工矿自动化

Research status and development trend of hydraulic support precision pushing and fast follow-up technology

REN Huaiwei, ZHANG Shuai, ZHANG Desheng, ZHOU Jie, REN Changzhong, MIAO Xing, LIU Ke, HOU Wei

2022, 48(8): 1-9, 15. doi: 10.13272/j.issn.1671-251x.2022060016

<Abstract>(422) <HTML> (46) <PDF>(78)

Abstract:
The hydraulic support precise pushing and fast follow-up is the key technical support to realize intelligent mining of working face. In order to realize intelligent mining, the precise pushing of hydraulic support is equivalent to the precise position control of valve-controlled cylinder system in coal mine environment, and fast follow-up of hydraulic support need to be realized through follow-up process, liquid supply with stable pressure, fast support movement, etc. Aiming at the precise advancing technology of hydraulic support, it is pointed out that the mature precise position control technology of valve control in related fields can be used for reference. This paper summarizes the research achievements of the electro-hydraulic proportional valve, high-speed on-off valve and electromagnetic directional valve control cylinder position control technology. This paper also summarizes the problems existing in the application of above achievements in the field of coal mines. It is proposed that the precise pushing of hydraulic support can be realized by developing large-flow high-pressure water-based electro-hydraulic proportional valve suitable for the underground environment and developing the intelligent optimization control algorithm. Aiming at the fast follow-up technology of hydraulic support, it is pointed out that the current automatic follow-up of hydraulic support is slow due to unreasonable follow-up process, unstable liquid supply system, and unreasonable support moving process. It is easy to appear the situation of not moving in place and losing support. The related research achievements of improving the follow-up speed are summarized from three aspects: optimizing the follow-up process, supplying liquid with stable pressure, and fast pushing support. The following points are pointed out. At present, the follow-up process cannot be dynamically adjusted according to the speed of the shearer, and the automatic follow-up based on equipment perception is still at the theoretical stage. Optimizing the structure and control algorithm of the liquid supply system is the main way to realize the liquid supply with stable pressure in the working face. But it can not effectively solve the problem of pressure and flow stability at the end of the hydraulic support when the multi-support cooperates. Improving the structure of the hydraulic system is the main way to achieve fast support pushing. But there are some problems such as the large pressure drop when high-pressure oil is transmitted over a long distance, the pipe explosion at the high-pressure point, and the difficulty of pipeline layout caused by increasing the pipe diameter. In view of the above problems, it is proposed to realize the precise pushing and fast follow-up of hydraulic support from four aspects: the constant pressure control of the working face liquid supply system, the improvement of the control precision of hydraulic support pushing, the guarantee of the automatic follow-up effect of hydraulic support, and the improvement of the whole follow-up speed of the working face. It is pointed out that the development trends of precise pushing and fast follow-up technology of the hydraulic support are centralized-distributed agile and efficient liquid supply, improvement of the edge computing capacity of hydraulic support controller, enhancement of adaptability of follow-up control strategy to stope environment, dynamic coupling and follow-up control of stope and equipment.hancement of adaptability of follow-up control strategy to stope environment, dynamic coupling and follow-up control of stope and equipment.

Research on blockchain mechanism of mine Internet of things

ZHANG Liya, LI Chenxin, LIU Bin, JIANG Yufeng

2022, 48(8): 10-15. doi: 10.13272/j.issn.1671-251x.17978

<Abstract>(300) <HTML> (47) <PDF>(59)

Abstract:
The mine Internet of things has the characteristics of large-scale and massive data transmission. These characteristics make the traditional network security and privacy protection methods unable to guarantee the traceability and reliability of key data. The main security risks of mine Internet of things are lack of data transmission traceability and credibility guarantee mechanism, lack of comprehensive signature verification guarantee mechanism of system equipment, and lack of security carrier deployment in system architecture. It is pointed out that blockchain technology can solve the above problems. The key technologies such as blockchain structure, encryption algorithm and consensus mechanism of mine Internet of things are introduced. This paper proposes a blockchain mechanism of mine Internet of things. The edge layer with edge computing power is added between the perception layer and the transmission layer of the mine Internet of things. The security carrier carrying the core functions of the blockchain is deployed. Thus the deployment architecture of the mine Internet of things blockchain is built. The data transmission process under the blockchain mechanism of the mine Internet of things is designed. The asymmetric encryption technology is adopted to ensure the security of data transmission. In the application layer of the Internet of things in mines, the data chain management platform is adopted to realize the functions of key data uplink, data traceability and distributed certificate storage. The blockchain mechanism of mine Internet of things can improve the information security guarantee capability and security level of mine Internet of things. The mechanism can make mine Internet of things to meet the expansion requirements in GB/T 22239-2019 Information security technology-Baseline for classified protection of cybersecurity, and reduce the demand for centralized operation and maintenance.

Review of discharge theory and numerical research on intrinsically safe low voltage DC circuits

ZHU Lin, LIU Shulin, LIU Boqing, JIANG Zhanghe

2022, 48(8): 16-25. doi: 10.13272/j.issn.1671-251x.2022050054

<Abstract>(209) <HTML> (59) <PDF>(31)

Abstract:
The discharge characteristics of intrinsically safe resistive, inductive and capacitive circuits are analyzed. It is pointed out that inductive and capacitive circuits have larger discharge energy and more complex discharge waveforms. The resistive circuits have relatively simple discharge characteristics. The discharge mechanism and mathematical models of the intrinsically safe inductive and capacitive circuits are summarized. The mathematical expressions of different models, such as linear decay model of discharge current, parabolic model of discharge current, static volt-ampere characteristic model, dynamic volt-ampere characteristic model and arc resistance index model, are given. The advantages and disadvantages of the numerical simulation method of macroscopic and microscopic gas discharge are introduced. The macroscopic methods have a small amount of calculation, but it can only simulate the external characteristics of gas discharge. The microscopic methods have a large amount of calculation, but it can accurately simulate the motion characteristics of particles in the discharge process. The microcosmic mechanism of the DC discharge circuit and discharge arc is studied. Under different electrode materials, different electrode distances and different initial electrical parameters, the influence of different surface emission mechanisms such as thermal field emission and field emission on gas discharge is obtained. According to the current research situation, the problems that need to be solved in the discharge research of intrinsically safe DC circuits are put forward. ① The macro experiment-mathematical model has complex expression and a large amount of calculation. Some models have a single scope of application and cannot truly achieve the non-explosive evaluation of intrinsically safe circuits. ② Most of the research on discharge in intrinsically safe circuits is based on IEC spark discharge devices, which affects the discharge of specific circuit parameters. ③ The numerical simulation of discharge arc cannot quantitatively study the arc formation mechanism during the contact breaking process of two electrodes. ④ There are no more convincing research results on the influence of inductance and capacitance of the inductive circuit and capacitive circuit on the characteristics of discharge arc. ⑤ At present, there are few theoretical studies on how to ignite dangerous gases by electric arc due to circuit break arc or short circuit spark.

Research on path planning of parallel gangue selection robot

HUANG Jinfeng, ZHANG Jianxi, YU Jiangtao, MIAO Shuji

2022, 48(8): 26-32, 42. doi: 10.13272/j.issn.1671-251x.2022040073

<Abstract>(845) <HTML> (51) <PDF>(48)

Abstract:
At present, the coal gangue selection manipulator is mostly used in series. Compared with the series manipulator, the parallel manipulator can achieve higher movement speed in a short time, and the load capacity is stronger. Therefore, it is more suitable for the selection of heavy coal gangue. Taking the parallel gangue selection robot as the research object, the two dynamic sorting path planning methods of "ladder" path planning and "V" path planning of parallel manipulator are compared and analyzed. "Ladder" path planning: after the end effector of the manipulator pushes the gangue out of the conveyor belt, it first lifts up a certain distance, and then completes the return movement. "V" path planning: after the end effector of the manipulator pushes the gangue out of the conveyor belt, it first returns to the standard line, and then quickly moves to the position parallel to the next target gangue, completing one movement cycle. By establishing the mechanical model of the parallel manipulator, the torque variation of the drive motor is explored when the manipulator moved along the two paths. The time for completing a movement cycle along the two paths is calculated on the premise that the torque met the requirements. And the working efficiency of the manipulator along the two paths is compared. The simulation results show that the time taken to complete a movement cycle along "ladder" path and "V" path is 1.2, 0.65 s respectively. The "V" path takes a shorter time and has a higher gangue selection efficiency. The site application results show that the average gangue selection rate is 94.23% and 88.28% respectively when the "V" path and the "ladder" path are adopted. The total time of the "V" path is nearly 19% less than that of the "ladder" path, and the gangue selection efficiency is higher.

Video object detection of the fully mechanized working face based on deep neural network

YANG Yi, FU Zefeng, GAO Youjin, CUI Kefei, WANG Keping

2022, 48(8): 33-42. doi: 10.13272/j.issn.1671-251x.2022040003

<Abstract>(326) <HTML> (50) <PDF>(67)

Abstract:
The environment of the fully mechanized working face is complex. The terrain is long and narrow. The multi-object and multi-equipment often appear in the same scene, which makes object detection more difficult. At present, the object detection method applied to the underground coal mine has the problems of high difficulty in characteristic extraction, poor generalization capability, and relatively single detection object category. The existing method is mainly applied to open scenes such as a roadway, a shaft bottom station, and is rarely applied to scenes of a fully mechanized working face. In order to solve the above problems, a video object detection method based on deep neural network is proposed. Firstly, in view of the unfavorable conditions such as complex and changeable environments, uneven illumination, and much coal dust in the fully mechanized working face, the monitoring videos are selected which containing key equipment and personnel of the fully mechanized working face at various angles and under various environmental conditions. By editing, deleting and selecting, an object detection data set covering various scenes of the working face site as much as possible is produced. Secondly, the LiYOLO object detection model is constructed by lightweight improvement of YOLOv4 model. The model fully extracts video characteristics by using CSPDarknet, SPP, PANet and other enhanced characteristic extraction modules. This model uses 6-classification YoloHead for object detection, which has good robustness to the dynamic change of environment and coal dust interference in fully mechanized working face. Finally, the LiYOLO object detection model is deployed to the fully mechanized working face. While the video stream is managed by Gstreamer, TensorRT is used to accelerate the reasoning of the model, and realize the real-time detection of multi-channel video streams. Compared with the YOLOv3 and YOLOv4 models, the LiYOLO object detection model has good detection capability, and can meet the real-time and precision requirements of video object detection in the fully mechanized working face. The mean average precision on the data set of fully mechanized working face is 96.48%, the recall rate is 95%, and the frame rate of video detection can reach 67 frames/s. The engineering application results show that the LiYOLO object detection model can detect and display 6-channel videos at the same time. The model has relatively good detection effect for detection of objects in different scenes.

Retinex mine image enhancement algorithm based on TopHat weighted guided filtering

HONG Yan, ZHU Danping, GONG Pingshun

2022, 48(8): 43-49. doi: 10.13272/j.issn.1671-251x.2022020029

<Abstract>(264) <HTML> (56) <PDF>(41)

Abstract:
The uneven distribution of light sources and weak light in coal mines lead to low brightness and unclear image. The traditional Retinex algorithm has the problems of detail loss, edge blur and halo when processing low illumination images of coal mines. In order to solve the above problems, a new algorithm named THWGIF-Retinex based on TopHat weighted guided filtering is proposed to enhance the mine image. Firstly, the image is transformed from RGB space to HSV space. Then the image is separated into three channel components of hue, saturation and brightness. Secondly, the TopHat transform is used to improve the weight factor of the weighted guided filtering. The illumination component of the image is extracted from the brightness component. The edge enhancement of the brightness component is realized. Thirdly, the illumination component and the saturation component are corrected by adopting a self-adaptive gamma correction function. The reflection component is obtained from the illumination component by the Retinex algorithm. The details and color effect of the image light source are further improved. Finally, the hue component, the corrected saturation component and the reflection component are combined and converted to RGB space to obtain an enhanced mine image. The THWGIF-Retinex algorithm, multi-scale Retinex (MSR) algorithm and weighted guided filtering Retinex (WGIF-Retinex) algorithm are compared and verified from subjective evaluation and objective evaluation. The subjective evaluation results show that the original image of low illumination without strong light is enhanced by the THWGIF-Retinex algorithm. The color reproduction degree of the image is higher, the image edge is clearer, and the visual effect is obviously enhanced. The THWGIF-Retinex algorithm has a good effect on halo reduction for the mine low-illumination original image with strong light. The THWGIF-Retinex algorithm is better than the WGIF-Retinex algorithm in restoring the details and clarity of dark areas. The objective evaluation results show that the information entropy, the average gradient, the standard deviation and the no-reference structural sharpness (NRSS) of the image enhanced by the THWGIF-Retinex algorithm are increased by 12.50%, 109.07%, 52.44% and 45.46% respectively for the low illumination images without strong light. Compared with the MSR algorithm, the information entropy, average gradient, standard deviation and NRSS of the image enhanced by the THWGIF-Retinex algorithm are increased by 1.24%, 81.44%, 18.23% and 36.67% respectively for the mine low illumination image with strong light. Compared with the WGIF-Retinex algorithm, the THWGIF-Retinex algorithm has lower information entropy. However, the average gradient and NRSS are improved by 72.34% and 23.87% respectively.

Coal and gangue image classification model based on improved feedback neural network

YAN Honglin

2022, 48(8): 50-55, 113. doi: 10.13272/j.issn.1671-251x.2022050026

<Abstract>(204) <HTML> (45) <PDF>(33)

Abstract:
The existing image classification methods based on deep learning have the problems of the large number of classification model parameters, long time consumption and low classification precision. It is difficult to achieve a compromise between the portability of the model and the classification precision. In order to solve the above problems, a coal and gangue image classification model based on improved Feedback-Net is proposed. The Feedback-Net model is built on the basis of the ResNet50 model. The high-order information and the low-order information are fused by building a feedback path in the ResNet50 model. Therefore, the representation capability of the features is improved. The constructed Feedback-Net model consumes more time while improving the classification accuracy. In order to solve this problem, the square convolution block in the Feedback-Net model is improved into an asymmetric convolution block (ACB). The feature extraction capability of the convolution kernel is increased by superposition and fusion. The full connection layer with the largest number of parameters is replaced by global covariance pooling (GCP) to reduce the number of network parameters. By simulating the environment of coal and gangue sorting in coal mines, the performance of the Feedback-Net model and the improved Feedback-Net model (Feedback-Net + ACB and Feedback-Net + ACB + GCP) is verified. The results show the following points. ① The precision of the Feedback-Net model is higher than that of the ResNet50 model, and the loss value is slightly lower than that of the ResNet50 model. ② Compared with the ResNet50 model, the training precision of the Feedback-Net model is improved by 1.20%. The testing precision is improved by 1.21%, but the training time is increased by 0.22%. ③ The precision of the Feedback-Net + ACB + GCP model is high than that of the Feedback-Net and Feedback-Net + ACB model. The Feedback-Net + ACB + GCP model's convergence rate is the fastest among the three models. It has the best performance. ④ Compared with the Feedback-Net model, the testing precision and training precision of the Feedback-Net + ACB model are improved by 1.39%. The time consumption is reduced by 15.53 minutes. Compared with the Feedback-Net model, the training precision and testing precision of the Feedback-Net + ACB + GCP model are improved by 1.62% and 1.59% respectively. The time consumption is reduced by 1.12%. Compared with the Feedback-Net+ACB model, the time consumption of the Feedback-Net+ACB+GCP model is reduced by 50.38 minutes. The performance of the Feed-Net+ACB+GCP model is better.

Research on the deformation and failure depth of the floor in fully mechanized top coal caving of extra-thick seam

HOU Junhua

2022, 48(8): 56-61, 121. doi: 10.13272/j.issn.1671-251x.2022050021

<Abstract>(221) <HTML> (59) <PDF>(22)

Abstract:
In order to explore the deformation and failure depth of the floor under the condition of fully mechanized top coal caving of extra-thick coal seam, this paper takes 1305 working face of Dongtan Coal Mine of Yankuang Energy Group Co., Ltd. as the background. The deformation and failure depth of the floor in the mining coal seam of the working face is comprehensively analyzed by using field measurement, numerical simulation and theoretical calculation. The field measurement results using the strain induction method and borehole imaging technology show the following results. The floor is affected by mining ground pressure, and there are obvious characteristics in horizontal and vertical directions. In the horizontal direction, the position near the advanced support measuring point of 50 m and at the depth of 10 m in the shallow part of the floor starts to be affected by the mining ground pressure. After the working face is pushed over a certain distance, the deformation and failure of the floor are severe. The variation range of crossover distance and lag distance in the horizontal direction of different depths of the floor is 96-115 m and 48-52 m respectively. The deformation and failure depth of the floor in fully mechanized top coal caving of the working face is 16-20 m. The floor rock below the vertical depth of 20 m is mainly elastic deformation. The distribution characteristics of the plastic zone in different depths of the floor by numerical simulation show that the farther the distance from the working face floor is, the smaller the influence of mining pressure is, and the smaller the range of the plastic zone is. The 20 m under the floor is basically not damaged. The result of the theoretical calculation confirms that the deformation and failure depth of the floor is 19.2 m. Based on the results of field measurement, numerical simulation and theoretical calculation, the deformation and failure depth of the floor in 1305 working face is less than 20 m. The research results can provide the quantitative basis for the prevention and control of floor water disasters in fully mechanized top coal caving of extra-thick coal seams.

Study on determination of development height of mining-induced fissure zone in deep outburst coal seam

GUO Minggong, TAO Yunqi, ZHANG Jianzhao

2022, 48(8): 62-68, 91. doi: 10.13272/j.issn.1671-251x.2022030039

<Abstract>(177) <HTML> (35) <PDF>(19)

Abstract:
The use of high-level directional long borehole gas extraction technology instead of high-level extraction roadway to extract mining pressure relief gas can greatly reduce the amount of rock roadway excavation. And it can effectively relieve the tension situation of mine mining replacement. Moreover, it can achieve remarkable gas control effect. But the high-level directional long borehole gas extraction technology often has problems in practical application. Due to inaccurate determination of the development height range of the upper "three zones" of mining overburden, the directional long borehole layout horizon is too high or too low. The application effect is poor. In order to solve this problem, taking the VI₁₅-15050 working face of No. 8 Coal Mine of Henan Pingdingshan Tian'an Coal Mining Co., Ltd. as the research background, the development height of mining-induced fissure zone in the coal seam of the working face is determined by using empirical formula method and numerical simulation experiment method. The maximum development height of the caving zone is 13.2 m, and the maximum development height of the fissure zone is 48 m. The kilometer directional drilling rig is used to construct high-level directional long borehole in the VI₁₅-15050 working face, and the fissure zone development height is verified. The results show that the lithology of overburden is relatively broken at 20 m from the roof of the coal seam, and the high concentration gas area in the fissure zone is more than 23 m from the roof. When the VI₁₅-15050 working face is pushed to 105 m, the high-level directional long borehole and the fissure zone in the goaf have been fully communicated. The gas in the upper corner and return air flow of the VI₁₅-15050 working face is kept at 0.47%. The maximum gas extraction volume fraction of a single hole of the high-level directional long borehole is 13.2%. The daily net gas extraction volume is kept at 3-4 m³/min, and the air distribution volume is calculated as 2500 m³/min. The gas extraction volume of high-level directional long boreholes can reach 25.5%-34.0% of the air exhaust gas volume. During this period, there is no gas overrun, and the high-level directional long boreholes arranged in the current layer can successfully control the gas in the upper corner and return air flow. The correctness of the development height of the fissure zone obtained by the two methods is verified.

Analysis of rock burst risk of mining in hanging wall of normal and reverse faults

WEI Shiming, WANG Fuying, ZHANG Zesheng, JIN Mengfan

2022, 48(8): 69-75. doi: 10.13272/j.issn.1671-251x.2022030041

<Abstract>(182) <HTML> (38) <PDF>(18)

Abstract:
The existing research on the rock burst risk of faults under different conditions is mostly carried out around the footwall mining or single fault form. The comparative research on the rock burst risk of hanging wall mining of different faults is seldom involved. In order to solve the above problems, the 12220 working face of Gengcun Coal Mine in Yima, Henan is taken as the research background. The rock burst risk of mining in hanging wall of normal and reverse faults is analyzed by means of theoretical analysis, numerical simulation and field monitoring. The mechanical model of mining in the hanging wall of normal and reverse faults is established. The mechanical condition of shear slip on the fault is obtained by analyzing the stress of fault rock. The results of the theoretical analysis show that the occurrence of shear slip is closely related to such factors as fault dip angle, internal friction angle of fault and fault surface force on rock block during hanging wall mining of normal and reverse faults. The closer the working face is to the fault, the greater the risk of shear slip. The numerical simulation of the mining process in the hanging wall of normal and reverse faults is carried out, and the normal stress, shear stress and slippage of the fault plane are analyzed. The results show that in the mining process of the working face, when the distance between the working face and the fault is less than 40 m, the risk of shear slip and rock burst increases gradually. When the distance from the fault is 10 m, the risk is the greatest. The most likely position for shear slip is the coal seam roof and coal seam of the fault plane. The influence degree of the coal seam floor is obviously less than that of the roof. The type of fault has a certain impact on the rock burst risk. The rock burst risk of reverse fault mining is higher than that of normal fault. Microseismic monitoring of rock burst risk is carried out on the 12220 working face. The results show that when the working face is less than 20 m from the fault, the microseismic events are frequent and the rock burst risk is high. The results are consistent with the numerical simulation results, which verifies the rationality of the numerical simulation analysis.

Method for extracting stressed rock crack based on light reflectivity mutation

GAO Xiang, GAO Yanan

2022, 48(8): 76-84. doi: 10.13272/j.issn.1671-251x.2022040066

<Abstract>(246) <HTML> (41) <PDF>(11)

Abstract:
The crack identification and extraction is the basis of understanding the evolution law of surrounding rock cracks. The existing methods for extracting stressed rock cracks based on visible light photos are poor in extracting the cracks of complex rocks (such as granite) composed of polychromatic minerals. In order to solve the problem, a method for extracting stressed rock cracks based on light reflectivity mutation is proposed. The method comprises four key steps of light reflectivity calculation, light reflectivity mutation point identification, light reflectivity mutation point space heterogeneity analysis and crack information extraction. The spatial differentiation of the mutation points of light reflectivity caused by crack growth is the key characteristic of crack identification. Therefore, the index-differentiation coefficient C, which reflects the concentration degree of spatial point distribution, is introduced. It is used to judge whether there is a crack in the digital image according to the spatial differentiation of the mutation points of light reflectivity. After the crack in the digital photo is judged, on one hand, the instantaneous information of the crack activity is reflected through the change speed of the light reflectivity, so as to study when and where cracks occur or expand in the specimen. On the other hand, the cumulative information of crack activity is extracted to analyze the development, propagation and penetration degree of rock surface cracks over a period of time. The experimental result shows that: ① The development and propagation of stress cracks in rock can cause the mutation of light reflectivity. The mutation speed can reach 0.2/s, which is much larger than the change speed (0.03/s) caused by other random factors. ② At the crack active time, the mutation point of light reflectance shows significant spatial differentiation (C value can reach 189), and the differentiation coefficient is much larger than that in random distribution (C value is 1). ③ The proposed method can extract the instantaneous information and cumulative information of crack activity. Finally, the reason for the change of light reflectivity during rock crack, the significance of rock mechanics of the proposed method and its application prospect in roadway safety inspection are discussed.

Study on coal crack propagation and failure mode with different moisture content under uniaxial compression

LU Weiyong, LIU Qi, QU Lina, ZHANG Haijun

2022, 48(8): 85-91. doi: 10.13272/j.issn.1671-251x.2022040036

<Abstract>(231) <HTML> (48) <PDF>(28)

Abstract:
In order to study the influence of moisture intrusion on crack propagation and failure mode of loaded coal, uniaxial compression tests and acoustic emission monitoring of coal with different moisture contents are carried out. The stress-strain characteristics, macroscopic failure patterns and change law of cumulative ringing counts of loaded coal with different moisture contents are compared and analyzed. The results of uniaxial compression tests show that with the increase of moisture content, the uniaxial compressive strength and elastic modulus of coal decrease continuously. The stress drop rate of coal gradually slows down in the post-peak stage. The macroscopic failure mode of coal samples changes from typical brittle failure to shear-tension combined failure. The acoustic emission monitoring results show that the cumulative ringing counts decreases with the increase of coal moisture content. The cumulative ringing counts curve's slope increases correspondingly, indicating that moisture intrusion can reduce the energy release when the coal cracks develop. However, the moisture intrusion aggravates the internal structure damage of coal. The results show that the water intrusion weakens the friction between crystal particles on the surface of cracks to some extent, and increases the possibility of coal sliding failure. At the same time, the water intrusion also reduces the surface active energy of the coal, resulting in a significant increase in the number of cracks generated during the loading process of the coal sample. This leads to a large drop in the macroscopic mechanical strength of the coal.

Fault line selection method for coal mine power grid based on RCMDE and KFCM

HAN Guoguo, SHI Xiaojun, WANG Hui, CHENG Weijian, MU Yanxiang

2022, 48(8): 92-99. doi: 10.13272/j.issn.1671-251x.17911

<Abstract>(142) <HTML> (52) <PDF>(25)

Abstract:
It is difficult to accurately select the fault line when the single-phase ground fault occurs in the coal mine power grid with the widely used resonant grounding system. In order to solve the above problem, a fault line selection method of the coal mine power grid based on the refined composite multiscale dispersion entropy (RCMDE) and the kernel fuzzy C-means clustering (KFCM) is proposed. The limitations of using amplitude, polarity and waveform similarity as line selection characteristic quantities: the applicability of the line selection method based on amplitude and polarity difference is limited. If the polarity of the zero sequence current transformer in the line is reversed, the method based on polarity will directly fail. When the sampling is not synchronized, the line selection method based on waveform similarity is difficult to obtain correct results. In order to overcome the above limitations, RCMDE is introduced to measure the complexity and irregularity of the transient zero sequence current signal of each line. RCMDE is used as the characteristic quantity of line selection. The KFCM algorithm is used to cluster the RCMDE to realize the automatic identification of fault lines. The bus fault and feeder fault are distinguished by judging whether the contour coefficient exceeds the threshold value. Finally, the feeder line with the fault point is judged through the membership degree matrix obtained by clustering. The simulation results show the following points. ① The RCMDE curve of the fault line is different from that of the non-fault line, and the curves can be divided into two types. RCMDE can be used as the fault characteristic index of fault line. ② When the bus fault occurs, there are clusters with an average contour coefficient less than the threshold value in the clustering results. However, when feeder fault occurs, the contour coefficients of the clustering results are all greater than the threshold value. Under various fault scenarios, the coal mine power grid fault line selection method based on RCMDE and KFCM can realize correct line selection. The results show that its accuracy is not affected by factors such as fault line, fault location, fault closing angle and grounding resistance. ③ Under the conditions of noise disturbance, the fault line selection method based on RCMDE and KFCM can realize correct line selection in the case of low resistance grounding or high resistance grounding. And the method has a strong anti-interference capability. ④ Under the conditions of asynchronous sampling and reverse polarity of zero-sequence current transformer in the fault line, the method based on RCMDE and KFCM can still realize correct line selection. And the line selection result has high robustness.

High-frequency isolated variable frequency speed regulation sensorless vector control in mine

LIU Wenzhuang, LIU Jiangong, WANG Yiying, BO Lei, HAO Yuhong

2022, 48(8): 100-106. doi: 10.13272/j.issn.1671-251x.2022050020

<Abstract>(231) <HTML> (48) <PDF>(16)

Abstract:
In the coal mine's medium and high voltage and limited occasions, the frequency converter is connected to the power grid by power frequency transformer. Most of the controlled motors are controlled by open-loop control, which has the problems of narrow working space, complex structure and poor robustness of motor control. In order to solve the above problems, a speed sensorless vector control strategy based on high frequency isolated variable frequency speed regulation topology is proposed. This paper analyzes the topology and power transmission of the main circuit of high-frequency isolated variable frequency speed regulation in mine. The input three-phase power frequency AC power supply is rectified into DC power supply through an uncontrollable rectification link. The pulsating DC power supply is smoothed and filtered to obtain a stable DC power supply. The DC power supply is transformed through high-frequency isolation (DC-DClevel). Then, through the three-phase inverter stage, the DC power supply is converted into AC power supply with adjustable voltage and frequency. In order to reduce IGBT switching loss, save the overall cost and reduce the complexity of its overall structure, the three-phase rectifier stage adopts a diode uncontrolled rectification strategy. The equal pulse width modulation (EPWM) strategy is adopted for the high-frequency isolated DC-DC stage. The speed sensorless vector control strategy is adopted in the three-phase inverter stage. In this control strategy, the model reference adaptive system (MRAS) is used to estimate the speed of the asynchronous motor. A 0.75 kW three-phase asynchronous motor is used as the tested motor to verify the speed sensorless vector control strategy of high-frequency isolated variable frequency speed regulation for mine. The results show the following points. ① The voltage fluctuation of the DC bus on both sides of the high-frequency isolation DC-DC level is less than 10 V and the high-frequency square wave voltage is equal. The voltage waveforms of the primary single-phase inverter square wave and the high-frequency transformer coupled square wave are smooth and the overall steady-state performance is good. ② The three-phase inverter voltage and current waveform sine degree are good. The waveform is symmetrical and smooth. The three-phase inverter level stability performance is good, which meets the requirements of motor operation. ③ With the increase of time, the excitation current change is stable. The torque current responds quickly at startup. The torque current is large at the start-up stage, which can generate large torque. ④ The speed fluctuation of the motor is small in the stable phase. The waveforms of acceleration and deceleration phases tend to be a linear function, and the motor can start and stop smoothly. When the motor is just started, the maximum torque can reach more than 5 times of the stable torque, and the motor can be started quickly to work.

Research on sorting reliability of cable-driven gangue sorting robot system based on fault tree

QIAO Xinzhou, WU Chenchen, LIU Peng, FAN Hongwei, MAO Qinghua

2022, 48(8): 107-113. doi: 10.13272/j.issn.1671-251x.2022050075

<Abstract>(861) <HTML> (28) <PDF>(20)

Abstract:
The sorting reliability of the gangue sorting robot is closely related to coal quality and sorting efficiency. It is necessary to study the sorting reliability of the sorting robot system. The existing reliability research of robot system mainly focuses on the structural reliability. There is no research on the task reliability of robot system, namely sorting reliability. In order to solve this problem, taking the cable-driven gangue sorting robot system as the research object, the sorting reliability is studied by fault tree analysis. Firstly, based on the structure of the gangue sorting robot system, the reasons for the sorting failure of the gangue sorting robot system are analyzed. The deductive method is used to construct the sorting fault tree of the gangue sorting robot system. Secondly, the occurrence probability of the bottom event of the fault tree is considered as an interval variable. The probability interval parameter of the top event of the sorting fault tree is obtained according to the interval property, the algorithm and the probability expression of the top event. According to the design requirements, the non-probabilistic reliability index which reflects the sorting reliability of the gangue sorting robot system is calculated. Finally, based on the formula of the non-probabilistic reliability index and the definition of fuzzy importance, an interval importance index is proposed. The interval importance of the events at the bottom of the sorting fault tree is solved and ranked. The results show that the sorting reliability can meet the requirements of sorting reliability of the gangue sorting robot. The increase of instantaneous gangue content in coal gangue flow and the failure of the industrial camera are important factors affecting the sorting reliability. According to the calculation result of the non-probability reliability index and the ranking of interval importance, the weak link of the gangue sorting robot system is found. Three improvement measures are proposed for the weak link. It is suggested to shake and mix the coal gangue flow before sorting. According to the identified gangue information, it is suggested to intelligently control the belt speed of the belt conveyor. It is suggested to add spare industrial camera in the gangue sorting robot system.

Non-coal mine safety supervision mode based on risk monitoring and early warning

JIANG Hongnian, CHEN Xiaolin, WANG Chao, HU Ran, ZHANG Yu

2022, 48(8): 114-121. doi: 10.13272/j.issn.1671-251x.2022030071

<Abstract>(217) <HTML> (40) <PDF>(25)

Abstract:
At present, non-coal mine safety supervision mainly includes safety management inspection and on-site safety supervision inspection. They rely on safety information management platform and on-site inspection by safety inspectors respectively. There are problems of low supervision efficiency, delayed information acquisition, and it is difficult to realize dynamic and comprehensive supervision. In view of the above problems, this paper puts forward a non-coal mine safety supervision mode based on risk monitoring and early warning, considering the characteristics of non-coal mines, such as large number, scattered, poor, small, and the differences in risks and informatization management and control of different types of non-coal mines. Based on the risk monitoring and early warning system of non-coal mine, the risk monitoring index data in five aspects of personnel, environment, equipment and facilities, management and monitoring topics are extracted. The single risk early warning analysis and comprehensive risk alarm analysis are carried out in two ways of risk point and risk surface respectively. The graded push of single risk early warning and the graded control of comprehensive risk alarm can be realized. The monitoring data and special topics of various types of non-coal mines are sorted out. The trigger and disposal mechanism of single risk graded early warning is introduced. This study focuses on the construction process of the model for comprehensive risk research and judgment and graded supervision. Based on the risk monitoring data of non-coal mines, the risk monitoring index system is established. The entropy weight method is adopted to give weight to the risk monitoring index, and the scoring standard is formulated to score the risk index of non-coal mines. Based on the index weight and score, the comprehensive risk level of mining enterprises is determined. The non-coal mine safety supervision mode based on risk monitoring and early warning realizes the graded supervision and inspection of non-coal mines by supervision departments under different supervision periods and ranges. The mode optimizes the allocation of supervision and inspection resources, and improves the efficiency of supervision and inspection.

Design of mine integrated dispatching management and control platform

CHEN Huaying, DU Zhigang, SONG Xingjia

2022, 48(8): 122-126. doi: 10.13272/j.issn.1671-251x.17965

<Abstract>(164) <HTML> (22) <PDF>(44)

Abstract:
Each system of the coal mine has independent management and control terminal platform. When an emergency occurs, the dispatcher needs to switch back and forth between different platforms. There are some problems such as low dispatching and commanding efficiency, incomplete information acquisition, incomplete data display on one screen, lack of unified visual management platform, etc. In view of the above problems, the mine integrated dispatching management and control platform is designed. The platform takes the dispatching host as the core, and realizes the interconnection and intercommunication of various heterogeneous communication systems and integrated voice dispatching through the voice gateway. Based on the wired/wireless IP transmission network, with the video access server as the core, the differences between video terminals are shielded through protocol docking. The unified video access is realized. At the same time, the video conference function is realized through the video exchange server. The GIS technology is used to introduce the plan of mine excavation engineering, create a "one map" mode to present different resources of multiple systems, and realize map scheduling. The data visualization interface is developed based on the B/S architecture. The data of different systems are gathered and displayed in the way of "one machine and three screens" , so as to improve the data utilization efficiency. The test results show that the platform integrates voice scheduling, video scheduling, map scheduling and data visualization. The platform can further strengthen the information communication and management and control capability of production scheduling command. The platform can improve the emergency rescue capability of coal mines. The platform can assist in the informatization construction of coal mine emergency management.

Research on key technologies of multi-element monitoring data integration in intelligent mine

LI Guomin, ZHANG Ao, HE Yaoyi, GAO Wen, HUANG Zongliu

2022, 48(8): 127-130, 146. doi: 10.13272/j.issn.1671-251x.2022060088

<Abstract>(280) <HTML> (44) <PDF>(43)

Abstract:
Currently, most coal mine monitoring systems adopt private data acquisition protocols, which are incompatible with each other. In order to solve this problem, the key technologies of multi-element monitoring data integration in intelligent mine are discussed from three aspects of data acquisition, data fusion and data storage. Data acquisition: In order to strengthen the openness and compatibility of the system, the private protocol can be encapsulated into a driver dynamic link library (DLL). The data acquisition of each business system can be realized by loading and adapting OPC, MQTT and other protocols and hooking the private protocol driver. The multithreading technology can be adopted to meet the requirements of high efficiency and real-time of multi-channel and multi-protocol data transmission. Data fusion: The data with the high frequency of sharing among various systems can be unified and standardized to form the master data of the coal mine. This will ensure the consistency of data among various systems. Data storage: For data with high real-time requirements, the time series database can be selected. For data with low real-time requirements, the relational database can be selected. Through comparative analysis, InfluxDB is more suitable for real-time storage of coal mine monitoring data, and MySQL Community is more suitable for data storage with low real-time requirements. Redis cache technology can be used to achieve efficient data cache so as to ensure the integrity of coal mine monitoring data.

Research on surrounding rock failure law of large mining height working face in thick loose layer based on microseismic monitoring

HENG Peiguo, ZHAI Changzhi, XIN Chongwei, WANG Yanlu, CHEN Yang

2022, 48(8): 131-139. doi: 10.13272/j.issn.1671-251x.2022040082

<Abstract>(224) <HTML> (85) <PDF>(23)

Abstract:
The research on the movement law of surrounding rock under the condition of thick loose layer and thin bedrock mostly adopts theoretical research methods such as establishing a mechanical model and numerical calculation. It lacks research based on field dynamic measurement. The microseismic monitoring technology has been widely used in mine dynamic disaster monitoring and early warning in recent years. However, there are few studies on the failure law of surrounding rock under the condition of thick loose layer and thin bedrock based on microseismic monitoring technology. In view of the above problems, taking the 16001 working face of Zhaogu No. 1 Coal Mine of Coking Coal Energy Co., Ltd. as the engineering background, a high-precision microseismic monitoring system is established. The system is built by selecting the network arrangement mode of the borehole-roadway union. Based on the microseismic monitoring results, the dynamic failure law of surrounding rock in large mining height working face under the condition of thick loose layer and thin bedrock is studied. According to the accumulated released energy of surrounding rock, the energy density of the microseismic event is analyzed by adopting a nuclear density analysis method so as to achieve the purpose of studying the fracture development of the surrounding rock. The analysis results show that the maximum roof damage height is 87.8 m, and the maximum floor damage depth is 21.7 m. The maximum values all appear in the square stage of the working face, at which the roof water inrush risk is the highest. In the square stage, the roof-bearing rock beam is damaged, abnormal pressure occurs, and the damage degree of the roof, floor and advanced support is intensified. The results verify the existence of the stress breakdown effect. The sandy mudstone 48.3 m away from the roof of the working face is the key layer of the roof water barrier. The siltstone 67.7 m away from the roof is the breakdown control layer. The sandy mudstone 26.6 m away from the floor is the key layer of the floor water barrier. The results of microseismic monitoring and analysis are verified by bottom borehole peeping. The results show that the floor damage depth in the square area is more than 18 m, and the floor damage depth in other areas is 12-18 m. These results are consistent with the microseismic monitoring results.

Risk assessment of water inrush from coal seam floor based on comprehensive weighting

ZHENG Jianying

2022, 48(8): 140-146. doi: 10.13272/j.issn.1671-251x.2022010016

<Abstract>(185) <HTML> (48) <PDF>(15)

Abstract:
The existing risk assessment model of water inrush from coal seam floor has the problems of weak generalization capability and low accuracy for the working face with complex geological structures. In order to solve the above problems, a risk assessment model of water inrush from coal seam floor based on comprehensive weighting by analytic hierarchy process (AHP) and improved entropy weight method (IEW) is proposed. Based on the unascertained measure of single index, the comprehensive weight of each assessment index affecting water inrush from coal seam floor is given by the AHP-IEW comprehensive weighting method. A comprehensive risk assessment model of water inrush from coal seam floor is established. The unascertained measure value of each assessment index is calculated by using the model. Then according to the recognition criteria of confidence, the grade is determined and the assessment result is obtained. The feasibility of the model is verified by taking 1305 working face of Pandao Coal Industry Co., Ltd. as the research object. ① According to the actual situation of the coal mine, the mining depth, coal seam thickness, coal seam dip angle, aquifer water pressure, effective water barrier thickness, floor brittle rock thickness, fault fractal dimension and floor integrity that affect the floor water inrush risk are selected as the assessment indexes. The graded standard of floor water inrush risk is established. ② The single index measure functions are constructed to obtain the measure value of each assessment index. ③ The comprehensive weight of each assessment index is obtained by AHP-IEW comprehensive weighting method. ④ The comprehensive measure assessment vector is determined by combining the comprehensive weight and the unascertained measure matrix of the assessment index. ⑤ According to the comprehensive measure assessment vector, the investigation points in the study area of the coal mine are classified into risk grades. The results are compared with the field investigation results. The verification results show that compared with IEW assessment results, the prediction accuracy of risk assessment model of water inrush from coal seam floor based on AHP-IEW comprehensive weighting is higher. The assessment results are consistent with the actual investigation situation in the mining process of the working face.

2022 Vol. 48, No. 8

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