Calibration-free Localization for Mobile Robots Using an External Stereo Camera

We propose a calibration-free method for localizing mobile robots using a stereo camera installed on the ceiling. We use both optical images and depth data obtained from the stereo camera to localize the robots. This method achieves 2.3 mm precision at the center of the field of view and 30 mm near the edge when the stereo camera is installed on an approximately 3.2-meter high ceiling, where the field of view is approximately 5m x 3 m. The accuracy, i.e., the average distance between the localization result by the proposed method and the ground truth, was obtained at 28 mm. This value is an improvement over that obtained from the localization using only the optical image (42 mm). We also show experimentally that it is possible to perform automatic control of a mobile robot on the basis of the location information measured by the proposed method.