Research On Coal Mine Underground Device-free Localization Method Based On Acoustic Signal

Coal mine underground localization technology plays an important role in safe mining,personnel monitoring and scheduling as well as post-disaster rescue.The device-free acoustic signal localization method does not require the target to carry a signal transceiver and has the advantages of no electromagnetic effect,antielectromagnetic interference,cheap and easy to deploy,etc.,which provides a new idea for underground localization.However,the research of device-free acoustic signal localization methods is not yet perfect,and the problems of severe acoustic signal propagation attenuation and limited sensing range limit the application of such localization methods in downhole scenarios.To this end,this thesis conducts a study on equipment-free acoustic signal localization methods in underground coal mines from three perspectives: signal enhancement,multi-target localization,and non-visual range localization.(1)To address the problems of severe attenuation of acoustic signal propagation and close localization distance,this thesis conducts research on the acoustic signal enhancement method for underground localization.It constructs an acoustic signal model for device-free localization,analyzes the key factors affecting the sensing distance of localization signals,and proposes a localization signal enhancement method based on the fusion of displaced transmit signals and beamforming,which mixes the displaced transmit signals with the received signals,increases the effective bandwidth,and performs weighted fusion of signals collected by multiple microphones to achieve the effect of signal enhancement and increase the target localization sensing distance.(2)To address the problem that the existing underground acoustic signal localization scheme can only localize and track targets carrying equipment,which cannot meet the localization needs of multiple device-free targets in underground coal mines,this thesis carries out research on the underground multi-target device-free acoustic signal localization method.It proposes a target multidimensional localization information determination method,corrects the target distance and angle errors caused by acoustic Doppler effect through velocity information,and designs multidimensional information fusion and background abatement algorithms to realize the separation and matching of multiple targets.In addition,in order to better describe the motion state of multiple targets,the trajectory optimization of downhole multiple targets is achieved by using the traceless Kalman filter algorithm to process the position points obtained from the acquisition.(3)To address the problem that there are many non-line-of-sight distance scenes in the downhole and the traditional acoustic signal localization method is not effective in the non-line-of-sight distance scenes,this thesis carries out the research on the nonline-of-sight distance localization method of the device-free acoustic signal in the downhole.Using multi-target localization technology,the obstacle target and the measured target are identified,and the line-of-sight area and non-line-of-sight area are divided according to the base station and obstacle position.When the measured target moves to the non-line-of-sight distance area,the non-line-of-sight distance localization algorithm based on the mirroring principle is designed to find the first reflection path from the target to the base station,the mirror position of the target relative to the walls on both sides of the alleyway is measured,and the target localization in the non-lineof-sight distance scene is realized by the weighted fusion of the mirror position.In summary,this thesis analyzes some problems of current downhole acoustic signal technology and carries out research from three perspectives: signal enhancement,multi-target localization,and non-line-of-sight localization.Meanwhile,this thesis conducts experiments in the underground tunnel laboratory and other environments,and the experimental results verify the effectiveness of the proposed method.