Improving Vision-Based Distance Measurements using Reference Objects .pdf

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1、ImprovingVision-BasedDistanceMeasurementsusingReferenceObjectsMatthiasJ•ungel,HeinrichMellmann,andMichaelSprangerHumboldt-Universit•atzuBerlin,K•unstlicheIntelligenzUnterdenLinden6,10099Berlin,Germany{juengel,mellmann,spranger}@informatik.hu-berlin.dehttp://www.aiboteamhumboldt.com/A

2、bstract.Robotsperceivingtheirenvironmentusingcamerasusuallyneedagoodrepresentationofhowthecameraisalignedtothebodyandhowthecameraisrotatedrelativetotheground.Thisisespeciallyim-portantforbearing-baseddistancemeasurements.Inthispaperweshowhowtousereferenceobjectstoimprovevision-basedd

3、istancemeasure-mentstoobjectsofunknownsize.Severalmethodsfordierentkindsofreferenceobjectsareintroduced.Theseareobjectsofknownsize(likeaball),objectsextendingoverthehorizon(likegoalsandbeacons),andobjectswithknownshapeontheground(likeeldlines).Wegiveade-taileddescriptionhowtodeterm

4、inetherotationoftherobot'scamerarelativetotheground,provideanerror-estimationforallmethodsanddescribetheexperimentsweperformedonanAiborobot.Keywords:RoboCup,humanoidrobots,Aibo,cameramatrix,refer-enceobjects1IntroductionAmaintaskinroboticvisionistodeterminethespatialrelationsbetweent

5、herobotandtheobjectsthatsurroundit.Usuallytherobotneedstoknowtheangleandthedistancetocertainobjectsinordertolocalize,navigateordosomehigh-levelplanning.Todeterminethedistancetoanobjectiseasywhenthesizeoftheobjectandthefocallengthofthecameraareknown.Todeterminethedistancetoanobjectofu

6、nknownsizeispossibleusingtheknowledgeabouttheheightofthecameraandthebearingtothepointwheretheobjectmeetstheground.Thisbearingisgivenbythepositionoftheobjectintheimageandtheknownorientationofthecamerarelativetotheground.Unfortunatelythisorientationisnotknowninalotofcases.Thecalculatio

7、nofthekinematicchainofaleggedrobotfromthegroundtothecameraisusuallydicultastheexactcontactpointsoftherobotandthegroundarehardtodetermine.Additionallyinaccuraciesinthejointanglesensorssumupthelongerthekinematicchainis.Butalsoforwheeledrobotstheorientationofthecamerarelativetothegroun

8、dcanbeunknow