ZigBee定位的煤矿环境监测系统
ZigBee定位的煤矿环境监测系统
摘要本文介绍并设计了I.个新类型的煤矿安全监控系统,它是I.种ZigBee技术的无线传感器网络系统.该系统包括地下和地面两部分.地下的无线传感器网络由固定节点.移动节点和网关构成.电脑监控软件部署在地面.该系统不仅可以实时采集矿井环境数据,也可以通过矿工所携带的移动节点实现实时定位.
关键字:ZigBee;定位;无线传感器网络;煤矿
I..研究现状
作为I.种重要的能源,煤炭在经济发展中起着举足轻重的作用.煤矿监控系统是煤矿安全和生产效率高的重要保证[I.].为了确保安全运行,环境监测节点的安装是非常重要的.然而,常用的传统监控节点通过有线连接获得与控制系统的通信,这个节点存在布线困难,价格昂贵等缺点.相比之下,无线传感器网络节点可以很容易地与当前矿井监测网络连接,并且拥有良好的兼容性,方便组成煤矿监测网络,以适应各种大小煤矿的应用.由于无线节点是电池供电,所以完全摆脱线缆的束缚,缩短建设周期,可以随时排布使用.
这是I.种新兴的短距离,低复杂度,低功耗,低数据速率,低成本的双向无线通信技术[II].现在,无线传感器ZigBee无线通信技术应用于煤矿环境监测系统.ZigBee技术的网络产品的数量和种类很多,但真正可以应用在地下环境中的特殊传感器节点是很少的[III].我们设计的系统,是真正能够适用于在井下环境,它通过无线传感器网络节点的安全认证.同时,由于无线网络的特殊性质,它可以传播无线信号,我们可以很容易地找到工作人员以便对煤矿安全监控提供更多的保护[IV].
II.系统架构
该系统是I.个软件和硬件综合监控系统的融合.硬件部分包括无线移动节点和固定节点的地下隧道部署,它的主要功能是收集煤炭矿山环境的数据和人的位置.电脑监控软件由VC++设计,是用于以总结和展示每个监控节点中移动 *好棒文|www.hbsrm.com +Q: ^3^5`1^9`1^6^0`7^2#
节点和固定节点的数据.这些数据由无线传输ZigBee负责,由于在固定节点也使用无线数据传输的方法,所以在地下巷道部署变得非常方便.由于移动节点是由矿工进行,就必须使用无线传输方法.在固定无线传感器网络节点是路由器设备,矿工移动节点通常是终端设备,ZigBee网络的路由器没有传感器设备,它是只负责数据转发,但考虑到实际应用,我们在路由器上附加的传感器设备,将更好地监测煤矿井下环境,这让我们进I.步确定ZigBee网路拓扑结构.因此,在我们的设计中,路由器还具有环境监测功能.
固定节点和移动节点通过网关发送接收到的数据,然后网关通过RSIIIIIII或光纤将数据传输到监控计算机.通过电脑的计算机软件处理所有数据,并通过I.个可视化窗口显示出来.根据从移动节点接收到的信号强度(RSSI),PC软件通过特定的定位算法计算每个移动节点的实时定位.
III.定位功能
无线传感器网络的重要功能之I.是定位,特别是地下隧道,它涉及到矿工的生命安全.目前使用最广泛的定位方法是GPS卫星定位,它是I.个高精度,全天候和全球无线电导航定位和定时的多功能系统,但全球定位系统定位是不适合煤矿井下工的作环境,I.旦你进入地下,就不能收到卫星信号,从而无法达到定位目标[V].因此我们需要考虑如何使用无线网络实现定位功能,现有的无线设备之间的距离测量技术使用无线信号基本上是以下几种方法:TOA,TDOA,AOA和RSSI.
?关于TOA方法,在两个设备之间的距离是由高速光传输时间确定[VI].虽然这种方法的精确度是准确的,但它需要I.个精确的时间同步,所以它对硬件要求高.
TDOA技术需要超声波信号,并在I.个节点上设置接收和发送功能.测量距离时,它可以发出超声波和无线信号.通过测量两个信号到达的时间差,我们可以计算出两个设备之间的距离[VII].使用这种方法也可以得到准确的结果,但该方法需要增加超声波的发送和接收节点上的电路装置,增加成本.
AOA技术需要安装多个天线,所以它可以通过节点直接获得相邻节点的信号[VIII].这可以从相邻节点的数目确定位置信息,并计算出自己的位置.这种方法不仅需要添加额外的硬件,并且它仍然很容易受到外界干扰,因此它不适.
RSSI的技术特点是廉价和容易,通过使用这种方法,我们不需要添加额外的硬件设计,我们也不必非常精确的时间要求.这种技术是通过测量无线信号强度的传播损失来衡量两个节点之间的距离.这种方法需要硬件设备少,算法简单,所以它已经在许多无线通信领域使用.
A.硬件定位引擎
无线微控制器芯片TI公司生产的CCIIIVIIII.有I.个硬件定位引擎.从软件的角度来看,CCIIIVIIII.的硬件定位引擎有I.个非常简单的API接口,只要编写必要的参数和计算,就可以读取位置结果[IX].
硬件定位引擎RSSI的技术,包括参考节点和盲节点,参考节点是I.个固定的节点,节点在I.个已知的位置,知道自己的位置和发送报文通知其他节点.盲节点是接收数据包的参考节点,从而获得参考节点的位置和相应的RSSI值,进入硬件定位引擎,然后盲节点的位置可以从中读取[I.0].
?表面上使用CCIIIVIIII.的硬件定位引擎是I.个不错的选择方案,但考虑到实际应用中,会遇到以下问题.首先,我们选择主芯片CCIIVIII0作为系统的固定节点,使用ZigBeeII00VII协 *好棒文|www.hbsrm.com +Q: ^3^5`1^9`1^6^0`7^2#
议,但CCIIIVIIII.内部运行的程序为I.个早期的芯片,它适只用于ZigBeeII00VI协议.第II,在CCIIIVIIII.和CCIIVIII0通信存在兼容性问题.CCIIIVIIII.的硬件定位引擎使用分布式计算,所有的移动节点自行计算位置,然后上传到网关节点,这不仅占据了移动节点的处理时间,而且占用更多的网络资源.出于这个原因,我们不得不暂时搁置这个方法,可以考虑如何实现使用CCIIVIII0芯片的定位功能.
B.软件定位引擎
?如果我们想使用CCIIVIII0实现定位功能,我们必须通过自己编写的软件定位引擎,因为该芯片它里面没有硬件定位引擎,该软件定位引擎仍然使用RSSI技术,而移动节点的位置由PC软件计算,从而减少移动节点的计算负担.要计算移动节点的位置,至少需要III个参考节点,我们将网络中的参考节点视为路由器节点,并记录每个参考节点的坐标(X,Y),然后我们让移动节点发送信号到每个参考节点,使每个参考节点可以获取RSSI值,通过这些参数我们可以使用III边测量方法来计算移动节点的相对位置.移动节点通过广播方式发送数据,然后围绕它的每I.个参考节点将收到来自移动节点的RSSI值.I.旦网络中移动节点的数量增加,这种方法就会使参考节点的负担加重,因为路由器节点接收每个数据都要从低层传送到上层,最后由应用层分析数据包.事实上,移动节点需要广播传输的数据,其它路由节点也可以接收移动节点的数据包.路由器子节点和移动节点将继续向上传输数据包,其它路由器节点将屏蔽掉在该协议底部的数据包.
?为了让所有路由器节点可以接收由移动节点广播的数据包,并将RSSI传送到网关节点,我们需要修改由TI提供的Z-Stack协议的相关功能.首先,我们发现afIncomingData功能涉及底部协议,在其中我们添加I.些代码,可以获取接收RSSI值的数据包,然后通过osal_set_event功能来添加和发送I.个RSSI值到MY_RSSI_REPORT_EVTOSAL轮询系统.此事件相应的功能将在OSAL中断驱动功能任务执行,因此,移动节点相应的RSSI值将被发送到网关节点.通过这种方法,我们可以得到相应的RSSI值,由协议的底层函数处理,节省移动节点的计算时间.
事实上,这个软件定位引擎不执行单个移动节点的定位,但通过整个系统的运作实现移动节点发送单播数据包.移动节点的父路由器节点负责转发网关路由器节点的数据包,不是转发这个包,只是裁剪移动节点的RSSI值,然后网关转发到终端.电脑监控软件获取所有移动节点相应的RSSI值并计算移动节点的位置,为了减少错误,监控软件将收集I.0组RSSI值,计算出平均值,然后用III边测量方法选择离固定节点最近的III个值计算移动节点的位置.
IV.系统实施
节点中所有嵌入式系统都Z-Stack.因为Z-Stack是I.个开源项目,它非常易于II次开发.这些节点测试是在I.个位于山西省的煤矿中,在隧道内每隔V0米部署固定节点,并在每个工作区的入口处设置了固定节点.由于固定节点携带大尺寸的数字LED显示屏,通过显示的内容可以了解远在矿井中的每个矿工携带移动节点的温度和气体浓度值.
网关节点被放置在矿井入口处,通过中控室的监控计算机连接RSIIIIIII电缆,这个系统由网关节点收集到的所有数据包通过串口传送到PC,它可以将历史数据备份到I.个SQL数据库.监控软件的主要功能是显示和存储每I.个有关移动节点位置的数据,根据RSSI值计算的监控软件有两个主要对话接口,I.个用于在个人主页上显示I.个两维煤矿,用户可以看到所有矿工的工作位置.另I.个接口是数据显示界面,显示这里的环境数据,上位机监控软件见图I..
图I..电脑监控软件
参考文献
[I.]XinyueZhongWanchengXie.Wirelesssensornetworkinthecoalmineenvironmentmonitoring.Coaltechnology,II00IX,Vol.IIVIII,No.IX,pp.I.0II-I.0III.
[II]ShouweiGao.ZigBeeTechnologyPracticeGuide".Beijing:BeijingUniversityofAeronauticsandAstronauticsPress,II00IX,pp.IIVII-IIVIII.
[III]YangWang,LiushengHuang,WeiYang.ANovelReal-TimeCoalMinerLocalizationandTrackingSystemBasedonSelf-OrganizedSensorNetworks".EURASIPJournalonWirelessCommunicationsandNetworking,VolumeII0I.0,ArticleIDI.IVII0IXII.
[IV]Sang-ilKo,Jong-sukChoi,Byoung-hoonKim.IndoorMobileLocalizationSystemandStabilizationofLocalizaionPerformanceusingPre-filtering".InternationalJournalofControl,AutomationandSystems,Vol.VI,No.II,pp.II0IV-III.III,AprilII00VIII.
[V]HawkinsWarren,DakuBrianL.F,PruggerArnfinnF.Positioninginundergroundmines".IECONII00VI-IIIIIndAnnualConferenceonIEEEIndustrialElectronics,II00VI,pp.IIII.VIX-IIII.VIIII.
[VI]Zhu,Shouhong,Ding,Zhiguo,MarkarianKarina.TOAbasedjointsynchronizationandlocalization".II0I.0IEEEInternationalConferenceonCommunications,ICCII0I.0,II0I.0,ArticleIDVV0II0IIIVI.
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[VIII]Dogan?ayKutluyil,HmamHatem.OptimalangularsensorseparationforAOAlocalization".SignalProcessing,II00VIII,Vol.VIIIVIII,No.V,pp.I.IIIVVIII-I.IIVI0.
[I.IX]K.Aamodt.CCIIIVIIII.LocationEngine".TexasInstruments,ApplicationNoteAN0IVII,SWRA0IXV.
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附件II:外文原文
毕业设计(论文)外文翻译
学生姓名:盛采兵学号:I.I.0I.II0VIII.IIIV
专业:电子科学与技术
设计(论文)集群室内实时定位系统
_软件设计
指导教师:张宇林
II0I.IV年II月IIVIII日
ACoalMineEnvironmentalMonitorSystemwithLocalizationFunctionBasedonZigBee-CompliantPlatform
Abstract_Thispaperdescribesandimplementsanewtypeofcoalminesafetymonitoringsystem,itisakindofwirelesssensornetworksystembasedonZigBeetechnology.Thesystemconsistsoftwopartsundergroundandsurface.Wirelesssensornetworksareconstitutedbyfixednodes,mobilenodesandagatewayinunderground.PCmonitoringsoftwareisdeployedinthesurface.Thesystemcannotonlygatherreal-timeenvironmentaldataformine,butalsocalculatethereal-timelocationofmobilenodeswornbyminers.
Keywords:ZigBee;localization;wirelesssensornetworks;coalMine
I.RESEARCHSTATUS
Asanimportantenergy,coalplaysapivotalroleintheeconomicdevelopment.Coalminemonitoringsystem,istheimportantguaranteeforcoalminesafetyandhighefficiencyproduction[I.].Inordertoensurethesafeoperation,theinstallationofenvironmentmonitoringnodeintunnelstoreal-timedetectionisveryimportant.However,commonlyusedtraditionalmonitoringnodewiredconnectiontoobtaincommunicationwiththecontrolsystem,thisnodeexistwiringdifficulties,expensiveandothershortcomings.Incontrast,wirelesssensornodecanbeeasilywithcurrentminemonitoringnetworkconnection,andgoodcompatibility,facilitateconstitutedminegasmonitoringnetwork,tosuitvarioussizeofmineapplications.Sincewirelessnodesarebatterypowered,socompletelyoutoftheshacklesofthecable,shortentheconstructionperiodcanbearrangedatanytimewheretheneedtouse.
TheZigBeewirelesscommunicationtechnologyisusedinthiscoalmineenvironmentalmonitorsystem.Thisisanewshort-range,lowcomplexity,lowpower,lowdatarate,low-costtwo-waywirelesscommunicationtechnology[II].Now,wirelesssensornetworkproductbasedonZigBeetechnologyarequantityandvariety,buttherealproductcanbeappliedinundergroundenvironmentsofspecialsensornodeisveryfew[III].Thesensornodethatwedesignedinthesystemistrulyabletoapplytoin-wellenvironment,itthroughthewirelesssensornodesecuritycertification.Atthesametime,duetothespecialnatureofthewirelessnetworkisthatitcanspreadthewirelesssignal,wecaneasilylocatestaffforcoalminesafetymonitoringprovidesmoreprotection[IV].
II.SYSTEMARCHITECTURE
Thissystemisacomprehensivemonitoringsystemwhichiscombinedwithsoftwareandhardware.Hardwarepartincludeswirelessmobilenodesandfixednodeswhichweredeployedintheundergroundtunnel,themainfunctionofthemistocollectcoalmineenvironmentdataandrequireperson’slocation.SoftwarepartreferstothePCmonitoringsoftwarewhichisdesignedinVC++isusedtosummarizeanddisplaythedataofeachnode.Monitoringnodeisdividedintomobilenodesandfixednodes;theyareusingZigBeeprotocolforwirelesstransmissionofdata.Becausethefixednodeisalsousingwirelessdatatransmissionmethod,soitsdeployedintheundergroundroadwaybecomesveryconvenient.Asthemobilenodeiscarriedbytheminer,itmustbeusingwirelesstransmissionmethod.ThisallowstheminetoformatopologyofZigBeewirelesssensornetwork.Thefixednodeinwirelesssensornetworkisrouterdeviceandthemobilenodecarriedbymineristheenddevice.Normally,therouterofZigBeenetworkhasnosensorequipment;itisonlyresponsiblefordataforwarding.Butconsideringthepracticalapplication,webelievethataddsensordevicesontherouterwillbebetteronmonitoringundergroundcoalmineenvironment.Soinourdesign,therouteralsohasanenvironmentmonitoringfunctionwhichisusuallydesignedinenddevice.
Fixednodewillsentreceiveddatafrommobilenodetothegateway,thenthegatewaytransmitsdatatomonitorcomputerthroughRSIIIIIIIoropticalfiber.ThePCmonitorsoftwareinthecomputerwillprocessalldataanddisplaytheminavisualizationwindow.ThePCsoftwarealsocalculateseachmobilenode’sreal-timelocationthroughthespecificlocalizationalgorithm,accordingtothereceivedsignalstrength(RSSI)obtainedfrommobilenodes.
III.POSITIONINGFUNCTION
Oneoftheimportantfunctionsofthewirelesssensornetworksislocalization,especiallyintheundergroundtunnel,itrelatestothesafeoftheminerslife.CurrentlymostwidelyusedorientationmethodisGPSsatellitepositioning,itisahighprecision,all-weatherandglobalmultifunctionalsystemwiththefunctionofradionavigation,positioningandtiming.ButtheGPSpositioningmethodisnotsuitablefortheundergroundworkenvironmentofcoalmine,onceyouentertheunderground,itcannotreceivesatellitesignal,thusunabletoachievetargeting[V].Weneedtoconsiderhowtousewirelessnetworktorealizepositioningfunction,meansusingwirelesssignalbetweenthecommunicationsofdevicesforpositioning.Theexistingdistancemeasuringtechnologybetweenthewireless-devicesbasicallyisthefollowingkindsofmethods:TOA,TDOA,AOAandRSSI.
AbouttheTOAmethod,thedistancebetweenthetwodevicesisdeterminedbytheproductofthespeedoflightandtransmissiontime[VI].Althoughtheprecisionofthismethodisaccurate,butitrequireaprecisetimesynchronization,soitdemandhardwareishigher.
TDOAtechnologyneedultrasonicsignal,whichissettingonanodewithreceiveandtransmitfunction.Whenmeasurethedistance,itcansentultrasonicwaveandwirelesssignalstogether.Bymeasuringthedifferencebetweentwosignalsarrivaltime,wecancalculatethedistancebetweentwodevices[VII].Usingthismethodcanalsoobtainaccurateresult,butthemethodneedtoincreaseultrasonicsendingandreceivingdeviceonthenodecircuit,itwillincreasecost.
AOAtechnologyneedstoinstallmultipleantennasthroughthenodessoitcanobtainadjacentnodes’signalsondeferentdirections[VIII].Withthisitcandeterminethelocationinformationfromnumberofadjacentnodesandcalculateitsownposition.Thismethodnotonlyneedtoaddadditionalhardware,butalsoitsstillveryvulnerabletoexternaldisturbance,thereforeitsnotsuitableforutilize.
RSSIrangingisacheapandeasytechnology.Byusingthismethod,wedontneedtoaddadditionalhardwaredesign.Wealsodonotneedveryprecisetimerequirements.Thistechniqueisaboutwithmeasuringthewirelesssignalsstrengthinthepropagationoftheloss,tomeasurethedistancebetweentwonodes.Becauseofthismethodrequireshardwareequipmentisless,algorithmissimple,soithasbeenusinginmanywirelesscommunicationfield.Comprehensiveallconditions,positioningontheuseofRSSIrangingtechnique.
A.HardwareLocationEngine
TheCCIIIVIIII.wirelessmicrocontrollerchipproducedbyTICompanyhasahardwarelocationengine.Fromthesoftwarespointofview,CCIIIVIIII.’shardwarelocationenginehasaverysimpleAPIinterface,aslongaswritingthenecessaryparametersandwaitingforcalculation,itcanreadthelocationresults[IX.
ThehardwarelocationengineisalsobasedonRSSItechnology.Thelocalizationsystemincludesreferencenodesandblindnodes.Thereferencenodeisafixednodethatlocatedinaknownposition,thenodeknowtheirplaceandsendapacketnotifytoothernodes.Theblindnodereceivespacketsfromreferencenodes,whichcanobtainsreferencenodes’locationandthecorrespondingRSSIvalueandputthemintothehardwarelocationengine,andthentheblindnode’slocationcanbereadfromtheengine[I.0].
Onthesurface,usingtheCCIIIVIIII.hardwarelocationenginetargetingtheprogramasagoodchoice,butconsideringthepracticalapplication,itwillencounterthefollowingproblems.Firstofall,wehavechoosetheCCIIVIII0asthemainchipoffixednodesofthesystem,itsinternalprogramsisrunninginZigBeeII00VIIprotocol,butCCIIIVIIII.asaearlychip,itappliesonlytoZigBeeII00VIprotocol.InthecommunicationsbetweenCCIIIVIIII.andCCIIVIII0thatwillhavecompatibilityproblems.Secondly,CCIIIVIIII.hardwarelocationengineusethedistributedcomputing,allmobilenodes’locationarecalculatedbythemselves,andthentheyuploadinformationtothegatewaynode,thiswillnotonlyoccupythemobilenodeprocessingtime,stillitcantakeupmorenetworkresources.Forthisreason,wehavetoshelvethisapproach,considerhowtoimplementlocationbyusingCCIIVIII0chip.
B.SoftwareLocationEngine
IfwewanttouseCCIIVIII0toimplementlocationfunction,thatwemustwritesoftwarelocationenginebyourselves.Becausethatchipdonothaveahardwarelocationengineinsideofit.ThissoftwarelocationengineisstillusedRSSItechnology;meanwhilemobilenodepositioniscalculatedbythePCsoftware,soastoreducetheburdenofmobilenodecomputing.Tocalculatethemobilenodelocation,theremustbeatleastthreereferencenodes.Wewillregardrouternodesasreferencenodesinnetwork,andrecordtheX,Ycoordinatesofeveryreferencenode.Thenweletthemobilenodesendsignaltoeachreferencenode,sothateachreferencenodecanobtainaRSSIvalues,withtheseparameters,wecanusetrilateralmeasurementmethodtocalculatethespecifiedlocationofthemobilenode.Thesimplerwaygivethemobilenodetobroadcastwaytosenddata,thenarounditeveryrouternodewouldreceivethedatafromthemobilenode,thusobtainsRSSIvalues.Oncethemobilenodenumberincreasingnetwork,thismethodwillmakerouternodesmoreburden,becausetheeveryradiomessagethattherouternodereceiveswilltransmitfromthelowlayertothetoplayer.Finallytheapplicationlayerwillanalyzedatapackets.Infact,themobilenodeneednottobroadcasttransmitteddata,otherroutingnodecanalsoreceivethemobilenodepackets.Onlychildmobilenodesoftherouternodewillcontinuetotransmitthepacketforwardingupward,theotherrouternodeswillshieldoutthepacketinthebottomoftheprotocol.
Inordertoletallrouternodescanreceivethepacketwhichsendingbymobilenodes,andsenditsRSSIvaluesuptothegatewaynode,weneedtomodifytherelevantfunctioninZ-StackprotocolwhichisprovidedbyTI.FirstwefindthefunctionnamedafIncomingData,itdealswiththereceiveddatafromthebottomofprotocol,inwhichweaddsomecodethatcanobtainpacket’sRSSIvalue.Thenthroughtheosal_set_eventfunctiontoaddandsendaneventMY_RSSI_REPORT_EVTofRSSIvaluetasktoOSALpollingsystem.Thisevent’scorrespondingfunctionwillbeexecutedinthetaskofOSALinterrupt-drivenfunction,thusthemobilenodecorrespondingRSSIvalueswillbesenttogatewaynode.Throughthismethod,thepacketwillonlybeprocessedbybottomfunctionoftheprotocol.AccordingtothismethodwecanobtaincorrespondingRSSIvalueandsavethecomputationtimeofmobilenodes.
Infact,thissoftwarelocationengineisnotimplementingwithasinglemobilenode,butthroughtheoperationofthewholesystemtoachieve.Bywhichthemobilenodeisonlyresponsibleforsendingunicastpackets.Themobilenode’sparentrouternodeisresponsibletoforwardthepackettothegateway.Otherrouternodesarenotresponsibleforforwardingthispacket,justclippingthemobilenodeofRSSIvalue,thenforwardedtothegateway.FinallythegatewaybringallRSSIvaluesofthemobilenodetoPCmonitoringsoftware,thecorrespondingmobilenode’slocationiscalculated.Inordertoreducetheerror,monitoringsoftwarewillcollectI.0timesoftheRSSIvalueandtakeaverageonit,andthenselectthenearestvalueofthethreefixednodes.Finallythetrilateralmeasurementmethodisusedtocalculatethelocationofmobilenodes.
IV．SYSTEMIMPLEMENTATION
AllsoftwaresystemsembeddedinnodesarebasedonZ-Stack.BecauseZ-Stackisanopen-sourceproject,itisverybeneficialtothesecondarydevelopment.ThesenodesweretestedinarealcoalminelocateinShanxiProvince.WedeployedthefixednodeeveryV0metersinthetunnel,andalsosetafixednodeineachentranceoftheworkarea.BecausethefixednodehavelargesizedigitalLEDdisplays,sothedisplaycontentofthefixednodecanbeseenfarfromawaytheminer.Eachminercarriesamobilenode,thetemperatureandgasconcentrationisdisplayedontheLCDscreenatreal-time.
Thegatewaynodeisplacedattheentranceofthemine,throughtheRSIIIIIIIcableconnectedtothemonitoringcomputerinthecontrolroom.InthissystemallpacketscollectedbythegatewaynodearetransmittedtoPCthroughaserialport,anditcansavehistoricaldatabackuptoaSQLdatabase.Themainfunctionofmonitoringsoftwareistodisplayandstorethedataofeverynode,andcalculatesrelatedmobilenodes’locationaccordingtoRSSIvalues.Themonitoringsoftwarehastwomaindialoginterfaces,oneisusedtodisplayatwo-dimensionalprofileofthecoalmine,andusercanseealltheminersworkingposition.Anotherinterfaceisdatadisplayinginterface,andenvironmentaldatawereshownhere.ThepictureofPCmonitoringsoftwareisshowninFig.I..
FigureI..PCmonitoringsoftware.
REFERENCES
[I.]XinyueZhongWanchengXie.Wirelesssensornetworkinthecoalmineenvironmentmonitoring.Coaltechnology,II00IX,Vol.IIVIII,No.IX,pp.I.0II-I.0III.
[II]ShouweiGao.ZigBeeTechnologyPracticeGuide".Beijing:BeijingUniversityofAeronauticsandAstronauticsPress,II00IX,pp.IIVII-IIVIII.
[III]YangWang,LiushengHuang,WeiYang.ANovelReal-TimeCoalMinerLocalizationandTrackingSystemBasedonSelf-OrganizedSensorNetworks".EURASIPJournalonWirelessCommunicationsandNetworking,VolumeII0I.0,ArticleIDI.IVII0IXII.
[IV]Sang-ilKo,Jong-sukChoi,Byoung-hoonKim.IndoorMobileLocalizationSystemandStabilizationofLocalizaionPerformanceusingPre-filtering".InternationalJournalofControl,AutomationandSystems,Vol.VI,No.II,pp.II0IV-III.III,AprilII00VIII.
[V]HawkinsWarren,DakuBrianL.F,PruggerArnfinnF.Positioninginundergroundmines".IECONII00VI-IIIIIndAnnualConferenceonIEEEIndustrialElectronics,II00VI,pp.IIII.VIX-IIII.VIIII.
[VI]Zhu,Shouhong,Ding,Zhiguo,MarkarianKarina.TOAbasedjointsynchronizationandlocalization".II0I.0IEEEInternationalConferenceonCommunications,ICCII0I.0,II0I.0,ArticleIDVV0II0IIIVI.
[VII]NiHao,RenGuangliang,ChangYilin.ATDOAlocationschemeinOFDMbasedWMANs".IEEETransactionsonConsumerElectronics,II00VIII,Vol.VIV,No.III,pp.I.0I.VII-I.0III..
[VIII]Dogan?ayKutluyil,HmamHatem.OptimalangularsensorseparationforAOAlocalization".SignalProcessing,II00VIII,Vol.VIIIVIII,No.V,pp.I.IIIVVIII-I.IIVI0.
[IX]K.Aamodt.CCIIIVIIII.LocationEngine".TexasInstruments,ApplicationNoteAN0IVII,SWRA0IXV.
[I.0]TenninaStefano,DiRenzoMarco,GraziosiFabio,SantucciFortunato.LocatingzigbeenodesusingthetisccIIIVIIII.locationengine:Atestbedplatformandnewsolutionsforpositioningestimationofwsnsindynamicindoorenvironments".ProcAnnuIntConfMobileComputNetworking,II00VIII,pp.IIIVII-IVII.
摘要本文介绍并设计了I.个新类型的煤矿安全监控系统,它是I.种ZigBee技术的无线传感器网络系统.该系统包括地下和地面两部分.地下的无线传感器网络由固定节点.移动节点和网关构成.电脑监控软件部署在地面.该系统不仅可以实时采集矿井环境数据,也可以通过矿工所携带的移动节点实现实时定位.
关键字:ZigBee;定位;无线传感器网络;煤矿
I..研究现状
作为I.种重要的能源,煤炭在经济发展中起着举足轻重的作用.煤矿监控系统是煤矿安全和生产效率高的重要保证[I.].为了确保安全运行,环境监测节点的安装是非常重要的.然而,常用的传统监控节点通过有线连接获得与控制系统的通信,这个节点存在布线困难,价格昂贵等缺点.相比之下,无线传感器网络节点可以很容易地与当前矿井监测网络连接,并且拥有良好的兼容性,方便组成煤矿监测网络,以适应各种大小煤矿的应用.由于无线节点是电池供电,所以完全摆脱线缆的束缚,缩短建设周期,可以随时排布使用.
这是I.种新兴的短距离,低复杂度,低功耗,低数据速率,低成本的双向无线通信技术[II].现在,无线传感器ZigBee无线通信技术应用于煤矿环境监测系统.ZigBee技术的网络产品的数量和种类很多,但真正可以应用在地下环境中的特殊传感器节点是很少的[III].我们设计的系统,是真正能够适用于在井下环境,它通过无线传感器网络节点的安全认证.同时,由于无线网络的特殊性质,它可以传播无线信号,我们可以很容易地找到工作人员以便对煤矿安全监控提供更多的保护[IV].
II.系统架构
该系统是I.个软件和硬件综合监控系统的融合.硬件部分包括无线移动节点和固定节点的地下隧道部署,它的主要功能是收集煤炭矿山环境的数据和人的位置.电脑监控软件由VC++设计,是用于以总结和展示每个监控节点中移动 *好棒文|www.hbsrm.com +Q: ^3^5`1^9`1^6^0`7^2#
节点和固定节点的数据.这些数据由无线传输ZigBee负责,由于在固定节点也使用无线数据传输的方法,所以在地下巷道部署变得非常方便.由于移动节点是由矿工进行,就必须使用无线传输方法.在固定无线传感器网络节点是路由器设备,矿工移动节点通常是终端设备,ZigBee网络的路由器没有传感器设备,它是只负责数据转发,但考虑到实际应用,我们在路由器上附加的传感器设备,将更好地监测煤矿井下环境,这让我们进I.步确定ZigBee网路拓扑结构.因此,在我们的设计中,路由器还具有环境监测功能.
固定节点和移动节点通过网关发送接收到的数据,然后网关通过RSIIIIIII或光纤将数据传输到监控计算机.通过电脑的计算机软件处理所有数据,并通过I.个可视化窗口显示出来.根据从移动节点接收到的信号强度(RSSI),PC软件通过特定的定位算法计算每个移动节点的实时定位.
III.定位功能
无线传感器网络的重要功能之I.是定位,特别是地下隧道,它涉及到矿工的生命安全.目前使用最广泛的定位方法是GPS卫星定位,它是I.个高精度,全天候和全球无线电导航定位和定时的多功能系统,但全球定位系统定位是不适合煤矿井下工的作环境,I.旦你进入地下,就不能收到卫星信号,从而无法达到定位目标[V].因此我们需要考虑如何使用无线网络实现定位功能,现有的无线设备之间的距离测量技术使用无线信号基本上是以下几种方法:TOA,TDOA,AOA和RSSI.
?关于TOA方法,在两个设备之间的距离是由高速光传输时间确定[VI].虽然这种方法的精确度是准确的,但它需要I.个精确的时间同步,所以它对硬件要求高.
TDOA技术需要超声波信号,并在I.个节点上设置接收和发送功能.测量距离时,它可以发出超声波和无线信号.通过测量两个信号到达的时间差,我们可以计算出两个设备之间的距离[VII].使用这种方法也可以得到准确的结果,但该方法需要增加超声波的发送和接收节点上的电路装置,增加成本.
AOA技术需要安装多个天线,所以它可以通过节点直接获得相邻节点的信号[VIII].这可以从相邻节点的数目确定位置信息,并计算出自己的位置.这种方法不仅需要添加额外的硬件,并且它仍然很容易受到外界干扰,因此它不适.
RSSI的技术特点是廉价和容易,通过使用这种方法,我们不需要添加额外的硬件设计,我们也不必非常精确的时间要求.这种技术是通过测量无线信号强度的传播损失来衡量两个节点之间的距离.这种方法需要硬件设备少,算法简单,所以它已经在许多无线通信领域使用.
A.硬件定位引擎
无线微控制器芯片TI公司生产的CCIIIVIIII.有I.个硬件定位引擎.从软件的角度来看,CCIIIVIIII.的硬件定位引擎有I.个非常简单的API接口,只要编写必要的参数和计算,就可以读取位置结果[IX].
硬件定位引擎RSSI的技术,包括参考节点和盲节点,参考节点是I.个固定的节点,节点在I.个已知的位置,知道自己的位置和发送报文通知其他节点.盲节点是接收数据包的参考节点,从而获得参考节点的位置和相应的RSSI值,进入硬件定位引擎,然后盲节点的位置可以从中读取[I.0].
?表面上使用CCIIIVIIII.的硬件定位引擎是I.个不错的选择方案,但考虑到实际应用中,会遇到以下问题.首先,我们选择主芯片CCIIVIII0作为系统的固定节点,使用ZigBeeII00VII协 *好棒文|www.hbsrm.com +Q: ^3^5`1^9`1^6^0`7^2#
议,但CCIIIVIIII.内部运行的程序为I.个早期的芯片,它适只用于ZigBeeII00VI协议.第II,在CCIIIVIIII.和CCIIVIII0通信存在兼容性问题.CCIIIVIIII.的硬件定位引擎使用分布式计算,所有的移动节点自行计算位置,然后上传到网关节点,这不仅占据了移动节点的处理时间,而且占用更多的网络资源.出于这个原因,我们不得不暂时搁置这个方法,可以考虑如何实现使用CCIIVIII0芯片的定位功能.
B.软件定位引擎
?如果我们想使用CCIIVIII0实现定位功能,我们必须通过自己编写的软件定位引擎,因为该芯片它里面没有硬件定位引擎,该软件定位引擎仍然使用RSSI技术,而移动节点的位置由PC软件计算,从而减少移动节点的计算负担.要计算移动节点的位置,至少需要III个参考节点,我们将网络中的参考节点视为路由器节点,并记录每个参考节点的坐标(X,Y),然后我们让移动节点发送信号到每个参考节点,使每个参考节点可以获取RSSI值,通过这些参数我们可以使用III边测量方法来计算移动节点的相对位置.移动节点通过广播方式发送数据,然后围绕它的每I.个参考节点将收到来自移动节点的RSSI值.I.旦网络中移动节点的数量增加,这种方法就会使参考节点的负担加重,因为路由器节点接收每个数据都要从低层传送到上层,最后由应用层分析数据包.事实上,移动节点需要广播传输的数据,其它路由节点也可以接收移动节点的数据包.路由器子节点和移动节点将继续向上传输数据包,其它路由器节点将屏蔽掉在该协议底部的数据包.
?为了让所有路由器节点可以接收由移动节点广播的数据包,并将RSSI传送到网关节点,我们需要修改由TI提供的Z-Stack协议的相关功能.首先,我们发现afIncomingData功能涉及底部协议,在其中我们添加I.些代码,可以获取接收RSSI值的数据包,然后通过osal_set_event功能来添加和发送I.个RSSI值到MY_RSSI_REPORT_EVTOSAL轮询系统.此事件相应的功能将在OSAL中断驱动功能任务执行,因此,移动节点相应的RSSI值将被发送到网关节点.通过这种方法,我们可以得到相应的RSSI值,由协议的底层函数处理,节省移动节点的计算时间.
事实上,这个软件定位引擎不执行单个移动节点的定位,但通过整个系统的运作实现移动节点发送单播数据包.移动节点的父路由器节点负责转发网关路由器节点的数据包,不是转发这个包,只是裁剪移动节点的RSSI值,然后网关转发到终端.电脑监控软件获取所有移动节点相应的RSSI值并计算移动节点的位置,为了减少错误,监控软件将收集I.0组RSSI值,计算出平均值,然后用III边测量方法选择离固定节点最近的III个值计算移动节点的位置.
IV.系统实施
节点中所有嵌入式系统都Z-Stack.因为Z-Stack是I.个开源项目,它非常易于II次开发.这些节点测试是在I.个位于山西省的煤矿中,在隧道内每隔V0米部署固定节点,并在每个工作区的入口处设置了固定节点.由于固定节点携带大尺寸的数字LED显示屏,通过显示的内容可以了解远在矿井中的每个矿工携带移动节点的温度和气体浓度值.
网关节点被放置在矿井入口处,通过中控室的监控计算机连接RSIIIIIII电缆,这个系统由网关节点收集到的所有数据包通过串口传送到PC,它可以将历史数据备份到I.个SQL数据库.监控软件的主要功能是显示和存储每I.个有关移动节点位置的数据,根据RSSI值计算的监控软件有两个主要对话接口,I.个用于在个人主页上显示I.个两维煤矿,用户可以看到所有矿工的工作位置.另I.个接口是数据显示界面,显示这里的环境数据,上位机监控软件见图I..
图I..电脑监控软件
参考文献
[I.]XinyueZhongWanchengXie.Wirelesssensornetworkinthecoalmineenvironmentmonitoring.Coaltechnology,II00IX,Vol.IIVIII,No.IX,pp.I.0II-I.0III.
[II]ShouweiGao.ZigBeeTechnologyPracticeGuide".Beijing:BeijingUniversityofAeronauticsandAstronauticsPress,II00IX,pp.IIVII-IIVIII.
[III]YangWang,LiushengHuang,WeiYang.ANovelReal-TimeCoalMinerLocalizationandTrackingSystemBasedonSelf-OrganizedSensorNetworks".EURASIPJournalonWirelessCommunicationsandNetworking,VolumeII0I.0,ArticleIDI.IVII0IXII.
[IV]Sang-ilKo,Jong-sukChoi,Byoung-hoonKim.IndoorMobileLocalizationSystemandStabilizationofLocalizaionPerformanceusingPre-filtering".InternationalJournalofControl,AutomationandSystems,Vol.VI,No.II,pp.II0IV-III.III,AprilII00VIII.
[V]HawkinsWarren,DakuBrianL.F,PruggerArnfinnF.Positioninginundergroundmines".IECONII00VI-IIIIIndAnnualConferenceonIEEEIndustrialElectronics,II00VI,pp.IIII.VIX-IIII.VIIII.
[VI]Zhu,Shouhong,Ding,Zhiguo,MarkarianKarina.TOAbasedjointsynchronizationandlocalization".II0I.0IEEEInternationalConferenceonCommunications,ICCII0I.0,II0I.0,ArticleIDVV0II0IIIVI.
[VII]NiHao,RenGuangliang,ChangYilin.ATDOAlocationschemeinOFDMbasedWMANs".IEEETransactionsonConsumerElectronics,II00VIII,Vol.VIV,No.III,pp.I.0I.VII-I.0III..
[VIII]Dogan?ayKutluyil,HmamHatem.OptimalangularsensorseparationforAOAlocalization".SignalProcessing,II00VIII,Vol.VIIIVIII,No.V,pp.I.IIIVVIII-I.IIVI0.
[I.IX]K.Aamodt.CCIIIVIIII.LocationEngine".TexasInstruments,ApplicationNoteAN0IVII,SWRA0IXV.
[I.0]TenninaStefano,DiRenzoMarco,GraziosiFabio,SantucciFortunato.LocatingzigbeenodesusingthetisccIIIVIIII.locationengine:Atestbedplatformandnewsolutionsforpositioningestimationofwsnsindynamicindoorenvironments".ProcAnnuIntConfMobileComputNetworking,II00VIII,pp.IIIVII-IVII.
附件II:外文原文
毕业设计(论文)外文翻译
学生姓名:盛采兵学号:I.I.0I.II0VIII.IIIV
专业:电子科学与技术
设计(论文)集群室内实时定位系统
_软件设计
指导教师:张宇林
II0I.IV年II月IIVIII日
ACoalMineEnvironmentalMonitorSystemwithLocalizationFunctionBasedonZigBee-CompliantPlatform
Abstract_Thispaperdescribesandimplementsanewtypeofcoalminesafetymonitoringsystem,itisakindofwirelesssensornetworksystembasedonZigBeetechnology.Thesystemconsistsoftwopartsundergroundandsurface.Wirelesssensornetworksareconstitutedbyfixednodes,mobilenodesandagatewayinunderground.PCmonitoringsoftwareisdeployedinthesurface.Thesystemcannotonlygatherreal-timeenvironmentaldataformine,butalsocalculatethereal-timelocationofmobilenodeswornbyminers.
Keywords:ZigBee;localization;wirelesssensornetworks;coalMine
I.RESEARCHSTATUS
Asanimportantenergy,coalplaysapivotalroleintheeconomicdevelopment.Coalminemonitoringsystem,istheimportantguaranteeforcoalminesafetyandhighefficiencyproduction[I.].Inordertoensurethesafeoperation,theinstallationofenvironmentmonitoringnodeintunnelstoreal-timedetectionisveryimportant.However,commonlyusedtraditionalmonitoringnodewiredconnectiontoobtaincommunicationwiththecontrolsystem,thisnodeexistwiringdifficulties,expensiveandothershortcomings.Incontrast,wirelesssensornodecanbeeasilywithcurrentminemonitoringnetworkconnection,andgoodcompatibility,facilitateconstitutedminegasmonitoringnetwork,tosuitvarioussizeofmineapplications.Sincewirelessnodesarebatterypowered,socompletelyoutoftheshacklesofthecable,shortentheconstructionperiodcanbearrangedatanytimewheretheneedtouse.
TheZigBeewirelesscommunicationtechnologyisusedinthiscoalmineenvironmentalmonitorsystem.Thisisanewshort-range,lowcomplexity,lowpower,lowdatarate,low-costtwo-waywirelesscommunicationtechnology[II].Now,wirelesssensornetworkproductbasedonZigBeetechnologyarequantityandvariety,buttherealproductcanbeappliedinundergroundenvironmentsofspecialsensornodeisveryfew[III].Thesensornodethatwedesignedinthesystemistrulyabletoapplytoin-wellenvironment,itthroughthewirelesssensornodesecuritycertification.Atthesametime,duetothespecialnatureofthewirelessnetworkisthatitcanspreadthewirelesssignal,wecaneasilylocatestaffforcoalminesafetymonitoringprovidesmoreprotection[IV].
II.SYSTEMARCHITECTURE
Thissystemisacomprehensivemonitoringsystemwhichiscombinedwithsoftwareandhardware.Hardwarepartincludeswirelessmobilenodesandfixednodeswhichweredeployedintheundergroundtunnel,themainfunctionofthemistocollectcoalmineenvironmentdataandrequireperson’slocation.SoftwarepartreferstothePCmonitoringsoftwarewhichisdesignedinVC++isusedtosummarizeanddisplaythedataofeachnode.Monitoringnodeisdividedintomobilenodesandfixednodes;theyareusingZigBeeprotocolforwirelesstransmissionofdata.Becausethefixednodeisalsousingwirelessdatatransmissionmethod,soitsdeployedintheundergroundroadwaybecomesveryconvenient.Asthemobilenodeiscarriedbytheminer,itmustbeusingwirelesstransmissionmethod.ThisallowstheminetoformatopologyofZigBeewirelesssensornetwork.Thefixednodeinwirelesssensornetworkisrouterdeviceandthemobilenodecarriedbymineristheenddevice.Normally,therouterofZigBeenetworkhasnosensorequipment;itisonlyresponsiblefordataforwarding.Butconsideringthepracticalapplication,webelievethataddsensordevicesontherouterwillbebetteronmonitoringundergroundcoalmineenvironment.Soinourdesign,therouteralsohasanenvironmentmonitoringfunctionwhichisusuallydesignedinenddevice.
Fixednodewillsentreceiveddatafrommobilenodetothegateway,thenthegatewaytransmitsdatatomonitorcomputerthroughRSIIIIIIIoropticalfiber.ThePCmonitorsoftwareinthecomputerwillprocessalldataanddisplaytheminavisualizationwindow.ThePCsoftwarealsocalculateseachmobilenode’sreal-timelocationthroughthespecificlocalizationalgorithm,accordingtothereceivedsignalstrength(RSSI)obtainedfrommobilenodes.
III.POSITIONINGFUNCTION
Oneoftheimportantfunctionsofthewirelesssensornetworksislocalization,especiallyintheundergroundtunnel,itrelatestothesafeoftheminerslife.CurrentlymostwidelyusedorientationmethodisGPSsatellitepositioning,itisahighprecision,all-weatherandglobalmultifunctionalsystemwiththefunctionofradionavigation,positioningandtiming.ButtheGPSpositioningmethodisnotsuitablefortheundergroundworkenvironmentofcoalmine,onceyouentertheunderground,itcannotreceivesatellitesignal,thusunabletoachievetargeting[V].Weneedtoconsiderhowtousewirelessnetworktorealizepositioningfunction,meansusingwirelesssignalbetweenthecommunicationsofdevicesforpositioning.Theexistingdistancemeasuringtechnologybetweenthewireless-devicesbasicallyisthefollowingkindsofmethods:TOA,TDOA,AOAandRSSI.
AbouttheTOAmethod,thedistancebetweenthetwodevicesisdeterminedbytheproductofthespeedoflightandtransmissiontime[VI].Althoughtheprecisionofthismethodisaccurate,butitrequireaprecisetimesynchronization,soitdemandhardwareishigher.
TDOAtechnologyneedultrasonicsignal,whichissettingonanodewithreceiveandtransmitfunction.Whenmeasurethedistance,itcansentultrasonicwaveandwirelesssignalstogether.Bymeasuringthedifferencebetweentwosignalsarrivaltime,wecancalculatethedistancebetweentwodevices[VII].Usingthismethodcanalsoobtainaccurateresult,butthemethodneedtoincreaseultrasonicsendingandreceivingdeviceonthenodecircuit,itwillincreasecost.
AOAtechnologyneedstoinstallmultipleantennasthroughthenodessoitcanobtainadjacentnodes’signalsondeferentdirections[VIII].Withthisitcandeterminethelocationinformationfromnumberofadjacentnodesandcalculateitsownposition.Thismethodnotonlyneedtoaddadditionalhardware,butalsoitsstillveryvulnerabletoexternaldisturbance,thereforeitsnotsuitableforutilize.
RSSIrangingisacheapandeasytechnology.Byusingthismethod,wedontneedtoaddadditionalhardwaredesign.Wealsodonotneedveryprecisetimerequirements.Thistechniqueisaboutwithmeasuringthewirelesssignalsstrengthinthepropagationoftheloss,tomeasurethedistancebetweentwonodes.Becauseofthismethodrequireshardwareequipmentisless,algorithmissimple,soithasbeenusinginmanywirelesscommunicationfield.Comprehensiveallconditions,positioningontheuseofRSSIrangingtechnique.
A.HardwareLocationEngine
TheCCIIIVIIII.wirelessmicrocontrollerchipproducedbyTICompanyhasahardwarelocationengine.Fromthesoftwarespointofview,CCIIIVIIII.’shardwarelocationenginehasaverysimpleAPIinterface,aslongaswritingthenecessaryparametersandwaitingforcalculation,itcanreadthelocationresults[IX.
ThehardwarelocationengineisalsobasedonRSSItechnology.Thelocalizationsystemincludesreferencenodesandblindnodes.Thereferencenodeisafixednodethatlocatedinaknownposition,thenodeknowtheirplaceandsendapacketnotifytoothernodes.Theblindnodereceivespacketsfromreferencenodes,whichcanobtainsreferencenodes’locationandthecorrespondingRSSIvalueandputthemintothehardwarelocationengine,andthentheblindnode’slocationcanbereadfromtheengine[I.0].
Onthesurface,usingtheCCIIIVIIII.hardwarelocationenginetargetingtheprogramasagoodchoice,butconsideringthepracticalapplication,itwillencounterthefollowingproblems.Firstofall,wehavechoosetheCCIIVIII0asthemainchipoffixednodesofthesystem,itsinternalprogramsisrunninginZigBeeII00VIIprotocol,butCCIIIVIIII.asaearlychip,itappliesonlytoZigBeeII00VIprotocol.InthecommunicationsbetweenCCIIIVIIII.andCCIIVIII0thatwillhavecompatibilityproblems.Secondly,CCIIIVIIII.hardwarelocationengineusethedistributedcomputing,allmobilenodes’locationarecalculatedbythemselves,andthentheyuploadinformationtothegatewaynode,thiswillnotonlyoccupythemobilenodeprocessingtime,stillitcantakeupmorenetworkresources.Forthisreason,wehavetoshelvethisapproach,considerhowtoimplementlocationbyusingCCIIVIII0chip.
B.SoftwareLocationEngine
IfwewanttouseCCIIVIII0toimplementlocationfunction,thatwemustwritesoftwarelocationenginebyourselves.Becausethatchipdonothaveahardwarelocationengineinsideofit.ThissoftwarelocationengineisstillusedRSSItechnology;meanwhilemobilenodepositioniscalculatedbythePCsoftware,soastoreducetheburdenofmobilenodecomputing.Tocalculatethemobilenodelocation,theremustbeatleastthreereferencenodes.Wewillregardrouternodesasreferencenodesinnetwork,andrecordtheX,Ycoordinatesofeveryreferencenode.Thenweletthemobilenodesendsignaltoeachreferencenode,sothateachreferencenodecanobtainaRSSIvalues,withtheseparameters,wecanusetrilateralmeasurementmethodtocalculatethespecifiedlocationofthemobilenode.Thesimplerwaygivethemobilenodetobroadcastwaytosenddata,thenarounditeveryrouternodewouldreceivethedatafromthemobilenode,thusobtainsRSSIvalues.Oncethemobilenodenumberincreasingnetwork,thismethodwillmakerouternodesmoreburden,becausetheeveryradiomessagethattherouternodereceiveswilltransmitfromthelowlayertothetoplayer.Finallytheapplicationlayerwillanalyzedatapackets.Infact,themobilenodeneednottobroadcasttransmitteddata,otherroutingnodecanalsoreceivethemobilenodepackets.Onlychildmobilenodesoftherouternodewillcontinuetotransmitthepacketforwardingupward,theotherrouternodeswillshieldoutthepacketinthebottomoftheprotocol.
Inordertoletallrouternodescanreceivethepacketwhichsendingbymobilenodes,andsenditsRSSIvaluesuptothegatewaynode,weneedtomodifytherelevantfunctioninZ-StackprotocolwhichisprovidedbyTI.FirstwefindthefunctionnamedafIncomingData,itdealswiththereceiveddatafromthebottomofprotocol,inwhichweaddsomecodethatcanobtainpacket’sRSSIvalue.Thenthroughtheosal_set_eventfunctiontoaddandsendaneventMY_RSSI_REPORT_EVTofRSSIvaluetasktoOSALpollingsystem.Thisevent’scorrespondingfunctionwillbeexecutedinthetaskofOSALinterrupt-drivenfunction,thusthemobilenodecorrespondingRSSIvalueswillbesenttogatewaynode.Throughthismethod,thepacketwillonlybeprocessedbybottomfunctionoftheprotocol.AccordingtothismethodwecanobtaincorrespondingRSSIvalueandsavethecomputationtimeofmobilenodes.
Infact,thissoftwarelocationengineisnotimplementingwithasinglemobilenode,butthroughtheoperationofthewholesystemtoachieve.Bywhichthemobilenodeisonlyresponsibleforsendingunicastpackets.Themobilenode’sparentrouternodeisresponsibletoforwardthepackettothegateway.Otherrouternodesarenotresponsibleforforwardingthispacket,justclippingthemobilenodeofRSSIvalue,thenforwardedtothegateway.FinallythegatewaybringallRSSIvaluesofthemobilenodetoPCmonitoringsoftware,thecorrespondingmobilenode’slocationiscalculated.Inordertoreducetheerror,monitoringsoftwarewillcollectI.0timesoftheRSSIvalueandtakeaverageonit,andthenselectthenearestvalueofthethreefixednodes.Finallythetrilateralmeasurementmethodisusedtocalculatethelocationofmobilenodes.
IV．SYSTEMIMPLEMENTATION
AllsoftwaresystemsembeddedinnodesarebasedonZ-Stack.BecauseZ-Stackisanopen-sourceproject,itisverybeneficialtothesecondarydevelopment.ThesenodesweretestedinarealcoalminelocateinShanxiProvince.WedeployedthefixednodeeveryV0metersinthetunnel,andalsosetafixednodeineachentranceoftheworkarea.BecausethefixednodehavelargesizedigitalLEDdisplays,sothedisplaycontentofthefixednodecanbeseenfarfromawaytheminer.Eachminercarriesamobilenode,thetemperatureandgasconcentrationisdisplayedontheLCDscreenatreal-time.
Thegatewaynodeisplacedattheentranceofthemine,throughtheRSIIIIIIIcableconnectedtothemonitoringcomputerinthecontrolroom.InthissystemallpacketscollectedbythegatewaynodearetransmittedtoPCthroughaserialport,anditcansavehistoricaldatabackuptoaSQLdatabase.Themainfunctionofmonitoringsoftwareistodisplayandstorethedataofeverynode,andcalculatesrelatedmobilenodes’locationaccordingtoRSSIvalues.Themonitoringsoftwarehastwomaindialoginterfaces,oneisusedtodisplayatwo-dimensionalprofileofthecoalmine,andusercanseealltheminersworkingposition.Anotherinterfaceisdatadisplayinginterface,andenvironmentaldatawereshownhere.ThepictureofPCmonitoringsoftwareisshowninFig.I..
FigureI..PCmonitoringsoftware.
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