Autonomous Go-and-Touch Exploration (AGATE)

This paper presents work done to enable a mobile manipulator to autonomously place, its tool with high accuracy and reliability, relative to a visually distinctive target. The work is novel in that the cameras are not calibrated a priori, rather, the system calibrates the cameras by moving the manipulator through the field of view, and the algorithm combines motion of the mobile base and the manipulator in order to achieve the task. Although not creating a globally improved camera calibration, the method provides very high precision in positioning a mobile manipulator relative to a visually selected target. The work was motivated by a desire to increase the precision and efficiency of the Mars exploration rovers (MER), allowing more science to be carried out in the same span of time. In addition to the algorithm, the paper describes a large number of experiments used to show the effectiveness of the method. For the experiments described in this paper, the starting distance of the rover relative to the point of interest ranged from about 2 to 8 m. Depending on the distance of traverse required, the rover had to use one to three sets of stereo cameras. Over a large range of distances, and many experiments, the system was shown to be robust and accurate. The paper further breaks down the sources of error and examines their importance based on a large number of experiments. (c) 2012 Wiley Periodicals, Inc.