一种新的方法通过移动的2D激光测距仪检测管线变形Word文档下载推荐.docx
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一种新的方法通过移动的2D激光测距仪检测管线变形Word文档下载推荐.docx
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Pipelinedeformation;
LaserRangeFinder(LRF)
ⅠINTRODUCTION
Buriedinfrastructuresuchaswaterandgassupplypipesaresubjecttosurfaceliveloadsasaresultofvehicleloadingandconstructionofsurfacefacilities.Theliveloads,groundmovementsduetoearthquakeorsimilarcausescouldmakethepipelinesfailure,includingpipedeflection,bendinganddeformationetc.Pipelinedeformationisalsoappliedtoestimatethestressinthepipeline,andthustokeepthe
pipelinestressbelowthecriticallevel[1].Therefore,itisnecessarytodetectpipelinedeformationregularly.
Traditionaltechniquesfordeformationdetectioninclude:
on-sitevisualinspection,photogrammetricsurveys(terrestrialoraerial),preciseconventionalsurveys,andgeotechnicalmeasurementsusingeithercontinuousdatacollectionorobservationepochs[2].ThemostrecentapproachesutilizetheGlobalPositioningSystem(GPS),opticalfibregyroscope[3],sensornetwork,etc.tohelpthedetecting.ThemethodwithGPScannotbeappliedforundergroundpipelines.Thecostofthedetectionsystemwithanopticalfibregyroscopehindersitbeusedwidely.Asensorsysteminstalledwithremotewirelesshasthecapabilitiestomonitorpipelines.Thissystemisrelativecostlyandshouldbeinstalledbeforehand.
In-piperobotswithCCTV,whichhavealonghistoryofdevelopment,havebeenemployedasmajortoolstomaintainpipelineutilities.However,pipelinedeformationishardtodetectaccuratelybyvisualinspection.Inthispaper,wefixaLRFonthein-pipeinspectionrobottofindthedistancebetweentherobotandtheinsidewallofthepipeline.Inthisway,weexpecttogetthethree-dimensionalreconstructionofthepipelines.Wefinditisagoodwaytodetectpipelinedeformation.AlthoughtheLRFcangetaccuraterangeinformation,therobotposturechangesinstantaneouswhentherobotisrunninginthepipeline,whichmakesthedeformationdetectiondifficult.
Thispaperisstructuredasfollows:
InsectionⅡwepresenttherobotsystemwithamoving2DLRF.TheframesoftheLRF,inspectionrobotandpipeareinstalledandtheirtransitionmatrixesareanalyzedinsectionⅢ.InsectionⅣ,wedescribehowtocalculatethepipelinedeformationwiththereceiveddatafromtheLRF.InsectionⅤwediscusstheexperimentalresultsanddemonstratetheaccuracyofthesystemandmethods.Finally,wepresentconclusionandfutureworkinsectionⅥ.
ⅡROBOTICSYSTEMANDCALIBRATION
ATheRoboticSystem
AsshowninFig1,theroboticsystemisawheeledmobilerobotwithCCTVforundergroundpipelinesinspection.APTZcameraisfixedonthearmoftherobot.Thepipelinecanbemonitoredandinspectedfromthevisualinformationcapturedbythecameraastherobotrunsinthepipeline.However
thepipedeformationcannotbemeasuredbyeyesightfromthisvisualinformation.Todetectthepipedeformation,aLRFisusedtofindthedistancefromthesensortotheinsidewall.
Fig.1Theroboticsystem
WechooseHOKUYOUBG-04LX[4]producedbyJapanastherangefindsensor.Itcanmeasure682stepson240°
peronerotation,andthereforetheangularresolutionis0.352°
ona2Dplane.Althoughitcan’tmeasurethewhole360°
thisrangeisenoughforourapplication.Thebelow120°
ofthepipelinewhichcan’tdetectisoftenfilledwithwater.Thissystemisalsoequippedwithencoderstomeasurethedistancewhichtherobotcoveredandaninclinometertoobservethepostureoftherobot.
BCalibration
BecausetheLRFfindsthedistancefromthesensortothewallortheobstacles,itsinstallationpositionisimportant.TheLRFisfixedhorizontallyinthemiddlebodyoftherobot.Tomakemaximizeusetheeffectivescope,thesensorisfixedontherobotwhereitcanfindtheup240°
.Inthisway,whenthereissomewaterinthepipe,itstillcanfindmostoftheinsidewallofthepipeline.
Afterfixation,wedesignasimplymethodtogetandcalibratetheheightofthesensor.AsshowninFig.2,weusethetableinourlaboratoryascalibrateplanewhichishorizontal.SincethebrightnessofthetargetinfluencestheprecisionoftheLRF[5],wechooseawhiteplanewhichisgoodforreflectivity.Furthermore,togetverticaldistancebetweentheLRFandplanes,weonlyselectthefrontstepwhoseindexnumberis382.ThischaracterizationisobservedbyChan-Soo[5].
Fig.2Calibration
AsshowninFig.2,Thedistancebetweentheplaneofthetableandgroundisd0,whichcanbemeasuredbyametrerule.ThedistancebetweentheLRFandtheplaneofthetableisdi,whichcanbedetectedbytheLRF.Wecalculatetheheightofthesensordjasfollows:
dj=d0-di
(1)
Wherediisthesensorreadingofthe382ndstep.However,thevalueofdiisdifferenteverytimewhentheLRFmeasures682stepson240°
peronerotation.Togettheminimummeasuringerror,wedetectdintimesandusethearithmeticmean,whichisgivenby
(2)
Thenwegettheheightofthesensordjasfollows:
dj=d0–di(3)
ⅢTANSFORMATIONANDPOSTUREANALYSIS
AThethreeframes
Wedescribethepostureoftheinspectionrobotmovinginroundpipeswiththecoordinates(x,y,z)ofoneoftheirpointswithrespecttotheinertialbasisandtheirEulerangles(ϕ,θ,ψ).
Fig.3Thethreeframesareestablished
Aninertialbaseframe{XWYWZW}isfixedinthepipeswithaxis-ZWalignedwiththeaxisoftheroundpipes,whileamovingframe{XRYRZR}isattachedtotheinspectionrobot.Therobotposturecanbedescribedintermsofthethreecoordinatesx0,y0,z0oftheoriginPofthemovingframeandtheorientationangle(ϕ,θ,ψ)ofthemovingframe,bothwithrespecttothebaseframewiththeoriginatP.Thequantities(ϕ,θ,ψ)arethebodyyaw,pitch,androlloftherobot,whichisshownasinFigure3.Anotherframe{XLYLZL}isattachedontheLRF.
BTransformationMatrix
ThedatacollectedbytheLRFisbasedonthecoordinateoftheLRF,namelyintheframe{XLYLZL},buttherealpipelinedeformationisrespecttothebaseframe.Therefore,thetransformationmatrixfromtheframeoftheLRFtothebaseframeshouldbededuced.AsshowninFig.3,thetransformationmatrixfromtheframeoftheLRFtotheframeoftherobotisasfollowing:
where(xL0,yL0,zL0)isthecoordinatesofthecentreoftheLRFintheframeoftherobot.
Thetransformationmatrixfromtheframeoftherobottothebaseframeis
Where
(6)
whichcanbededucedaccordingtothedefinitionofEulerangles[6],and
Therefore,thetransformationmatrixfromtheframeoftheLRFtothebaseframeisgivenby
Forthewheeledmobilerobotworkinginroundpipes,ithas3degreesoffreedomifthepostureisdescribedintermsofthreecoordinatesx0,y0,z0andtheorientationangle(ϕ,θ,ψ)[6].Twooftheorientationangle(ϕ,θ,ψ)canbeobservedbyatwo-axisinclinometer.Thedistanceoftherobotran,namelyz0canbedetectedbytheencoder.Therefore,thetransformationmatrixcanbecalculatedinstantaneously.
CPostureanalysisoftheinspectionrobotsinroundpipes
Thepostureofwheeledmobilerobotsinroundpipescanbeanalyzedbythreecasesasfollows.
(1)Therobotishorizontal.Inthiscase,thepostureanglessatisfy
ϕ=θ=ψ=0asshowninFig.4(a).Fourwheelsoftherobotkeepintouchwiththewallofthepipesinthiscase.
(2)TherobotisslantedbutitsdirectionisparalleltotheaxisofthepipesasshowninFig.4(b).Inthiscase,thepostureanglessatisfyϕ=0,
θ=0andψ≠0.Whenthepostureangleϕisrelativelylarge,therobotwillslidetothebottomorevenbeoverturned.(3)Therobotisslantedbutitsdirectionisnotparalleltotheaxisofthepipes/ducts,whichisequivalenttotheconditionsϕ≠0,
θ≠0andψ≠0asshowninFig.4(c).Onlythreewheelsofthefour-wheelrobotstayintouchwiththewallatthesametimeinthiscase.
(a)Firstcaseϕ=θ=ψ=0(b)Secondcaseϕ=0,θ=0andψ≠0(c)Thirdcaseϕ≠0,θ≠0andψ≠0
Fig.4Differentpostureoftherobotinthepipeline
AsweseefromFig.4,thefirstandthesecondcasehaveperfectpostureforcollectingtheaccurateinformationandareeasytocalculatethepipelinedeformation.Inthesecases,thedatacollectedbytheLRFneednotrotatetransformationifweonlycalculatethedeformationrate.Unfortunately,thesetwocasesarespecialcondit
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