Mobile robot localization system using multiple ceiling mounted cameras

Almost all robotics applications require accurate robot positioning. However, most of the developed methods lacks in ground truth reference to verify its accuracy relative to the real world. This paper proposes an effective vision based system to accurately track mobile robot´s true position and orientation using multiple overhead cameras. This system is able to track and localize multiple mobile robots simultaneously within a 3m × 6m arena. Images from the cameras are calibrated using calibration grid image to remove fish eye effect and further calibrated based on point coordinates (x, y) to eliminate camera angle distortion error. Each robot is assigned with a symbol marker for identification. A geometric feature based pattern matching algorithm is used to track the markers position and orientation. Data obtained from all four cameras are merged according to its relative offsets to obtain localization in a global coordinate frame. The developed system is able to localize multiple robots with errors of less than 1 cm and 1°.