Technical Report CIS9709

Title: Visual Homing: Surfing on the Epipoles
Authors: Ronen Basri Ehud Rivlin Ilan Shimshoni
Abstract: We introduce a novel method for visual homing. Using this method a robot can be sent to desired positions and orientations in 3-D space specified by single images taken from these positions. Our method is based on recovering the epipolar geometry relating the current image taken by the robot and the target image. Using the epipolar geometry, most of the parameters which specify the differences in position and orientation of the camera between the two images are recovered. However, since not all of the parameters can be recovered from two images, we have developed specific methods to bypass these missing parameters and resolve the ambiguities that exist. We present two homing algorithms for two standard projection models, weak and full perspective. Our method determines the path of the robot on-line, the starting position of the robot is not constrained, and a 3-D model of the environment is not required. One of the advantages of our method is that it is almost entirely memoryless, in the sense that at every step the path to the target position is independent of the previous path taken by the robot. Because of this property the robot may be able, while moving toward the target, to perform auxiliary tasks or to avoid obstacles, without this impairing its ability to eventually reach the target position. Our method enables a robot to locate objects that may change their position in the environment and to follow moving objects keeping them in a constant view. We have performed simulations and real experiments demonstrating the robustness of the method and that the algorithms always converge to the target pose.
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