Classifying and sorting cluttered piles of unknown objects with robots: a learning approach

TL;DR

This paper presents a robotic system that autonomously learns to sort densely cluttered unknown objects by predicting object classes during grasping, using a two-stage grasp selection process and RGBD images, improving waste sorting efficiency.

Contribution

The authors introduce a learning-based approach that predicts object classes during grasping and implicitly segments cluttered scenes without explicit segmentation, advancing robotic sorting capabilities.

Findings

System quickly learned effective grasping and classification.

Achieved successful sorting of objects by color in cluttered piles.

Demonstrated autonomous learning in a waste sorting task.

Abstract

We consider the problem of sorting a densely cluttered pile of unknown objects using a robot. This yet unsolved problem is relevant in the robotic waste sorting business. By extending previous active learning approaches to grasping, we show a system that learns the task autonomously. Instead of predicting just whether a grasp succeeds, we predict the classes of the objects that end up being picked and thrown onto the target conveyor. Segmenting and identifying objects from the uncluttered target conveyor, as opposed to the working area, is easier due to the added structure since the thrown objects will be the only ones present. Instead of trying to segment or otherwise understand the cluttered working area in any way, we simply allow the controller to learn a mapping from an RGBD image in the neighborhood of the grasp to a predicted result---all segmentation etc. in the working area is implicit in the learned function. The grasp selection operates in two stages: The first stage is hardcoded and outputs a distribution of possible grasps that sometimes succeed. The second stage uses a purely learned criterion to choose the grasp to make from the proposal distribution created by the first stage. In an experiment, the system quickly learned to make good pickups and predict correctly, in advance, which class of object it was going to pick up and was able to sort the objects from a densely cluttered pile by color.