Joint object recognition and pose estimation using multiple-anchor triplet learning of canonical plane

Accurate object recognition and pose estimation models are essential for practical applications of robot arms, such as picking products on a shelf. Training such a model often requires a large-scale dataset with qualified labels for both object classes and pose parameters, and collecting accurate pose labels is particularly costly. A recent paper Ueno et al.(2019)[28] proposed a triplet learning framework for joint object recognition and pose estimation without explicit pose labels by learning a spatial transformer network to estimate the pose difference of an input image from an anchor image depicting the same object in a reference pose. However, our analysis suggests that the pose estimation accuracy is severely degraded for input images with large pose differences. To address this problem, we propose a new learning approach called multiple-anchor triplet learning. The basic idea is to give dense reference poses by preparing multiple anchors so that there is at least one anchor image having a small pose difference to the input image. Our multiple-anchor triplet learning is an extension of the standard single-anchor triplet learning to the multiple-anchor case. Inspired by the idea of multiple instance learning, we introduce a selection layer that automatically chooses the best anchor for each input image and allows the network to be trained end-to-end to minimize triplet-based losses. Experiments with three benchmark datasets in product picking scenarios demonstrate that our method significantly outperforms existing methods in both object recognition and pose estimation accuracy. (c) 2021 Elsevier B.V. All rights reserved.