Research On Electromagnetic Wave Ground-Penetrating Positioning Technology In Underground Coal Mine

Coal mine is one of the main energy sources in China at this stage.Safe production in coal mining industry has always been a constant task for government.If mine disaster just happened in traditional coal mine positioning system,equipment is easily damaged,causing the system to paralyze.This leads to the failure of ground rescuers and trapped people to communicate properly,and miss the best time to rescue.Therefore,in view of mine production,it is one of the complex and important task to establish an effective ground-penetrating positioning system,to realize fast positioning of trapped underground personnel and to ensure timely rescue by ground rescuers.Stratum structure of coal mine area is relatively complex.Therefore,it is necessary to study the transmission characteristics of electromagnetic wave in formation media,and to explore a set of wireless electromagnetic wave positioning scheme.At present,research results by use of wireless electromagnetic wave for transmission and positioning in complex formation media channels are still insufficient.In this paper,electromagnetic wave ground-penetrating positioning technology in underground coal mine has been deeply studied.The main conclusions obtained are as follows:(1)Coal seam channel structure and its characteristics are analyzed.Transmission characteristics of electromagnetic wave in lossy media are studied.Attenuation of different frequency electromagnetic wave in different media is simulated.It lays a theoretical foundation for electromagnetic wave frequency selection of coal mine underground-penetrating positioning technology.For single-layered stratum medium,a model for measuring distance loss based on RSSI is established,which is of a great value for the subsequent study of underground-penetrating positioning technology in single-layered stratum medium.(2)Based on the established RSSI-based measurement distance loss model applied to single-layered formation media,three-dimensional quadrilateral positioning method in accordance with coal mine application scenario is deduced.In order to reduce positioning error,least squares method is used to optimize three-dimensional quadrilateral positioning method.The influencing factors of the positioning method are discussed and GDOP is calculated.The simulation results show that the method can use electromagnetic wave with different frequencies to realize underground-penetrating positioning in different formations media.(3)Transmission characteristics of electromagnetic wave in layered media are analyzed.The transmission of TE wave and TM wave at the interface of formation media is analyzed in detail.The expressions of reflection and transmission coefficients'are given.The simulation results show that for same transmit power,TM mode electromagnetic wave penetrates more energy into earth's medium than TE mode electromagnetic wave.Therefore,in electromagnetic wave ground-penetrating positioning system,TM mode wave should be selected to transmit signal.In addition,the relationship between incident angle and transmission angle of electromagnetic wave in three-dimensional space and the transmission loss of the electromagnetic wave with different frequencies in multilayered formation media are analyzed.It provides theoretical support for further study of wireless ground-penetrating positioning in double-layered media.(4)Transmission of electromagnetic wave in double-layered media is more complex than in single-layered media.Direction parameter is a relatively reliable information in radiation source parameters.Aiming at the transmission environment of electromagnetic wave in double-layered media,this paper proposes a positioning method based on RSSI and AO A and an orientation-only positioning method based on AOA.There are fewer base stations required based on RSSI and AOA positioning method.The AOA-based orientation-only positioning method doesn't need to know signal power,which reduces complexity of device.The experimental simulation shows that both methods can achieve positioning of blind spots in coal mine.