start-ver=1.4 cd-journal=joma no-vol= cd-vols= no-issue= article-no= start-page=6053 end-page=6058 dt-received= dt-revised= dt-accepted= dt-pub-year=2015 dt-pub=20150928 dt-online= en-article= kn-article= en-subject= kn-subject= en-title= kn-title=Path Tracking by a Mobile Robot Equipped with Only a Downward Facing Camera en-subtitle= kn-subtitle= en-abstract= kn-abstract=This paper presents a practical path-tracking method for a mobile robot with only a downward camera facing the passage plane. A unique algorithm for tracking and searching ground images with natural texture is used to localize the robot without a feature-point extraction scheme commonly used in other visual odometry methods. In our tracking algorithm, groups of reference pixels are used to detect the relative translation and rotation between frames. Furthermore, a reference pixel group of another shape is registered both to record a path and to correct errors accumulated during localization. All image processing and robot control operations are carried out with low memory consumption for image registration and fast calculation times for completing the searches on a laptop PC. We also describe experimental results in which a vehicle developed by the proposed method repeatedly performed precise path tracking under indoor and outdoor environments. en-copyright= kn-copyright= en-aut-name=NagaiIsaku en-aut-sei=Nagai en-aut-mei=Isaku kn-aut-name=永井伊作 kn-aut-sei=永井 kn-aut-mei=伊作 aut-affil-num=1 ORCID= en-aut-name=WatanabeKeigo en-aut-sei=Watanabe en-aut-mei=Keigo kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=2 ORCID= affil-num=1 en-affil= kn-affil=岡山大学大学院自然科学研究科 affil-num=2 en-affil= kn-affil=岡山大学大学院自然科学研究科 END