Author name cluster

Robert Platt 0001

Possible papers associated with this exact author name in Arrow. This page groups case-insensitive exact name matches and is not a full identity disambiguation profile.

35 papers

1 author row

ICML Conference 2025 Conference Paper

Hierarchical Equivariant Policy via Frame Transfer

Haibo Zhao 0001
Dian Wang 0001
Yizhe Zhu
Xupeng Zhu
Owen Lewis Howell
Linfeng Zhao
Yaoyao Qian
Robin Walters 0001

Recent advances in hierarchical policy learning highlight the advantages of decomposing systems into high-level and low-level agents, enabling efficient long-horizon reasoning and precise fine-grained control. However, the interface between these hierarchy levels remains underexplored, and existing hierarchical methods often ignore domain symmetry, resulting in the need for extensive demonstrations to achieve robust performance. To address these issues, we propose Hierarchical Equivariant Policy (HEP), a novel hierarchical policy framework. We propose a frame transfer interface for hierarchical policy learning, which uses the high-level agent’s output as a coordinate frame for the low-level agent, providing a strong inductive bias while retaining flexibility. Additionally, we integrate domain symmetries into both levels and theoretically demonstrate the system’s overall equivariance. HEP achieves state-of-the-art performance in complex robotic manipulation tasks, demonstrating significant improvements in both simulation and real-world settings.

ICRA Conference 2025 Conference Paper

Match Policy: A Simple Pipeline from Point Cloud Registration to Manipulation Policies

Haojie Huang 0001
Haotian Liu
Dian Wang 0001
Robin Walters 0001
Robert Platt 0001

Many manipulation tasks require the robot to rearrange objects relative to one another. Such tasks can be described as a sequence of relative poses between parts of a set of rigid bodies. In this work, we propose Match Policy, a simple but novel pipeline for solving high-precision pick and place tasks. Instead of predicting actions directly, our method registers the pick and place targets to the stored demonstrations. This transfers action inference into a point cloud registration task and enables us to realize nontrivial manipulation policies without any training. Match Policy is designed to solve high-precision tasks with a key-frame setting. By leveraging the geometric interaction and the symmetries of the task, it achieves extremely high sample efficiency and generalizability to unseen configurations. We demonstrate its state-of-the-art performance across various tasks on RLbench benchmark compared with several strong baselines and test it on a real robot with six tasks. Videos and code are available on https://haojhuang.github.io/match_page/.

ICRA Conference 2025 Conference Paper

On-Robot Reinforcement Learning with Goal-Contrastive Rewards

Ondrej Biza
Thomas Weng
Lingfeng Sun
Karl Schmeckpeper
Tarik Kelestemur
Yecheng Jason Ma 0001
Robert Platt 0001
Jan-Willem van de Meent

Reinforcement Learning (RL) has the potential to enable robots to learn from their own actions in the real world. Unfortunately, RL can be prohibitively expensive, in terms of on-robot runtime, due to inefficient exploration when learning from a sparse reward signal. Designing dense reward functions is labour-intensive and requires domain expertise. In our work, we propose Goal-Contrastive Rewards (GCR), a dense reward function learning method that can be trained on passive video demonstrations. By using videos without actions, our method is easier to scale, as we can use arbitrary videos. GCR combines two loss functions, an implicit value loss function that models how the reward increases when traversing a successful trajectory, and a goal-contrastive loss that discriminates between successful and failed trajectories. We perform experiments in simulated manipulation environments across RoboMimic and MimicGen tasks, as well as in the real world using a Franka arm and a Spot quadruped. We find that GCR leads to a more-sample efficient RL, enabling model-free RL to solve about twice as many tasks as our baseline reward learning methods. We also demonstrate positive cross-embodiment transfer from videos of people and of other robots performing a task. Website: https://gcr-robot.github.io/.

ICLR Conference 2024 Conference Paper

Fourier Transporter: Bi-Equivariant Robotic Manipulation in 3D

Haojie Huang 0001
Owen Lewis Howell
Dian Wang 0001
Xupeng Zhu
Robert Platt 0001
Robin Walters 0001

Many complex robotic manipulation tasks can be decomposed as a sequence of pick and place actions. Training a robotic agent to learn this sequence over many different starting conditions typically requires many iterations or demonstrations, especially in 3D environments. In this work, we propose Fourier Transporter ($\text{FourTran}$), which leverages the two-fold $\mathrm{SE}(d)\times\mathrm{SE}(d)$ symmetry in the pick-place problem to achieve much higher sample efficiency. $\text{FourTran}$ is an open-loop behavior cloning method trained using expert demonstrations to predict pick-place actions on new configurations. $\text{FourTran}$ is constrained by the symmetries of the pick and place actions independently. Our method utilizes a fiber space Fourier transformation that allows for memory-efficient computation. Tests on the RLbench benchmark achieve state-of-the-art results across various tasks.

ICRA Conference 2024 Conference Paper

Symmetric Models for Visual Force Policy Learning

Colin Kohler
Anuj Shrivatsav Srikanth
Eshan Arora
Robert Platt 0001

While it is generally acknowledged that force feedback is beneficial to robotic control, applications of policy learning to robotic manipulation typically only leverage visual feedback. Recently, symmetric neural models have been used to significantly improve the sample efficiency and performance of policy learning across a variety of robotic manipulation domains. This paper explores an application of symmetric policy learning to visual-force problems. We present Symmetric Visual Force Learning (SVFL), a novel method for robotic control which leverages visual and force feedback. We demonstrate that SVFL can significantly outperform state of the art baselines for visual force learning and report several interesting empirical findings related to the utility of learning force feedback control policies in both general manipulation tasks and scenarios with low visual acuity.

ICRA Conference 2023 Conference Paper

Edge Grasp Network: A Graph-Based SE(3)-invariant Approach to Grasp Detection

Haojie Huang 0001
Dian Wang 0001
Xupeng Zhu
Robin Walters 0001
Robert Platt 0001

Given point cloud input, the problem of 6-DoF grasp pose detection is to identify a set of hand poses in SE(3) from which an object can be successfully grasped. This important problem has many practical applications. Here we propose a novel method and neural network model that enables better grasp success rates relative to what is available in the literature. The method takes standard point cloud data as input and works well with single-view point clouds observed from arbitrary viewing directions. Videos and code are available at https://haojhuang.github.io/edge_grasp_page/.

ICLR Conference 2023 Conference Paper

Image to Sphere: Learning Equivariant Features for Efficient Pose Prediction

David Klee
Ondrej Biza
Robert Platt 0001
Robin Walters 0001

Predicting the pose of objects from a single image is an important but difficult computer vision problem. Methods that predict a single point estimate do not predict the pose of objects with symmetries well and cannot represent uncertainty. Alternatively, some works predict a distribution over orientations in $\mathrm{SO}(3)$. However, training such models can be computation- and sample-inefficient. Instead, we propose a novel mapping of features from the image domain to the 3D rotation manifold. Our method then leverages $\mathrm{SO}(3)$ equivariant layers, which are more sample efficient, and outputs a distribution over rotations that can be sampled at arbitrary resolution. We demonstrate the effectiveness of our method at object orientation prediction, and achieve state-of-the-art performance on the popular PASCAL3D+ dataset. Moreover, we show that our method can model complex object symmetries, without any modifications to the parameters or loss function. Code is available at \url{https://dmklee.github.io/image2sphere}.

ICRA Conference 2023 Conference Paper

SEIL: Simulation-augmented Equivariant Imitation Learning

Mingxi Jia
Dian Wang 0001
Guanang Su
David Klee
Xupeng Zhu
Robin Walters 0001
Robert Platt 0001

In robotic manipulation, acquiring samples is extremely expensive because it often requires interacting with the real world. Traditional image-level data augmentation has shown the potential to improve sample efficiency in various machine learning tasks. However, image-level data augmentation is insufficient for an imitation learning agent to learn good manipulation policies in a reasonable amount of demonstrations. We propose Simulation-augmented Equivariant Imitation Learning (SEIL), a method that combines a novel data augmentation strategy of supplementing expert trajectories with simulated transitions and an equivariant model that exploits the O(2) symmetry in robotic manipulation. Experimental evaluations demonstrate that our method can learn non-trivial manipulation tasks within ten demonstrations and outperform the baselines by a significant margin.

ICLR Conference 2023 Conference Paper

The Surprising Effectiveness of Equivariant Models in Domains with Latent Symmetry

Dian Wang 0001
Jung Yeon Park
Neel Sortur
Lawson L. S. Wong
Robin Walters 0001
Robert Platt 0001

Extensive work has demonstrated that equivariant neural networks can significantly improve sample efficiency and generalization by enforcing an inductive bias in the network architecture. These applications typically assume that the domain symmetry is fully described by explicit transformations of the model inputs and outputs. However, many real-life applications contain only latent or partial symmetries which cannot be easily described by simple transformations of the input. In these cases, it is necessary to learn symmetry in the environment instead of imposing it mathematically on the network architecture. We discover, surprisingly, that imposing equivariance constraints that do not exactly match the domain symmetry is very helpful in learning the true symmetry in the environment. We differentiate between extrinsic and incorrect symmetry constraints and show that while imposing incorrect symmetry can impede the model's performance, imposing extrinsic symmetry can actually improve performance. We demonstrate that an equivariant model can significantly outperform non-equivariant methods on domains with latent symmetries both in supervised learning and in reinforcement learning for robotic manipulation and control problems.

ICLR Conference 2022 Conference Paper

$\mathrm{SO}(2)$-Equivariant Reinforcement Learning

Dian Wang 0001
Robin Walters 0001
Robert Platt 0001

Equivariant neural networks enforce symmetry within the structure of their convolutional layers, resulting in a substantial improvement in sample efficiency when learning an equivariant or invariant function. Such models are applicable to robotic manipulation learning which can often be formulated as a rotationally symmetric problem. This paper studies equivariant model architectures in the context of $Q$-learning and actor-critic reinforcement learning. We identify equivariant and invariant characteristics of the optimal $Q$-function and the optimal policy and propose equivariant DQN and SAC algorithms that leverage this structure. We present experiments that demonstrate that our equivariant versions of DQN and SAC can be significantly more sample efficient than competing algorithms on an important class of robotic manipulation problems.

IROS Conference 2022 Conference Paper

Graph-Structured Policy Learning for Multi-Goal Manipulation Tasks

David Klee
Ondrej Biza
Robert Platt 0001

Multi-goal policy learning for robotic manipu-lation is challenging. Prior successes have used state-based representations of the objects or provided demonstration data to facilitate learning. In this paper, by hand-coding a high-level discrete representation of the domain, we show that policies to reach dozens of goals can be learned with a single network using Q-learning from pixels. The agent focuses learning on simpler, local policies which are sequenced together by planning in the abstract space. We compare our method against standard multi-goal RL baselines, as well as other methods that leverage the discrete representation, on a challenging block construction domain. We find that our method can build more than a hundred different block structures, and demonstrate forward transfer to structures with novel objects. Lastly, we deploy the policy learned in simulation on a real robot.

IROS Conference 2021 Conference Paper

Efficient and Accurate Candidate Generation for Grasp Pose Detection in SE(3)

Andreas ten Pas
Colin Keil
Robert Platt 0001

Grasp detection of novel objects in unstructured environments is a key capability in robotic manipulation. For 2D grasp detection problems where grasps are assumed to lie in the plane, it is common to design a fully convolutional neural network that predicts grasps over an entire image in one step. However, this is not possible for grasp pose detection where grasp poses are assumed to exist in SE(3). In this case, it is common to approach the problem in two steps: grasp candidate generation and candidate classification [1], [2], [3], [4]. Since grasp candidate classification is typically expensive, the problem becomes one of efficiently identifying high quality candidate grasps. This paper proposes a new grasp candidate generation method that significantly outperforms major 3D grasp detection baselines. Supplementary material is available at this website.

IROS Conference 2021 Conference Paper

Policy Learning for Visually Conditioned Tactile Manipulation

Tarik Kelestemur
Taskin Padir
Robert Platt 0001

Recent work on robot learning with visual observations has shown great success in solving many manipulation tasks. While visual observations contain rich information about the environment and the robot, they can be unreliable in the presence of visual noise or occlusions. In these cases, we can leverage tactile observations generated by the interaction between the robot and the environment. In this paper, we propose a framework for learning manipulation policies that fuse visual and tactile feedback. The control problems considered in this work are to localize a gripper with respect to the environment image and navigate to desired states. Our method uses a learned Bayes filter to estimate the state of a gripper by conditioning the tactile observations on the environment image. We use deep reinforcement learning for solving the localization and navigation problems provided with the belief of the gripper’s state and the environment image. We compare our method against two baselines where the agent uses tactile observation directly with a recurrent neural network or uses a point estimate of the state instead of the full belief state. We also transfer the policies to the real world and validate them on a physical robot.

IROS Conference 2020 Conference Paper

Learning Bayes Filter Models for Tactile Localization

Tarik Kelestemur
Colin Keil
John P. Whitney
Robert Platt 0001
Taskin Padir

Localizing and tracking the pose of robotic grippers are necessary skills for manipulation tasks. However, the manipulators with imprecise kinematic models (e. g. low-cost arms) or manipulators with unknown world coordinates (e. g. poor camera-arm calibration) cannot locate the gripper with respect to the world. In these circumstances, we can leverage tactile feedback between the gripper and the environment. In this paper, we present learnable Bayes filter models that can localize robotic grippers using tactile feedback. We propose a novel observation model that conditions the tactile feedback on visual maps of the environment along with a motion model to recursively estimate the gripper's location. Our models are trained in simulation with self-supervision and transferred to the real world. Our method is evaluated on a tabletop localization task in which the gripper interacts with objects. We report results in simulation and on a real robot, generalizing over different sizes, shapes, and configurations of the objects.

ICRA Conference 2018 Conference Paper

Pick and Place Without Geometric Object Models

Marcus Gualtieri
Andreas ten Pas
Robert Platt 0001

We propose a novel formulation of robotic pick and place as a deep reinforcement learning (RL) problem. Whereas most deep RL approaches to robotic manipulation frame the problem in terms of low level states and actions, we propose a more abstract formulation. In this formulation, actions are target reach poses for the hand and states are a history of such reaches. We show this approach can solve a challenging class of pick-place and regrasping problems where the exact geometry of the objects to be handled is unknown. The only information our method requires is: 1) the sensor perception available to the robot at test time; 2) prior knowledge of the general class of objects for which the system was trained. We evaluate our method using objects belonging to two different categories, mugs and bottles, both in simulation and on real hardware. Results show a major improvement relative to a shape primitives baseline.

ICRA Conference 2017 Conference Paper

Open world assistive grasping using laser selection

Marcus Gualtieri
James Kuczynski
Abraham M. Shultz
Andreas ten Pas
Robert Platt 0001
Holly A. Yanco

Many people with motor disabilities are unable to complete activities of daily living (ADLs) without assistance. This paper describes a complete robotic system developed to provide mobile grasping assistance for ADLs. The system is comprised of a robot arm from a Rethink Robotics Baxter robot mounted to an assistive mobility device, a control system for that arm, and a user interface with a variety of access methods for selecting desired objects. The system uses grasp detection to allow previously unseen objects to be picked up by the system. The grasp detection algorithms also allow for objects to be grasped in cluttered environments. We evaluate our system in a number of experiments on a large variety of objects. Overall, we achieve an object selection success rate of 88% and a grasp detection success rate of 90% in a non-mobile scenario, and success rates of 89% and 72% in a mobile scenario.

IROS Conference 2017 Conference Paper

Viewpoint selection for grasp detection

Marcus Gualtieri
Robert Platt 0001

In grasp detection, the robot estimates the position and orientation of potential grasp configurations directly from sensor data. This paper explores the relationship between viewpoint and grasp detection performance. Specifically, we consider the scenario where the approximate position and orientation of a desired grasp is known in advance and we want to select a viewpoint that will enable a grasp detection algorithm to localize it more precisely and with higher confidence. Our main findings are that the right viewpoint can dramatically increase the number of detected grasps and the classification accuracy of the top-n detections. We use this insight to create a viewpoint selection algorithm and compare it against a random viewpoint selection strategy and a strategy that views the desired grasp head-on. We find that the head-on strategy and our proposed viewpoint selection strategy can improve grasp success rates on a real robot by 8% and 4%, respectively. Moreover, we find that the combination of the two methods can improve grasp success rates by as much as 12%.

IROS Conference 2016 Conference Paper

High precision grasp pose detection in dense clutter

Marcus Gualtieri
Andreas ten Pas
Kate Saenko
Robert Platt 0001

This paper considers the problem of grasp pose detection in point clouds. We follow a general algorithmic structure that first generates a large set of 6-DOF grasp candidates and then classifies each of them as a good or a bad grasp. Our focus in this paper is on improving the second step by using depth sensor scans from large online datasets to train a convolutional neural network. We propose two new representations of grasp candidates, and we quantify the effect of using prior knowledge of two forms: instance or category knowledge of the object to be grasped, and pretraining the network on simulated depth data obtained from idealized CAD models. Our analysis shows that a more informative grasp candidate representation as well as pretraining and prior knowledge significantly improve grasp detection. We evaluate our approach on a Baxter Research Robot and demonstrate an average grasp success rate of 93% in dense clutter. This is a 20% improvement compared to our prior work.

IROS Conference 2015 Conference Paper

The Baxter Easyhand: A robot hand that costs $150 US in parts

Giulia Franchi
Andreas ten Pas
Robert Platt 0001
Stefano Panzieri

This paper introduces and characterizes the Baxter Easyhand, a new 3D printed hand derived from the Yale T42 hand [5], [10], but designed specifically to be mounted on the Baxter robot from Rethink robotics. Because this hand is designed specifically for Baxter, we are able to make some important simplifications in the design relative to other 3D printed hands. In particular, the Easyhand is smaller than most other 3D printed hands and it is powered by the native Baxter gripper actuator. As a result, our hand is cheaper, lighter, and easier to interface with than other robot hands available for Baxter. This paper details the design of the hand and its mechanical characteristics and reports results from experiments that characterize its grasping performance.

IROS Conference 2014 Conference Paper

Localization and manipulation of small parts using GelSight tactile sensing

Rui Li 0017
Robert Platt 0001
Wenzhen Yuan 0001
Andreas ten Pas
Nathan Roscup
Mandayam A. Srinivasan
Edward H. Adelson

Robust manipulation and insertion of small parts can be challenging because of the small tolerances typically involved. The key to robust control of these kinds of manipulation interactions is accurate tracking and control of the parts involved. Typically, this is accomplished using visual servoing or force-based control. However, these approaches have drawbacks. Instead, we propose a new approach that uses tactile sensing to accurately localize the pose of a part grasped in the robot hand. Using a feature-based matching technique in conjunction with a newly developed tactile sensing technology known as GelSight that has much higher resolution than competing methods, we synthesize high-resolution height maps of object surfaces. As a result of these high-resolution tactile maps, we are able to localize small parts held in a robot hand very accurately. We quantify localization accuracy in benchtop experiments and experimentally demonstrate the practicality of the approach in the context of a small parts insertion problem.

ICRA Conference 2013 Conference Paper

Optimal sampling-based planning for linear-quadratic kinodynamic systems

Gustavo Nunes Goretkin
Alejandro Perez
Robert Platt 0001
George Konidaris 0001

We propose a new method for applying RRT* to kinodynamic motion planning problems by using finite-horizon linear quadratic regulation (LQR) to measure cost and to extend the tree. First, we introduce the method in the context of arbitrary affine dynamical systems with quadratic costs. For these systems, the algorithm is shown to converge to optimal solutions almost surely. Second, we extend the algorithm to non-linear systems with non-quadratic costs, and demonstrate its performance experimentally.

IROS Conference 2013 Conference Paper

Voxel planes: Rapid visualization and meshification of point cloud ensembles

Julian Ryde
Vikas Dhiman
Robert Platt 0001

Conversion of unorganized point clouds to surface reconstructions is increasingly required in the mobile robotics perception processing pipeline, particularly with the rapid adoption of RGB-D (color and depth) image sensors. Many contemporary methods stem from the work in the computer graphics community in order to handle the point clouds generated by tabletop scanners in a batch-like manner. The requirements for mobile robotics are different and include support for real-time processing, incremental update, localization, mapping, path planning, obstacle avoidance, ray-tracing, terrain traversability assessment, grasping/manipulation and visualization for effective human-robot interaction. We carry out a quantitative comparison of Greedy Projection and Marching cubes along with our voxel planes method. The execution speed, error, compression and visualization appearance of these are assessed. Our voxel planes approach first computes the PCA over the points inside a voxel, combining these PCA results across 2×2×2 voxel neighborhoods in a sliding window. Second, the smallest eigenvector and voxel centroid define a plane which is intersected with the voxel to reconstruct the surface patch (3-6 sided convex polygon) within that voxel. By nature of their construction these surface patches tessellate to produce a surface representation of the underlying points. In experiments on public datasets the voxel planes method is 3 times faster than marching cubes, offers 300 times better compression than Greedy Projection, 10 fold lower error than marching cubes whilst allowing incremental map updates.

ICRA Conference 2012 Conference Paper

LQR-RRT*: Optimal sampling-based motion planning with automatically derived extension heuristics

Alejandro Perez
Robert Platt 0001
George Konidaris 0001
Leslie Pack Kaelbling
Tomás Lozano-Pérez

The RRT* algorithm has recently been proposed as an optimal extension to the standard RRT algorithm [1]. However, like RRT, RRT* is difficult to apply in problems with complicated or underactuated dynamics because it requires the design of a two domain-specific extension heuristics: a distance metric and node extension method. We propose automatically deriving these two heuristics for RRT* by locally linearizing the domain dynamics and applying linear quadratic regulation (LQR). The resulting algorithm, LQR-RRT*, finds optimal plans in domains with complex or underactuated dynamics without requiring domain-specific design choices. We demonstrate its application in domains that are successively torque-limited, underactuated, and in belief space.

ICRA Conference 2012 Conference Paper

Non-Gaussian belief space planning: Correctness and complexity

Robert Platt 0001
Leslie Pack Kaelbling
Tomás Lozano-Pérez
Russ Tedrake

We consider the partially observable control problem where it is potentially necessary to perform complex information-gathering operations in order to localize state. One approach to solving these problems is to create plans in belief-space, the space of probability distributions over the underlying state of the system. The belief-space plan encodes a strategy for performing a task while gaining information as necessary. Unlike most approaches in the literature which rely upon representing belief state as a Gaussian distribution, we have recently proposed an approach to non-Gaussian belief space planning based on solving a non-linear optimization problem defined in terms of a set of state samples [1]. In this paper, we show that even though our approach makes optimistic assumptions about the content of future observations for planning purposes, all low-cost plans are guaranteed to gain information in a specific way under certain conditions. We show that eventually, the algorithm is guaranteed to localize the true state of the system and to reach a goal region with high probability. Although the computational complexity of the algorithm is dominated by the number of samples used to define the optimization problem, our convergence guarantee holds with as few as two samples. Moreover, we show empirically that it is unnecessary to use large numbers of samples in order to obtain good performance.

ICRA Conference 2012 Conference Paper

Position control of tendon-driven fingers with position controlled actuators

Muhammad E. Abdallah
Robert Platt 0001
Brian K. Hargrave
Frank Permenter

Conventionally, tendon-driven manipulators implement some force-based controller using either tension feedback or dynamic models of the actuator. The force control allows the system to maintain proper tensions on the tendons. In some cases, whether it is due to the lack of tension feedback or actuator torque control, a purely position-based controller is needed. This work compares three position controllers for tendon-driven manipulators that implement a nested actuator position controller. A new controller is introduced that achieves the best overall performance with regards to speed, accuracy, and transient behavior. To compensate for the lack of tension control, the controller nominally maintains the internal tension on the tendons through a range-space constraint on the actuator positions. These control laws are validated experimentally on the Robonaut-2 humanoid hand.

ICRA Conference 2011 Conference Paper

A miniature load cell suitable for mounting on the phalanges of human-sized robot fingers

Robert Platt 0001
Chris Ihrke
Lyndon B. Bridgwater
Douglas Linn
Ron Diftler
Muhammad E. Abdallah
R. Scott Askew
Frank Permenter

It is frequently accepted that tactile sensing must play a key role in robust manipulation and assembly. The potential exists to complement the gross shape information that vision or range sensors can provide with fine-scale information about the texture, stiffness, and shape of the object grasped. Nevertheless, no widely accepted tactile sensing technology currently exists for robot hands. Furthermore, while several proposals exist in the robotics literature regarding how to use tactile sensors to improve manipulation, there is little consensus. This paper describes the electro-mechanical design of the Robonaut 2 phalange load cell. This is a miniature load cell suitable for mounting on the phalanges of humanoid robot fingers. The important design characteristics of these load cells are the shape of the load cell spring element and the routing of small-gauge wires from the sensor onto a circuit board. The paper reports results from a stress analysis of the spring element and establishes the theoretical sensitivity of the device to loads in different directions. The paper also compares calibrated load cell data to ground truth load measurements for four different manufactured sensors. Finally, the paper analyzes the response of the load cells in the context of a flexible materials localization task.

ICRA Conference 2011 Conference Paper

Multiple-priority impedance control

Robert Platt 0001
Muhammad E. Abdallah
Charles W. Wampler

Impedance control is well-suited to robot manipulation applications because it gives the designer a measure of control over how the manipulator to conforms to the environment. However, in the context of end-effector impedance control when the robot manipulator is redundant with respect to end-effector configuration, the question arises regarding how to control the impedance of the redundant joints. This paper considers multi-priority impedance control where a second-priority joint space impedance operates in the null space of a first-priority Cartesian impedance at the end-effector. A control law is proposed that realizes both impedances while observing the priority constraint such that a weighted quadratic error function is optimized. This control law is shown to be a generalization of several motion and impedance control laws found in the literature. The paper makes explicit two forms of the control law. In the first, parametrization by passive inertia values allows the control law to be implemented without requiring end-effector force measurements. In the second, a class of parametrizations is introduced that makes the null space impedance independent of end-effector forces. The theoretical results are illustrated in simulation.

ICRA Conference 2011 Conference Paper

Robonaut 2 - The first humanoid robot in space

Myron A. Diftler
Joshua S. Mehling
Muhammad E. Abdallah
Nicolaus A. Radford
Lyndon B. Bridgwater
Adam M. Sanders
R. Scott Askew
D. Marty Linn

NASA and General Motors have developed the second generation Robonaut, Robonaut 2 or R2, and it is scheduled to arrive on the International Space Station in early 2011 and undergo initial testing by mid-year. This state of the art, dexterous, anthropomorphic robotic torso has significant technical improvements over its predecessor making it a far more valuable tool for astronauts. Upgrades include: increased force sensing, greater range of motion, higher bandwidth, and improved dexterity. R2's integrated mechatronic design results in a more compact and robust distributed control system with a fraction of the wiring of the original Robonaut. Modularity is prevalent throughout the hardware and software along with innovative and layered approaches for sensing and control. The most important aspects of the Robonaut philosophy are clearly present in this latest model's ability to allow comfortable human interaction and in its design to perform significant work using the same hardware and interfaces used by people. The following describes the mechanisms, integrated electronics, control strategies, and user interface that make R2 a promising addition to the Space Station and other environments where humanoid robots can assist people.

ICRA Conference 2011 Conference Paper

Using prioritized relaxations to locate objects in points clouds for manipulation

Robert Truax
Robert Platt 0001
John J. Leonard

This paper considers the problem of identifying objects of interest in laser range point clouds for the purposes of manipulation. One of the characteristics of perception for manipulation is that while it is unnecessary to label all objects in the scene, it may be very important to maximize the likelihood of correctly locating a desired object. This paper leverages this and proposes an approach for locating the most likely object configurations given an object parameterization and a point cloud. While many other approaches to object localization need to explicitly associate points with hypothesized objects, our proposed method avoids this by optimizing relaxations of the likelihood function rather than the exact likelihood. The result is a simple, efficient, and robust method for locating objects that makes few assumptions beyond the desired object parameterization and with few parameters that require tuning.

ICRA Conference 2010 Conference Paper

A measurement model for tracking hand-object state during dexterous manipulation

Craig Corcoran
Robert Platt 0001

It is frequently accepted in the manipulation literature that tactile sensing is needed to improve the precision of robot manipulation. However, there is no consensus on how this may be achieved. This paper applies particle filtering to the problem of localizing the pose and shape of an object that the robot touches. We are motivated by the situation where the robot has enclosed its fingers around an object but has not yet grasped it. This might be the case just prior to grasping or when the robot is holding on to something fixtured elsewhere in the environment. In order to solve this problem, we propose a new model for position measurements of points on the robot manipulator that tactile sensing indicates are touching the object. We also propose a model for points on the manipulator that tactile measurements indicate are not touching the object. Finally, we characterize the approach in simulation and use it to localize an object that Robonaut 2 holds in its hand.

ICRA Conference 2004 Conference Paper

Manipulation Gaits: Sequences of Grasp Control Tasks

Robert Platt 0001
Andrew H. Fagg
Roderic A. Grupen

In dexterous manipulation, an object must be reconfigured while maintaining a stable grasp. This may require that the object be re-grasped in order to avoid finger workspace limits. We present a set of closed-loop controllers designed to achieve force-related objectives such as wrench closure, and show how they may be concurrently combined. Furthermore, we show that dexterous manipulation behavior may be generated by sequencing concurrent combinations of these controllers. We show that dexterous manipulation can be viewed as a task that is accomplished in the context of a wrench closure constraint. We hypothesize this approach can generalize to any task that must be accomplished while maintaining a set of constraints.

ICRA Conference 2004 Conference Paper

Tactile Gloves for Autonomous Grasping with the NASA/DARPA Robonaut

Toby B. Martin
Robert O. Ambrose
Myron A. Diftler
Robert Platt 0001
Melissa Butzer

Tactile data from rugged gloves are providing the foundation for developing autonomous grasping skills for the NASA/DARPA Robonaut, a dexterous humanoid robot. These custom gloves compliment the human like dexterity available in the Robonaut hands. Multiple versions of the gloves are discussed, showing a progression in using advanced materials and construction techniques to enhance sensitivity and overall sensor coverage. The force data provided by the gloves can be used to improve dexterous, tool and power grasping primitives. Experiments with the latest gloves focus on the use of tools, specifically a power drill used to approximate an astronaut's torque tool.

ICRA Conference 2003 Conference Paper

Evolution of the NASA/DARPA robonaut control system

Myron A. Diftler
Robert Platt 0001
C. J. Culbert
Robert O. Ambrose
William Bluethmann

The NASA/DARPA Robonaut system is evolving from a purely teleoperator controlled anthropomorphic robot towards a humanoid system with multiple control pathways. Robonaut is a human scale robot designed to approach the dexterity of a space suited astronaut. Under teleoperator control, Robonaut has been able to perform many high payoff tasks indicating that it could significantly reduce the maintenance workload for human's working in space. Throughout its development, Robonaut has been augmented to include new sensors and software resulting in increased skills that allow for more shared control with the teleoperator, and ever increasing levels of autonomy. These skills range from simple compliance control, and short term memory, to, most recently, reflexive grasping and haptic object identification using a custom tactile glove, and real-time visual object tracking.

ICRA Conference 2003 Conference Paper

Extending fingertip grasping to whole body grasping

Robert Platt 0001
Andrew H. Fagg
Roderic A. Grupen

Although it is mechanically possible for a robot manipulator to grasp using non-fingertip contacts, there are few examples of this. We call non-fingertip grasping such as grasping with proximal finger phalanges or grasping with the sides of arms "whole body grasping". While robotic demonstrations are rare, humans commonly use whole body grasps to interact with the world. One of the distinctive features of whole body grasping is the kinematic coupling among potential contacts. This kinematic coupling introduces extra constraints into the grasp synthesis problem. In this paper, we extend recent grasp control techniques to whole body grasping. We show how the grasp control may be parameterized with a set of contact points on the surface of the robot manipulator that enables the grasp search to handle the extra kinematic coupling constraints and find whole body grasps.

IROS Conference 2002 Conference Paper

Nullspace composition of control laws for grasping

Robert Platt 0001
Andrew H. Fagg
Roderic A. Grupen

Much of the tradition in robot grasping is rooted in geometrical, planning-based approaches in which it is assumed that object geometries are well modeled a priori. Some recent approaches have chosen instead to deal with objects of unknown geometry. These techniques treat grasping as an active sensory-driven problem. At any given time, finger contacts are incrementally displaced along the object's local surface using a single control law. In this paper, we extend this approach by allowing multiple control laws to be active simultaneously. Three control laws are combined by projecting the actions of subordinate control laws into other control law nullspaces. The resulting composite controller finds grasps that are more robust than the component primitives in isolation. Finally, we show how this approach may be used on hand/arm manipulation systems with arbitrary kinematics.