Publications

@article{sun2024force,  title={Force-Constrained Visual Policy: Safe Robot-Assisted Dressing via Multi-Modal Sensing},  author={Sun, Zhanyi and Wang, Yufei and Held, David and Erickson, Zackory},  journal={IEEE Robotics and Automation Letters},  year={2024} }

Robot-assisted dressing could profoundly enhance the quality of life of adults with physical disabilities. To achieve this, a robot can benefit from both visual and force sensing. The former enables the robot to ascertain human body pose and garment deformations, while the latter helps maintain safety and comfort during the dressing process. In this paper, we introduce a new technique that leverages both vision and force modalities for this assistive task. Our approach first trains a vision-based dressing policy using reinforcement learning in simulation with varying body sizes, poses, and types of garments. We then learn a force dynamics model for action planning to ensure safety. Due to limitations of simulating accurate force data when deformable garments interact with the human body, we learn a force dynamics model directly from real-world data. Our proposed method combines the vision-based policy, trained in simulation, with the force dynamics model, learned in the real world, by solving a constrained optimization problem to infer actions that facilitate the dressing process without applying excessive force on the person. We evaluate our system in simulation and in a real-world human study with 10 participants across 240 dressing trials, showing it greatly outperforms prior baselines. Video demonstrations are available on our project website.

@article{gupta2023object,  title={Object Importance Estimation using Counterfactual Reasoning for Intelligent Driving},  author={Gupta, Pranay and Biswas, Abhijat and Admoni, Henny and Held, David},  journal={arXiv preprint arXiv:2312.02467},  year={2023}  }

The ability to identify important objects in a complex and dynamic driving environment is essential for autonomous driving agents to make safe and efficient driving decisions. It also helps assistive driving systems decide when to alert drivers. We tackle object importance estimation in a data-driven fashion and introduce HOIST - Human-annotated Object Importance in Simulated Traffic. HOIST contains driving scenarios with human-annotated importance labels for vehicles and pedestrians. We additionally propose a novel approach that relies on counterfactual reasoning to estimate an object's importance. We generate counterfactual scenarios by modifying the motion of objects and ascribe importance based on how the modifications affect the ego vehicle's driving. Our approach outperforms strong baselines for the task of object importance estimation on HOIST. We also perform ablation studies to justify our design choices and show the significance of the different components of our proposed approach.

@article{eisner2024deep,  title={Deep {SE}(3)-Equivariant Geometric Reasoning for Precise Placement Tasks},  author={Ben Eisner and Yi Yang and Todor Davchev and Mel Vecerik and Jonathan Scholz and David Held},  booktitle={The Twelfth International Conference on Learning Representations},  year={2024},  url={https://openreview.net/forum?id=2inBuwTyL2}  }

Many robot manipulation tasks can be framed as geometric reasoning tasks, where an agent must be able to precisely manipulate an object into a position that satisfies the task from a set of initial conditions. Often, task success is defined based on the relationship between two objects - for instance, hanging a mug on a rack. In such cases, the solution should be equivariant to the initial position of the objects as well as the agent, and invariant to the pose of the camera. This poses a challenge for learning systems which attempt to solve this task by learning directly from high-dimensional demonstrations - the agent must learn to be both equivariant as well as precise, which can be challenging without any inductive biases about the problem. In this work, we propose a method for precise relative pose prediction which is provably SE(3)-equivariant, can be learned from only a few demonstrations, and can generalize across variations in a class of objects. We accomplish this by factoring the problem into learning an SE(3) invariant task-specific representation of the scene and then interpreting this representation with novel geometric reasoning layers which are provably SE(3) equivariant. We demonstrate that our method can yield substantially more precise placement predictions in simulated placement tasks than previous methods trained with the same amount of data, and can accurately represent relative placement relationships data collected from real-world demonstrations.

@article{yang2023reinforcement,  title={Reinforcement Learning in a Safety-Embedded MDP with Trajectory Optimization},  author={Yang, Fan and Zhou, Wenxuan and Liu, Zuxin and Zhao, Ding and Held, David},  journal={arXiv preprint arXiv:2310.06903},  year={2023}  }

Safe Reinforcement Learning (RL) plays an important role in applying RL algorithms to safety-critical real-world applications, addressing the trade-off between maximizing rewards and adhering to safety constraints. This work introduces a novel approach that combines RL with trajectory optimization to manage this trade-off effectively. Our approach embeds safety constraints within the action space of a modified Markov Decision Process (MDP). The RL agent produces a sequence of actions that are transformed into safe trajectories by a trajectory optimizer, thereby effectively ensuring safety and increasing training stability. This novel approach excels in its performance on challenging Safety Gym tasks, achieving significantly higher rewards and near-zero safety violations during inference. The method's real-world applicability is demonstrated through a safe and effective deployment in a real robot task of box-pushing around obstacles.

@article{wang2024taxposed,  title={Learning Distributional Demonstration Spaces for Task-Specific Cross-Pose Estimation},  author={Wang, Jenny and Donca, Octavian and Held, David},  journal={IEEE International Conference on Robotics and Automation (ICRA), 2024},  year={2024}  }

Relative placement tasks are an important category of tasks in which one object needs to be placed in a desired pose relative to another object. Previous work has shown success in learning relative placement tasks from just a small number of demonstrations, when using relational reasoning networks with geometric inductive biases. However, such methods fail to consider that demonstrations for the same task can be fundamentally multimodal, like a mug hanging on any of n racks. We propose a method that retains the provably translation-invariant and relational properties of prior work but incorporates additional properties that account for multimodal, distributional examples. We show that our method is able to learn precise relative placement tasks with a small number of multimodal demonstrations with no human annotations across a diverse set of objects within a category.

@inproceedings{zhang2023fbpp,
   title={FlowBot++: Learning Generalized Articulated Objects Manipulation via Articulation Projection},
   author={Zhang, Harry and Eisner, Ben and Held, David},
   journal={Conference on Robot Learning (CoRL)},
   year={2023},
}

Understanding and manipulating articulated objects, such as doors and drawers, is crucial for robots operating in human environments. We wish to develop a system that can learn to articulate novel objects with no prior interaction, after training on other articulated objects. Previous approaches for articulated object manipulation rely on either modular methods which are brittle or end-to-end methods, which lack generalizability. This paper presents FlowBot++, a deep 3D vision-based robotic system that predicts dense per-point motion and dense articulation parameters of articulated objects to assist in downstream manipulation tasks. FlowBot++ introduces a novel per-point representation of the articulated motion and articulation parameters that are combined to produce a more accurate estimate than either method on their own. Simulated experiments on the PartNet-Mobility dataset validate the performance of our system in articulating a wide range of objects, while real-world experiments on real objects' point clouds and a Sawyer robot demonstrate the generalizability and feasibility of our system in real-world scenarios.

@inproceedings{zhou2023hacman,
   title={HACMan: Learning Hybrid Actor-Critic Maps for 6D Non-Prehensile Manipulation},
   author={Zhou, Wenxuan and Jiang, Bowen and Yang, Fan and Paxton, Chris and Held, David},
   journal={Conference on Robot Learning (CoRL)},
   year={2023},
}

Manipulating objects without grasping them is an essential component of human dexterity, referred to as non-prehensile manipulation. Non-prehensile manipulation may enable more complex interactions with the objects, but also presents challenges in reasoning about gripper-object interactions. In this work, we introduce Hybrid Actor-Critic Maps for Manipulation (HACMan), a reinforcement learning approach for 6D non-prehensile manipulation of objects using point cloud observations. HACMan proposes a temporally-abstracted and spatially-grounded object-centric action representation that consists of selecting a contact location from the object point cloud and a set of motion parameters describing how the robot will move after making contact. We modify an existing off-policy RL algorithm to learn in this hybrid discrete-continuous action representation. We evaluate HACMan on a 6D object pose alignment task in both simulation and in the real world. On the hardest version of our task, with randomized initial poses, randomized 6D goals, and diverse object categories, our policy demonstrates strong generalization to unseen object categories without a performance drop, achieving an 89% success rate on unseen objects in simulation and 50% success rate with zero-shot transfer in the real world. Compared to alternative action representations, HACMan achieves a success rate more than three times higher than the best baseline. With zero-shot sim2real transfer, our policy can successfully manipulate unseen objects in the real world for challenging non-planar goals, using dynamic and contact-rich non-prehensile skills.

@inproceedings{slipbagging2023,
   title={{Bagging by Learning to Singulate Layers Using Interactive Perception}},
   author={Lawrence Yunliang Chen and Baiyu Shi and Roy Lin and Daniel Seita and Ayah Ahmad and Richard Cheng and Thomas Kollar and David Held and Ken Goldberg},
   booktitle={IEEE/RSJ International Conference on Intelligent Robots and Systems (IROS)},
   year={2023}
}

Many fabric handling and 2D deformable material tasks in homes and industry require singulating layers of material such as opening a bag or arranging garments for sewing. In contrast to methods requiring specialized sensing or end effectors, we use only visual observations with ordinary parallel jaw grippers. We propose SLIP, Singulating Layers using Interactive Perception, and apply SLIP to the task of autonomous bagging. We develop SLIP-Bagging, a bagging algorithm that manipulates a plastic or fabric bag from an unstructured state, and uses SLIP to grasp the top layer of the bag to open it for object insertion. In physical experiments, a YuMi robot achieves a success rate of 67% to 81% across bags of a variety of materials, shapes, and sizes, significantly improving in success rate and generality over prior work. Experiments also suggest that SLIP can be applied to tasks such as singulating layers of folded cloth and garments.

@inproceedings{Wang2023One,
            title={One Policy to Dress Them All: Learning to Dress People with Diverse Poses and Garments},
            author={Wang, Yufei and Sun, Zhanyi and Erickson, Zackory and Held, David},
            booktitle={Robotics: Science and Systems (RSS)},
            year={2023}
       }

Robot-assisted dressing could benefit the lives of many people such as older adults and individuals with disabilities. Despite such potential, robot-assisted dressing remains a challenging task for robotics as it involves complex manipulation of deformable cloth in 3D space. Many prior works aim to solve the robot-assisted dressing task, but they make certain assumptions such as a fixed garment and a fixed arm pose that limit their ability to generalize. In this work, we develop a robot-assisted dressing system that is able to dress different garments on people with diverse poses from partial point cloud observations, based on a learned policy. We show that with proper design of the policy architecture and Q function, reinforcement learning (RL) can be used to learn effective policies with partial point cloud observations that work well for dressing diverse garments. We further leverage policy distillation to combine multiple policies trained on different ranges of human arm poses into a single policy that works over a wide range of different arm poses. We conduct comprehensive real-world evaluations of our system with 510 dressing trials in a human study with 17 participants with different arm poses and dressed garments. Our system is able to dress 86\% of the length of the participants arms on average. Videos can be found on the anonymized project webpage: https://sites.google.com/view/one-policy-dress.

@inproceedings{ancha2023rss,
  title     = {Active Velocity Estimation using Light Curtains via Self-Supervised Multi-Armed Bandits},
  author    = {Siddharth Ancha AND Gaurav Pathak AND Ji Zhang AND Srinivasa Narasimhan AND David Held},
  booktitle = {Proceedings of Robotics: Science and Systems},
  year      = {2023},
  address   = {Daegu, Republic of Korea},
  month     = {July},
 }

To navigate in an environment safely and autonomously, robots must accurately estimate where obstacles are and how they move. Instead of using expensive traditional 3D sensors, we explore the use of a much cheaper, faster, and higher resolution alternative: programmable light curtains. Light curtains are a controllable depth sensor that sense only along a surface that the user selects. We adapt a probabilistic method based on particle filters and occupancy grids to explicitly estimate the position and velocity of 3D points in the scene using partial measurements made by light curtains. The central challenge is to decide where to place the light curtain to accurately perform this task. We propose multiple curtain placement strategies guided by maximizing information gain and verifying predicted object locations. Then, we combine these strategies using an online learning framework. We propose a novel self-supervised reward function that evaluates the accuracy of current velocity estimates using future light curtain placements. We use a multi-armed bandit framework to intelligently switch between placement policies in real time, outperforming fixed policies. We develop a full-stack navigation system that uses position and velocity estimates from light curtains for downstream tasks such as localization, mapping, path-planning, and obstacle avoidance. This work paves the way for controllable light curtains to accurately, efficiently, and purposefully perceive and navigate complex and dynamic environments.

@inproceedings{Khurana2023point,
  title={Point Cloud Forecasting as a Proxy for 4D Occupancy Forecasting},
  author={Khurana, Tarasha and Hu, Peiyun and Held, David and Ramanan, Deva},
  booktitle={Proceedings of the IEEE/CVF Conference on Computer Vision and Pattern Recognition (CVPR)},
  year={2023}
  }

Predicting how the world can evolve in the future is crucial for motion planning in autonomous systems. Classical methods are limited because they rely on costly human annotations in the form of semantic class labels, bounding boxes, and tracks or HD maps of cities to plan their motion — and thus are difficult to scale to large unlabeled datasets. One promising self-supervised task is 3D point cloud forecasting from unannotated LiDAR sequences. We show that this task requires algorithms to implicitly capture (1) sensor extrinsics (i.e., the egomotion of the autonomous vehicle), (2) sensor intrinsics (i.e., the sampling pattern specific to the particular LiDAR sensor), and (3) the shape and motion of other objects in the scene. But autonomous systems should make predictions about the world and not their sensors! To this end, we factor out (1) and (2) by recasting the task as one of spacetime (4D) occupancy forecasting. But because it is expensive to obtain ground-truth 4D occupancy, we “render” point cloud data from 4D occupancy predictions given sensor extrinsics and intrinsics, allowing one to train and test occupancy algorithms with unannotated LiDAR sequences. This also allows one to evaluate and compare point cloud forecasting algorithms across diverse datasets, sensors, and vehicles.

@inproceedings{Longhini2023elastic,
  title={Elastic Context: Encoding Elasticity for Data-driven Models of Textiles },
  author={Longhini, Alberta and Moletta, Marco  and  Reichlin, Alfredo and Welle, Michael C.  and  Kravberg, Alexander and Wang, Yufei and Held, David and Erickson, Zackory  and Kragic, Danica },
  booktitle={IEEE International Conference on Robotics and Automation (ICRA), 2023},
  year={2023}
  }

Physical interaction with textiles, such as assistive dressing, relies on advanced dextreous capabilities. The underlying complexity in textile behavior when being pulled and stretched, is due to both the yarn material properties and the textile construction technique. Today, there are no commonly adopted and annotated datasets on which the various interaction or property identification methods are assessed. One important property that affects the interaction is material elasticity that results from both the yarn material and construction technique: these two are intertwined and, if not known a-priori, almost impossible to identify through sensing commonly available on robotic platforms. We introduce Elastic Context (EC), a concept that integrates various properties that affect elastic behavior, to enable a more effective physical interaction with textiles. The definition of EC relies on stress/strain curves commonly used in textile engineering, which we reformulated for robotic applications. We employ EC using Graph Neural Network (GNN) to learn generalized elastic behaviors of textiles. Furthermore, we explore the effect the dimension of the EC has on accurate force modeling of non-linear real-world elastic behaviors, highlighting the challenges of current robotic setups to sense textile properties.

@inproceedings{Longhini2023EDO,
  title={EDO-Net: Learning Elastic Properties of Deformable Objects from Graph Dynamics },
  author={Longhini, Alberta and Moletta, Marco and  Reichlin, Alfredo and Welle, Michael C. and Held, David  and Erickson, Zackory  and Kragic, Danica },
  booktitle={IEEE International Conference on Robotics and Automation (ICRA), 2023},
  year={2023}
  }

We study the problem of learning graph dynamics of deformable objects which generalize to unknown physical properties. In particular, we leverage a latent representation of elastic physical properties of cloth-like deformable objects which we explore through a pulling interaction. We propose EDO-Net (Elastic Deformable Object - Net), a model trained in a self-supervised fashion on a large variety of samples with different elastic properties. EDO-Net jointly learns an adaptation module, responsible for extracting a latent representation of the physical properties of the object and a forward-dynamics module, which leverages the latent representation to predict future states of cloth-like objects, represented as graphs. We evaluate EDO-Net both in simulation and real world, assessing its capabilities of: 1) generalizing to unknown physical properties of cloth-like deformable objects, 2) transferring the learned representation to new downstream tasks.

@inproceedings{huang2023act,
  title={Self-supervised Cloth Reconstruction via Action-conditioned Cloth Tracking},
  author={Huang, Zixuan and Lin, Xingyu and Held, David},
  booktitle={IEEE International Conference on Robotics and Automation (ICRA), 2023},
  year={2023}
  }

State estimation is one of the greatest challenges for cloth manipulation due to cloth's high dimensionality and self-occlusion. Prior works propose to identify the full state of crumpled clothes by training a mesh reconstruction model in simulation. However, such models are prone to suffer from a sim-to-real gap due to differences between cloth simulation and the real world. In this work, we propose a self-supervised method to finetune a mesh reconstruction model in the real world. Since the full mesh of crumpled cloth is difficult to obtain in the real world, we design a special data collection scheme and an action-conditioned model-based cloth tracking method to generate pseudo-labels for self-supervised learning. By finetuning the pretrained mesh reconstruction model on this pseudo-labeled dataset, we show that we can improve the quality of the reconstructed mesh without requiring human annotations, and improve the performance of downstream manipulation task.

@article{weng2023ngdf,
   title={Neural Grasp Distance Fields for Robot Manipulation},
   author={Weng, Thomas and Held, David and Meier, Franziska and Mukadam, Mustafa},
   booktitle={IEEE International Conference on Robotics and Automation (ICRA)},
   year={2023}
}

We formulate grasp learning as a neural field and present Neural Grasp Distance Fields (NGDF). Here, the input is a 6D pose of a robot end effector and output is a distance to a continuous manifold of valid grasps for an object. In contrast to current approaches that predict a set of discrete candidate grasps, the distance-based NGDF representation is easily interpreted as a cost, and minimizing this cost produces a successful grasp pose. This grasp distance cost can be incorporated directly into a trajectory optimizer for joint optimization with other costs such as trajectory smoothness and collision avoidance. During optimization, as the various costs are balanced and minimized, the grasp target is allowed to smoothly vary, as the learned grasp field is continuous. In simulation benchmarks with a Franka arm, we find that joint grasping and planning with NGDF outperforms baselines by 63% execution success while generalizing to unseen query poses and unseen object shapes.

@inproceedings{autobag2023,
   title={{AutoBag: Learning to Open Plastic Bags and Insert Objects}},
   author={Lawrence Yunliang Chen and Baiyu Shi and Daniel Seita and Richard Cheng and Thomas Kollar and David Held and Ken Goldberg},
   booktitle={IEEE International Conference on Robotics and Automation (ICRA), 2023},
   year={2023}
}

Thin plastic bags are ubiquitous in retail stores, healthcare, food handling, recycling, homes, and school lunchrooms. They are challenging both for perception (due to specularities and occlusions) and for manipulation (due to the dynamics of their 3D deformable structure). We formulate the task of manipulating common plastic shopping bags with two handles from an unstructured initial state to a state where solid objects can be inserted into the bag for transport. We propose a self-supervised learning framework where a dual-arm robot learns to recognize the handles and rim of plastic bags using UV-fluorescent markings; at execution time, the robot does not use UV markings or UV light. We propose Autonomous Bagging (AutoBag), where the robot uses the learned perception model to open plastic bags through iterative manipulation. We present novel metrics to evaluate the quality of a bag state and new motion primitives for reorienting and opening bags from visual observations. In physical experiments, a YuMi robot using AutoBag is able to open bags and achieve a success rate of 16/30 for inserting at least one item across a variety of initial bag configurations

@inproceedings{zhou2022ungraspable,
  title={{Learning to Grasp the Ungraspable with Emergent Extrinsic Dexterity}},
  author={Zhou, Wenxuan and Held, David},
  booktitle={Conference on Robot Learning (CoRL)},
  year={2022}
  }

A simple gripper can solve more complex manipulation tasks if it can utilize the external environment such as pushing the object against the table or a vertical wall, known as "Extrinsic Dexterity." Previous work in extrinsic dexterity usually has careful assumptions about contacts which impose restrictions on robot design, robot motions, and the variations of the physical parameters. In this work, we develop a system based on reinforcement learning (RL) to address these limitations. We study the task of “Occluded Grasping” which aims to grasp the object in configurations that are initially occluded; the robot needs to move the object into a configuration from which these grasps can be achieved. We present a system with model-free RL that successfully achieves this task using a simple gripper with extrinsic dexterity. The policy learns emergent behaviors of pushing the object against the wall to rotate and then grasp it without additional reward terms on extrinsic dexterity. We discuss important components of the system including the design of the RL problem, multi-grasp training and selection, and policy generalization with automatic curriculum. Most importantly, the policy trained in simulation is zero-shot transferred to a physical robot. It demonstrates dynamic and contact-rich motions with a simple gripper that generalizes across objects with various size, density, surface friction, and shape with a 78% success rate.

@inproceedings{pan2022tax,
  title={TAX-Pose: Task-Specific Cross-Pose Estimation for Robot Manipulation},
  author={Pan, Chuer and Okorn, Brian and Zhang, Harry and Eisner, Ben and Held, David},
  booktitle={Conference on Robot Learning (CoRL)},
  year={2022}
  }

How do we imbue robots with the ability to efficiently manipulate unseen objects and transfer relevant skills based on demonstrations? End-to-end learning methods often fail to generalize to novel objects or unseen configurations. Instead, we focus on the task-specific pose relationship between relevant parts of interacting objects. We conjecture that this relationship is a generalizable notion of a manipulation task that can transfer to new objects in the same category; examples include the relationship between the pose of a pan relative to an oven or the pose of a mug relative to a mug rack. We call this task-specific pose relationship “cross-pose” and provide a mathematical definition of this concept. We propose a vision-based system that learns to estimate the cross-pose between two objects for a given manipulation task using learned cross-object correspondences. The estimated cross-pose is then used to guide a downstream motion planner to manipulate the objects into the desired pose relationship (placing a pan into the oven or the mug onto the mug rack). We demonstrate our method’s capability to generalize to unseen objects, in some cases after training on only 10 demonstrations in the real world. Results show that our system achieves state-of-the-art performance in both simulated and real-world experiments across a number of tasks.

@inproceedings{Seita2022toolflownet,
  title={{ToolFlowNet: Robotic Manipulation with Tools via Predicting Tool Flow from Point Clouds}},
  author={Seita, Daniel and Wang, Yufei and Shetty, Sarthak, and Li, Edward and Erickson, Zackory and Held, David},
  booktitle={Conference on Robot Learning (CoRL)},
  year={2022}
  }

Point clouds are a widely available and canonical data modality which conveys the 3D geometry of a scene. Despite significant progress in classifica- tion and segmentation from point clouds, policy learning from such a modality remains challenging, and most prior works in imitation learning focus on learn- ing policies from images or state information. In this paper, we propose a novel framework for learning policies from point clouds for robotic manipulation with tools. We use a novel neural network, ToolFlowNet, which predicts dense per- point flow on the tool that the robot controls, and then uses the flow to derive the transformation that the robot should execute. We apply this framework to imita- tion learning of challenging deformable object manipulation tasks with continuous movement of tools, including scooping and pouring, and demonstrate significantly improved performance over baselines which do not use flow. We perform 50 phys- ical scooping experiments with ToolFlowNet and attain 82% scooping success. See https://tinyurl.com/toolflownet for supplementary material.

@inproceedings{
  lin2022planning,
  title={Planning with Spatial-Temporal Abstraction from Point Clouds for Deformable Object Manipulation},
  author={Xingyu Lin and Carl Qi and Yunchu Zhang and Yunzhu Li and Zhiao Huang and Katerina Fragkiadaki and Chuang Gan and David Held},
  booktitle={6th Annual Conference on Robot Learning},
  year={2022},
  url={https://openreview.net/forum?id=tyxyBj2w4vw}
  }

Effective planning of long-horizon deformable object manipulation requires suitable abstractions at both the spatial and temporal levels. Previous methods typically either focus on short-horizon tasks or make strong assumptions that full-state information is available, which prevents their use on deformable objects. In this paper, we propose PlAnning with Spatial-Temporal Abstraction (PASTA), which incorporates both spatial abstraction (reasoning about objects and their relations to each other) and temporal abstraction (reasoning over skills instead of low-level actions). Our framework maps high-dimension 3D observations such as point clouds into a set of latent vectors and plans over skill sequences on top of the latent set representation. We show that our method can effectively perform challenging sequential deformable object manipulation tasks in the real world, which require combining multiple tool-use skills such as cutting with a knife, pushing with a pusher, and spreading dough with a roller.

@inproceedings{okorndeep,
  title={Deep Projective Rotation Estimation through Relative Supervision},
  author={Okorn, Brian and Pan, Chuer and Hebert, Martial and Held, David},
  booktitle={Conference on Robot Learning (CoRL)}
  year={2022},
  }

Orientation estimation is the core to a variety of vision and robotics tasks such as camera and object pose estimation. Deep learning has offered a way to develop image-based orientation estimators; however, such estimators often require training on a large labeled dataset, which can be time-intensive to collect. In this work, we explore whether self-supervised learning from unlabeled data can be used to alleviate this issue. Specifically, we assume access to estimates of the relative orientation between neighboring poses, such that can be obtained via a local alignment method. While self-supervised learning has been used successfully for translational object keypoints, in this work, we show that naively applying relative supervision to the rotational group SO(3) will often fail to converge due to the non-convexity of the rotational space. To tackle this challenge, we propose a new algorithm for self-supervised orientation estimation which utilizes Modified Rodrigues Parameters to stereographically project the closed manifold of SO(3) to the open manifold of R3, allowing the optimization to be done in an open Euclidean space. We empirically validate the benefits of the proposed algorithm for rotational averaging problem in two settings: (1) direct optimization on rotation parameters, and (2) optimization of parameters of a convolutional neural network that predicts object orientations from images. In both settings, we demonstrate that our proposed algorithm is able to converge to a consistent relative orientation frame much faster than algorithms that purely operate in the SO(3) space.

@INPROCEEDINGS{tirumala2022reskin,
  author={Tirumala, Sashank and Weng, Thomas and Seita, Daniel and Kroemer, Oliver and Temel, Zeynep and Held, David},
  booktitle={2022 IEEE/RSJ International Conference on Intelligent Robots and Systems (IROS)},
  title={Learning to Singulate Layers of Cloth using Tactile Feedback},
  year={2022},
  volume={},
  number={},
  pages={7773-7780},
  doi={10.1109/IROS47612.2022.9981341}
}

Robotic manipulation of cloth has applications ranging from fabrics manufacturing to handling blankets and laundry. Cloth manipulation is challenging for robots largely due to their high degrees of freedom, complex dynamics, and severe self-occlusions when in folded or crumpled configurations. Prior work on robotic manipulation of cloth relies primarily on vision sensors alone, which may pose challenges for fine-grained manipulation tasks such as grasping a desired number of cloth layers from a stack of cloth. In this paper, we propose to use tactile sensing for cloth manipulation; we attach a tactile sensor (ReSkin) to one of the two fingertips of a Franka robot and train a classifier to determine whether the robot is grasping a specific number of cloth layers. During test-time experiments, the robot uses this classifier as part of its policy to grasp one or two cloth layers using tactile feedback to determine suitable grasping points. Experimental results over 180 physical trials suggest that the proposed method outperforms baselines that do not use tactile feedback and has a better generalization to unseen fabrics compared to methods that use image classifiers.

@ARTICLE{qi2022dough, 
author={Qi, Carl and Lin, Xingyu and Held, David},
journal={IEEE Robotics and Automation Letters}, 
title={Learning Closed-Loop Dough Manipulation Using a Differentiable Reset Module}, 
year={2022},
volume={7},
number={4},
pages={9857-9864},
doi={10.1109/LRA.2022.3191239}}

Deformable object manipulation has many applications such as cooking and laundry folding in our daily lives. Manipulating elastoplastic objects such as dough is particularly challenging because dough lacks a compact state representation and requires contact-rich interactions. We consider the task of flattening a piece of dough into a specific shape from RGB-D images. While the task is seemingly intuitive for humans, there exist local optima for common approaches such as naive trajectory optimization. We propose a novel trajectory optimizer that optimizes through a differentiable "reset" module, transforming a single-stage, fixed-initialization trajectory into a multistage, multi-initialization trajectory where all stages are optimized jointly. We then train a closed-loop policy on the demonstrations generated by our trajectory optimizer. Our policy receives partial point clouds as input, allowing ease of transfer from simulation to the real world. We show that our policy can perform real-world dough manipulation, flattening a ball of dough into a target shape.

@article{wang2022visual, 
  title={Visual Haptic Reasoning: Estimating Contact Forces by Observing Deformable Object Interactions}, 
  author={Wang, Yufei and Held, David and Erickson, Zackory}, 
  journal={IEEE Robotics and Automation Letters}, 
  volume={7}, 
  number={4}, 
  pages={11426--11433}, 
  year={2022}, 
  publisher={IEEE} 
  }

Robotic manipulation of highly deformable cloth presents a promising opportunity to assist people with several daily tasks, such as washing dishes; folding laundry; or dressing, bathing, and hygiene assistance for individuals with severe motor impairments. In this work, we introduce a formulation that enables a collaborative robot to perform visual haptic reasoning with cloth -- the act of inferring the location and magnitude of applied forces during physical interaction. We present two distinct model representations, trained in physics simulation, that enable haptic reasoning using only visual and robot kinematic observations. We conducted quantitative evaluations of these models in simulation for robot-assisted dressing, bathing, and dish washing tasks, and demonstrate that the trained models can generalize across different tasks with varying interactions, human body sizes, and object shapes. We also present results with a real-world mobile manipulator, which used our simulation-trained models to estimate applied contact forces while performing physically assistive tasks with cloth.

@inproceedings{EisnerZhang2022FLOW,
            title={FlowBot3D: Learning 3D Articulation Flow to Manipulate Articulated Objects},
            author={Eisner*, Ben and Zhang*, Harry and Held,David},
            booktitle={Robotics: Science and Systems (RSS)},
            year={2022}
       }

We explore a novel method to perceive and manipulate 3D articulated objects that generalizes to enable a robot to articulate unseen classes of objects. We propose a vision-based system that learns to predict the potential motions of the parts of a variety of articulated objects to guide downstream motion planning of the system to articulate the objects. To predict the object motions, we train a neural network to output a dense vector field representing the point-wise motion direction of the points in the point cloud under articulation. We then deploy an analytical motion planner based on this vector field to achieve a policy that yields maximum articulation. We train the vision system entirely in simulation, and we demonstrate the capability of our system to generalize to unseen object instances and novel categories in both simulation and the real world, deploying our policy on a Sawyer robot with no finetuning. Results show that our system achieves state-of-the-art performance in both simulated and real-world experiments.

@inproceedings{huang2022medor,
            title={Mesh-based Dynamics Model with Occlusion Reasoning for Cloth Manipulation},
            author={Huang, Zixuan and Lin, Xingyu and Held,David},
            booktitle={Robotics: Science and Systems (RSS)},
            year={2022}
       }

Self-occlusion is challenging for cloth manipulation, as it makes it difficult to estimate the full state of the cloth. Ideally, a robot trying to unfold a crumpled or folded cloth should be able to reason about the cloth's occluded regions. We leverage recent advances in pose estimation for cloth to build a system that uses explicit occlusion reasoning to unfold a crumpled cloth. Specifically, we first learn a model to reconstruct the mesh of the cloth. However, the model will likely have errors due to the complexities of the cloth configurations and due to ambiguities from occlusions. Our main insight is that we can further refine the predicted reconstruction by performing test-time finetuning with self-supervised losses. The obtained reconstructed mesh allows us to use a mesh-based dynamics model for planning while reasoning about occlusions. We evaluate our system both on cloth flattening as well as on cloth canonicalization, in which the objective is to manipulate the cloth into a canonical pose. Our experiments show that our method significantly outperforms prior methods that do not explicitly account for occlusions or perform test-time optimization.

@inproceedings{

lin2022diffskill,
title={DiffSkill: Skill Abstraction from Differentiable Physics for Deformable Object Manipulations with Tools},
author={Xingyu Lin and Zhiao Huang and Yunzhu Li and David Held and Joshua B. Tenenbaum and Chuang Gan},
booktitle={International Conference on Learning Representations},
year={2022},
url={https://openreview.net/forum?id=Kef8cKdHWpP}}

We consider the problem of sequential robotic manipulation of deformable objects using tools. Previous works have shown that differentiable physics simulators provide gradients to the environment state and help trajectory optimization to converge orders of magnitude faster than model-free reinforcement learning algorithms for deformable object manipulations. However, such gradient-based trajectory optimization typically requires access to the full simulator states and can only solve short-horizon, single-skill tasks due to local optima. In this work, we propose a novel framework, named DiffSkill, that uses a differentiable physics simulator for skill abstraction to solve long-horizon deformable object manipulation tasks from sensory observations. In particular, we first obtain short-horizon skills for using each individual tool from a gradient-based optimizer and then learn a neural skill abstractor from the demonstration videos; Finally, we plan over the skills to solve the long-horizon task. We show the advantages of our method in a new set of sequential deformable object manipulation tasks over previous reinforcement learning algorithms and the trajectory optimizer.

@inproceedings{icra2022pouring,

title={Self-supervised Transparent Liquid Segmentation for Robotic Pouring},
author={Gautham Narayan Narasimhan, Kai Zhang, Ben Eisner, Xingyu Lin, David Held},
booktitle={International Conference on Robotics and Automation (ICRA)},
year={2022}}

Liquid state estimation is important for robotics tasks such as pouring; however, estimating the state of transparent liquids is a challenging problem. We propose a novel segmentation pipeline that can segment transparent liquids such as water from a static, RGB image without requiring any manual annotations or heating of the liquid for training. Instead, we use a generative model that is capable of translating images of colored liquids into synthetically generated transparent liquid images, trained only on an unpaired dataset of colored and transparent liquid images. Segmentation labels of colored liquids are obtained automatically using background subtraction. Our experiments show that we are able to accurately predict a segmentation mask for transparent liquids without requiring any manual annotations. We demonstrate the utility of transparent liquid segmentation in a robotic pouring task that controls pouring by perceiving the liquid height in a transparent cup. Accompanying video and supplementary materials can be found on our project page.

@ARTICLE{ral2022ossid,
  author={Gu, Qiao and Okorn, Brian and Held, David},
  journal={IEEE Robotics and Automation Letters}, 
  title={OSSID: Online Self-Supervised Instance Detection by (And For) Pose Estimation}, 
  year={2022},
  volume={7},
  number={2},
  pages={3022-3029},
  doi={10.1109/LRA.2022.3145488}}

Real-time object pose estimation is necessary for many robot manipulation algorithms. However, state-of-the-art methods for object pose estimation are trained for a specific set of objects; these methods thus need to be retrained to estimate the pose of each new object, often requiring tens of GPU-days of training for optimal performance. In this paper, we propose the OSSID framework, leveraging a slow zero-shot pose estimator to self-supervise the training of a fast detection algorithm. This fast detector can then be used to filter the input to the pose estimator, drastically improving its inference speed. We show that this self-supervised training exceeds the performance of existing zero-shot detection methods on two widely used object pose estimation and detection datasets, without requiring any human annotations. Further, we show that the resulting method for pose estimation has a significantly faster inference speed, due to the ability to filter out large parts of the image. Thus, our method for self-supervised online learning of a detector (trained using pseudo-labels from a slow pose estimator) leads to accurate pose estimation at real-time speeds, without requiring human annotations.

@article{mittal2021self,
  title={Self-Supervised Point Cloud Completion via Inpainting},
  author={Mittal, Himangi and Okorn, Brian and Jangid, Arpit and Held, David},
  journal={British Machine Vision Conference (BMVC), 2021},
  year={2021}
}

When navigating in urban environments, many of the objects that need to be tracked and avoided are heavily occluded. Planning and tracking using these partial scans can be challenging. The aim of this work is to learn to complete these partial point clouds, giving us a full understanding of the object's geometry using only partial observations. Previous methods achieve this with the help of complete, ground-truth annotations of the target objects, which are available only for simulated datasets. However, such ground truth is unavailable for real-world LiDAR data. In this work, we present a self-supervised point cloud completion algorithm, PointPnCNet, which is trained only on partial scans without assuming access to complete, ground-truth annotations. Our method achieves this via inpainting. We remove a portion of the input data and train the network to complete the missing region. As it is difficult to determine which regions were occluded in the initial cloud and which were synthetically removed, our network learns to complete the full cloud, including the missing regions in the initial partial cloud. We show that our method outperforms previous unsupervised and weakly-supervised methods on both the synthetic dataset, ShapeNet, and real-world LiDAR dataset, Semantic KITTI.

Benchmarks offer a scientific way to compare algorithms using scientific performance metrics. Good benchmarks have two features: (a) wide audience appeal; (b) easily reproducible. In robotics, there is a tradeoff between reproducibility and broad accessibility. If the benchmark is kept restrictive (fixed hardware, objects), the numbers are reproducible but it becomes niche. On the other hand, benchmark could be just loose set of protocols but the underlying varying setups make it hard to reproduce the results. In this paper, we re-imagine robotics benchmarks – we define a robotics benchmark to be a set of experimental protocols and state of the art algorithmic implementations. These algorithm implementations will provide a way to recreate baseline numbers in a new local robotic setup in less than few hours and hence help provide credible relative rankings between different approaches. These credible local rankings are pooled from several locations to help establish global rankings and SOTA algorithms that work across majority of setups. We introduce RB2 — a benchmark inspired from human SHAP tests. Our benchmark was run across three different labs and reveals several surprising findings.

@article{wang2021sodtgnn,
title={Semi-supervised 3D Object Detection via Temporal Graph Neural Networks},
author={Wang, Jianren and Gang, Haiming and Ancha, Siddharth and Chen, Yi-ting and Held, David},
journal={International Conference on 3D Vision (3DV)},
year={2021}}

3D object detection plays an important role in autonomous driving and other robotics applications. However, these detectors usually require training on large amounts of annotated data that is expensive and time-consuming to collect. Instead, we propose leveraging large amounts of unlabeled point cloud videos by semi-supervised learning of 3D object detectors via temporal graph neural networks. Our insight is that temporal smoothing can create more accurate detection results on unlabeled data, and these smoothed detections can then be used to retrain the detector. We learn to perform this temporal reasoning with a graph neural network, where edges represent the relationship between candidate detections in different time frames.

@inproceedings{lin2021VCD,
title={Learning Visible Connectivity Dynamics for Cloth Smoothing},
author={Lin, Xingyu and Wang, Yufei and Huang, Zixuan and Held, David},
booktitle={Conference on Robot Learning},
year={2021}}

Robotic manipulation of cloth remains challenging for robotics due to the complex dynamics of the cloth, lack of a low-dimensional state representation, and self-occlusions. In contrast to previous model-based approaches that learn a pixel-based dynamics model or a compressed latent vector dynamics, we propose to learn a particle-based dynamics model from a partial point cloud observation. To overcome the challenges of partial observability, we infer which visible points are connected on the underlying cloth mesh. We then learn a dynamics model over this visible connectivity graph. Compared to previous learning-based approaches, our model poses strong inductive bias with its particle based representation for learning the underlying cloth physics; it is invariant to visual features; and the predictions can be more easily visualized. We show that our method greatly outperforms previous state-of-the-art model-based and model-free reinforcement learning methods in simulation. Furthermore, we demonstrate zero-shot sim-to-real transfer where we deploy the model trained in simulation on a Franka arm and show that the model can successfully smooth different types of cloth from crumpled configurations. Videos can be found on our project website.

@inproceedings{weng2021fabricflownet,
 title={FabricFlowNet: Bimanual Cloth Manipulation 
    with a Flow-based Policy},
 author={Weng, Thomas and Bajracharya, Sujay and 
    Wang, Yufei and Agrawal, Khush and Held, David},
 booktitle={Conference on Robot Learning},
 year={2021}
}

We address the problem of goal-directed cloth manipulation, a challenging task due to the deformability of cloth. Our insight is that optical flow, a technique normally used for motion estimation in video, can also provide an effective representation for corresponding cloth poses across observation and goal images. We introduce FabricFlowNet (FFN), a cloth manipulation policy that leverages flow as both an input and as an action representation to improve performance. FabricFlowNet also elegantly switches between dual-arm and single-arm actions based on the desired goal. We show that FabricFlowNet significantly outperforms state-of-the-art model-free and model-based cloth manipulation policies. We also present real-world experiments on a bimanual system, demonstrating effective sim-to-real transfer. Finally, we show that our method generalizes when trained on a single square cloth to other cloth shapes, such as T-shirts and rectangular cloths.

@inproceedings{sikchi2021learning,
title={Learning Off-policy for Online Planning},
author={Sikchi, Harshit and Zhou, Wenxuan and Held, David},
booktitle={Conference on Robot Learning},
year={2021}}

Reinforcement learning (RL) in low-data and risk-sensitive domains requires performant and flexible deployment policies that can readily incorporate constraints during deployment. One such class of policies are the semi-parametric H-step lookahead policies, which select actions using trajectory optimization over a dynamics model for a fixed horizon with a terminal value function. In this work, we investigate a novel instantiation of H-step lookahead with a learned model and a terminal value function learned by a model-free off-policy algorithm, named Learning Off-Policy with Online Planning (LOOP). We provide a theoretical analysis of this method, suggesting a tradeoff between model errors and value function errors and empirically demonstrate this tradeoff to be beneficial in deep reinforcement learning. Furthermore, we identify the "Actor Divergence" issue in this framework and propose Actor Regularized Control (ARC), a modified trajectory optimization procedure. We evaluate our method on a set of robotic tasks for Offline and Online RL and demonstrate improved performance. We also show the flexibility of LOOP to incorporate safety constraints during deployment with a set of navigation environments. We demonstrate that LOOP is a desirable framework for robotics applications based on its strong performance in various important RL settings.

@INPROCEEDINGS{Ancha-RSS-21,
    AUTHOR    = {Siddharth Ancha AND Gaurav Pathak AND Srinivasa G. Narasimhan AND David Held},
    TITLE     = {Active Safety Envelopes using Light Curtains with Probabilistic Guarantees},
    BOOKTITLE = {Proceedings of Robotics: Science and Systems},
    YEAR      = {2021},
    MONTH     = {July}
}

To safely navigate unknown environments, robots must accurately perceive dynamic obstacles. Instead of directly measuring the scene depth with a LiDAR sensor, we explore the use of a much cheaper and higher resolution sensor:

@inproceedings{okorn2021zephyr,
                    title={Zephyr: Zero-shot pose hypothesis rating},
                    author={Okorn, Brian and Gu, Qiao and Hebert, Martial and Held, David},
                    booktitle={2021 IEEE International Conference on Robotics and Automation (ICRA)},
                    pages={14141--14148},
                    year={2021},
                    organization={IEEE}
                  }

Pose estimation is a basic module in many robot manipulation pipelines. Estimating the pose of objects in the environment can be useful for grasping, motion planning, or manipulation. However, current state-of-the-art methods for pose estimation either rely on large annotated training sets or simulated data. Further, the long training times for these methods prohibit quick interaction with novel objects. To address these issues, we introduce a novel method for zero-shot object pose estimation in clutter. Our approach uses a hypothesis generation and scoring framework, with a focus on learning a scoring function that generalizes to objects not used for training. We achieve zero-shot generalization by rating hypotheses as a function of unordered point differences. We evaluate our method on challenging datasets with both textured and untextured objects in cluttered scenes and demonstrate that our method significantly outperforms previous methods on this task. We also demonstrate how our system can be used by quickly scanning and building a model of a novel object, which can immediately be used by our method for pose estimation. Our work allows users to estimate the pose of novel objects without requiring any retraining.

@inproceedings{cvpr2021raajexploiting,
    title     = {Exploiting & Refining Depth Distributions with Triangulation Light Curtains},
    author    = {Yaadhav Raaj, Siddharth Ancha, Robert Tamburo, David Held, Srinivasa Narasimhan},
    booktitle = {Proceedings of the IEEE/CVF Conference on Computer Vision and Pattern Recognition (CVPR)},
    year      = {2021}
}

Active sensing through the use of Adaptive Depth Sensors is a nascent field, with potential in areas such as Advanced driver-assistance systems (ADAS). They do however require dynamically driving a laser / light-source to a specific location to capture information, with one such class of sensor being the Triangulation Light Curtains (LC). In this work, we introduce a novel approach that exploits prior depth distributions from RGB cameras to drive a Light Curtain's laser line to regions of uncertainty to get new measurements. These measurements are utilized such that depth uncertainty is reduced and errors get corrected recursively. We show real-world experiments that validate our approach in outdoor and driving settings, and demonstrate qualitative and quantitative improvements in depth RMSE when RGB cameras are used in tandem with a Light Curtain.

@inproceedings{cvpr2021husafe,
                    title={Safe Local Motion Planning with Self-Supervised Freespace Forecasting},
                    author={Peiyun Hu, Aaron Huang, John Dolan, David Held, Deva Ramanan},
                    booktitle={Proceedings of the IEEE/CVF Conference on Computer Vision and Pattern Recognition (CVPR)},
                    year={2021}}

Safe local motion planning for autonomous driving in dynamic environments requires forecasting how the scene evolves. Practical autonomy stacks adopt a semantic object-centric representation of a dynamic scene and build object detection, tracking, and prediction modules to solve forecasting. However, training these modules comes at an enormous human cost of manually annotated objects across frames. In this work, we explore future freespace as an alternative representation to support motion planning. Our key intuition is that it is important to avoid straying into occupied space regardless of what is occupying it. Importantly, computing ground-truth future freespace is annotation-free. First, we explore freespace forecasting as a self-supervised learning task. We then demonstrate how to use forecasted freespace to identify collision-prone plans from off-the-shelf motion planners. Finally, we propose future freespace as an additional source of annotation-free supervision. We demonstrate how to integrate such supervision into the learning process of learning-based planners. Experimental results on nuScenes and CARLA suggest both approaches lead to significant reduction in collision rates.

@inproceedings{corl2020softgym,
title={SoftGym: Benchmarking Deep Reinforcement Learning for Deformable Object Manipulation},
author={Lin, Xingyu and Wang, Yufei and Olkin, Jake and Held, David},
booktitle={Conference on Robot Learning},
year={2020}}

Manipulating deformable objects has long been a challenge in robotics due to its high dimensional state representation and complex dynamics. Recent success in deep reinforcement learning provides a promising direction for learning to manipulate deformable objects with data driven methods. However, existing reinforcement learning benchmarks only cover tasks with direct state observability and simple low-dimensional dynamics or with relatively simple image-based environments, such as those with rigid objects. In this paper, we present SoftGym, a set of open-source simulated benchmarks for manipulating deformable objects, with a standard OpenAI Gym API and a Python interface for creating new environments. Our benchmark will enable reproducible research in this important area. Further, we evaluate a variety of algorithms on these tasks and highlight challenges for reinforcement learning algorithms, including dealing with a state representation that has a high intrinsic dimensionality and is partially observable. The experiments and analysis indicate the strengths and limitations of existing methods in the context of deformable object manipulation that can help point the way forward for future methods development. Code and videos of the learned policies can be found on our project website.

@inproceedings{corl2020roll,
title={ROLL: Visual Self-Supervised Reinforcement Learning with Object Reasoning},
author={Wang, Yufei and Narasimhan Gautham and Lin, Xingyu and Okorn, Brian and Held, David},
booktitle={Conference on Robot Learning},
year={2020}
}

Current image-based reinforcement learning (RL) algorithms typically operate on the whole image without performing object-level reasoning. This leads to inefficient goal sampling and ineffective reward functions. In this paper, we improve upon previous visual self-supervised RL by incorporating object-level reasoning and occlusion reasoning. Specifically, we use unknown object segmentation to ignore distractors in the scene for better reward computation and goal generation; we further enable occlusion reasoning by employing a novel auxiliary loss and training scheme. We demonstrate that our proposed algorithm, ROLL (Reinforcement learning with Object Level Learning), learns dramatically faster and achieves better final performance compared with previous methods in several simulated visual control tasks. Project video and code are available at https://sites.google.com/andrew.cmu.edu/roll.

@inproceedings{PLAS_corl2020,

title={PLAS: Latent Action Space for Offline Reinforcement Learning},
author={Zhou, Wenxuan and Bajracharya, Sujay and Held, David},
booktitle={Conference on Robot Learning},
year={2020}
}

The goal of offline reinforcement learning is to learn a policy from a fixed dataset, without further interactions with the environment. This setting will be an increasingly more important paradigm for real-world applications of reinforcement learning such as robotics, in which data collection is slow and potentially dangerous. Existing off-policy algorithms have limited performance on static datasets due to extrapolation errors from out-of-distribution actions. This leads to the challenge of constraining the policy to select actions within the support of the dataset during training. We propose to simply learn the Policy in the Latent Action Space (PLAS) such that this requirement is naturally satisfied. We evaluate our method on continuous control benchmarks in simulation and a deformable object manipulation task with a physical robot. We demonstrate that our method provides competitive performance consistently across various continuous control tasks and different types of datasets, outperforming existing offline reinforcement learning methods with explicit constraints.

@inproceedings{xia20panonet3d,
    author = "Chen, Xia 
    and Wang, Jianren 
    and Held, David 
    and Hebert, Martial",
    title = "PanoNet3D: Combining Semantic and Geometric Understanding for LiDARPoint Cloud Detection",
    booktitle = "3DV",
    year = "2020"
}

Visual data in autonomous driving perception, such as camera image and LiDAR point cloud, can be interpreted as a mixture of two aspects: semantic feature and geometric structure. Semantics come from the appearance and context of objects to the sensor, while geometric structure is the actual 3D shape of point clouds. Most detectors on LiDAR point clouds focus only on analyzing the geometric structure of objects in real 3D space. Unlike previous works, we propose to learn both semantic feature and geometric structure via a unified multi-view framework. Our method exploits the nature of LiDAR scans -- 2D range images, and applies well-studied 2D convolutions to extract semantic features. By fusing semantic and geometric features, our method outperforms state-of-the-art approaches in all categories by a large margin. The methodology of combining semantic and geometric features provides a unique perspective of looking at the problems in real-world 3D point cloud detection.

@InProceedings{Ancha_2020_ECCV,
  author="Ancha, Siddharth
  and Raaj, Yaadhav
  and Hu, Peiyun
  and Narasimhan, Srinivasa G.
  and Held, David",
  editor="Vedaldi, Andrea
  and Bischof, Horst
  and Brox, Thomas
  and Frahm, Jan-Michael",
  title="Active Perception Using Light Curtains for Autonomous Driving",
  booktitle="Computer Vision -- ECCV 2020",
  year="2020",
  publisher="Springer International Publishing",
  address="Cham",
  pages="751--766",
  isbn="978-3-030-58558-7"
}

Most real-world 3D sensors such as LiDARs perform fixed scans of the entire environment, while being decoupled from the recognition system that processes the sensor data. In this work, we propose a method for 3D object recognition using light curtains, a resource-efficient controllable sensor that measures depth at user-specified locations in the environment. Crucially, we propose using prediction uncertainty of a deep learning based 3D point cloud detector to guide active perception. Given a neural network’s uncertainty, we derive an optimization objective to place light curtains using the principle of maximizing information gain. Then, we develop a novel and efficient optimization algorithm to maximize this objective by encoding the physical constraints of the device into a constraint graph and optimizing with dynamic programming. We show how a 3D detector can be trained to detect objects in a scene by sequentially placing uncertainty-guided light curtains to successively improve detection accuracy.

@InProceedings{Qian_2020_IROS,
 author={Qian, Jianing and Weng, Thomas and Zhang, Luxin and Okorn, Brian and Held, David}, booktitle={2020 IEEE/RSJ International Conference on Intelligent Robots and Systems (IROS)}, title={Cloth Region Segmentation for Robust Grasp Selection}, year={2020}, volume={}, number={}, pages={9553-9560}, doi={10.1109/IROS45743.2020.9341121}}

Cloth detection and manipulation is a common task in domestic and industrial settings, yet such tasks remain a challenge for robots due to cloth deformability. Furthermore, in many cloth-related tasks like laundry folding and bed making, it is crucial to manipulate specific regions like edges and corners, as opposed to folds. In this work, we focus on the problem of segmenting and grasping these key regions. Our approach trains a network to segment the edges and corners of a cloth from a depth image, distinguishing such regions from wrinkles or folds. We also provide a novel algorithm for estimating the grasp location, direction, and directional uncertainty from the segmentation. We demonstrate our method on a real robot system and show that it outperforms baseline methods on grasping success. Video and other supplementary materials are available at:

@inproceedings{jianren20s3da,
    author = "Wang, Jianren 
    and Ancha, Siddharth 
    and Chen, Yi-Ting 
    and Held, David",
    title = "Uncertainty-aware Self-supervised 3D Data Association",
    booktitle = "IROS",
    year = "2020"
}

3D object trackers usually require training on large amounts of annotated data that is expensive and time-consuming to collect. Instead, we propose leveraging vast unlabeled datasets by self-supervised metric learning of 3D object trackers, with a focus on data association. Large scale annotations for unlabeled data are cheaply obtained by automatic object detection and association across frames. We show how these self-supervised annotations can be used in a principled manner to learn point-cloud embeddings that are effective for 3D tracking. We estimate and incorporate uncertainty in self-supervised tracking to learn more robust embeddings, without needing any labeled data. We design embeddings to differentiate objects across frames, and learn them using uncertainty-aware self-supervised training. Finally, we demonstrate their ability to perform accurate data association across frames, towards effective and accurate 3D tracking.

@article{Weng2020_AB3DMOT, 
author = {Weng, Xinshuo and Wang, Jianren and Held, David and Kitani, Kris}, 
journal = {IROS}, 
title = {3D Multi-Object Tracking: A Baseline and New Evaluation Metrics}, 
year = {2020} 
}

3D multi-object tracking (MOT) is an essential component for many applications such as autonomous driving and assistive robotics. Recent work on 3D MOT focuses on developing accurate systems giving less attention to practical considerations such as computational cost and system complexity. In contrast, this work proposes a simple real-time 3D MOT system. Our system first obtains 3D detections from a LiDAR point cloud. Then, a straightforward combination of a 3D Kalman filter and the Hungarian algorithm is used for state estimation and data association. Additionally, 3D MOT datasets such as KITTI evaluate MOT methods in the 2D space and standardized 3D MOT evaluation tools are missing for a fair comparison of 3D MOT methods. Therefore, we propose a new 3D MOT evaluation tool along with three new metrics to comprehensively evaluate 3D MOT methods. We show that, although our system employs a combination of classical MOT modules, we achieve state-of-the-art 3D MOT performance on two 3D MOT benchmarks (KITTI and nuScenes). Surprisingly, although our system does not use any 2D data as inputs, we achieve competitive performance on the KITTI 2D MOT leaderboard. Our proposed system runs at a rate of 207.4 FPS on the KITTI dataset, achieving the fastest speed among all modern MOT systems.

@InProceedings{Mittal_2020_CVPR,
author = {Mittal, Himangi and Okorn, Brian and Held, David},
title = {Just Go With the Flow: Self-Supervised Scene Flow Estimation},
booktitle = {Proceedings of the IEEE/CVF Conference on Computer Vision and Pattern Recognition (CVPR)},
month = {June},
year = {2020}
}

When interacting with highly dynamic environments, scene flow allows autonomous systems to reason about the non-rigid motion of multiple independent objects. This is of particular interest in the field of autonomous driving, in which many cars, people, bicycles, and other objects need to be accurately tracked. Current state-of-the-art methods require annotated scene flow data from autonomous driving scenes to train scene flow networks with supervised learning. As an alternative, we present a method of training scene flow that uses two self-supervised losses, based on nearest neighbors and cycle consistency. These self-supervised losses allow us to train our method on large unlabeled autonomous driving datasets; the resulting method matches current state-of-the-art supervised performance using no real world annotations and exceeds state-of-the-art performance when combining our self-supervised approach with supervised learning on a smaller labeled dataset.

@ARTICLE{9001238,
author={Thomas Weng and Amith Pallankize and Yimin Tang and Oliver Kroemer and David Held},
journal={IEEE Robotics and Automation Letters},
title={Multi-Modal Transfer Learning for Grasping Transparent and Specular Objects},
year={2020},
volume={5},
number={3},
pages={3791-3798},
doi={10.1109/LRA.2020.2974686}}

State-of-the-art object grasping methods rely on depth sensing to plan robust grasps, but commercially available depth sensors fail to detect transparent and specular objects. To improve grasping performance on such objects, we introduce a method for learning a multi-modal perception model by bootstrapping from an existing uni-modal model. This transfer learning approach requires only a pre-existing uni-modal grasping model and paired multi-modal image data for training, foregoing the need for ground-truth grasp success labels nor real grasp attempts. Our experiments demonstrate that our approach is able to reliably grasp transparent and reflective objects. Video and supplementary material are available at

@inproceedings{FlowVerify2019CoRL,
  author    = {Siddharth Ancha and
               Junyu Nan and
               David Held},
  editor    = {Leslie Pack Kaelbling and
               Danica Kragic and
               Komei Sugiura},
  title     = {Combining Deep Learning and Verification for Precise Object Instance
               Detection},
  booktitle = {3rd Annual Conference on Robot Learning, CoRL 2019, Osaka, Japan,
               October 30 - November 1, 2019, Proceedings},
  series    = {Proceedings of Machine Learning Research},
  volume    = {100},
  pages     = {122--141},
  publisher = ,
  year      = {2019},
  url       = {http://proceedings.mlr.press/v100/ancha20a.html},
  timestamp = {Mon, 25 May 2020 15:01:26 +0200},
  biburl    = {https://dblp.org/rec/conf/corl/AnchaNH19.bib},
  bibsource = {dblp computer science bibliography, https://dblp.org}
}

Deep learning object detectors often return false positives with very high confidence. Although they optimize generic detection performance, such as mean average precision (mAP), they are not designed for reliability. For a reliable detection system, if a high confidence detection is made, we would want high certainty that the object has indeed been detected. To achieve this, we have developed a set of verification tests which a proposed detection must pass to be accepted. We develop a theoretical framework which proves that, under certain assumptions, our verification tests will not accept any false positives. Based on an approximation to this framework, we present a practical detection system that can verify, with high precision, whether each detection of a machine-learning based object detector is correct. We show that these tests can improve the overall accuracy of a base detector and that accepted examples are highly likely to be correct. This allows the detector to operate in a high precision regime and can thus be used for robotic perception systems as a reliable instance detection method.