Estimating workpiece pose using the feature points method

Abstract

The ability of a robot to estimate workpiece pose is necessary for many industrial tasks. An automatic method of visually estimating the pose of a workpiece in a robot hand has been investigated. This method is applicable to workpieces that have six continuous unknown degrees of freedom. Furthermore, partial occlusion of the workpiece by the robot hand is allowed. Workpiece pose was estimated using the three-dimensional locations of at least three noncollinear workpiece feature points. A second view of the workpiece was obtained by rotating the workpiece in front of the camera. Corresponding image features on the second view were found by searching along lines on the image which were determined by the rotation of the workpiece. A very accurate camera calibration procedure has been developed to compute rays in space from image locations. The location of workpiece features was computed by trigonometric relations between rays of corresponding image features from two views of the workpiece. The pose of a workpiece was estimated by the correspondence between the workpiece features located and the feature points of a workpiece model. Experiments have been performed on a complete functional system. The major limitation of the current system was due to the image feature extraction algorithm which only detected corners and small holes.