RGB-X Classification for Electronics Sorting

TL;DR

This paper introduces RGB-X, a multi-modal classification method combining RGB and X-ray images with a novel network architecture, iCAM, to accurately identify electronic waste objects for improved recycling, achieving high accuracy with synthetic data.

Contribution

The work presents a new multi-modal classification approach and a novel network architecture, iCAM, along with a synthetic dataset creation method for electronic object classification.

Findings

Achieved 98.6% accuracy on smartphone classification

RGB-X outperforms individual RGB or X-ray classifiers

Synthetic dataset effectively trains the classifier

Abstract

Effectively disassembling and recovering materials from waste electrical and electronic equipment (WEEE) is a critical step in moving global supply chains from carbon-intensive, mined materials to recycled and renewable ones. Conventional recycling processes rely on shredding and sorting waste streams, but for WEEE, which is comprised of numerous dissimilar materials, we explore targeted disassembly of numerous objects for improved material recovery. Many WEEE objects share many key features and therefore can look quite similar, but their material composition and internal component layout can vary, and thus it is critical to have an accurate classifier for subsequent disassembly steps for accurate material separation and recovery. This work introduces RGB-X, a multi-modal image classification approach, that utilizes key features from external RGB images with those generated from X-ray images to accurately classify electronic objects. More specifically, this work develops Iterative Class Activation Mapping (iCAM), a novel network architecture that explicitly focuses on the finer-details in the multi-modal feature maps that are needed for accurate electronic object classification. In order to train a classifier, electronic objects lack large and well annotated X-ray datasets due to expense and need of expert guidance. To overcome this issue, we present a novel way of creating a synthetic dataset using domain randomization applied to the X-ray domain. The combined RGB-X approach gives us an accuracy of 98.6% on 10 generations of modern smartphones, which is greater than their individual accuracies of 89.1% (RGB) and 97.9% (X-ray) independently. We provide experimental results3 to corroborate our results.