Online First have been peer-reviewed and accepted, which are not yet assigned to volumes /issues, but are citable by Digital Object Identifier (DOI).
Design of a High Isolation Tri-Frequency MIMO Antenna for Coal Mine Applications
Multi-frequency MIMO antenna technology has been attracting widely attention due to the advantages of fast data transmission rate, large capacity and strong reliability. However, it also has the serious problem of inter-signal interference caused by the strong coupling between array elements. In order to take full advantages of multi-frequency MIMO antenna technology in the process of coal mine informatization, a three-frequency MIMO antenna with high isolation characteristics is designed in this paper. The antenna works in three frequency bands: 1.85-2.70 GHz, 3.24-3.99 GHz and 4.65-5.80 GHz. It is composed of two Trident planar monopole with an array spacing of 0.18 λ ( λ is the wavelength at 2.3 GHz), which can effectively cover the operating frequency band of WiMAX/WiFi/4G/5G NR in coal mine. The isolation between the elements is higher than 20 dB in the whole frequency band by placing the two elements symmetrically firstly, loading T-shaped branches and etching rectangular slots on the floor successively. The designed tri-frequency MIMO antenna has the advantages of low profile, compact structure and easy to conform with the carriers, thus having a broad prospect in coal mine applications.
Research on mine wireless signal detection method based on dual path neural network
Aiming at the problems of high bit error rate and easy channel interference of wireless communication signals in complex mine environment, a new signal detection method based on orthogonal frequency division multiplexing (OFDM) and filter bank multicarrier technology (FBMC) was proposed. This model combines the advantages of ResNet and DenseNet, and constructs an improved Dual Path Network Receiver. The receiver can suppress the problem of gradient disappearance and gradient explosion in the network well, extract different levels of features, and enrich the feature dimension. The experimental results show that when the SNR is 11, the bit error rate of DPNR in OFDM is about two orders of magnitude lower than that of conventional receiver DNN. DPNR is not interfered with by the channel, and it is also applicable in FBMC. Therefore, DPNR has strong interference and stability in the identification of input signals in different scenarios, which improves the quality of wireless communication and enables the signal to be recovered more accurately.
Research and application of gas drainage technology in goaf across working face
Gob-side entry retaining has the advantages of reducing the loss of coal pillars, reducing the amount of excavation works, and alleviating the tension of the connection between extraction and mining, and its application is becoming more and more common. However, the application of the middle gangue retaining bracket not only facilitates the hanging and injection molding, but also forms a drawer-type semi-enclosed space, which is easy to accumulate gas, which has become the focus and difficulty of gas management. Aiming at the problem of gas control in the gob area of the Y-type ventilation continuous mining face, a gas control technology is proposed to use the inclined directional long boreholes to drain the gob area across the working face, and form a gas extraction method for the gob area and the mining face across the working face. It reduces the gas accumulation in the adjacent goaf, and can effectively prevent the gas disaster caused by the sudden fan-out of the gas in the goaf when the roof collapses in a large area. The test in Dongfeng Coal Mine shows that the construction tends to drill holes from high positions to the cracks in the roof of the old goaf, and continue to extract the gas in the old gob. The gas concentration in the upper corner is reduced from 0.67% to 0.22%, and the gas concentration in the return air flow is reduced from 0.47%. It is reduced to 0.18%, and the gas storage in the goaf and its roof crack zone is minimized, and the ideal effect is achieved, and the gas control effect is remarkable.
Research on video stabilization algorithm of roadheader based on adaptive enhancement and Kalman filter
The vibration of the fuselage causes the blurred image of the onboard surveillance camera during the travel and operation, which leads to the decrease of the accuracy and reliability of the machine vision application based on the onboard image. To solve this problem, a video stabilization algorithm based on adaptive enhancement and Kalman filtering is proposed. In the motion estimation stage, the image contrast is limited in the dynamic range. Compared with the original video sequence, the successful matching number of feature points is in-creased by 58%. In the motion smoothing and compensation stage, the Kalman filter is used to preserve the subjective motion of the airborne camera while removing the random jitter, and the compensation between adjacent frames is obtained. After the jitter video is com-pensated frame by frame, the stable video sequence is generated. The experimental results show that the average PSNR after video stabilization is increased by 10% compared with the original dithered video, and the image information between adjacent frames is decreased by 39%. Therefore, the algorithm has a good video stabilization effect.
Spatial and temporal gas concentration prediction based on GCN-GRU
Traditional gas concentration prediction methods only use the temporal characteristics of gas data for prediction, but in fact gas concentration has a distribution with space and time, and predicting its spatio-temporal distribution is more valuable for gas safety work. In order to improve the accuracy of gas concentration prediction, a graph neural network (GNN) based model for predicting the spatio-temporal distribution of mine gas is proposed for the complex dependencies of gas data in the temporal and spatial dimensions, which uses a graph convolutional neural network to model the spatial dependence of gas monitoring stations and a gated recurrent network (GRU) to model the temporal dependence of gas sequences, after the graph signal and temporal After encoding the graph signal and time-dimensional features, the model is fed to a decoder to obtain the prediction output. The results show that the model prediction results have a high prediction accuracy in predicting the spatial and temporal distribution of multiple monitoring points, with an average absolute error percentage of 3.0%, which is more than 2% lower than the tradi-tional time series prediction method.
Research on autonomous Positioning technology of inspection robot in Fully mechanized Mining face
Because the work space is small and the environment is changing with the advancing of the working face, a kind of inspection robot system is designed which can complete the inspection task independently. The robot is equipped with 3d scanner to complete the recon-struction of underground space working face scene, and the rigid-flexible track design is adopted to adapt to the environment of the fully mechanized working face. Aiming at the design characteristics of rigid-flexible integrated track, in order to reduce the influence of the track connectors on the inertial navigation and positioning of the inspection robots. Inertial navigation/odometer incremental navigation is used to complete the positioning of the inspection robot,the experiment shows that the positioning accuracy of this scheme can reach 10-3 magnitude on 40km road. At the same time, through the dynamic analysis of the gyroscope data when the inspection robot passes through the track connection point, the identification of the track connection piece and the detection of the jitter point are completed, and the segmentation filtering is realized through the jitter detection to improve the positioning accuracy of the inspection robot. The experi-mental results show that the judgment of track connection is accurate, and the piecewise filtering based on jitter detection can effectively improve the positioning accuracy of inspection robot.
[Academic Column of Editorial Board Member]
Research on the safety threshold of radio wave explosion-proof
SUN Jiping, PENG Ming, PAN Tao, ZHANG Gaomin
2023, 49(2): 1-5.   doi: 10.13272/j.issn.1671-251x.18072
Abstract: The powerful radio waves can ignite explosive gases. Therefore, it is necessary to reasonably set the radio wave explosion-proof safety power and energy threshold emitted by the radio transmitter to limit the radio wave power and energy emitted by the radio transmitter. The radio wave explosion-proof safety power and energy thresholds specified in European Standard CLC/TR 50427:2004 Assessment of inadvertent ignition of flammable atmospheres by radio-frequency radiation-Guide are the ignition power and energy threshold. The national standard GB/T 3836.1-2021 Explosive atmospheres-Part 1: Equipment-General requirements and the international standard IEC 60079-0:2017 Explosive atmospheres-Part 0: Equipment-General requirements directly cite the radio wave explosion-proof safe power and energy threshold specified in the European standard CLC/TR 50427:2004. But the continuous radio wave explosion-proof safe ignition power threshold is incorrectly modified as the product of the effective output power of the transmitter and the antenna gain. This leads to the reduction of the continuous radio wave explosion-proof safe transmission power threshold. Under certain transmission attenuation and reception sensitivity conditions, the wireless transmission distance is reduced. This is not conducive to the promotion and application of mine wireless communication system and personnel positioning system. Therefore, the safe power threshold for continuous radio wave explosion-proof specified in national standard GB/T 3836.1-2021 and international standard IEC 60079-0:2017 should be the ignition power threshold, not the product of the effective output power of the transmitter and the antenna gain.
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[Academic Column of Editorial Board Member]
Study on the technical specification of communication interface and protocol for intelligent mine
DING Zhen, SUN Jiping, ZHANG Fan, WANG Peng, HU Eryi, DENG Wenge, GAO Jing, ZHENG Yaotao, WANG Bo, GAO Qiuqiu, LI Ximin, QIAN Haijun, LIU Jianhua, QIAO Shaoli, BAO Zhen, YANG Yongsheng, YANG Zhenyu, LI Yuxue, LI Yuhan, SHAO Guangyao
2023, 49(2): 6-13.   doi: 10.13272/j.issn.1671-251x.18061
Abstract: At present, there are some problems in the construction of the intelligent mine, such as the non-uniform interface protocol and the formation of new "information island". They lead to the difficulty of data fusion and sharing in mines and the difficulty of realizing the high-quality development of intelligent mine. It is pointed out that the key problem of mine intelligent construction lies in the lack of standardized and unified data acquisition, transmission and sharing standards. According to the core specification, application specification, and operation and maintenance specification, the technology system of intelligent mine communication interface and protocol is designed. The communication interface and protocol model of intelligent mine is proposed. The perception layer, transmission layer and application layer of the model are defined. The model of intelligent mining equipment is constructed, and the communication interface is described formally. The intelligent mine data is divided into perception data, text data and audio-visual data. The message structures of the three kinds of data are defined. According to the current mining equipment, technology application and development direction, the intelligent mine data acquisition modes are divided into equipment direct acquisition, protocol conversion acquisition, and system transfer acquisition. The application scenarios of three data acquisition modes are pointed out. The acquisition and transmission process of perception data, text data, and audio-visual data are described. The technical specification of intelligent mine communication interface and protocol covers the whole process of mine data fusion communication. It provides unified interface mode and communication protocol specification for intelligent mine data acquisition, transmission, fusion and sharing. And it realizes interconnection and intercommunication among various systems of the mine.
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[Academic Column of Editorial Board Member]
Research on precise positioning technology and optimization method of mine moving targets
ZHENG Xuezhao, YAN Ruijin, CAI Guobin, WANG Baoyuan, HE Qinjian
2023, 49(2): 14-22.   doi: 10.13272/j.issn.1671-251x.18020
Abstract: The existing mine moving target positioning system has the problems of serious attenuation of underground wireless signal transmission, large non-line-of-sight error, complex underground electromagnetic environment, wide sensing range of dynamic and static targets, strong linkage of multi-system information fusion, etc. At present, the research on mine moving target precise positioning technology and optimization method does not comprehensively analyze the characteristics and technical requirements of the moving target accurate positioning service. It lacks a comprehensive comparison between the mainstream and emerging positioning technologies. In order to solve the above problems, the advantages and disadvantages of the common signal transmission technology and the positioning and ranging method applied in the mine moving target precise positioning system are analyzed. The radio positioning technology is pointed out to be a more suitable and feasible mine moving target precise positioning technology. This paper analyzes the research status and existing problems of the optimization method of the mine moving target precise positioning in China from four aspects: signal anti-collision technology, error elimination method, positioning result optimization method and fusion positioning technology. ① The comprehensiveness of the signal anti-collision algorithm still needs to be improved. ② The efficiency of ranging error control means needs to be improved. ③ The application of the fusion positioning method in the production site is not yet mature. ④ The auxiliary role of the system in emergency rescue is not fully played. In view of the shortcomings of the existing technology, the development trend of the mine moving target precise positioning technology is proposed: ① It is suggested to study the signal collision mechanism and post-conflict recovery mechanism in dynamic environment, and design a comprehensive signal anti-collision scheme. ② It is suggested to research precise, efficient and economical ranging error control scheme to save communication costs. ③ It is suggested to study dynamic positioning scheme design with deep integration of multiple positioning methods to improve the reliability, flexibility and applicability of the system. ④ It is suggested to study the multi-system linkage scheme and the emergency communication and positioning recovery mechanism in extreme cases, and give full play to the role of the system in emergency rescue.
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[Special of Digital Twin and Virtual Reality Technology of Intelligent Mine]
Research on intelligent mine disaster digital twin based on industrial Internet
XING Zhen, HAN An, CHEN Xiaojing, CHEN Haijian, SHEN Yi
2023, 49(2): 23-30, 55.   doi: 10.13272/j.issn.1671-251x.2022120050
Abstract: The comprehensive control of coal mine disasters is a key problem to be solved in the process of intelligent mine construction. It is an inevitable requirement for the construction of intelligent mines to realize the normalization control of coal mine disasters with the help of digital twin technology. Based on the connotation and essence of the digital twin, this paper analyzes the recognition rule of the digital twin and puts forward the application mode of digital twin technology in coal mine disaster research combining with data interactive process of mine disaster digital twin. Real-time monitoring is carried out by coal mine underground disaster monitoring sensor. The monitoring data is uploaded to the cloud through the edge communication module and cloud communication module. The digital twin numerical simulation software is deployed in the cloud. The monitoring data uploaded by the sensor is used as the initial condition parameter, boundary condition parameter and effect verification parameter. The best optimization parameters and solutions are sought through real-time simulation analysis and continuous trial and error. When the technical means are mature in the twin world, they can be used to analyze, judge and make decisions on the best parameters and solutions for virtual entities. The decision instructions can be sent to underground actuators to control the action of disaster prevention equipment. This paper discusses the practical application of digital twin enabling disaster predictive management and control from three aspects: disaster monitoring scheme optimization, disaster rehearsal and precise planning of disaster avoidance route, and post-disaster rescue scheme formulation and accident investigation. Based on the "cloud-pipe-edge-end" architecture of the industrial Internet, the digital twin service system for coal mine disasters is constructed. The key technologies of digital twin for mine disasters are analyzed. The technologies include intelligent sensing and execution equipment for coal mine disasters, simulation software for coal mine disasters and common support technologies. It is expected to provide reference for the construction of digital twin-enabling intelligent mines.
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[Special of Digital Twin and Virtual Reality Technology of Intelligent Mine]
Straightness solution of the fully mechanized working face based on VR and DT technology
YAN Zewen, XIE Jiacheng, LI Suhua, SHEN Weidong, WANG Yirong, WANG Xuewen
2023, 49(2): 31-37.   doi: 10.13272/j.issn.1671-251x.18066
Abstract: The straightness problem is one of the neck problems in the intelligent construction of the fully mechanized working face. The key to solve this problem is to obtain the position and posture of the scraper conveyor or hydraulic support group. At present, most of the research on the straightness of fully mechanized working face is to discuss the straightness of hydraulic support and scraper conveyor separately. There are problems such as high cost and difficulty in implementation. In order to solve this problem, based on virtual reality(VR) and digital twin(DT) technology, the method to solve the straightness problem of the fully mechanized working face is explored. The hydraulic support, floating connection mechanism and scraper conveyor are considered as a whole system. The straightness solution framework of the fully mechanized working face is built. There are mainly five steps: mechanism analysis, model construction, fusion deduction, reconstruction monitoring and predictive control. It is pointed out that the key to the analysis of the relative position relationship of the fully mechanized supporting equipment is the floating connection mechanism connecting the hydraulic support base and the scraper conveyor. According to the motion characteristics of the floating connection mechanism, it is simplified into a robot model and solved by forward and reverse motion. According to the real coal seam environment, the motion simulation model of fully mechanized mining support equipment based on joints is established in Unity3D, and the VR scene is constructed to realize virtual and real mapping. Through non-contact visual sensor, virtual sensor, virtual-real fusion and other technologies, the information of sensor and point cloud are fused to perform the position and posture deduction of support equipment. Using the technology of virtual and reality interaction, combined with a real physical scenario, a DT system is constructed to achieve virtual monitoring of the fully mechanized working face. The travel distance required to ensure straightness is predicted in the virtual scene and fed back to the physical scene for straightness control.
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[Special of Digital Twin and Virtual Reality Technology of Intelligent Mine]
Research on the application of digital twin in coal mine power grid
ZHAO Jianwen, MENG Xuhui
2023, 49(2): 38-46.   doi: 10.13272/j.issn.1671-251x.2022040019
Abstract: Based on the basic concepts and connotations of digital twin, this paper analyzes the application advantages of digital twin technology in coal mine power grid. The operation management of the coal mine power grid is assisted by two means of synchronous entity operation status and digital simulation operation. The technology has the characteristics of data-driven, real-time update and synchronous feedback. The basic framework of the digital twin system of the coal mine power grid is proposed. The framework is composed of physical entity layer, digital twin model layer, user service management layer and data exchange layer. The operation mode of the digital twin system of the coal mine power grid is explored from two aspects of the physical entity and the digital twin model. This paper introduces the key technologies for establishing the digital twin system of the coal mine power grid. The technologies include digital twin model construction of coal mine power grid, intelligent data acquisition, intelligent communication based on 5G, digital twin intelligent database, and digital twin equipment intelligent management platform. The application scenarios of digital twin technology in the coal mine power grid are proposed. The scenarios include the condition evaluation of underground electrical equipment, fault location and protection of the coal mine power grid, intelligent monitoring of the coal mine power grid and intelligent inspection of underground lines. The digital twin technology is applied to the coal mine power grid to carry out dynamic simulation modeling on the state and operation of the coal mine power grid. On the one hand, the higher operation requirement of the current large-scale coal mine power grid relative to the ground power grid can be met. The safety of coal mine production can be guaranteed. On the other hand, the intelligent process of the coal mine power grid can be promoted. The efficient and reasonable utilization of data resources can be realized.
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[Special of Digital Twin and Virtual Reality Technology of Intelligent Mine]
A three machine digital twin and collaborative modeling method for fully mechanized working face
LIU Qing, ZHANG Long, LI Tianyue, DU Pengfei
2023, 49(2): 47-55.   doi: 10.13272/j.issn.1671-251x.2022120061
Abstract: The existing coal mine equipment digital twin modeling method mainly focuses on single equipment modeling. It lacks three machine coupling collaborative relationship analysis. In order to solve the above problems, the paper puts forward three machine digital twin and collaborative modeling method for fully mechanized working face. By adopting an intelligent modeling method, the method constructs agent-based models of a coal mining machine, a hydraulic support and a scraper conveyor which comprise a sensing unit, a control unit and an execution unit. The method constructs corresponding visual models according to a three-dimensional modeling process. The method drives the three-dimensional models to move by the intelligent models. The combination of the two forms a digital twin model of three machines. A discrete event modeling method is used to construct a collaborative process model covering the interaction process of the three machine digital twin model. The three machine mining process is sorted out according to the time sequence to form a three machine collaborative process time sequence table. The digital twin model is used to describe the state and behavior of the three machines in fully mechanized mining and to simulate the calculation at the individual level. The collaborative process model is used to represent the sequential action transformation between digital twin models and realize the deduction of the whole three machine collaborative process. The simulation of rocker lifting and lowering for the digital twin model of the shearer is carried out. The simulation results show that compared with the measured data of real equipment, the model error is small, an average error of rocker arm dip angle is 2.3°. The simulation of continuous column lifting action for the digital twin model of hydraulic support is carried out. The simulation results show good consistency between the model and real equipment. Compared with the measured data of the real equipment, the average angle error is 0.14° and the average stroke error is 6.3 mm. Combined with the actual production log of the coal mine, the virtual and real simulation experiment of the three machine collaborative model is carried out. The results show that the three machine digital twin model of the fully mechanized working face and real equipment realize mutual mapping. The simulation results are close to the real records. The three machine collaborative model can accurately reflect the collaborative mining process. The method of three machine digital twin and collaborative modeling for fully mechanized working face provides a new idea for the digital twin modeling of fully mechanized coal mining equipment and its collaborative relationship.
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[Special of Digital Twin and Virtual Reality Technology of Intelligent Mine]
Digital twin system architecture and key technology of following process for fully mechanized mining
CUI Yao, LI Tianyue, YE Zhuang, LIU Junwei
2023, 49(2): 56-62, 76.   doi: 10.13272/j.issn.1671-251x.18055
Abstract: The process design and parameter debugging of automatic following machine for fully mechanized mining are costly, time-consuming and cumbersome. In order to solve the above problems, the digital twin system architecture of following process for fully mechanized mining is proposed. The study analyzes the aspects of physical equipment, virtual and real interaction, twin data, mechanism model, simulation algorithm and process application. The key technologies such as the transmission and storage of the following process data, the playback of the following process history, the real-time following process twin deduction, the rehearsal simulation of following process, and the instruction scheduling of following process are described in detail. The paper puts forward the technical roadmap of the digital twin system of following process for fully mechanized machining. Through 10 Gigabit optical fiber ring network+5G communication, the shearer process action data is collected to the shearer host. The support process action data sent by the serial support controller is collected to the electrohydraulic control host. The process data is collected, classified and coded according to the action sequence as the data source for the playback of the process. At the same time, the host computer forwards the real-time reported following process data to the 3D digital twin system. The twin system deduces the following process in the 3D virtual scene. After the following process parameters are configured on the human-computer interface, the following process for fully mechanized mining can be previewed in the 3D scene. During the real-time mining process, the system will collect all kinds of sensor data and issue process scheduling instructions in combination with the rehearsal of error-free following process. The support controller is changed from a decision-maker to an executor to overcome the limitation of the limited computing power of the controller due to the lack of underground space. The field application results show that the digital twin system can provide technical reference for the process design, parameter configuration and simulation test of following process for fully mechanized mining. The system can shorten the development cycle of the following process from 14 days to 1 day, making the modification of the following process design more convenient. The system improves the following automation rate in working face to more than 90%.
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