Robotics: Science and Systems XVII

Untangling Dense Non-Planar Knots by Learning Manipulation Features and Recovery Policies

Priya Sundaresan*, Jennifer Grannen*, Brijen Thananjeyan, Ashwin Balakrishna, Jeffrey Ichnowski, Ellen Novoseller, Minho Hwang, Michael Laskey, Joseph Gonzalez, Ken Goldberg
* These authors contributed equally


Robot manipulation for untangling 1D deformable structures such as ropes; cables; and wires is challenging due to their infinite dimensional configuration space; complex dynamics; and tendency to self-occlude. Analytical controllers often fail in the presence of dense configurations; due to the difficulty of grasping between adjacent cable segments. We present two algorithms that enhance robust cable untangling; LOKI and SPiDERMan; which operate alongside HULK; a high-level planner from prior work. LOKI uses a learned model of manipulation features to refine a coarse grasp keypoint prediction to a precise; optimized location and orientation; while SPiDERMan uses a learned model to sense task progress and apply recovery actions. We evaluate these algorithms in physical cable untangling experiments with 336 knots and over 1500 actions on real cables using the da Vinci surgical robot. We find that the combination of HULK; LOKI; and SPiDERMan is able to untangle dense overhand; figure-eight; double-overhand; square; bowline; granny; stevedore; and triple-overhand knots. The composition of these methods successfully untangles a cable from a dense initial configuration in 68.3% of 60 physical experiments and achieves 50% higher success rates than baselines from prior work. Supplementary material; code; and videos can be found at



    AUTHOR    = {Priya Sundaresan AND Jennifer Grannen AND Brijen Thananjeyan AND Ashwin Balakrishna AND Jeffrey Ichnowski AND Ellen Novoseller AND Minho Hwang AND Michael Laskey AND Joseph Gonzalez AND Ken Goldberg}, 
    TITLE     = {{Untangling Dense Non-Planar Knots by Learning Manipulation Features and Recovery Policies}}, 
    BOOKTITLE = {Proceedings of Robotics: Science and Systems}, 
    YEAR      = {2021}, 
    ADDRESS   = {Virtual}, 
    MONTH     = {July}, 
    DOI       = {10.15607/RSS.2021.XVII.013}