Active 6-D position-pose estimation of a spatial circle using monocular eye-in-hand system

Xin Ma,Jindong Tan,Junbing Feng,Yibin Li

doi:10.1177/1729881417753692

Abstract

Nuts and bolts are common components in assembly lines. Their position and pose estimation is a vital step for automatic assembling. Although many approaches using a monocular camera have been proposed, few works consider a monocular camera’s active movements for improving estimation accuracy. This article presents an active movement strategy for a monocular eye-in-hand camera for high position and pose estimation accuracy of a spatial circle. Extensive experiments are conducted to validate the effectiveness of the proposed method for position and pose estimation of circles printed on paper, real circular flat washers, and nuts.

Highlights

Anthropomorphic dual arm robots that can execute complex bimanual operations to replace or work with human workers in unstructured environments have been attracting more and more attention.[1]
In order to deal with challenges due to changes in illumination, rotation, scale, and viewpoint, several invariant feature descriptors, such as scale invariant feature transform (SIFT),[7] speeded up robust features,[8] and Affine-SIFT9 are being used to find the correspondence between an input image and a data set
In order to validate the effectiveness of the active movement strategy, the comparison experiments have been done for 6-D position-pose estimation of one circle flat washer and one nut

Summary

Introduction

Anthropomorphic dual arm robots that can execute complex bimanual operations to replace or work with human workers in unstructured environments have been attracting more and more attention.[1]. After computing the spatial circle’s center Xc 1⁄4 ðxc; yc; zcÞT and its normal vector n, and the two elliptical cones, the representation of the spatial circle in ðOw À xwywzwÞ can be obtained as follows,. With two different images taken by the monocular eye-inhand system from two different views, the estimation performance for the spatial circle’s center coordinate Xc, its normal vector n, and its radius r are different, which is shown in section entitled “Experiments and discussions”. The camera’s perspective can be reflected with the position of the projection ellipse in the image and the ratio of the semi-minor axis of length to the semi-major axis of length.

The projection ellipses should locate in the images’

Spatial circle’s normal vector n

Experiments and discussions

Conclusions