Research On Emergency Communication And Location Technology Based On Railroad Channel

Track is a common equipment of tunnel transportation,while the mine accident occuring,the traditional wire/wireless communication channels may be destroyed by collapsed rock,soil,etc.Due to the physical characteristics,the track usually isn't broken off even that the collapse occurs.The track can pass through the collapsed object and connect the trapped persons and rescue persons directly with the elastic guided waves.The track is the channel in which the vibration elastic wave signal transmits.The system transmits the low bit rate digital signals,which contain the key rescue information.The emergency communication system based the track can be used as a supplementary to the unconventional emergency communication.Firstly,the paper introduces the basic theory and concepts of elastic wave vibration in the process of researching the transmission features of the viberation signal in rail channel.Then,the application of finite element numerical analysis method in elastic guided wave is studies.And then,the model of track based on finite element analysis is established in ANSYS,the propagation characteristics of medium elastic guided wave and rail channel are studied with the conventional waveguide structure and rail structure with arbitrary cross-section.The theoretical basis for selecting the carrier frequency in the rail communication system,the band gap characteristics of elastic wave in the periodic track structure,is clearly described in the process of analyzing the major factors which influnce the vibration signal propagation in rail waveguide firstly.And the influence of rail length and restraint modes to the eigen frequency of rail are further studied according to the different external conditions on the track after the disaster.Finally,the reflection and transmission characteristics of elastic wave signal in rail with different boundary conditions are studied based on elastic wave boundary theory.The principles of the excitation source and the receiving transducer are studied with the condtions which the information loading and the vibration signal detecting process is under the low bandwidth and complex environment firstly.And the denoise algorithm is researched according to the characteristics of noise and channel when the vibration signals propagate.In view of the small bandwidth of the rail channel,this thesis studies the voice coding method suitable for rail transmission to realize compressing voice and reduce the data transmission volume in the channel.The multi-weighted composite method is presented for locating the vibration source position.The method of locating the vibration source according to the signal attenuation is provided firstly,and the influences because of disaster,which the track is buried,damaged and forked on the accuracy of locating vibration source are classificated.Then,since that the spectrum features of the excitation sources in different locations are different,the spectrum features are considered to be the tag for locating the excitation sources.And then,the methods of Ethernet delay test based on RFC2544 and RFC2588 protocols are intruduced,the time measurement method is proposed for locating the excitation source.Based on the software radio principle,the hardware and software implementation scheme is proposed in the design of rail communication system at first.Then,the paper studies the communication principle of rail communication system,according to the features of source,channel and sink.The whole implementation scheme,communication protocol and communication processing mechanism are designed for practical application.And then,the implementation scheme of rail communication system is studied.This paper also analyzes the interference noise source in the vibration communication system,the influence of the noise,and puts forward the corresponding anti-interference technology to realize the normal transmission of the key voice information and the key text with low bit error rate.At the end of the paper,the innovation points and research work of the project are summarized,furthermore the future research direction is discussed.