine, uses intelligent interactive evolution of digital twin mine and physical mine to achieve coal mine safety, high efficiency, green production control. A three-layer structure of intelligent mine which integrates artificial intelligence technology with mine was constructed, including equipment layer, intelligent layer and application layer. The application layer is at the highest level of the intelligent mine, in which the digital twin mine sub-layer is equivalent to "digital brain" to realize intelligent control of the highest level of the mine. The agent in the intelligent layer requires the subsystem not only to use artificial intelligence technology to process the data generated by the subsystem, but also to integrate intelligent computing, intelligent communication and intelligent control in the architecture. The development trend of intelligent mine construction was prospected: intelligent mine need to strengthen in-depth study of the artificial intelligence technology and the mine fusion, existing fault detection and diagnosis based on artificial intelligence and advanced intervention technology are applied to robot system, inspection robot integrated intelligent computing, intelligent communication, intelligent control will be one of the earliest underground intelligent agent; it is necessary to further strengthen the research on the modeling technology of complex giant system in the intelligent mine. Only by establishing the complex giant system model of the mine, the collaborative interaction between mining activities and the environment can be realized, and the accurate control of coal mining activities can be realized. The lack of complex giant system model will be an urgent problem to be solved in intelligent mine construction in the future.

Research on digital twin technology for smart mine and new engineering discipline

ZHANG Fan, LI Chuang, LI Hao, LIU Yi

2020, 46(5): 15-20. doi: 10.13272/j.issn.1671-251x.2020040042

<Abstract>(234) <HTML> (13) <PDF>(33)

Abstract:
Combining digital twin with artificial intelligence (AI) technology, a new idea for smart mine construction based on digital twin + AI was proposed. Development path of smart mine technology was explored, and characteristics, application fields and development trends of digital twin technology were studied, and it was pointed out that digital twin is an inevitable trend of digital mine development. The theoretical framework of smart mine based on digital twin + AI was proposed, and mine digital twin model was constructed which includes mine full element physical entity, mine information physics fusion layer, mine digital twin model, mine twin data interaction layer, mine application intelligent service layer from bottom to top. Ubiquitous perception, collaborative control and intelligent decision-making and optimization of the intelligent mine can be realized based on the model. Starting from actual application requirements, key technologies such as smart mine model construction technology, smart mining digital twin technology, mine intelligent control technology, mine equipment fault prediction, and human-computer interaction based on digital twin were discussed. By studying the application of digital twin in smart mine, it provides ideas for the application of AI technology in smart mine and theoretical reference for the construction of new engineering discipline in smart mine in the future.

Simulation analysis on influencing factors of cutting head load of longitudinal roadheader

FENG Junling, TIAN Muqin, HE Ying, WANG Xi

2020, 46(5): 21-27. doi: 10.13272/j.issn.1671-251x.2019090068

<Abstract>(96) <HTML> (12) <PDF>(20)

Abstract:
In view of problem that single influencing factor can not fully reflect cutting head load and its fluctuation variation law in existing research methods of cutting head load characteristics for roadheader, by analyzing instantaneous load of cutting head, the main influencing factors on cutting head load of longitudinal roadheader under horizontal cutting condition were determined， including cutting rock character, slotting depth, cutting depth of cutting head, rotating speed of cutting head and swing speed of cutting boom. For horizontal cutting condition of a longitudinal roadheader, a comprehensive simulation analysis of various factors that affect cutting head load was carried out using Matlab, and variation laws of cutting head load and its fluctuation with various factors were obtained: the load of the cutting head increases with the increase of the Protodyakonov coefficient of the rock faces, and the increase of the lateral resistance is particularly obvious. The degree of lateral resistance fluctuation is higher than the others, and it decreases with the increase of the Protodyakonov coefficient of the rock faces. As the slotting depth increases, the load in each direction of the cutting head increases approximately linearly and the lifting load increases most, and the load fluctuations in all directions decrease with the slotting depth increases. With the increase of the cutting depth, the cutting head load generally increases, and the degree of load fluctuation decreases. Under the condition that the rotating speed of the cutting head is constant, the cutting head load increases with the increase of the cutting boom swing speed. At the same swing speed, the cutting head load increases with the rotating speed of the cutting head decreasing. The lateral resistance fluctuation is significantly higher than the lifting and propulsion resistance fluctuations, the lateral resistance and propulsion resistance fluctuations change according to the cutting head load law, and the lifting fluctuation is opposite. The variation law of the load fluctuation is not consistent with that of the cutting head load, and sometimes even conflicts with each other. Therefore, the operating parameters(slotting depth,cutting depth) and motion parameters (cutting head rotating speed and cutting arm swing speed) of the cutting head should be selected reasonably during operation of the roadheader, so that the parameters can be matched with each other to reduce the roadheader vibration and extend life of the roadheader.

Applicability of two grey models in earth-surface subsidence prediction of mining area

SHI Xiaoyu, ZHANG Yanhai, YANG Keming, YAO Shuyi, WANG Jian

2020, 46(5): 28-33. doi: 10.13272/j.issn.1671-251x.2019090088

<Abstract>(59) <HTML> (12) <PDF>(10)

Abstract:
Existing dynamic single-point subsidence prediction methods of mining area earth-surface are mainly based on traditional leveling measurement data, which have single monitoring mode, high cost and easily destroyed observation points, and cannot guarantee real-time of earth-surface deformation information. Moreover, application of grey model for earth-surface subsidence prediction is only for a single model and its applicability is not analyzed according to characteristics of the model itself. Taking 7221 working face of Yuandian No.2 Mine as an experimental zone, earth-surface subsidence value is measured by differential interferometry synthetic aperture radar technology, and then GM(1,1) and grey Verhulst model that describe the relationship between subsidence and time are built separately for predicting earth-surface subsidence value, so as to realize the integration of earth-surface subsidence monitoring and dynamic prediction of mining area. Through comparing and analyzing fitting and prediction results of earth-surface subsidence value between GM(1,1) and grey Verhulst model, the applicability of the two grey models in earth-surface subsidence prediction of mining area is obtained: GM(1,1) should be used for short-term prediction from beginning of mining subsidence to early active stage if subsidence value curve of single point is approximately unimodal; when earth-surface subsidence enters into decline stage and subsidence value curve of single point is in flat-bottom saturation, gray Verhulst model should be used for medium and long-term prediction.

Analysis on structural faults of mine-used linear vibrating scree

LI Dong, LIU Yue, WANG Shuai, MENG Guoying

2020, 46(5): 34-38. doi: 10.13272/j.issn.1671-251x.2019080095

<Abstract>(146) <HTML> (20) <PDF>(13)

Abstract:
In view of structural faults that occurred during operation of linear vibrating screen in coal preparation plant, the method combining finite element simulation and field test was used to analyze and study the cause of faults of vibrating screen. The main structure and common faults of vibrating screen are introduced, taking the vibrating screen with beam fracture in a coal preparation plant as an example, three-dimensional modeling and finite element modal analysis are carried out on the vibrating screen. Analysis results show that with the increase of the mode order, the change of the vibration shape gradually changes from the movement to distortion of the structure itself. Vibration test by intrinsically safe portable vibration measuring recorder is performed on the vibrating screen under no-load working state and the test signal is processed to obtain working frequency of the vibrating screen. Combined with the modal analysis results and the actual test results, it is concluded that frequent operation of the vibrating screen during no-load is the main reason for beam fracture. Maintenance suggestions are given according to the fault cause: the vibrating screen should be avoided to run for a long time under the condition of no load or less material; before the vibrating screen is put into use, the working state and possible weak links of the vibrating screen should be known in advance to avoid structural fault as much as possible and to ensure the reliable operation of the vibrating screen.

Concept, realization path and key technologies of intelligent mining based on transparent longwall face

WANG Feng

2020, 46(5): 39-42. doi: 10.13272/j.issn.1671-251x.17509

<Abstract>(104) <HTML> (13) <PDF>(20)

Abstract:
Taking transparent coal seam, transparent fully-mechanized mining equipment and transparent decision-making and control as core, concept of intelligent mining based on transparent longwall face was put forward, namely based on enhanced geological perception of coal seam in fully-mechanized mining face, comprehensive perception, information integration and analysis, intelligent production decision-making and adaptive control of fully-mechanized mining equipment are realized in mining process. Realization path of intelligent mining based on transparent longwall face was pointed out from four levels of perception, analysis, decision-making and execution, that is, advanced detection of coal seam, equipment-environment model correlation, pre-mining planning and decision-making and intelligent control wihile mining. Three key technologies of intelligent mining based on transparent longwall face were described, which were geological exploration technology, fully-mechanized mining equipment positioning technology and 3D laser scanning technology. Intelligent mining based on transparent longwall face aims to achieve intelligent decision-making and autonomous implementation of fully-mechanized mining equipment, which can lay a solid foundation for realization of unmanned mining.

Cooperative control technology of shear and hydraulic support on fully-mechanized coal mining face

LIU Qing, HAN Xiuqi, XU Lanxin, QIN Wenguang

2020, 46(5): 43-48. doi: 10.13272/j.issn.1671-251x.17520

<Abstract>(170) <HTML> (20) <PDF>(25)

Abstract:
Aiming at low cooperative control efficiency of shearer and hydraulic support on fully-mechanized coal mining face, a cooperative control technology of shearer and hydraulic support on fully-mechanized coal mining face was proposed based on technologies of shearer memory coal cutting and automatic control of hydraulic support following. According to production process of fully-mechanized coal mining face, operation processes of shearer and hydraulic support are divided and then re-matched to generate cooperative operation process of shearer and hydraulic support. In each operation process, cooperative control of direction and speed of shearer traction and hydraulic support following movement are realized through cooperative control logic. The application results show that compared with manual intervention control mode, the technology reduces dependence of shearer and hydraulic support on manual intervention, improves automation level of fully-mechanized coal mining face, and provides technical support for realization of unmanned mining.

Application of WiFi communication in fully-mechanized coal mining face of thin seam

DONG Wenbo, GAO Siwei

2020, 46(5): 49-53. doi: 10.13272/j.issn.1671-251x.17507

<Abstract>(86) <HTML> (10) <PDF>(13)

Abstract:
Aiming at requirements of high reliability, high bandwidth, low delay and wide coverage of wireless communication in fully-mechanized coal mining face of thin seam, and taking 43101 fully mechanized mining face of thin seam of Yujialiang Coal Mine as application background, WiFi communication scheme applied to fully-mechanized coal mining face of thin seam was proposed from aspects of frequency band selection, network topology, base station layout and fast roaming switching mechanism. 5.8 GHz as the optimal band for WiFi communication was selected. The face has been wired network, WiFi base station directly connected to the wired network. In order to determine distance between WiFi base stations, two test points were selected on the working face for signal strength test, and it was concluded that one WiFi base station should be set at intervals of about 57 supports to achieve overlapping coverage of wireless signals between adjacent WiFi base stations. Based on online scanning, client connection quality sorting, intelligent learning, pre-connection and data caching, the fast roaming switch was completed to ensure that the client on the working face was always connected to the WiFi base station with the best signal. The test results show that the scheme has achieved full coverage of wireless signal on the working face, and has good communication stability. The communication rate is more than 30 Mbit/s, and the roaming switching time is 25-50 ms, so as to achieve goal of fast roaming.

Intelligent cooperative control of hydraulic support inspired by driveless car

NIU Jianfeng

2020, 46(5): 54-56. doi: 10.13272/j.issn.1671-251x.17569

<Abstract>(98) <HTML> (15) <PDF>(17)

Abstract:
For problems such as low control accuracy, poor coordination and uneven pushing of hydraulic support in fully-mechanized coal mining face, an intelligent cooperative control method of hydraulic support is proposed based on driverless car technology . Each hydraulic support is regarded as a "car" in fully mechanized mining face. The "car" moves forward by moving support and adjusts driving direction by bottom adjustment and side guard plate adjustment. The group of hydraulic support is like a row of "cars" moving forward in a certain order and maintaining alignment. Each hydraulic support has a fixed target travel, and is constrained by position of left and right side supports, so it can pay attention to operation of shearer in front and take into account status of the neighboring support, so as to realize intelligent cooperative control of hydraulic support. The method discusses intelligent cooperative control of hydraulic support from aspects of hydraulic support precise pushing control, parallel advancing control, protection plate control and closed-loop control of automatic following, which provides an idea for solving the control problems of hydraulic support in fully-mechanized coal mining face.

Coal-gangue image recognition in fully-mechanized caving face based on random forest

XUE Guanghui, LI Xiuying, QIAN Xiaoling, ZHANG Yunfei

2020, 46(5): 57-62. doi: 10.13272/j.issn.1671-251x.2019110064

<Abstract>(111) <HTML> (16) <PDF>(15)

Abstract:
Aiming at problems of high difficulty in parameter adjustment, low prediction accuracy and easy over-fitting in present coal-gangue image recognition methods in fully-mechanized caving face, a coal-gangue image recognition method in fully mechanized caving face based on random forest (RF) algorithm is proposed. Taking 6203 fully-mechanized caving face of Danshuigou Coal Mine as project background, coal-gangue image of caving mouth are collected and pre-processed by clipping, gray conversion, contrast enhancement and image filtering. Fifteen texture features of coal-gangue image are extracted by gray-gradient co-occurrence matrix. RF algorithm is used to rank the importance of the fifteen coal-gangue texture features, and the first five features are selected for dimension reduction. Recognition effect of RF algorithm on coal-gangue images before and after dimension reduction is analyzed. The results show that when the number of decision tree is 150 and the number of features in each split is calculated by logM2+1 method, accuracy rate of coal-gangue classification of RF model after dimension reduction is 97%, which is 4% higher than that before dimension reduction, accuracy rate coal-gangue classification is 0.98, recall rate is 0.96, and out-of-bag error rate reaches 9% after 50 iterations with stronger generalization.

A detection method for large blocks in underground coal transportation

DU Jingyi, HAO Le, WANG Yueyang, YANG Ruonan, WEN Jingyi

2020, 46(5): 63-68. doi: 10.13272/j.issn.1671-251x.2019090067

<Abstract>(105) <HTML> (15) <PDF>(14)

Abstract:
In view of problems that the existing detection methods for large blocks in underground coal transportation cannot detect quantity of large blocks and detection accuracy is not high, a detection method for large blocks in underground coal transportation based on improved HED neural network and Canny operator was proposed. Firstly, extracted reflection component combined with edge reservation filtering method is used to preprocess collected image, so as to enhance the image brightness and contrast and deepen image edge information. Then, the preprocessed image is substituted into the fusion model of improved HED neural network and Canny operator to obtain the continuous large blocks edge image, and the binarization filled image is obtained by doing non-operation according to the edge image. The large blocks in the binarization image are marked with rectangle and the pixel number and area of the large blocks are calculated. Finally, the number of large blocks is counted and judge whether the area of large blocks is higher than the set threshold. If the area is higher than the set threshold, the alarm will be given.The experimental results show that the detection method for large blocks in underground coal transportation based on improved HED neural network with Canny operator has a good edge detection effect, which can effectively reduce the image edge detection error, and count the number of large blocks, calculate the area of large blocks.

Research on RAW regrouping in underground monitoring sensor network based on 802.11ah

YANG Junqiu, WANG Yanfen, WANG Qianyu, CHEN Xiaojing, LIU Fengzhen, SUN Yanjing

2020, 46(5): 69-75. doi: 10.13272/j.issn.1671-251x.17547

<Abstract>(70) <HTML> (10) <PDF>(8)

Abstract:
Existing communication technologies of underground wireless sensor network such as ZigBee, ultra wide band, WiFi and so on have some shortcomings, for example, transmission distance is short, transmission rate is low, or coverage and access devices are limited. However, IEEE 802.11ah protocol meets requirements of transmission range, power consumption, network capacity and transmission rate of underground wireless sensor network, and can be used for underground monitoring sensor network to transmit periodic monitoring data. For problems of inflexible grouping for sensor nodes and load imbalance among groups existed in standard restricted access window (RAW) mechanism of MAC layer in 802.11ah protocol, a RAW regrouping method based on time delay optimization was proposed, which regrouped all the sensor nodes for three times according to projected transmission time of data packages, so as to decrease node colliding in a RAW group and transmission time delay. In order to realize RAW regrouping, an assignment identifier(AID) group reassignment method was proposed, which redistributed AID to sensor nodes group by group according to regrouped RAW group and made the AID map to MAC of the nodes by use of part nodes disconnecting access point, so as to decrease RAW regrouping time consumption and avoid network performance degradation caused by no data transmission during AID redistribution. The simulation results show that when underground monitoring sensor network adopts the RAW regrouping method, the network has less time delay, larger throughput and lower packet loss rate than the standard RAW mechanisms with sensor nodes increase, and regrouping process has little influence on the network performance.

A mine-used frequency converter filter device

RONG Xiang, SHI Han, JIANG Dezhi, SUI Xianming, WANG Yue

2020, 46(5): 76-81. doi: 10.13272/j.issn.1671-251x.17504

<Abstract>(98) <HTML> (12) <PDF>(12)

Abstract:
The mine-used frequency converter is connected with motor through a long cable, and there is phenomenon of voltage reflection in transmission process of pulse width modulation(PWM) pulse, which causes spike voltage at the motor end and seriously affects operation reliability of frequency conversion driving system. At present, mine-used flame-proof frequency converter usually adopts series output reactor to suppress spike voltage, but suppression effect is limited. And the methods of suppressing spike voltage by using RC filter device and LRC filter device mainly aim at 380 V and 660 V frequency converter, which cannot meet requirement of suppressing spike voltage by 1 140 V frequency converter in underground coal mine. In view of the spike phenomenon caused by long-distance transmission of long cable, the effects of motor load, PWM rising time and cable length on the spike voltage in practical application were analyzed. The reflection coefficient of long cable terminal is not sensitive to change of motor load, and influence of motor load can be ignored in design process of filter parameters. The longer the rising time of PWM and the shorter the cable length, the smaller the spike voltage at the end of the motor.According to the above analysis, combined with cable length and device power loss, a design scheme of LRC filter device suitable for 1 140 V frequency converter in underground coal mine was proposed. Before PWM pulse signal is introduced into the long cable, the LRC filter device is used to delay PWM rising time, so as to achieve the purpose of suppressing spike voltage and high du/dt. Simulation and experimental results verify effectiveness of the filter device.

Open-circuit fault diagnosis of three-level inverter based on Park transformatio

REN Xiaohong, WAN Hong, YU Xiao, DING Enjie

2020, 46(5): 82-86. doi: 10.13272/j.issn.1671-251x.17523

<Abstract>(102) <HTML> (9) <PDF>(11)

Abstract:
In view of problems that existing neutral point clamped (NPC) three-level inverter fault diagnosis method needs large amount of calculation and its accuracy is affected by noise and load, an open-circuit fault diagnosis method of three-level inverter based on Park transformation was proposed. Park transformation is carried out on three-phase output current of the three-level inverter to calculate average current Park vector;sliding window is used to obtain a single-cycle current signal, and output current change is analyzed in case of IGBT fault according to inverter circuit structure; iterative method is used to determine threshold value of average current Park vector modulus, and 13 kinds of open-circuit faults of three-level inverter power tube are identifid and located combining phase angle and modulus.Simulation results show that the fault diagnosis accuracy of the method reaches 98.31%. Compared with traditional open-circuit fault diagnosis method, the proposed method does not need to learn and train the data of 13 kinds of open-circuit faults, which greatly reduces calculation amount and improves efficiency and accuracy of fault diagnosis.

Control strategy of mine-used LCL three-level static var generator

ZHANG Chuanjin, LI Yutan, LIU Zhan, TANG Yi, ZHANG Xiao

2020, 46(5): 87-93. doi: 10.13272/j.issn.1671-251x.2020010065

<Abstract>(91) <HTML> (9) <PDF>(9)

Abstract:
In order to adapt to special environment of coal mine and reduce volume and quality of mine-used static var generator(SVG), LCL filter and three-level inverter were used as main circuit topology of mine-used SVG. For problems of current resonance of LCL filter and potential imbalancein three-level inverter, a control strategy of mine-used LCL three-level SVG based on series double current loop active damping control and dynamic proportional space vector modulation was proposed. On the basis of PI control of grid-side current outer loop, LCL filter has damping characteristics by adding feedback control of filter capacitor current inner loop, which can effectively suppress current resonance. Dynamic proportional space vector modulation introduces dynamic proportional adjustment factor into basic space vector to control average neutral-point current in unit switching cycle in realtime, so as to achieve balance control of three-level neutral-point potential. The simulation and experimental results verify the feasibility and good effect of the control strategy under condition of LCL filter without damping resistance and small DC busbar capacitance.

Experimental research on time-varying law of coal gas desorptio

YAO Zhuangzhuang

2020, 46(5): 94-98. doi: 10.13272/j.issn.1671-251x.2019080084

<Abstract>(92) <HTML> (10) <PDF>(15)

Abstract:
In view of problems that current gas desorption research has small sampling range and there is error between desorption model calculation results and measured data, desorption experiments were carried out on coal samples from multiple mines, so as to expand collection range of coal samples. Based on experimental platform for gas desorption of coal particles, time-varying law of coal particles at different adsorption equilibrium pressures, different temperatures and different particle sizes was analyzed by using the control variable method, and the following conclusions were drawn: the greater the adsorption equilibrium pressure, the greater the gas desorption amount; the larger the particle size, the smaller the desorption amount and desorption speed, but after reaching the threshold particle size, the particle size has less effect on the desorption amount and desorption speed; the higher the temperature, the greater the gas desorption amount; the desorption amount gradually increases and the gas desorption speed gradually decreases with the increase of time.The experimental study on desorption of coal samples under different geological conditions has improved applicability of gas desorption model, and further verified influence of temperature, particle size and other main control factors on gas desorption rule.

Design of an adaptive wireless communication system for mine hoist

YAN Donghui

2020, 46(5): 99-103. doi: 10.13272/j.issn.1671-251x.2020010004

<Abstract>(92) <HTML> (12) <PDF>(11)

Abstract:
At present, mine hoist's wired communication system is complicated in wiring and maintenance, however, due to fixed transmission power, frequency and radiation direction of antenna, the mine hoist's wireless communication system has disadvantages of limited wireless communication distance, the signal cannot be flexibly covered according to shape and length of shaft, and communication signal is unstable. In view of the above problems, an adaptive wireless communication system for mine hoist was designed.The data of all equipments in the system is input through Ethernet interface, and wireless communication part adopts the adaptive antenna with automatic sensing of received signal strength, automatic adjustment of working frequency and radiation beam, which can wirelessly interconnect wireless camera,wireless telephone and other mine-used equipments, so as to realize video monitoring, data monitoring and voice communication of main equipments such as hoist, cage ear, oil cylinder, steel wire rope and hoisting sheave. When the hoist is in operating, the system can automatically adjust working parameters of the antenna located at the top of the shaft according to structure, depth and size of vertical shaft, so that the antenna can always be aligned with the moving hoist, communications equipment operating frequency and power is always in the best state, ensuring good coverage of wireless signals.The field application verifies when the hoist is in operating, the ground dispatching personnel can real-timely monitor internal conditions of the hoisting sheave, shaft, cage ears and hoist, and can realize telephone and broadcasting with the relevant personnel in the cage at any time, the image is clear, the voice communication is smooth, and the equipment power consumption is low.

Application of load balancing algorithm in smart mine software platform

GUO Xiucai, ZHANG Yue, HE Yaoyi

2020, 46(5): 104-107. doi: 10.13272/j.issn.1671-251x.2019110054

<Abstract>(67) <HTML> (10) <PDF>(11)

Abstract:
For problems of current load balancing algorithms such as slow processing speed and unreasonable use of existing resources to complete task scheduling in processing data of smart mine system, a cuckoo search based weighted least connection (CS-WLC) algorithm was proposed and applied to smart mine software platform for load balancing. The algorithm synthetically considers backend server indexes including processing speed, RAM, disc IO speed, network throughput and process quantity, and calculates availability of each backend server through assigning weight to each index. Cuckoo search algorithm is used for global optimization of the backend servers according to the calculation results, so as to get an optimal solution collection. The backend servers are assigned weights considering linking number and usage frequency, and weighted least connection (WLC) algorithm is used to select a backend server with lighter load in the optimal solution collection to process real-time data and user access requests. Load balancing test is carried out on software platform of distributed fusion monitoring system. The results show that CS-WLC algorithm has shorter response time-delay and larger linking number than WLC algorithm under the condition of data increase, which verifies CS-WLC algorithm has better load balancing effect.

Research on cross-platform mine emergency rescue path optimization scheme

HAO Tianxuan, ZHAO Lizhen

2020, 46(5): 108-112. doi: 10.13272/j.issn.1671-251x.2019100068

<Abstract>(81) <HTML> (10) <PDF>(7)

Abstract:
At present, research on coal mine emergency rescue path optimization is mostly in the stage of computer simulation calculation. In order to further promote its application in the actual environment of complex roadway, a cross-platform mine emergency rescue path optimization scheme was proposed.Influencing factors of roadway passage are abstracted as impact factors for easy calculation, and actual length of the roadway and passage difficulty are combined to calculate equivalent value of the roadway; Dijkstra algorithm is adopted to solve mine emergency rescue path using the equivalent value as the path length; the emergency search path optimization algorithm can runs on platforms such as computers and mobile terminals taking advantage of the cross-platform nature of Unity engine. Practical application results show that the scheme can bypass road sections that are impassable due to accidents, and provide accurate and effective underground disaster avoidance paths, thus providing technical support for the field application of underground emergency rescue path optimization.

2020 Vol. 46, No. 5

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