Realtime 2D code based localization for indoor robot navigation

In this paper ceiling affixed ARToolKitPlus 2D code artificial landmarks are evaluated for purposes of robot localization and navigation. Ceiling affixed codes rarely come in contact with people, equipment or robots, and for this reason they are more likely to stay detectable over a longer period of time. Multi threshold averaging, light gradient compensation and neighbourhood search techniques further enhanced AR-ToolKitPlus performance. Multi threshold averaging collects positioning results at each gray scale threshold level. After all of the threshold levels are analyzed, the related results are averaged into a final result. Light gradient compensation eliminates effects of uneven lighting in the neighbourhood of a 2D code. Neighbourhood search for a 2D code requires fewer computational resources than a global search. Further repeatability improvements are achieved by means of averaging localizations. Localization performance is evaluated at varying distances of the 2D code from the camera. Experimental results show substantial improvements in repeatability and reliability over the baseline ARToolKitPlus performance. Improved performance will allow for realtime 2D code based localization for indoor robot navigation.