ZigBee-Compliant平台定位功能的煤矿环境监测系统
ZigBee-Compliant平台定位功能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收集矿井环境数据,也可以通过计算矿工所穿的移动节点来实时定位.
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,和良好的兼容性,方便组成煤矿瓦斯监测网络,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,可以随时安排使用.
这是I.个新的短距离,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,但真正的产品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而被地下隧道部署,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 *好棒文|www.hbsrm.com +Q: ￥3^5`1^9`1^6^0`7^2$
用于以总结和展示每个监控节点中移动节点和固定节点的数据.他们正在使用的数据由无线传输ZigBee协议传输,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网络的路由器有没有传感器设备;,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.节点设计
目前市场上出售的ZigBee无线网络平台,适用于I.般的环境,而在特殊的地下,所以他们不适合的环境,因此,我们需要定制I.个适合地下特殊的硬件电路系统.节点的照片如图I..
无线单片机CCIIVIII0的芯片是节点设备的核心处理器,它可以用很少的外围电路构成I.个ZigBee网络.CCIIVIII0是I.个IEEEVIII0II.I.V.IV兼容的系统的芯片,支持专有的VIII0II.I.V.IV市场以及的ZigBee的ZigBeePRO和ZigBeeRFIVCE的标准.CCIIVIII0不同于其他的无线芯片,内置VIII0VI.单片机集成电路的内核,因此我们不再需要使用I.个单I.的单片机控制电路,这为我们节省了大量的成本[V].
A.移动节点
移动节点是I.个由ZigBee网络组成的矿工移动的终端设备,它应该是I.种便携式低功耗节点,所以我们设计的移动节点是小如手机,它是通过内置锂离子电池供电,CCIIVIII0的核心处理器是低功耗的芯片,它在睡眠模式时,只需要使用小于I.uA的工作电流.为了尽可能降低在显示屏上的功耗,使用I.I.00*IIIII无背光液晶屏幕的像素矩阵.移动节点的的电池容量是I.V00mAh,所以它足以满足矿工在地下长时间工作的产品,电池充电管理芯片是TPIV0VVII,最大充电电流可高达V00mA.
图I.:节点的照片
移动节点的电路包括气体浓度的传感器MJIV.0和温度传感器PT-I.000.据我们所知,许多无线传感器平台使用数字式传感器,数字传感器和MCU之间的通信需要严格的时序要求.考虑到实际应用中,无线MCU通常有I.个I.般的实时操作系统,如果我们用微机模拟严格的时序,它会影响整个操作系统的实时.这两个传感器输出的模拟信号,而不是数字信号.输入到差分放大器,我们可以得到适当的信号,可以由CCIIVIII0的芯片内的ADC模式转换为数字信号.为了方便携带,不使用外接天线,在我们的移动节点天线是我们定制I.个像手机大小的外壳,而不是使用I.个II.IVGHz贴片天线.设计的PCB和元件选择,都进行了安全评估,这足以考虑到它所有的电路板.传感器和电池爆炸性能不是很好.
B.固定节点
固定节点安装在地下隧道的墙壁.因为它是比大的移动节点,它是不适合随身携带.电路的固定节点与移动节点几乎是相同的,它也使用CCIIVIII0的芯片核心处理 *好棒文|www.hbsrm.com +Q: ￥3^5`1^9`1^6^0`7^2$
器.由于在地下隧道,I.般部署电力电缆,固定节点可以使用电缆供电模式.同时,因为我们使用的无线信号传输,新的固定节点的部署变得非常方便,这也解决了问题信号线条部署.
作为I.个固定的节点,做的工作可能远非如此,为了方便矿工观察周围的固定节点的环境数据,它使用LED数字显示.同时,大电流LED灯和蜂鸣器的设计电路.考虑到固定节点可能会出现无电的紧急声光报警功能,固定节点也内置锂离子电池,正常情况下锂离子电池在充电状态,当外部电缆断开,固定节点是自动切换到电池供电,可确保移动节点可以接收固定节点提供的信息.
固定节点不方便携带,我们有I.个定制的外壳,具有良好的爆炸性能,内部空间足以容纳II.IVGHz天线.为了确保安全,所有的电缆和传感器的位置放置,特别是胶密封,因此它具有良好的密封性.
IV.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,但在全球定位系统定位方法是不适合的煤矿井下工作环境,I.旦你进入地下,就不能收到卫星信号,从而无法达到目标[VI].我们需要考虑如何使用无线网络实现定位功能.定位现有的无线设备之间的距离测量技术的设备之间的通信手段使用无线信号基本上是以下几种方法:TOA,TDOA,AOA和RSSI.
?关于的TOA方法,在两个设备之间的距离是由产品的高速光传输时间确定[VII].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,所以它要求的硬件高.
TDOA技术需要的超声波信号,这是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之间的差异,我们可以计算出两个距离设备[VIII].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,它会增加成本.
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[IX].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.这种技术是关于测量无线信号强度的传播损失,两个节点之间的距离来衡量的,因为这种方法.需要硬件设备少,算法很简单,所以它已经在许多无线通信领域使用.综合所有条件,使用的RSSI测距技术的定位.
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[I.0].
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发动机读取[I.I.].
?表面上使用了CCIIIVIIII.的硬件定位引擎是为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,我们选择作为主芯片CCIIVIII0的系统固定节点ZigBeeII00VII协议,但CCIIIVIIII.的其内部运行的程序为I.个早期的芯片,它适只用于ZigBeeII00VI协议.第II,在CCIIIVIIII.和CCIIVIII0的之间的通信,这将有兼容性问题.CCIIIVIIII.的硬件定位引擎使用分布式计算,所有的移动自行计算节点的位置,然后上传到网关节点的信息,这将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的CCIIVIII0芯片的定位功能.
B.软件定位引擎
???如果我们想使用CCIIVIII0的实现定位功能,我们必须通过自己编写的软件的位置引擎,因为该芯片没有它里面的硬件定位引擎,该软件定位引擎仍然使用的RSSI技术,同时移动节点的位置是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,必须有至少III个参考节点,我们将网络中的参考节点视为路由器节点,并记录在X,Y为每个参考节点的坐标,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指定位置.通过这个简单的方法给移动节点以广播方式发送数据,然后围绕它每I.个路由器节点将收到来自移动节点的数据获得RSSI值.I.旦移动节点数量网络的增加,这种方法会使路由器节点更多的负担因为每个电台消息,路由器节点接收从低层传送到上层,最后应用层分析数据包.事实上,移动节点需要广播传输的数据,其他路由节点也可以接收移动节点的数据包.子节点的路由器节点和移动节点将继续向上传输的数据包转发,其他的路由器节点在该协议的底部将屏蔽掉的数据包.
?为了让所有的路由器节点可以接收由移动节点发送的数据包,并传送到网关节点的RSSI值,我们需要修改这由TI提供的Z-Stack协议相关的功能.首先,我们发现名为afIncomingData函数,它涉及从底部协议,在其中我们添加I.些代码,可以获取包的RSSI的值接收数据,然后通过该osal_set_event函数来添加和发送I.个RSSI值到MY_RSSI_REPORT_EVTOSAL轮询系统.此事件的相应的函数将在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,只会协议的底层函数处理.据这种方法,我们可以得到相应的RSSI值,并保存移动节点的计算时间.
事实上,这个软件的位置引擎不执行单个移动节点,但通过整个系统的运作实现移动节点负责发送单播数据包.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,然后转发网关负责最后的网关,使电脑监控软件监控所有移动节点相应的RSSI值的位置计算.为了减少错误,监控软件将收集RSSI值的I.0倍,并采取上的平均,和然后选择固定节点最近的III个值用III边测量方法用于计算移动节点的位置.
V.系统实施
节点中的所有软件嵌入式系统Z-Stack.因为Z-Stack是I.个开源项目,它非常有益的II次开发.这些节点测试是在I.个位于山西省的煤矿,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还设置了固定节点.由于固定的节点有大尺寸的数字LED显示屏,使固定节点的显示内容可以看到远在矿井中每个矿工携带I.个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,在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,它可以保存历史数据备份到I.个SQL数据库.监控软件的主要功能是显示和存储的每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II.
图II.电脑监控软件
VI.系统评价
我们通过反复的系统测试,系统客观的评估首先是节点的硬件功耗评估,固定节点的工作电压在IXV～IIIVV,电源通过电缆提供.固定节点的最大工作电流目前是IXIII毫安,当断开电源线,固定节点由电池供电的锂离子电池供电,平均工作电流是IXII.II毫安,固定节点的最大工作电流是I.IVVII毫安平均工作电流是I.IVVI.III毫安,固定节点可以至少工作VIII小时.
节点的另外I.个很重要的表现是系统的定位功能.在隧道和工作区的IV个不同地点,移动节点被放置在那里.两套不同的平均错误数据,从表I.所示,由于本系统使用的RSSI技术和它主要依赖信号强度,信号质量将受干扰的影响,从不同的地点的错误我们可以看到,在工作领域更大的地方误差更大,因为隧道是I.般直,但工作领域有不确定性.
表I..定位误差结果
序号在隧道在不同地点
Error(m)Error(m)Error(m)Error(m)
I.II.IIII0.V%III.VIIIIV.III%
IIII.VIIII..II%III.I.IIIII.VII%
IIIII.IIII.IX.VI%III.IIIIIIV.VIII%
IVII.VIIII0.IX%III.IVIIII.IX%
我们非常感谢德州仪器公司为我们免费提供的设备,而且还感谢给予我们支持系统测试XinNuoJin公司的员工.
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附件II:外文原文(复印件)
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.NODEDESIGN
SincetheZigBeewirelessnetworkplatformsoldonpresentmarketwasdesignedforthegeneralenvironment,forspecialundergroundsotheyarenotsuitablefortheenvironment.Therefore,weneedtocustomizethesystemforundergroundenvironmentwhitaspecialhardwarecircuit.NodephotoareshowninFig.I.
ThenwirelessmicrocontrollerCCIIVIII0chipisthecoreprocessorofthenodedevice,itcanconstituteaZigBeenetworkwithveryfewperipheralcircuits.TheCCIIVIII0isanIEEEVIII0II.I.V.IVcomplianttrueSystem-on-Chip,supportingtheproprietaryVIII0II.I.V.IVmarketaswellastheZigBee,ZigBeePRO,andZigBeeRFIVCEstandards.Unlikeotherwirelesschip,CCIIVIII0built-inVIII0VI.monolithicintegratedcircuitskernel,thereforewenolongerneedtouseasingleMCUtocontrolthecircuit,andthissaveusalotofcost[V].
MobileNode
ThemobilenodeistheenddeviceofaZigBeenetworkthatcanbecarriedbyminer;itshouldbeaportableandlowpowerconsumptionnode.Sothemobilenodewedesignedisonlyassmallasamobilephone,anditisbybuilt-inlithiumionbatterypowersupply.Inpowerloss,thecoreprocessorCCIIVIII0isalowpowerconsumptionchip,whenitisinthesleepmode,itonlyneedtouselessthenI.uAworkcurrent.Inordertoreducepowerconsumptionasmuchaspossibleonthedisplay,aI.00*IIIIIpixelmatrixwithnobacklightingLCDscreenwasused.Thebattery’scapacityofthemobilenodeisI.V00mAh,soitisenoughtomeettheminer’slonghourworksintheunderground.ThebatterychargemanagementchipisTPIV0VVII,themaximumchargecurrentcanuptoV00Ma.
FigureI..Nodephoto.
ThemobilenodecircuitincludesthegasconcentrationsensorMJIV.0andtemperaturesensorPT-I.000.Asfarasweknow,manywirelesssensorplatformsusethedigitaltypesensor.ThecommunicationbetweenthedigitalsensorandtheMCUneedstricttimingrequirements.Butconsideringtheactualapplication,thewirelessMCUusuallyhasareal-timeoperatingsystemingeneral,ifweusethemicrocomputertosimulatethestricttiming,itwillaffectthereal-timeofwholeoperatingsystem.Thesetwosensorsoutputanalogsignalsnotdigitalsignals.Onlyinputthissignalintoadifferentialamplifier,canwegetanappropriatesignalthatcanbeconvertedtoadigitalsignalbyanADCmodewithintheCCIIVIII0chip.Inordertofacilitatethecarrying,externalantennawasnotusedinourmobilenode,insteadofusingaII.IVGHzpatchantenna.Andwecustomizeashelllikeacellphonesize;itisenoughtoputallPCBs,sensorsandbatteryinit.Takingintoaccountthesmallshelloftheexplosiveperformanceisnotverygood,thedesignofPCBsandtheselectionofcomponentareallcarriedoutthesafetyassessment.
B.FixedNode
Fixednodeisinstalledinthewalloftheundergroundtunnel.Becauseitisbigthanthemobilenode,itisnotappropriatetocarryaround.Thecircuitofthefixednodeisalmostsamewiththemobilenode,italsouseaCCIIVIII0chipascoreprocessor.Becauseofundergroundtunnelsgenerallydeploywithpowercable,fixednodescanusecablepower-supplymodes.Atthesametime,becauseweusewirelesssignaltransmission,thedeploymentofnewfixednodesbecomeveryconvenient,whichalsoresolvestheproblemofthesignallinesdeployment.
Asafixednode,theminorwhoisdoingworkmayfarfromit,inordertofacilitatetheminersobservedenvironmentaldataaroundthefixednodes,itusesLEDdigitaldisplay.Atthesametime,thelargecurrentLEDlightsandbuzzeraredesignedinthecircuit;itmakesthefixednodewiththefunctionofsound-lightalarm.Consideringthatitmayoccurtheemergencyofwithoutelectricity,fixednodealsobuilt-inalithium-ionbattery.Undernormalconditions,lithium-ionbatteryisinchargingstatus,whenexternalcabledisconnect,fixednodeisautomaticswitchedtobatterypower,whichcanensurethemobilenodecandelivertheinformationthroughfixednodesinunderground.
Withoutregardingtofixednodes’portability,wehaveacustomizedshellthathasexcellentexplosionproperties,andtheinternalspaceisenoughtoholddowntheII.IVGHzantenna.Toensuresafety,allcablesandthelocationofsensorsareplacedwithparticulargluesealed,sothatithasagoodseal.
IV.POSITIONINGFUNCTION
Oneoftheimportantfunctionsofthewirelesssensornetworksislocalization,especiallyintheundergroundtunnel,itrelatestothesafeoftheminerslife.CurrentlymostwidelyusedorientationmethodisGPSsatellitepositioning,itisahighprecision,all-weatherandglobalmultifunctionalsystemwiththefunctionofradionavigation,positioningandtiming.ButtheGPSpositioningmethodisnotsuitablefortheundergroundworkenvironmentofcoalmine,onceyouentertheunderground,itcannotreceivesatellitesignal,thusunabletoachievetargeting[VI].Weneedtoconsiderhowtousewirelessnetworktorealizepositioningfunction,meansusingwirelesssignalbetweenthecommunicationsofdevicesforpositioning.Theexistingdistancemeasuringtechnologybetweenthewireless-devicesbasicallyisthefollowingkindsofmethods:TOA,TDOA,AOAandRSSI.
AbouttheTOAmethod,thedistancebetweenthetwodevicesisdeterminedbytheproductofthespeedoflightandtransmissiontime[VII].Althoughtheprecisionofthismethodisaccurate,butitrequireaprecisetimesynchronization,soitdemandhardwareishigher.
TDOAtechnologyneedultrasonicsignal,whichissettingonanodewithreceiveandtransmitfunction.Whenmeasurethedistance,itcansentultrasonicwaveandwirelesssignalstogether.Bymeasuringthedifferencebetweentwosignalsarrivaltime,wecancalculatethedistancebetweentwodevices[VIII].Usingthismethodcanalsoobtainaccurateresult,butthemethodneedtoincreaseultrasonicsendingandreceivingdeviceonthenodecircuit,itwillincreasecost.
AOAtechnologyneedstoinstallmultipleantennasthroughthenodessoitcanobtainadjacentnodes’signalsondeferentdirections[IX].Withthisitcandeterminethelocationinformationfromnumberofadjacentnodesandcalculateitsownposition.Thismethodnotonlyneedtoaddadditionalhardware,butalsoitsstillveryvulnerabletoexternaldisturbance,thereforeitsnotsuitableforutilize.
RSSIrangingisacheapandeasytechnology.Byusingthismethod,wedontneedtoaddadditionalhardwaredesign.Wealsodonotneedveryprecisetimerequirements.Thistechniqueisaboutwithmeasuringthewirelesssignalsstrengthinthepropagationoftheloss,tomeasurethedistancebetweentwonodes.Becauseofthismethodrequireshardwareequipmentisless,algorithmissimple,soithasbeenusinginmanywirelesscommunicationfield.Comprehensiveallconditions,positioningontheuseofRSSIrangingtechnique.
A.HardwareLocationEngine
TheCCIIIVIIII.wirelessmicrocontrollerchipproducedbyTICompanyhasahardwarelocationengine.Fromthesoftwarespointofview,CCIIIVIIII.’shardwarelocationenginehasaverysimpleAPIinterface,aslongaswritingthenecessaryparametersandwaitingforcalculation,itcanreadthelocationresults[I.0].
ThehardwarelocationengineisalsobasedonRSSItechnology.Thelocalizationsystemincludesreferencenodesandblindnodes.Thereferencenodeisafixednodethatlocatedinaknownposition,thenodeknowtheirplaceandsendapacketnotifytoothernodes.Theblindnodereceivespacketsfromreferencenodes,whichcanobtainsreferencenodes’locationandthecorrespondingRSSIvalueandputthemintothehardwarelocationengine,andthentheblindnode’slocationcanbereadfromtheengine[I.I.].
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.
V．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.II.
FigureII.PCmonitoringsoftware.
VI．SYSTEMEVALUATION
Throughrepeatedtestingofthesystem,wemadethesystemanobjectiveassessment.Firstisthepowerconsumptionassessfornodehardware,fixednode’sworkingvoltageisinIXV~IIIVVwhenthepowersuppliedbycable.ThemaximumoperatingcurrentforfixednodeisIXIIImA;theaverageoperatingcurrentisIXII.IImA.Whenthepowercablewasdisconnected,fixednodepoweredbylithium-ionbattery.Onbatterypower,thefixednode’smaximumworkingcurrentisI.IVVIImA;averageworkingcurrentisI.IVVI.IIImA.FixednodescanworkVIIIhoursonbatterypoweratleast.
Anotherquiteimportantperformanceisthelocationfunctionofthesystemperformance.Atfourdifferentlocationsoftunnelandworkingareas,mobilenodeswereplacedthere.TwosetsofdifferentaverageerrordatawereshowninFromtableI..BecausethissystemusesRSSItechnologyanditreliesmainlyonthesignalstrength,thesignalqualitywillbeaffectedbyinterferences.Fromdifferentlocations’errorswecanseethat,theerrorinworkingareaswaslargerthanitintunnels,becausethetunnelisgenerallystraight,buttheshapeoftheworkingareasareuncertainty.
TABLEI.RESULTOFLOCALIZATIONERROR
NumInTheTunnelInTheRoom
Error(m)Error(m)Error(m)Error(m)
I.II.IIII0.V%III.VIIIIV.III%
IIII.VIIII..II%III.I.IIIII.VII%
IIIII.IIII.IX.VI%III.IIIIIIV.VIII%
IVII.VIIII0.IX%III.IVIIII.IX%
ACKNOWLEDGMENT
WegratefullyacknowledgeTexasInstrumentsfordevicesprovidedtousfreeofcharge.AndalsothankstaffsofXinNuoJinCompanyforgivingussupportsonsystemtesting.
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]http://www.ti.com.
[VI]HawkinsWarren,DakuBrianL.F,PruggerArnfinnF.Positioninginundergroundmines".IECONII00VI-IIIIIndAnnualConferenceonIEEEIndustrialElectronics,II00VI,pp.IIII.VIX-IIII.VIIII.
[VII]Zhu,Shouhong,Ding,Zhiguo,MarkarianKarina.TOAbasedjointsynchronizationandlocalization".II0I.0IEEEInternationalConferenceonCommunications,ICCII0I.0,II0I.0,ArticleIDVV0II0IIIVI.
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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收集矿井环境数据,也可以通过计算矿工所穿的移动节点来实时定位.
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,和良好的兼容性,方便组成煤矿瓦斯监测网络,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,可以随时安排使用.
这是I.个新的短距离,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,但真正的产品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而被地下隧道部署,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 *好棒文|www.hbsrm.com +Q: ￥3^5`1^9`1^6^0`7^2$
用于以总结和展示每个监控节点中移动节点和固定节点的数据.他们正在使用的数据由无线传输ZigBee协议传输,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网络的路由器有没有传感器设备;,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.节点设计
目前市场上出售的ZigBee无线网络平台,适用于I.般的环境,而在特殊的地下,所以他们不适合的环境,因此,我们需要定制I.个适合地下特殊的硬件电路系统.节点的照片如图I..
无线单片机CCIIVIII0的芯片是节点设备的核心处理器,它可以用很少的外围电路构成I.个ZigBee网络.CCIIVIII0是I.个IEEEVIII0II.I.V.IV兼容的系统的芯片,支持专有的VIII0II.I.V.IV市场以及的ZigBee的ZigBeePRO和ZigBeeRFIVCE的标准.CCIIVIII0不同于其他的无线芯片,内置VIII0VI.单片机集成电路的内核,因此我们不再需要使用I.个单I.的单片机控制电路,这为我们节省了大量的成本[V].
A.移动节点
移动节点是I.个由ZigBee网络组成的矿工移动的终端设备,它应该是I.种便携式低功耗节点,所以我们设计的移动节点是小如手机,它是通过内置锂离子电池供电,CCIIVIII0的核心处理器是低功耗的芯片,它在睡眠模式时,只需要使用小于I.uA的工作电流.为了尽可能降低在显示屏上的功耗,使用I.I.00*IIIII无背光液晶屏幕的像素矩阵.移动节点的的电池容量是I.V00mAh,所以它足以满足矿工在地下长时间工作的产品,电池充电管理芯片是TPIV0VVII,最大充电电流可高达V00mA.
图I.:节点的照片
移动节点的电路包括气体浓度的传感器MJIV.0和温度传感器PT-I.000.据我们所知,许多无线传感器平台使用数字式传感器,数字传感器和MCU之间的通信需要严格的时序要求.考虑到实际应用中,无线MCU通常有I.个I.般的实时操作系统,如果我们用微机模拟严格的时序,它会影响整个操作系统的实时.这两个传感器输出的模拟信号,而不是数字信号.输入到差分放大器,我们可以得到适当的信号,可以由CCIIVIII0的芯片内的ADC模式转换为数字信号.为了方便携带,不使用外接天线,在我们的移动节点天线是我们定制I.个像手机大小的外壳,而不是使用I.个II.IVGHz贴片天线.设计的PCB和元件选择,都进行了安全评估,这足以考虑到它所有的电路板.传感器和电池爆炸性能不是很好.
B.固定节点
固定节点安装在地下隧道的墙壁.因为它是比大的移动节点,它是不适合随身携带.电路的固定节点与移动节点几乎是相同的,它也使用CCIIVIII0的芯片核心处理 *好棒文|www.hbsrm.com +Q: ￥3^5`1^9`1^6^0`7^2$
器.由于在地下隧道,I.般部署电力电缆,固定节点可以使用电缆供电模式.同时,因为我们使用的无线信号传输,新的固定节点的部署变得非常方便,这也解决了问题信号线条部署.
作为I.个固定的节点,做的工作可能远非如此,为了方便矿工观察周围的固定节点的环境数据,它使用LED数字显示.同时,大电流LED灯和蜂鸣器的设计电路.考虑到固定节点可能会出现无电的紧急声光报警功能,固定节点也内置锂离子电池,正常情况下锂离子电池在充电状态,当外部电缆断开,固定节点是自动切换到电池供电,可确保移动节点可以接收固定节点提供的信息.
固定节点不方便携带,我们有I.个定制的外壳,具有良好的爆炸性能,内部空间足以容纳II.IVGHz天线.为了确保安全,所有的电缆和传感器的位置放置,特别是胶密封,因此它具有良好的密封性.
IV.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,但在全球定位系统定位方法是不适合的煤矿井下工作环境,I.旦你进入地下,就不能收到卫星信号,从而无法达到目标[VI].我们需要考虑如何使用无线网络实现定位功能.定位现有的无线设备之间的距离测量技术的设备之间的通信手段使用无线信号基本上是以下几种方法:TOA,TDOA,AOA和RSSI.
?关于的TOA方法,在两个设备之间的距离是由产品的高速光传输时间确定[VII].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,所以它要求的硬件高.
TDOA技术需要的超声波信号,这是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之间的差异,我们可以计算出两个距离设备[VIII].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,它会增加成本.
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[IX].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.这种技术是关于测量无线信号强度的传播损失,两个节点之间的距离来衡量的,因为这种方法.需要硬件设备少,算法很简单,所以它已经在许多无线通信领域使用.综合所有条件,使用的RSSI测距技术的定位.
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[I.0].
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发动机读取[I.I.].
?表面上使用了CCIIIVIIII.的硬件定位引擎是为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,我们选择作为主芯片CCIIVIII0的系统固定节点ZigBeeII00VII协议,但CCIIIVIIII.的其内部运行的程序为I.个早期的芯片,它适只用于ZigBeeII00VI协议.第II,在CCIIIVIIII.和CCIIVIII0的之间的通信,这将有兼容性问题.CCIIIVIIII.的硬件定位引擎使用分布式计算,所有的移动自行计算节点的位置,然后上传到网关节点的信息,这将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的CCIIVIII0芯片的定位功能.
B.软件定位引擎
???如果我们想使用CCIIVIII0的实现定位功能,我们必须通过自己编写的软件的位置引擎,因为该芯片没有它里面的硬件定位引擎,该软件定位引擎仍然使用的RSSI技术,同时移动节点的位置是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,必须有至少III个参考节点,我们将网络中的参考节点视为路由器节点,并记录在X,Y为每个参考节点的坐标,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指定位置.通过这个简单的方法给移动节点以广播方式发送数据,然后围绕它每I.个路由器节点将收到来自移动节点的数据获得RSSI值.I.旦移动节点数量网络的增加,这种方法会使路由器节点更多的负担因为每个电台消息,路由器节点接收从低层传送到上层,最后应用层分析数据包.事实上,移动节点需要广播传输的数据,其他路由节点也可以接收移动节点的数据包.子节点的路由器节点和移动节点将继续向上传输的数据包转发,其他的路由器节点在该协议的底部将屏蔽掉的数据包.
?为了让所有的路由器节点可以接收由移动节点发送的数据包,并传送到网关节点的RSSI值,我们需要修改这由TI提供的Z-Stack协议相关的功能.首先,我们发现名为afIncomingData函数,它涉及从底部协议,在其中我们添加I.些代码,可以获取包的RSSI的值接收数据,然后通过该osal_set_event函数来添加和发送I.个RSSI值到MY_RSSI_REPORT_EVTOSAL轮询系统.此事件的相应的函数将在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,只会协议的底层函数处理.据这种方法,我们可以得到相应的RSSI值,并保存移动节点的计算时间.
事实上,这个软件的位置引擎不执行单个移动节点,但通过整个系统的运作实现移动节点负责发送单播数据包.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,然后转发网关负责最后的网关,使电脑监控软件监控所有移动节点相应的RSSI值的位置计算.为了减少错误,监控软件将收集RSSI值的I.0倍,并采取上的平均,和然后选择固定节点最近的III个值用III边测量方法用于计算移动节点的位置.
V.系统实施
节点中的所有软件嵌入式系统Z-Stack.因为Z-Stack是I.个开源项目,它非常有益的II次开发.这些节点测试是在I.个位于山西省的煤矿,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还设置了固定节点.由于固定的节点有大尺寸的数字LED显示屏,使固定节点的显示内容可以看到远在矿井中每个矿工携带I.个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,在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,它可以保存历史数据备份到I.个SQL数据库.监控软件的主要功能是显示和存储的每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II.
图II.电脑监控软件
VI.系统评价
我们通过反复的系统测试,系统客观的评估首先是节点的硬件功耗评估,固定节点的工作电压在IXV～IIIVV,电源通过电缆提供.固定节点的最大工作电流目前是IXIII毫安,当断开电源线,固定节点由电池供电的锂离子电池供电,平均工作电流是IXII.II毫安,固定节点的最大工作电流是I.IVVII毫安平均工作电流是I.IVVI.III毫安,固定节点可以至少工作VIII小时.
节点的另外I.个很重要的表现是系统的定位功能.在隧道和工作区的IV个不同地点,移动节点被放置在那里.两套不同的平均错误数据,从表I.所示,由于本系统使用的RSSI技术和它主要依赖信号强度,信号质量将受干扰的影响,从不同的地点的错误我们可以看到,在工作领域更大的地方误差更大,因为隧道是I.般直,但工作领域有不确定性.
表I..定位误差结果
序号在隧道在不同地点
Error(m)Error(m)Error(m)Error(m)
I.II.IIII0.V%III.VIIIIV.III%
IIII.VIIII..II%III.I.IIIII.VII%
IIIII.IIII.IX.VI%III.IIIIIIV.VIII%
IVII.VIIII0.IX%III.IVIIII.IX%
我们非常感谢德州仪器公司为我们免费提供的设备,而且还感谢给予我们支持系统测试XinNuoJin公司的员工.
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]http://www.ti.com.
[VI]HawkinsWarren,DakuBrianL.F,PruggerArnfinnF.Positioninginundergroundmines".IECONII00VI-IIIIIndAnnualConferenceonIEEEIndustrialElectronics,II00VI,pp.IIII.VIX-IIII.VIIII.
[VII]Zhu,Shouhong,Ding,Zhiguo,MarkarianKarina.TOAbasedjointsynchronizationandlocalization".II0I.0IEEEInternationalConferenceonCommunications,ICCII0I.0,II0I.0,ArticleIDVV0II0IIIVI.
[VIII]NiHao,RenGuangliang,ChangYilin.ATDOAlocationschemeinOFDMbasedWMANs".IEEETransactionsonConsumerElectronics,II00VIII,Vol.VIV,No.III,pp.I.0I.VII-I.0III..
[IX]Dogan?ayKutluyil,HmamHatem.OptimalangularsensorseparationforAOAlocalization".SignalProcessing,II00VIII,Vol.VIIIVIII,No.V,pp.I.IIIVVIII-I.IIVI0.
[I.0]K.Aamodt.CCIIIVIIII.LocationEngine".TexasInstruments,ApplicationNoteAN0IVII,SWRA0IXV.
[I.I.]TenninaStefano,DiRenzoMarco,GraziosiFabio,SantucciFortunato.LocatingzigbeenodesusingthetisccIIIVIIII.locationengine:Atestbedplatformandnewsolutionsforpositioningestimationofwsnsindynamicindoorenvironments".ProcAnnuIntConfMobileComputNetworking,II00VIII,pp.IIIVII-IVII.
附件II:外文原文(复印件)
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.NODEDESIGN
SincetheZigBeewirelessnetworkplatformsoldonpresentmarketwasdesignedforthegeneralenvironment,forspecialundergroundsotheyarenotsuitablefortheenvironment.Therefore,weneedtocustomizethesystemforundergroundenvironmentwhitaspecialhardwarecircuit.NodephotoareshowninFig.I.
ThenwirelessmicrocontrollerCCIIVIII0chipisthecoreprocessorofthenodedevice,itcanconstituteaZigBeenetworkwithveryfewperipheralcircuits.TheCCIIVIII0isanIEEEVIII0II.I.V.IVcomplianttrueSystem-on-Chip,supportingtheproprietaryVIII0II.I.V.IVmarketaswellastheZigBee,ZigBeePRO,andZigBeeRFIVCEstandards.Unlikeotherwirelesschip,CCIIVIII0built-inVIII0VI.monolithicintegratedcircuitskernel,thereforewenolongerneedtouseasingleMCUtocontrolthecircuit,andthissaveusalotofcost[V].
MobileNode
ThemobilenodeistheenddeviceofaZigBeenetworkthatcanbecarriedbyminer;itshouldbeaportableandlowpowerconsumptionnode.Sothemobilenodewedesignedisonlyassmallasamobilephone,anditisbybuilt-inlithiumionbatterypowersupply.Inpowerloss,thecoreprocessorCCIIVIII0isalowpowerconsumptionchip,whenitisinthesleepmode,itonlyneedtouselessthenI.uAworkcurrent.Inordertoreducepowerconsumptionasmuchaspossibleonthedisplay,aI.00*IIIIIpixelmatrixwithnobacklightingLCDscreenwasused.Thebattery’scapacityofthemobilenodeisI.V00mAh,soitisenoughtomeettheminer’slonghourworksintheunderground.ThebatterychargemanagementchipisTPIV0VVII,themaximumchargecurrentcanuptoV00Ma.
FigureI..Nodephoto.
ThemobilenodecircuitincludesthegasconcentrationsensorMJIV.0andtemperaturesensorPT-I.000.Asfarasweknow,manywirelesssensorplatformsusethedigitaltypesensor.ThecommunicationbetweenthedigitalsensorandtheMCUneedstricttimingrequirements.Butconsideringtheactualapplication,thewirelessMCUusuallyhasareal-timeoperatingsystemingeneral,ifweusethemicrocomputertosimulatethestricttiming,itwillaffectthereal-timeofwholeoperatingsystem.Thesetwosensorsoutputanalogsignalsnotdigitalsignals.Onlyinputthissignalintoadifferentialamplifier,canwegetanappropriatesignalthatcanbeconvertedtoadigitalsignalbyanADCmodewithintheCCIIVIII0chip.Inordertofacilitatethecarrying,externalantennawasnotusedinourmobilenode,insteadofusingaII.IVGHzpatchantenna.Andwecustomizeashelllikeacellphonesize;itisenoughtoputallPCBs,sensorsandbatteryinit.Takingintoaccountthesmallshelloftheexplosiveperformanceisnotverygood,thedesignofPCBsandtheselectionofcomponentareallcarriedoutthesafetyassessment.
B.FixedNode
Fixednodeisinstalledinthewalloftheundergroundtunnel.Becauseitisbigthanthemobilenode,itisnotappropriatetocarryaround.Thecircuitofthefixednodeisalmostsamewiththemobilenode,italsouseaCCIIVIII0chipascoreprocessor.Becauseofundergroundtunnelsgenerallydeploywithpowercable,fixednodescanusecablepower-supplymodes.Atthesametime,becauseweusewirelesssignaltransmission,thedeploymentofnewfixednodesbecomeveryconvenient,whichalsoresolvestheproblemofthesignallinesdeployment.
Asafixednode,theminorwhoisdoingworkmayfarfromit,inordertofacilitatetheminersobservedenvironmentaldataaroundthefixednodes,itusesLEDdigitaldisplay.Atthesametime,thelargecurrentLEDlightsandbuzzeraredesignedinthecircuit;itmakesthefixednodewiththefunctionofsound-lightalarm.Consideringthatitmayoccurtheemergencyofwithoutelectricity,fixednodealsobuilt-inalithium-ionbattery.Undernormalconditions,lithium-ionbatteryisinchargingstatus,whenexternalcabledisconnect,fixednodeisautomaticswitchedtobatterypower,whichcanensurethemobilenodecandelivertheinformationthroughfixednodesinunderground.
Withoutregardingtofixednodes’portability,wehaveacustomizedshellthathasexcellentexplosionproperties,andtheinternalspaceisenoughtoholddowntheII.IVGHzantenna.Toensuresafety,allcablesandthelocationofsensorsareplacedwithparticulargluesealed,sothatithasagoodseal.
IV.POSITIONINGFUNCTION
Oneoftheimportantfunctionsofthewirelesssensornetworksislocalization,especiallyintheundergroundtunnel,itrelatestothesafeoftheminerslife.CurrentlymostwidelyusedorientationmethodisGPSsatellitepositioning,itisahighprecision,all-weatherandglobalmultifunctionalsystemwiththefunctionofradionavigation,positioningandtiming.ButtheGPSpositioningmethodisnotsuitablefortheundergroundworkenvironmentofcoalmine,onceyouentertheunderground,itcannotreceivesatellitesignal,thusunabletoachievetargeting[VI].Weneedtoconsiderhowtousewirelessnetworktorealizepositioningfunction,meansusingwirelesssignalbetweenthecommunicationsofdevicesforpositioning.Theexistingdistancemeasuringtechnologybetweenthewireless-devicesbasicallyisthefollowingkindsofmethods:TOA,TDOA,AOAandRSSI.
AbouttheTOAmethod,thedistancebetweenthetwodevicesisdeterminedbytheproductofthespeedoflightandtransmissiontime[VII].Althoughtheprecisionofthismethodisaccurate,butitrequireaprecisetimesynchronization,soitdemandhardwareishigher.
TDOAtechnologyneedultrasonicsignal,whichissettingonanodewithreceiveandtransmitfunction.Whenmeasurethedistance,itcansentultrasonicwaveandwirelesssignalstogether.Bymeasuringthedifferencebetweentwosignalsarrivaltime,wecancalculatethedistancebetweentwodevices[VIII].Usingthismethodcanalsoobtainaccurateresult,butthemethodneedtoincreaseultrasonicsendingandreceivingdeviceonthenodecircuit,itwillincreasecost.
AOAtechnologyneedstoinstallmultipleantennasthroughthenodessoitcanobtainadjacentnodes’signalsondeferentdirections[IX].Withthisitcandeterminethelocationinformationfromnumberofadjacentnodesandcalculateitsownposition.Thismethodnotonlyneedtoaddadditionalhardware,butalsoitsstillveryvulnerabletoexternaldisturbance,thereforeitsnotsuitableforutilize.
RSSIrangingisacheapandeasytechnology.Byusingthismethod,wedontneedtoaddadditionalhardwaredesign.Wealsodonotneedveryprecisetimerequirements.Thistechniqueisaboutwithmeasuringthewirelesssignalsstrengthinthepropagationoftheloss,tomeasurethedistancebetweentwonodes.Becauseofthismethodrequireshardwareequipmentisless,algorithmissimple,soithasbeenusinginmanywirelesscommunicationfield.Comprehensiveallconditions,positioningontheuseofRSSIrangingtechnique.
A.HardwareLocationEngine
TheCCIIIVIIII.wirelessmicrocontrollerchipproducedbyTICompanyhasahardwarelocationengine.Fromthesoftwarespointofview,CCIIIVIIII.’shardwarelocationenginehasaverysimpleAPIinterface,aslongaswritingthenecessaryparametersandwaitingforcalculation,itcanreadthelocationresults[I.0].
ThehardwarelocationengineisalsobasedonRSSItechnology.Thelocalizationsystemincludesreferencenodesandblindnodes.Thereferencenodeisafixednodethatlocatedinaknownposition,thenodeknowtheirplaceandsendapacketnotifytoothernodes.Theblindnodereceivespacketsfromreferencenodes,whichcanobtainsreferencenodes’locationandthecorrespondingRSSIvalueandputthemintothehardwarelocationengine,andthentheblindnode’slocationcanbereadfromtheengine[I.I.].
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.
V．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.II.
FigureII.PCmonitoringsoftware.
VI．SYSTEMEVALUATION
Throughrepeatedtestingofthesystem,wemadethesystemanobjectiveassessment.Firstisthepowerconsumptionassessfornodehardware,fixednode’sworkingvoltageisinIXV~IIIVVwhenthepowersuppliedbycable.ThemaximumoperatingcurrentforfixednodeisIXIIImA;theaverageoperatingcurrentisIXII.IImA.Whenthepowercablewasdisconnected,fixednodepoweredbylithium-ionbattery.Onbatterypower,thefixednode’smaximumworkingcurrentisI.IVVIImA;averageworkingcurrentisI.IVVI.IIImA.FixednodescanworkVIIIhoursonbatterypoweratleast.
Anotherquiteimportantperformanceisthelocationfunctionofthesystemperformance.Atfourdifferentlocationsoftunnelandworkingareas,mobilenodeswereplacedthere.TwosetsofdifferentaverageerrordatawereshowninFromtableI..BecausethissystemusesRSSItechnologyanditreliesmainlyonthesignalstrength,thesignalqualitywillbeaffectedbyinterferences.Fromdifferentlocations’errorswecanseethat,theerrorinworkingareaswaslargerthanitintunnels,becausethetunnelisgenerallystraight,buttheshapeoftheworkingareasareuncertainty.
TABLEI.RESULTOFLOCALIZATIONERROR
NumInTheTunnelInTheRoom
Error(m)Error(m)Error(m)Error(m)
I.II.IIII0.V%III.VIIIIV.III%
IIII.VIIII..II%III.I.IIIII.VII%
IIIII.IIII.IX.VI%III.IIIIIIV.VIII%
IVII.VIIII0.IX%III.IVIIII.IX%
ACKNOWLEDGMENT
WegratefullyacknowledgeTexasInstrumentsfordevicesprovidedtousfreeofcharge.AndalsothankstaffsofXinNuoJinCompanyforgivingussupportsonsystemtesting.
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