A Hierarchical Manipulation Scheme for Robotic Sorting of Multiwire Cables With Hybrid Vision

A key step in manufacturing multiwire cables in the factory is to sort the wires according to the desired color sequence. Owing to their deformable nature, it is challenging for robots to carry out sorting tasks on wires. Specifically, the wires are very small in size, multiple wires are closely coupled, and the initial color sequence is random. In this article, a new hierarchical manipulation scheme is proposed for the robotic sorting of multiwire cables. The sorting task is carried out by a vision-guided robotic gripper, whose control objective is formulated in two layers: 1) the high-level planner outputs an optimal grasping sequence and the grasping position, according to the initial status of wires; and 2) the low-level planner shapes the gripper's reference trajectory by monitoring the wires' changes online. The proposed hierarchical manipulation scheme explores the advantages of both 3-D and 2-D vision to effectively deal with the existing issues (e.g., overlapping and occlusion) of multiple wires and also unforeseen changes during the sorting task (e.g., slipping and collision), which then guarantees the feasibility of wire sorting. Experimental results in various scenarios are presented to validate the performance of the proposed scheme.