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

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