Reseach Of The Mine Positioning Method Based On Spread Spectrum Ranging

Coal mine personnel positioning system is one of the “Six-Major Systems” of coal mine safety and avoiding danger.The research and application of personnel positioning system has significant meaning for coal mine safety production and emergency rescue.As mine underground radio positioning is one system engineering,the overall research idea of this dissertation is to take research of target positioning method applied to mine tunnel as the core,take researching spread-spectrum ranging technology as guarantee,take research of communication and positioning integration program as support,apply theoretical analysis and simulation experiment to research each link of ranging mechanism,positioning algorithm and others of coal mine positioning.Ranging is the fundamental of wireless positioning.This dissertation has researched the basic principles of DSSS(Direct Sequence Spread Spectrum)and has analyzed its limitation in underground mines application.Spread spectrum ranging technology requires high bandwidth occupation and long duration of PN code acquisition,furthermore,its PN code phase delay problem is serious because of multi-path effect.These factors make it difficult to apply spread spectrum ranging technology in underground coal mines.In order to resolve the awkward situation,a parallel algorithm for PN code precision synchronization was designed making full use of FPGA processor's excellent parallel processing capability.In FPGA,L-1 correlation channels which have a PN code phase differences from each other are allocated,digital baseband signal modulated by PN code is sampled with high sampling after it correlates with the local PN code.This high sampling frequency can greatly improve signal processing bandwidth,so a high time resolution can be obtained only through the coarse synchronization.Experimental results of simulation show that the performance of proposed method is more efficient than the precise ranging with tracking loop.Positioning accuracy depends on ranging accuracy,and CSS(Chirp Spread Spectrum)technology is widely used in ranging,so this dissertation has also researched CSS property in underground mine ranging,put forward one ranging model aiming at CSS specially.The model focuses on the statistical rule of CSS signal receiving end,therefore,it can describe CSS signal propagation characteristic in mine by Rayleigh channel simply and effectively,at the same,extract area influence factors which can reflect characteristics of tunnel and multi-path delay,confirm multi-path signal ofminimum power that can be received,and fit them reasonably into multi-path power delay profile model which is filed by IEEE802.11 mission group,and describe various different paths signals through exponential models.According to CSS ranging principle,establish one CSS ranging model for mine environment at receiving end.Through a large number of actual measurement tests,the statistical characteristics of established ranging model are basically matched with the measured data,and the model can describe CSS ranging statistics characteristics at receiving end.Conduct analysis based on established model and then achieve several valuable conclusions about underground tunnel CSS ranging and give out a concise mathematical formula of underground tunnel CSS ranging errors calculation.This dissertation has researched the characteristics of long tunnels,put forward three principles for underground tunnel positioning calculation sticking to underground tunnel facts: improve accuracy;take full advantage of mine tunnels information sticking to mine tunnel actual environment;optimize cost performance.On this basis,this dissertation puts forward one positioning method of projection tunnel space under ranging planar constraints.First ranging plane coordinate system is established considering extension direction of tunnel as x-axis and width of tunnel as y-axis.As mine tunnel is a long and narrow chain-like space,positional information of its x-direction is primarily concerned while its cross section can be neglected.So projected onto x-axis,moving target can be positioned in one dimensional space.By making full use of redundant information of y-data the position estimate of target within designated zone of ranging plane can be constrained so that the accuracy of estimated x value is optimized evidently.The experiment results show that the proposed method can obtain the zero mean error of estimate position in mine tunnel with RMS error no more then 1 m,so the method can realize target precise positioning of long-straight tunnel.Similar statistical law of time delay between NLOS signal and LOS signal at their receiving ends is discovered based on spread spectrum ranging deviation characteristics of mine tunnel research by CSS ranging model,Thus a positioning method based on the two-reconstructing ranging value for curved tunnels is presented.Taking fully advantage of location information of tunnels,this method firstly conducts the first reconstruction on the NLOS ranging value of curved tunnels in order to get the estimate of linear distance between the moving target and the corresponding base station so the observation equation with the reconstruction figure can be established.Secondly,thismethod carries out the secondary reconstruction and projects the solution point of observation equation to tunnel space so that location estimate point can be got.Finally,Kalman filter is used to further optimize positioning accuracy of position estimation point and hence make it possible for positioning under a more general curved tunnel.Simulation performance shows that the method can obtain desired positioning accuracy in curved tunnel with mean curvature from 0 to 0.30.The experiment,which conducted in the pedestrian curved tunnel of certain subway with mean curvature 0.192,shows that the Root Mean Square(RMS)of positioning error is 0.891 m and the cumulative distribution of the error is ideal so that it is adoptable for accurate positioning in underground mine.According to requirements for coal mine informationization and intelligent,this dissertation researches the method of WIFI platform integrated with TOA accurate positioning function,and puts forward one TOA ranging method to obtain high time resolution by conducting re-spread spectrum to WIFI signals aiming at the current situation that WIFI has no accurate positioning functions basically.Take advantage of existing WIFI platform,adopt DSSS-DSSS combined signal new system,spread spectrum and reuse WIFI signals under circumstance of no influence on WIFI system normal operation,and improve WIFI signal speed.Then,A spread spectrum code capture algorithm with high digital matched filter is designed by using FPGA.This algorithm can capture the sub-chip of ranging signal,thus,the high signal's propagation delay time resolution is obtained.The result of test show that proposed method can provide reliable ranging data with mean-error less than 2 m which attains the CSS ranging performance.Under the support of above methods,put forward a scheme of seamless docking existing WIFI communication platform,and give out the method of establishing integration of personnel positioning and communication.Innovative works of this dissertation are mainly reflected in following five aspects:(1)Give out mine tunnel CSS ranging model firstly.Several valuable conclusions about mine tunnel CSS ranging are obtained by analysis through established model,such as: ranging error characteristics under circumstance of NLOS,relationship between tunnel section area and ranging error,etc.Conclude and put forward the mathematical expression for CSS ranging calculation under mine tunnel environment.These conclusions have provided a theoretical basis and a feasible simulation platform for researching CSS raging accuracy of mine tunnel environment,and the CSS ranging model has theoretical introduction meaning forresearch of positioning method and design of high-accuracy positioning system based on TOA ranging.(2)Put forward the idea of unifying NLOS and LOS positioning of mine tunnel,and under the guidance of this idea,solve the problem of curved tunnel target positioning.The positioning method which applies to curved tunnel and is based on ranging value two-reconstruction has taken full advantage of tunnel positioning information and has realized target positioning for more general curved tunnel.Comparing with current existing mine positioning method,it has greater universality.NLOS signal can affect ranging accuracy on the one hand,and on the other hand,it has similar time delay statistics law with the LOS signal at receiving end,and also contains available ranging information.The idea of unifying mine tunnel NLOS and LOS positioning has created one new thought for positioning method applies under more complex environment.(3)Put forward the positioning method for long-straight mine tunnel of restraining ranging errors under ranging planar constrains.As mine tunnel is a long and narrow chain-like space,its cross section can be neglected,the proposed method realizes One-dimensional positioning by originally making full use of redundant information of y-data position estimate of target to constrain the x-data so that the accuracy of estimated x value is optimized evidently.The method realization only needs two base stations,which reduce cost of the TOA positioning system and suit to long-straight mine tunnel.Furthermore,the designed method follows fully the three principles of design.Method designing thought deserves reference.(4)Put forward one kind of mine tunnel DSSS ranging method which doesn't need precise synchronization.The proposed parallel algorithm for PN code precision synchronization solve spread spectrum code time problem efficiently,and needn't to design PN code tracking loop separately,and be able to provide reliable ranging technical support for coal mine tunnel accurate positioning system.(5)Put forward a two-in-one WIFI solution of communication system and TOA positioning system.The method adopts DSSS-DSSS combined signal new system to improve the WIFI code speed without effecting original WIFI system.Unifying down hole variouswireless systems is one challenging issue.It can seamlessly dock current existing mine WIFI communication platform while enduing WIFI system with TOA accurate ranging ability.The given scheme has directive significance for establishing integration system of personnel positioning and communication on coal mine WIFI platform.